The investigation addressed a conspicuous gap between laboratory knowledge and field ecology. Two-spotted crickets are widely used in physiology, developmental biology, neuroscience, ethology, ecology and evolutionary research because they are moderately sized, straightforward to rear and exhibit pronounced sexual dimorphism, particularly in their acoustic communication. Many studies have examined their mating behavior, sexual selection and predator avoidance under natural conditions, but their natural diet and trophic position have received much less attention. Although crickets are generally described as omnivores capable of consuming weed seeds, seedlings and dead or living arthropods, quantitative information about the food of G. bimaculatus in the wild remains limited.

For the preliminary assessment, researchers collected six adult two-spotted crickets—five females and one male—from a park on Ishigaki Island in Okinawa Prefecture, Japan, in November 2024. The sampling locality was at 24.33° N, 124.16° E. They also collected eight adults of the co-occurring grasshopper Aiolopus thalassinus tamulus, which served as a reference for estimating trophic position. All insects were captured by hand, frozen within five hours and transported to the laboratory, where they were stored at –20°C until processing. Each cricket’s digestive tract was removed for DNA analysis, while remaining body tissue was retained for isotope measurements. The restricted sample and single locality limit how broadly the findings can be generalized across the species’ range.

The two analytical approaches capture different aspects of feeding ecology. Gut-content DNA metabarcoding provides a short-term record of recently ingested material and can identify plant and animal food items using taxonomic markers. Stable isotope analysis reflects assimilated dietary sources over a longer period and can provide information about trophic position. Extracted cricket gut tissues were homogenized, freeze-dried and subjected to DNA extraction and cleanup. Plant-derived food was screened with chloroplast plant-barcode primers, while an approximately 380-base-pair region of the mitochondrial cytochrome c oxidase subunit I gene was targeted for animal DNA. A cricket-specific blocking primer was included to reduce amplification of host DNA. Libraries underwent paired-end sequencing with two 300-base-pair reads, and the resulting sequences were assigned against the NCBI nucleotide database.

The crickets carried a notably broad assortment of plant DNA. In total, 15 plant taxa were detected, encompassing four Fabaceae species and six Poaceae species. Frequently observed taxa included alyce clover, soybean, common wheat and corn, while yellow bluestem, scented-top grass, Illinois bundleflower, violet crabgrass, pillpod sandmat, brownbeard rice and other plants were also recorded. Sand palm, black medick, yellow evening primrose, Bermuda buttercup and turkey tangle frogfruit appeared less frequently. Some assignments were necessarily limited: where several plant species produced similar sequences, researchers selected the taxon known to occur on Ishigaki Island and most consistent with the sequence data, while also consulting regional floras and national distribution records. The presence of a sequence therefore establishes occurrence at the assigned taxonomic level but does not quantify how much of any plant made up the diet.

Animal-derived DNA was detected in only a minority of the sampled crickets. The identified items included a land snail, domestic fowl, an ant belonging to the genus Prenolepis, and a sequence assigned to Sus scrofa. The genetic sequence could not distinguish wild boar from domestic pig. Detection frequencies for the animal taxa were 16.7% or 33.3%, depending on the item. These are frequency-of-occurrence measurements among the six crickets, not estimates of the proportion of dietary energy supplied by animals. Moreover, the study did not establish that the crickets consumed any detected taxon directly. The results show that animal-derived DNA was present in some gut samples, but they do not determine the original source of that DNA or its nutritional contribution.

Stable isotope measurements produced a different picture of trophic position. Mean nitrogen isotope values, δ15N, were 2.11‰ ± 2.41‰ in the crickets and 0.35‰ ± 1.41‰ in the grasshoppers. Because the crickets had higher values on average, the researchers calculated a trophic position of 2.52 using the grasshopper as a herbivorous baseline and a nitrogen trophic enrichment factor of 3.4‰. The difference between the species was not statistically significant in a Welch’s t test, however, with t = 1.59 and p = 0.15. The estimate is therefore approximate, especially because the grasshopper was assumed to feed exclusively on plants and no isotope baseline was measured directly from potential plant foods. The authors also note that the estimate may be conservative if the grasshopper’s true trophic position was higher than assumed.

Carbon isotope values differed more clearly between the insects. Mean δ13C was –23.84‰ ± 3.72‰ in the crickets and –13.56‰ ± 5.24‰ in the grasshoppers, a statistically significant difference in a Welch’s t test (t = 4.29, p < 0.01). Such differences are consistent with the grasshopper having a stronger association with C4 plant resources, whose tissues generally have higher δ13C values than those of C3 plants. The crickets’ broader plant detections and lower carbon isotope values were interpreted as evidence that they exploited a wider range of plant resources, predominantly C3 plants. The contrast with the higher nitrogen isotope value of the crickets may reflect occasional assimilation of nitrogen-rich animal material, even though animal DNA was rarely detected. This remains a possible explanation rather than a direct demonstration, particularly because the two methods represent different temporal windows.

Some detected food traces may have originated in human activity rather than natural vegetation. The crickets were collected in a park containing rubbish bins, and free-ranging cats were frequently observed there. Sequences from domestic fowl or pig could have come from discarded food or pet food, while wheat and maize may likewise have represented agricultural products rather than locally growing plants. These possibilities remain unresolved because the study did not establish where individual food items were acquired or whether the vertebrates and crops were consumed directly. The findings nevertheless raise the possibility that human-derived resources contribute to the diet of G. bimaculatus in urban or peri-urban settings. That possibility is consistent with the species’ broad diet and its occurrence in parks, gardens and agricultural fields, but the present data do not quantify the contribution of any particular resource.

The study’s implications extend to the design of laboratory work on a species whose physiology and behavior are studied intensively. Artificial feeds such as cat food, rabbit food, rodent food and ornamental-fish food are commonly used to rear G. bimaculatus. The field evidence suggests that an exclusively animal-product diet may not reproduce the nutritional environment experienced by most of the sampled wild crickets. This interpretation is compatible with previous research on other crickets, in which herbivore-oriented diets supported growth and survival better than cat food alone. Incorporating plant-based foods may therefore provide a more ecologically relevant experimental condition in studies intended to connect laboratory phenotypes with conditions in nature, although the present observations did not directly test any diet or its effects on laboratory performance.

Several limitations keep the findings firmly within the category of a preliminary case study. The sample comprised only six adult crickets from one locality, including just one male, and eight grasshoppers used as the isotopic comparison. The researchers could not assess dietary differences between sexes or developmental stages, and the results cannot be generalized across the species’ extensive range across Africa, southern Europe and Asia, including Japan. Gut-content metabarcoding captures only recently ingested material, while isotope signals integrate food over a longer but less taxonomically specific period. Future work should sample multiple populations, habitats, seasons and life stages, pair molecular gut analysis with vegetation surveys, and measure isotope baselines from the plants actually consumed. Such studies would help distinguish selective feeding from use of locally abundant vegetation and clarify whether vertebrate or crop DNA reflects direct consumption. The present evidence nevertheless offers a useful field-based foundation: the sampled two-spotted crickets showed a wide range of plant-derived DNA, infrequent animal-derived detections, an approximate trophic position of 2.52 and possible use of food resources associated with human activity.

Subject of Research: Preliminary assessment of the field diet and trophic position of wild two-spotted crickets using DNA metabarcoding and stable isotope analysis

Article Title: A preliminary assessment of the field diet and trophic position of the two-spotted cricket Gryllus bimaculatus using DNA metabarcoding and stable isotope analysis

Article References: Kuriwada, T., & Kawanishi, M. (2026). A preliminary assessment of the field diet and trophic position of the two-spotted cricket Gryllus bimaculatus using DNA metabarcoding and stable isotope analysis. Journal of Orthoptera Research, 35(2), 337-342. https://doi.org/10.3897/jor.35.208967

Image Credits: AI Generated

DOI: 10.3897/jor.35.208967

Keywords: two-spotted cricket, Gryllus bimaculatus, field diet, DNA metabarcoding, stable isotopes, trophic position, plant-derived food, Ishigaki Island, wild ecology, animal-derived DNA, preliminary, assessment

The colony occupies the left side of the cave’s sulfidic stream in a permanently dark passage beginning about 50 metres from the entrance. The entrance is in Greece and the deeper sections extend into Albania. The stream maintains a year-round temperature of 26 °C and carries hydrogen sulfide concentrations as high as 65 mg l⁻¹, while the cave atmosphere can reach 14 ppm H₂S. White biofilms containing filamentous sulfur-oxidizing bacteria, including Beggiatoa and Thiothrix, cover the stream sediments.

Researchers combined field surveys, microscopy, DNA barcoding, stable-isotope analysis and preliminary 16S metabarcoding. For population estimates, they placed 15-by-15-centimetre quadrants at 30 randomly selected wall locations and counted funnel-shaped T. domestica webs in photographs. T. domestica had a mean estimated density of 652 ± 149 individuals per square metre, with local values ranging from 178 to 2,756. P. vagans averaged 823 ± 556 individuals per square metre, with a range of 133 to 2,200. The counting method may overestimate abundance because abandoned or unoccupied funnel webs are difficult to distinguish from occupied webs.

The web coincided with a dense swarm of the non-biting midge Tanytarsus albisutus above the stream. Resting midges were estimated at 45,500 per square metre, and their observed distribution across roughly half the colony’s area produced an extrapolation of 2,414,440 flies. The authors considered abundant chironomid prey to be the most likely driver of T. domestica colonization, although that explanation was presented as a hypothesis rather than directly tested experimentally.

Carbon and nitrogen stable-isotope measurements indicated a food web associated with material produced inside the cave. Adult T. albisutus and the agelenid and linyphiid spiders inhabiting the colony had δ¹⁵N and δ¹³C values ranging from −2‰ to −10‰, compared with values of 1‰ to 4‰ in conspecific or ecologically similar surface-dwelling taxa. Together with observations of microbial biofilms and abundant terrestrial invertebrates, these measurements support the interpretation that sulfur-oxidizing chemoautotrophs form an important basal resource in the cave food web. The study did not directly trace the transfer of carbon from microbes to midges and spiders, however, and the proposed pathway through chironomids to the colony predators remains inferential.

Morphological examination of genital structures and analysis of mitochondrial cytochrome c oxidase sequences identified T. domestica as the web-forming species and P. vagans as its colony associate. Three additional species—Metellina merianae, Lepthyphantes magnesiae and Kryptonesticus eremita—occurred elsewhere in the cave, while a small, blind and depigmented Cataleptoneta species was reported from deeper sections. All 32 sequenced T. domestica individuals shared a haplotype one mutation from a common haplotype represented across North America, Europe, Turkey, Pakistan and New Zealand. The three sequenced P. vagans individuals shared a haplotype three mutations from a widespread haplotype, while the two K. eremita individuals had a distinct haplotype. The study interpreted these patterns as evidence consistent with limited exchange between some cave and surface populations, but it did not directly measure gene flow.

Reproduction also varied among sampling periods. The researchers opened 86 T. domestica egg sacs collected in June 2024, October 2024 and March 2025. Clutches averaged 16.15 ± 0.62 eggs, with a range of 6–33, and egg size averaged 0.53 ± 0.05 mm, ranging from 0.4 to 0.6 mm. An analysis of variance detected differences among months. June clutches averaged 26 eggs, significantly more than October clutches at 14.5 and March clutches at 13, while October and March did not differ significantly. The authors did not determine why cave clutches may contain fewer eggs than the first cocoons reported for surface-dwelling females.

Preliminary microbiome comparisons found lower bacterial diversity in T. domestica from the cave than in one surface individual collected near Pixaria Cave. The cave spiders had a mean Shannon diversity index of 0.82 ± 0.25, compared with 2.99 for the surface specimen, and many reads came from intracellular symbionts including Mycoplasmopsis, Mycoplasma and Wolbachia. This comparison involved one surface individual and 29 analyzable cave individuals, and whole opisthosomas were used, so the results could not separate microbial contributions from different abdominal organs.

The study provides a detailed field characterization of a mixed T. domestica–P. vagans colony in a chemoautotrophic cave ecosystem, while also documenting reproduction, genetic variation and microbiome differences. Its principal limitations are the extrapolated population estimates, small microbiome comparison and inferential linkage between sulfur-oxidizing biofilms, chironomid prey and the spiders. The authors hypothesized that darkness may reduce the larger T. domestica’s visual detection of the smaller P. vagans, allowing the two species to coexist within the shared web, but no dedicated experiment tested that explanation.

Subject of Research: Field documentation and trophic characterization of a mixed-species spider colony in a sulfidic cave on the Albania–Greece border

Article Title: An extraordinary colonial spider community in Sulfur Cave (Albania/Greece) sustained by chemoautotrophy

Article References: Urák, I., Vrenozi, B., Głąbiak, Z., Lecoquierre, N., Eiberger, C., Maraun, M., Ştefan, A., Flot, J.-F., Brad, T., Dainelli, L., Sarbu, S. M., & Băncilă, R. I. (2025). An extraordinary colonial spider community in Sulfur Cave (Albania/Greece) sustained by chemoautotrophy. Subterranean Biology, 53, 155-177. https://doi.org/10.3897/subtbiol.53.162344

Image Credits: AI Generated

DOI: 10.3897/subtbiol.53.162344

Keywords: Sulfur Cave, spider colony, Tegenaria domestica, Prinerigone vagans, chemoautotrophy, sulfur-oxidizing bacteria, stable isotopes, Albania, Greece, subterranean ecology, extraordinary, colonial

The observational study focused on the Jiulong River Basin, the second-largest river system in Fujian Province, which provides water for approximately 12 million people in Longyan, Zhangzhou, and Xiamen. Researchers sampled native and non-native fishes at 16 sites in July 2024 using gillnets in pelagic areas and traps in benthic areas. Benthic invertebrates were collected concurrently to establish an isotopic baseline. The overall catch comprised 761 fish from five orders, 11 families and 38 genera: 39 native species and eight non-native species. A total of 298 fish samples underwent stable isotope analysis.

Tissue preparation involved removing scales and skin, excising muscle above the lateral line, drying samples at 60 °C for 48 hours and grinding them to powder. Carbon and nitrogen isotope ratios were measured with an elemental analyzer coupled to a stable isotope ratio mass spectrometer, with analytical precision better than ±0.3‰ for both elements. The Asian clam, Corbicula fluminea, served as the primary-consumer baseline for trophic-position calculations, using its mean δ15N value of 6.43‰ and an assumed 3.4‰ enrichment between adjacent trophic levels.

Across the sampled fish, δ13C values ranged from −27.27 ± 0.05‰ to −14.88 ± 0.58‰, while δ15N values ranged from 7.54 ± 0.04‰ to 14.15 ± 0.81‰. Estimated fish trophic positions extended from 2.33 to 4.27, producing an estimated food-chain length of about 4.27 trophic positions. Pelteobagrus fulvidraco occupied the highest estimated trophic position, while Sinibrama macrops occupied the lowest. The authors compared this value with other large river systems and described the vertical pathway from primary consumers to top predators as structurally intact, while noting that the comparison does not establish long-term stability.

Isotopic niche width varied substantially among species. Individual tilapia generally occupied broader niches than most native species: the average sample-size-corrected standard ellipse area across the four tilapia species for which the study reported values was 3.06‰², with a standard deviation of 0.79‰². Coptodon zillii had a sample-size-corrected area of 3.47‰², Sarotherodon galilaeus 3.51‰² and Oreochromis aureus 3.40‰². By contrast, the native assemblage as a whole had a larger sample-size-corrected area of 13.08‰² than the non-native assemblage at 4.97‰², while total isotopic niche area was 67.81‰² for native fishes and 19.64‰² for non-native fishes.

Bayesian niche analysis estimated that 63.59% of native fish niche space overlapped with non-native fish niche space, while 99.56% of the non-native niche space was encompassed within the native niche space. Overlap was concentrated among intermediate omnivores. Across all tilapia–native pairings, the average was 50.78%. C. zillii had an average overlap of 60% with native species, including 100% with Pseudogobio vaillanti, 86% with Acrossocheilus fasciatus and 80% with Xenocypris davidi. S. galilaeus averaged 58%, with complete overlap with P. vaillanti and 87% overlap with A. fasciatus. Oreochromis aureus and O. niloticus averaged 44% and 41%, respectively.

Among other non-native fishes, Pterygoplichthys pardalis averaged 52% overlap with native species, including 100% with P. vaillanti, 84% with Carassius auratus and 82% with X. davidi. Clarias batrachus averaged 27%. Separate comparisons between tilapia and fish in lower or upper trophic groups also showed overlap: C. zillii averaged 43% with native fishes in those groups, and O. aureus averaged 33%. Pairwise estimates were generated with 2,500 Monte Carlo simulations and quantified the probability that individuals of one species would fall within the 95% niche region of another.

Habitat distributions differed between the groups. Native fishes were more often associated with riffles, cobble or gravel substrates and clearer water, whereas non-native fishes were concentrated in places with muddy or sandy substrates, turbid and eutrophic conditions, and abundant aquatic vegetation. At several such sites, non-native fish made up more than 65% of relative abundance. The authors associated this pattern with the concentration of tilapia in intermediate trophic positions and proposed that their flexible feeding could create competitive pressure on native benthic omnivores and detritivores, particularly when resources are limited. This remains a potential mechanism inferred from isotope similarity and habitat association, not a measured effect on native abundance or survival.

Based on the observed overlap, the study proposed targeted removal of tilapia in high-density areas during the breeding peak, protection or restoration of benthic microhabitats, and enhanced populations of native fishes. It also recommended long-term monitoring combining environmental DNA, stable isotopes and routine surveys so management responses could be assessed. The study was limited to a single July sampling campaign in one basin, and its isotope-based estimates characterize trophic niches rather than directly observing feeding interactions or quantifying realized competition. The results therefore identify areas where further interaction data and community responses would be needed to determine whether high overlap translates into displacement of native fishes.

Subject of Research: Stable isotope assessment of trophic niches and potential competition between native and non-native fish in the Jiulong River Basin

Article Title: Fish trophic structure and potential competitive interactions in a typical subtropical river

Article References: Feng, S., Wang, J., Liu, W., Hui, Y., Wang, G., Li, J., Pan, X., Wu, C., Lin, L., Wang, X., Wu, Q., Wu, Z., Xiao, Y., Sun, X., Huang, L., & Ji, F. (2026). Fish trophic structure and potential competitive interactions in a typical subtropical river. NeoBiota, 108, 1-20. https://doi.org/10.3897/neobiota.108.187010

Image Credits: AI Generated

DOI: 10.3897/neobiota.108.187010

Keywords: Jiulong River Basin, non-native fish, tilapia, stable isotopes, trophic structure, isotopic niche overlap, resource competition, fish conservation, subtropical river, Fish, trophic, structure

The project is designed to make a dispersed body of research more accessible to international audiences. The authors searched Google Scholar, Web of Science and Science Direct using English and other relevant languages, including Russian, Ukrainian, Azerbaijani, Georgian and Kazakh. Their summary notes that much of the regional literature was published in Russian and was largely absent from the international literature.

The atlas contains measurements for six stable-isotope systems: carbon, reported as δ13C; nitrogen as δ15N; oxygen as δ18O; sulphur as δ34S; strontium as 87Sr/86Sr; and lead as 206Pb/204Pb. These are the measurement types recorded in the source studies. The compilation does not describe a new laboratory experiment or a single unified analytical campaign.

Instead, it gathers results already obtained and reported by separate research teams, retaining their associated archaeological and source-article information. Each dataset entry records the originating archaeological site, including GPS coordinates, and links the associated isotope data to a relevant source article. Where those details were available, the compilation also includes the source of the analyzed sample, its dating and information about its deposition.

This structure preserves the context supplied by the original studies and allows database users to return from a compiled measurement to the publication in which it was reported. The first accompanying dataset is titled “Compilation of carbon, nitrogen, oxygen, sulphur and strontium stable isotope data from the Mesolithic to the Late Modern period in the Black Sea area.” The second is presented as “A landmark compilation of stable isotope data from archaeological contexts in the post-Soviet space.” Both are associated with the IsoArcH database, and the preprint lists them as accessible data sets connected to the compilation. The stated purpose of the atlas is to serve as a comprehensive source for further research and as a reference set for the geographic and temporal area it covers.

Its scale is substantial: the authors collected results from more than one hundred studies spanning archaeological contexts across the former USSR, with the accessible collection incorporating ancient human and animal remains from Asia and the Caucasus. The resources are intended to support researchers who may not have encountered the region’s studies in international publications. Because the project is a literature compilation, its reach is defined by the papers found through the stated searches and by the information reported within them.

The datasets contain multiple isotope systems and archaeological metadata, but the supplied preprint description does not present a new statistical assessment, population-level estimate or uniform analytical protocol across the 114 papers. The collection is instead an openly connected archive of published measurements, site records and source references, preserving the diversity of the underlying studies rather than replacing their original methodological context. The work is currently a preprint under review for Earth System Science Data, with discussion beginning on 20 October 2026.

Its central contribution is organizational rather than experimental: by bringing 114 papers, 435 locations and six stable-isotope measurement types into two linked datasets, the authors have created an open resource for studying the archaeological record of the post-Soviet space. The authors describe it as a comprehensive source for future research and a geographic and temporal reference set, while the associated source articles remain the foundation for assessing the context of every compiled observation.

Subject of Research: Stable-isotope datasets compiled from archaeological studies across the former Soviet space

Article Title: Stable isotope bioarchaeological atlas from the post-Soviet space

Article References: Hagarová, A., Gorbulina, M., & Salesse, K. (2026). Stable isotope bioarchaeological atlas from the post-Soviet space. https://doi.org/10.5194/essd-2026-619

Image Credits: AI Generated

DOI: 10.5194/essd-2026-619

Keywords: stable isotopes, bioarchaeology, archaeological data, former Soviet space, Black Sea region, Caucasus, open datasets, IsoArcH, archaeological atlas, Stable, isotope, bioarchaeological

The research team analyzed seven cave populations of Astyanax mexicanus across two karst regions in the Mexican states of San Luis Potosí and Tamaulipas: the Sierra de El Abra and the Sierra de Guatemala. These two mountain systems host at least 30 known cavefish populations and represent distinct evolutionary lineages that arose independently from surface ancestors. By measuring the ratios of two stable isotopes, carbon-13 and nitrogen-15, in the muscle tissue of 47 fish collected during the dry season of 2017, the researchers reconstructed the trophic ecology of each population and compared it between regions, caves, and geological settings.

Stable isotope analysis works like a biological passport. The carbon isotope ratio, written as δ13C, reflects the diversity of primary productivity at the base of the food web, essentially telling researchers what kinds of carbon sources feed the ecosystem. The nitrogen isotope ratio, δ15N, increases predictably with each step up the food chain, so it reveals the trophic level of an organism. In caves, where photosynthesis is impossible and organic matter must be transported from the surface or produced by chemoautotrophic bacteria, these isotope signals become powerful tools for understanding how energy flows through an ecosystem that most people never see.

The results showed significant differences in both isotope signals among the seven cave populations. Within the Sierra de El Abra, Montecillos cave had the highest δ15N value at 10.9 parts per thousand, while Yerbaniz had the lowest at 9.2 parts per thousand. In the Sierra de Guatemala, Molino cave registered the lowest nitrogen signal at 8.6 parts per thousand. When the researchers compared the two regions directly, they found that populations from the Sierra de El Abra occupied a broader trophic niche area with lower trophic redundancy, meaning individuals within those populations were feeding on a wider variety of resources and competing less intensely for the same food items.

This regional difference is striking. The Sierra de El Abra system showed a total niche area of 3.27 compared to just 1.41 in the Sierra de Guatemala, along with higher values for mean distance to centroid and mean distance to nearest neighbor, all indicators of greater trophic diversity and less clustering around similar diets. The researchers suggest this could be linked to the geological history of the two systems, which have followed different evolutionary paths and may support different structures of trophic networks. Palma Seca cave in the Sierra de El Abra had the widest niche amplitude of any population at 7.06, while Vásquez cave in the Sierra de Guatemala had the narrowest at just 0.42.

To connect these isotope patterns to cave structure, the team developed a new metric called the Nutrient Input Index, or NI. This index compares the distance from the cave entrance to the first fish pool against the cave’s depth relative to the local groundwater level. A value greater than one indicates that the pool is closer to the entrance and receives more allochthonous material, organic matter transported from the surface. A value less than one means the pool is deeper and more isolated, where autochthonous sources, those generated within the cave itself, dominate. The researchers calculated NI values using topographic cave maps, published depth data, and measurements of the local phreatic mantle.

The relationship between the NI index and the isotope signals revealed something important. For carbon, the researchers found a significant negative relationship: as the NI index increased, meaning pools were closer to the surface and receiving more plant-derived material, the δ13C values became more depleted. This makes sense chemically, because surface plant material typically carries δ13C values between -35 and -25 parts per thousand, consistent with the range observed in the cavefish. Even in Vásquez cave, which reaches a depth of 270 meters, the fish showed carbon signals consistent with surface plant material, suggesting that decomposing organic matter still reaches even the deepest pools, either directly in the fish diet or through the prey they consume.

For nitrogen, the trend was positive but not statistically significant, hinting that caves with shallower pools and shorter distances from the entrance may support more complex trophic networks with additional trophic levels. The researchers propose that the influx of allochthonous material, driven by water currents, rainwater percolation, and animal access, significantly influences the trophic ecology within each cave. Caves with positive NI values, such as Montecillos and Palma Seca in the Sierra de El Abra and Molino and Caballo Moro in the Sierra de Guatemala, receive more surface-derived nutrients and may support richer food webs.

The findings carry broader implications for understanding how extreme environments shape evolution. Cavefish populations of Astyanax mexicanus have evolved at least three times independently from surface ancestors, losing their eyes and pigmentation while developing remarkable starvation tolerance and altered metabolism. The new study suggests that the selective pressures driving these adaptations may differ from cave to cave, depending on how much food reaches each population. In deeper caves with negative NI values, such as Escondido, Yerbaniz, and Vásquez, fish may face more intense competition for scarcer resources, potentially driving stronger selection for efficient foraging and energy conservation.

The researchers acknowledge limitations in their approach. The isotope signals of a consumer alone cannot fully reconstruct a trophic position without an appropriate isotopic baseline from primary producers and prey. Seasonality could also affect the results, as previous studies have reported variation in cavefish feeding across the year. Future studies should examine the entire trophic network, incorporate stomach content analysis, and measure resource inputs directly. Still, the Nutrient Input Index represents a pioneering tool for indirectly describing the trophic ecology of cave systems based on geomorphology alone, offering a promising approach to infer the intensity of selective pressures on cave-dwelling organisms across the world’s karst landscapes.

Subject of Research: Stable isotope analysis of blind Mexican tetra cave populations reveals trophic ecology differences linked to cave geomorphology

Article Title: Isotopic variability of δ 13 C and δ 15 N signals in cave systems: insights from the blind tetra Astyanax mexicanus

Article References: Hernández-Lozano, J., Córdova-Tapia, F., Miranda-Gamboa, R., Vázquez-Cruz, M. D. L., Garita-Alvarado, C., Mercado-Silva, N., & Ornelas-García, C. P. (2025). Isotopic variability of δ13C and δ15N signals in cave systems: insights from the blind tetra Astyanax mexicanus. Subterranean Biology, 51, 31-47. https://doi.org/10.3897/subtbiol.51.140856

Image Credits: AI Generated

DOI: 10.3897/subtbiol.51.140856

Keywords: cavefish, stable isotopes, Astyanax mexicanus, trophic ecology, karst caves, Sierra de El Abra, Sierra de Guatemala, nutrient input, blind tetra, subterranean ecosystems, Mexico, Isotopic

The research team, led by Fernando Álvarez of the Universidad Nacional Autónoma de México and colleagues, compiled published carbon and nitrogen isotope data for Typhlatya shrimps from the Yucatan Peninsula and added new measurements from five cenotes. In total, the dataset covered three of the four species present in the region, Typhlatya mitchelli, T. pearsei, and T. dzilamensis, across thirteen cave systems. The fourth Mexican species, T. campecheae, is so rare that no ecological or isotopic data exist for it, so it was excluded from the analysis.

Stable isotope analysis works because the ratio of heavy to light isotopes in an animal’s tissue reflects the food it has consumed. Carbon isotope values, expressed as δ13C, distinguish between different basal food sources: decaying plant material and particulate organic matter typically produce values around -20 to -35 per mil, while biomass from methanotrophic bacteria, which oxidize methane rising from anoxic sediments, yields far more negative values that can reach below -50 per mil. Nitrogen isotope values, δ15N, indicate trophic position, increasing roughly 3 to 4 per mil with each step up the food chain. By reading these signatures, researchers can reconstruct what an animal has been eating without observing it directly.

The results show that Typhlatya shrimps span almost the complete range of δ13C values found in the entire anchialine community, from -22.31 to -55.48 per mil, reflecting the diversity of microbial resources they exploit. The three species showed partially overlapping but distinct carbon ranges. Typhlatya mitchelli had the least negative values, from -22.31 to -39.65 per mil, consistent with feeding on decaying vegetation and bacterial mats dominated by nitrifying bacteria in shallower cave sections. Typhlatya pearsei showed the most negative values, reaching -55.48 per mil, indicating a diet rich in methanotrophic bacteria. Typhlatya dzilamensis fell in between, from -31.26 to -43.78 per mil, likely exploiting resources associated with the halocline, the sharp salinity gradient that traps imported organic material in deeper cave layers.

Statistical comparisons confirmed these differences. A Kruskal-Wallis test revealed significant variation among species, and Dunn’s multiple comparison showed that T. mitchelli differed significantly from T. pearsei and from unidentified Typhlatya individuals. The unidentified specimens from Cenote Bang, reported by Brankovits and colleagues in 2017, showed carbon values between -29.27 and -49.65 per mil, a range consistent with any of the three known species or potentially with a yet undescribed lineage suggested by prior molecular analyses.

To examine how the two dominant freshwater species partition resources, the team constructed convex hulls in δ13C-δ15N space. The hulls for T. mitchelli and T. pearsei overlapped by roughly 20 percent, with T. mitchelli sharing 23.05 percent of its area and T. pearsei sharing 17.62 percent. This limited overlap leaves ample margin for coexistence. Typhlatya pearsei showed broader carbon and nitrogen ranges and a larger total hull area than T. mitchelli, indicating a wider diversity of exploited resources. The overlap zone, at carbon values between -33 and -40 per mil, appears to mark a transition between the two primary feeding strategies.

Seasonal comparisons between the rainy and dry seasons showed no significant differences in carbon isotope values for either species across four cenotes. Paired Wilcoxon signed-rank tests conducted separately for each species and site revealed no seasonal shifts. This stability contrasts with expectations based on prior work showing an inverse relationship between methane concentration and rainfall in an inland cenote of the Ox Bel Ha system. The authors caution that their samples came from geographically distant cenotes collected in 2022 and 2023, whereas the earlier methane study examined a single site during 2015 and 2016, so larger standardized datasets will be needed to determine whether seasonal methane variation consistently affects shrimp isotopic signatures.

Geography mattered. Cenotes in the Ring of Cenotes, an arch of deep, short, unconnected passages around the city of Mérida, showed narrower and less negative carbon ranges for Typhlatya species, averaging -28.65 per mil, than those in the Caribbean Cave Area of Quintana Roo, which averaged -36.20 per mil. The Caribbean Cave Area contains shallower caves with tens to hundreds of kilometers of interconnected passages and strong lateral flows. In this region, organic matter from the overlying rainforest percolates through the rock matrix, generating small amounts of methane that are oxidized by methanotrophic bacteria near cave ceilings. These bacteria provide an additional basal resource that complements direct organic inputs, producing broader carbon ranges consistent with mixed reliance on particulate organic matter and methanotrophic biomass. This process depends on the integrity of the rainforest, which is crucial for maintaining the rich anchialine fauna in remote cave sections where surface organic matter is not transported.

The evolutionary context adds weight to these findings. The family Atyidae is an ancient group of primary freshwater shrimps that probably arose around the Permo-Triassic boundary roughly 250 million years ago. The clade inhabiting anchialine caves may have evolved in late Jurassic or early Cretaceous times, possibly occupying coastal areas of the ancient Tethys Sea. The contemporary distribution of Typhlatya in coastal areas of the Greater Caribbean, Mediterranean Sea, Ascension and Galapagos Islands, and Indian Ocean, along with related genera in Madagascar and Australia, supports this Tethyan origin hypothesis. Fifteen of forty-two atyid genera include cave-dwelling species, a success probably linked to their specialized filter-feeding and scraping mouthparts.

Support for trophic convergence comes from Australia, where Stygiocaris stylifera, a close relative of Typhlatya endemic to the Cape Range Peninsula and Barrow Island, displays isotope values indicative of partial reliance on chemoautotrophic bacterial biomass. This parallel evolution of bacterial-based feeding in distant atyid lineages suggests that the ability to exploit chemoautotrophic production may explain the persistence of anchialine systems as ecological refugia over geological timescales. The versatile feeding apparatus of atyids, with modified first and second pairs of pereopods adapted for scraping rather than cutting, likely facilitates this opportunistic strategy, setting them apart from epigean filter-feeding relatives.

The study’s authors propose that Typhlatya shrimps function as keystone species, introducing nutrients to the anchialine trophic web by taking advantage of microbial production from nitrifying bacteria acting on plant debris and methanotrophic bacteria consuming methane from the water column. Other anchialine species that could feed on bacterial mats, such as the thermosbaenacean Tulumella unidens, occur in numbers too low to play a comparable central role. By converting microbial biomass into animal tissue accessible to predators, Typhlatya shrimps connect primary producers and particulate organic matter with higher trophic levels, potentially facilitating the arrival of other species once they colonize a cave. The breadth of their isotopic niches underscores their trophic importance, the diversity of resources they exploit, and the influence of regional geomorphological differences. Continued study of these shrimps promises to further illuminate the functioning of this still poorly known ecosystem, one of the largest anchialine cave networks on Earth, which may exceed 1,700 kilometers in Quintana Roo alone.

Subject of Research: Stable isotope analysis of trophic niches of Typhlatya cave shrimps in Yucatan anchialine caves

Article Title: The trophic role of cave shrimps of the genus Typhlatya seen through stable isotope eyes

Article References: Durán, B., & Álvarez, F. (2026). The trophic role of cave shrimps of the genus Typhlatya seen through stable isotope eyes. Subterranean Biology, 55, 43-56. https://doi.org/10.3897/subtbiol.55.164068

Image Credits: AI Generated

DOI: 10.3897/subtbiol.55.164068

Keywords: Typhlatya, anchialine caves, stable isotopes, trophic ecology, Yucatan Peninsula, cenotes, methanotrophic bacteria, food webs, Subterranean Biology, isotopic niche, cave shrimps, chemoautotrophy

The concern over mercury stems from two intertwined properties. First, it can travel enormous distances: released into the atmosphere, it circulates globally and returns to the surface through deposition onto vegetation, soils and ocean waters. Second, once in the environment, inorganic mercury can be converted by bacteria into monomethylmercury, a toxic and bioaccumulative form that concentrates in seafood and other foods, posing health risks to humans and wildlife. Anthropogenic emissions now far exceed natural inputs, driven both by the intentional use of mercury in artisanal and small-scale gold mining and by its presence as a trace contaminant in coal, ores and other primary resources extracted and used by humans.

Technically, mercury exists in many different inorganic and organic forms, and this speciation is central to its fate. In the dissolved phase, it can occur as elemental mercury vapor, ionic mercury, monomethylmercury and dimethylmercury, while also binding to organic ligands in water or attaching strongly to particles. In the atmosphere, mercury is mainly present in the gaseous phase as elemental mercury and dimethylmercury. The element can be taken up into vegetation and soils and into ocean surface waters primarily from the atmosphere, and it can be released back to the air after reduction to elemental mercury, a process enhanced by anthropogenically influenced activities such as biomass burning and deforestation. This exchange between the reservoirs of the biosphere makes the overall cycling extraordinarily intricate.

The conversion of inorganic mercury to the more toxic methylated forms is primarily mediated by bacteria. Recent advances have identified methylating genes in numerous microbes, yet the factors controlling the net methylation of mercury in natural systems are not fully understood. This gap in knowledge is significant because monomethylmercury is the form that bioaccumulates in aquatic food webs, ultimately reaching seafood consumed by people. Understanding what drives methylation, and equally what drives demethylation, is therefore a priority for assessing exposure risks across the globe.

A growing methodological frontier in mercury research is the use of stable isotope fractionation. Rather than relying solely on concentration measurements and kinetic characterizations of transport and transformation, scientists increasingly exploit differences in the isotopic composition of mercury in different source materials to trace the origin and fate of industrial pollution. This environmental fractionation of mercury stable isotopes offers a forensic tool for distinguishing atmospheric deposition from watershed inputs and plant uptake, and several of the papers in the Research Topic highlight its potential for understanding cycling in specific ecosystems.

Six papers make up the volume, each probing a different compartment of the biosphere. Haugk and colleagues examined the impact of permafrost thaw on mercury cycling and found that even after 17 years of thaw, there was no difference in mercury stock or in monomethylmercury production, even though thawing enhanced the potential for methylation by changing the microbial community. This result suggests that structural changes in microbial communities can alter methylation potential without immediately translating into measurable changes in mercury stocks or methylmercury levels, a nuance with implications for Arctic and subarctic regions undergoing rapid thaw.

Irei reviewed the cycling of mercury in grasslands, highlighting the major sources and sinks for the element and discussing how mercury isotopes could help unravel cycling in these systems. Goss and colleagues examined mercury cycling in different soils of a river delta, including a pitch pine bog, a silver maple floodplain forest and a wild rice marsh, documenting the variability in the long-term retention of mercury supplied from atmospheric deposition, watershed inputs and plant uptake of elemental mercury. Their work demonstrates that even within a single delta, different soil environments can retain mercury supplied from the same sources with markedly different efficiency.

Weiss-Penzias and colleagues used in situ and transported lichens to quantify the release and transport of mercury from contaminated soils in the New Almaden Mining District, a historically significant mercury mining area. They demonstrated that mercury was being released and transported while active uptake into the lichens occurred, and that this mercury was strongly sequestered within the lichen tissue. Lichens, which absorb nutrients directly from the atmosphere, thus serve as both sentinels of contamination and active participants in the local mercury cycle, capturing mercury released from legacy mining soils.

In the marine realm, Mason and colleagues detailed the air-sea exchange and mass balance for mercury and monomethylmercury in the Gulf of Maine. Their analysis concluded that external inputs of monomethylmercury were not the primary driver of water column concentrations, suggesting substantial methylation occurring within the water column itself. This finding is important for coastal seas, where methylmercury in seafood is a persistent exposure concern, because it implies that local production within the water, rather than transport from outside sources, controls the levels of the toxic form available for bioaccumulation.

Finally, Bakour and colleagues studied the impact of added cysteine and sulfide on mercury methylation and monomethylmercury demethylation by a sulfate-reducing bacterium. They found that the added ligands decreased methylation but had no impact on demethylation. Modeling suggested that the addition of reduced sulfur altered the rate of methylation by making mercury less bioavailable, a result that underscores how the chemical speciation of mercury, governed by the ligands present in the environment, directly controls the accessibility of the element to methylating microbes. Together, these six studies highlight the complexity of mercury’s environmental chemistry and the intricate transformations between its different forms across the multiple compartments of the biosphere, from thawing permafrost and grassland soils to river deltas, mining districts and coastal seas, reinforcing why mercury remains a pollutant of major global concern.

Subject of Research: Environmental chemistry of mercury

Article Title: Editorial: Environmental chemistry of mercury: sources, pathways, transformations and impact vol II

Article References: Mason, R. P., Bjorn, E., & Amyot, M. (2026). Editorial: Environmental chemistry of mercury: sources, pathways, transformations and impact vol II. Frontiers in Environmental Chemistry, 7, Article 1833826. https://doi.org/10.3389/fenvc.2026.1833826

Image Credits: AI Generated

DOI: 10.3389/fenvc.2026.1833826

Keywords: mercury, methylmercury, environmental chemistry, permafrost thaw, stable isotopes, air-sea exchange, soil contamination, Frontiers in Environmental Chemistry, Editorial, Environmental, chemistry, sources

The research team, led by Paola Gioacchini and Martina Mazzon, took two contrasting agricultural soils, a loamy Cambisol rich in silt and clay and a sandy Arenosol dominated by coarse particles, and mixed in fragments of a commercial biodegradable mulch film made of Mater-Bi, a starch-based polymer produced by Novamont. The fragments, sized between two and five millimeters, were added at three concentrations: 100, 1,000 and 10,000 milligrams per kilogram of dry soil, corresponding to 0.01, 0.1 and 1 percent by weight. The lowest dose mirrors the estimated annual input of biodegradable mulch material in a realistic agronomic setting, while the highest matches the loading rate recommended by the European standard EN 17033 for testing biodegradability. The soils were then incubated at 23 degrees Celsius, held at 60 percent of their water-holding capacity, for a full twelve months, with microbial measurements taken at the start, at six months and at the end of the experiment.

The clearest signal emerged at the highest dose, and it was dramatic. After one year, microbial biomass carbon, a measure of the living microbial community, was 69 percent higher in the loamy soil and 25 percent higher in the sandy soil compared with untreated controls. Because the biodegradable plastic contains roughly 60 percent carbon and no nitrogen, the highest dose delivered a hefty 6,000 milligrams of carbon per kilogram of soil, essentially a feast for soil microbes. At the six-month mark, the effect was already visible, with microbial biomass reaching approximately 583 milligrams per kilogram in the loamy soil and 238 in the sandy soil. Even though microbial biomass declined in all treatments between six and twelve months, the highest-dose treatment remained significantly elevated above both the control and the lower doses, suggesting that a large pulse of plastic-derived carbon can sustain microbial growth for a remarkably long time.

Quantitative PCR of bacterial 16S rRNA genes and fungal target genes revealed a more nuanced, and partly surprising, story. In the sandy soil, the intermediate dose of 1,000 milligrams per kilogram produced the highest bacterial and fungal gene abundance across the two sampling times, outperforming even the highest dose. The researchers suspect this counterintuitive result relates to carbon losses measured in a companion study: at the highest dose, the sandy soil had released extremely large amounts of carbon dioxide early in the incubation, meaning much of the available carbon may have escaped as gas rather than being converted into microbial cells. In the loamy soil, by contrast, microbial responses were strongly time-dependent, with the highest dose producing peak fungal abundance at six months. The prominence of fungi fits with earlier work showing that fungi are key colonizers and degraders of biodegradable plastics, thanks in part to their ability to produce cutinases, enzymes that accelerate polymer breakdown and carbon release.

Beyond the microbes, the plastic fragments physically restructured both soils. At the end of the year, the researchers used wet sieving to separate each soil into three size classes: macroaggregates larger than 250 micrometers, microaggregates between 250 and 50 micrometers, and the free silt-clay fraction below 50 micrometers. The highest plastic dose increased macroaggregate abundance by 32 percent in the loamy soil and 11 percent in the sandy soil, while sharply reducing the free silt-clay fraction, which fell to just 8.9 percent of the loamy soil’s mass compared with 28.5 percent in the untreated control. The likely mechanism is twofold: the plastic fragments can act as nuclei around which mineral particles, microbial biomass and organic matter coalesce into larger aggregates, and the surge in microbial growth supplies the sticky residues and extracellular substances that bind those particles together.

Crucially, the researchers corrected aggregate weights for sand content, since the sandy soil’s aggregates were up to 90 percent sand by weight, allowing a fair comparison between the two textures. This revealed that the loamy soil inherently holds far more real aggregate material, with 78 percent more macroaggregates and 71 percent more microaggregates than the sandy soil. The lower plastic doses produced weaker and more soil-specific effects: in the loamy soil, the two lower doses increased the recovery of microaggregates to about 50 percent of the soil mass, possibly because macroaggregates formed early in the incubation broke down and freed microaggregates previously locked inside them. In the sandy soil, only the highest dose shifted aggregate composition at all, underscoring how coarse-textured soils resist structural change unless the input is large.

The redistribution of aggregates carried carbon and nitrogen with it. The highest plastic dose increased carbon and nitrogen contents in macroaggregates in both soils, and also in the sandy soil’s microaggregates, while the free silt-clay fraction lost both elements. According to the classic aggregate-turnover model of Six and colleagues, this occlusion of fine particles within macroaggregates may actually protect carbon and nitrogen from microbial attack and mineralization, since physical barriers inside aggregates limit oxygen diffusion and enzyme access. The carbon-to-nitrogen ratio narrowed steadily from macroaggregates down to the silt-clay fraction in both soils, a signature of the predominantly microbial origin of organic matter in the finest fractions, where nitrogen-rich microbial residues accumulate and bind chemically to mineral surfaces.

Stable isotopes added a final layer of insight, and an unexpected one. Nitrogen isotope values, expressed as δ15N, rose progressively from macroaggregates to the finest fractions in both soils, indicating extensive microbial recycling of nitrogen in the smaller fractions, although the plastic itself had no effect on this pattern in the loamy soil and only a modest one in the sandy soil. Carbon isotopes told a different story in each soil: in the loamy soil, the silt-clay fraction was enriched in carbon-13, consistent with repeated microbial processing leaving heavier isotopes behind, while in the sandy soil the finest fraction was actually depleted in carbon-13, possibly reflecting rapid mineralization in which microbes preferentially consumed the lighter, labile compounds and left recalcitrant, carbon-13-depleted molecules stabilized on mineral surfaces. These isotopic shifts were driven by soil texture rather than by the plastic, showing that the soil itself, not the added carbon, governs the pathways of transformation and stabilization.

The authors are careful to note the caveats. The strongest responses occurred at 1 percent plastic by weight, an order of magnitude above realistic annual inputs, and the closed incubation system prevented nitrate leaching, which may have masked some nitrogen isotope effects. Yet the fact that even the lowest, field-realistic dose produced detectable changes in microaggregate recovery and associated carbon and nitrogen is a warning worth heeding. As biodegradable mulches are tilled into fields season after season, their residues will accumulate, and whether the effects documented here persist, amplify or fade over years of repeated incorporation remains an open question. The researchers argue that long-term field studies with repeated applications, focused on realistic doses, are now essential before the soil-biodegradable plastic revolution can be declared truly benign for the ground it is meant to protect.

Subject of Research: Effects of biodegradable plastic mulch residues on soil microbial biomass, aggregation, and carbon and nitrogen stabilization in loamy and sandy soils

Article Title: Contrasting responses of loamy and sandy soils to biodegradable plastic residues: microbial biomass, aggregation, and aggregate-associated carbon and nitrogen

Article References: Gioacchini, P., Mazzon, M., Guerrini, S., Alberoni, D., Cupi, J., Di Gioia, D., & Marzadori, C. (2026). Contrasting responses of loamy and sandy soils to biodegradable plastic residues: microbial biomass, aggregation, and aggregate-associated carbon and nitrogen. Frontiers in Soil Science, 6, Article 1950823. https://doi.org/10.3389/fsoil.2026.1950823

Image Credits: AI Generated

DOI: 10.3389/fsoil.2026.1950823

Keywords: biodegradable plastic mulch, soil aggregates, microbial biomass carbon, soil organic carbon, nitrogen cycling, stable isotopes, soil texture, microplastics, soil biogeochemistry, Mater-Bi, qPCR, carbon sequestration

One of the most striking findings at Jingtoushan concerns the dogs. In many archaeological contexts, dogs are effective proxies for human foodways because they tend to eat leftovers, scraps, and deliberately provided meals that mirror what people themselves consumed. At Jingtoushan, the dogs displayed isotope values consistent with a strongly marine-based diet, which indirectly implies that the humans living at the site were themselves heavily reliant on marine resources such as fish, shellfish, and marine mammals. This indirect inference is valuable because human skeletal material from such early coastal contexts is often scarce or poorly preserved, whereas animal remains can be more abundant. The approach therefore allows researchers to reconstruct human dietary patterns even when direct human samples are limited, a methodological advantage that is increasingly recognized in the broader field of isotopic archaeology.

The Lower Yangtze Delta is uniquely important for this kind of research because it sits at the intersection of two major stories in Chinese prehistory: the development of rice agriculture and the long-term adaptation of coastal communities to marine environments. Rice cultivation in this region has deep roots, with evidence of rice exploitation and early cultivation stretching back several millennia before the Jingtoushan occupation. Yet the pace at which rice became the dietary staple, rather than simply one resource among many, has been difficult to establish. Isotopic data provide a direct measure of what people actually ate, rather than what was available or what they might have grown, and thus offer a way to track the real dietary consequences of agricultural intensification.

By combining the new Jingtoushan data with previously published isotopic results from across the region, the researchers were able to trace a broad temporal pattern. During the early Neolithic, coastal populations in the Lower Yangtze Delta drew heavily on marine resources, a pattern consistent with the rich shell middens, fishing gear, and aquatic faunal remains found at sites of this period. As time passed, and particularly through the middle and late Neolithic, the isotopic signatures shifted decisively toward C3 terrestrial resources, reflecting a growing dependence on rice and the terrestrial animals associated with agricultural landscapes. This transition was not instantaneous but unfolded over centuries, mirroring the gradual intensification of rice farming documented by archaeobotanical and other archaeological evidence from the region.

The implications of this dietary shift extend beyond simple subsistence questions. A move from marine-dominated to agriculture-dominated diets would have reshaped nearly every aspect of coastal life. Marine foraging tends to be mobile and opportunistic, tied to tides, seasons, and the movements of fish and shellfish beds. Rice agriculture, by contrast, requires settled occupation, land management, water control, and labor organization, all of which carry social and political consequences. A dietary transition of the kind documented isotopically at Jingtoushan and across the region therefore likely accompanied, and perhaps helped drive, broader changes in settlement patterns, social organization, and even belief systems during the Neolithic.

It is worth noting that the relationship between agriculture and marine resource use is not necessarily one of simple replacement. In many coastal settings worldwide, farming and fishing coexisted for long periods, with marine foods continuing to contribute important protein and nutrients even after crops became central. The isotopic evidence from the Lower Yangtze suggests that while marine resources remained part of the dietary repertoire, their relative importance declined markedly as rice agriculture intensified. Understanding the precise timing and pace of this decline, and whether it varied between sites, communities, or social groups, remains an important avenue for future research. Sites with well-preserved human and animal remains spanning multiple phases of occupation will be particularly valuable for testing and refining the regional pattern identified in this study.

The Jingtoushan findings also contribute to a wider comparative conversation about coastal adaptations globally. In many parts of the world, the transition from foraging to farming in coastal settings has been debated intensely, with some scholars arguing that productive marine environments delayed the adoption of agriculture, and others pointing to cases where farming spread rapidly even among communities with abundant aquatic resources. The Lower Yangtze evidence suggests a middle path: marine adaptation was robust and persistent during the early Neolithic, but it eventually gave way to agricultural dependence as rice cultivation matured. This kind of regional, chronologically controlled isotopic evidence is exactly what is needed to compare trajectories of change across different coastal regions of the world.

Methodologically, the study demonstrates the value of pairing isotopic data from multiple species at the same site. Establishing local faunal baselines is essential for interpreting human isotope values, because isotopic signatures can vary with geology, climate, and food web structure from one location to another. By measuring dogs, pigs, and other animals alongside humans, the researchers could distinguish between genuinely marine diets and terrestrial diets with confidence, rather than relying on generic reference values. This careful baseline approach is increasingly standard in best-practice isotopic studies and strengthens the reliability of the dietary reconstructions presented.

The research also highlights the enduring scientific value of open access publication and data sharing. The availability of supplementary tables containing the isotopic measurements allows other researchers to reanalyze the data, test alternative interpretations, and incorporate the results into broader regional or global syntheses. As isotopic datasets accumulate across East Asia, meta-analyses will become possible that can address questions no single site can answer, such as how quickly agricultural diets spread, whether the transition was uniform across social groups, and how climate fluctuations interacted with subsistence change.

Finally, the study underscores the importance of coastal archaeological sites, which are often threatened by erosion, sea level change, and modern development. Sites like Jingtoushan preserve a unique record of the early relationship between humans and the sea, a relationship that is increasingly relevant today as coastal communities around the world face environmental change. Understanding how Neolithic populations adapted, shifted their economies, and reorganized their societies in response to changing opportunities and pressures offers a deep-time perspective on human resilience and transformation. The isotopic evidence from Jingtoushan, by revealing a clear dietary transition tied to the rise of rice agriculture, adds an important chapter to this ongoing story and demonstrates how modern scientific techniques can illuminate fundamental questions about the human past.

Subject of Research: Dietary shift from marine to agriculture in coastal Lower Yangtze Delta during Neolithic revealed by isotopic evidence from Jingtoushan

Article Title: Dietary shift from marine to agriculture in coastal Lower Yangtze Delta during Neolithic revealed by isotopic evidence from Jingtoushan

Article References: Deng, C., Sun, G., Wang, Y., & Guo, Y. (2026). Dietary shift from marine to agriculture in coastal Lower Yangtze Delta during Neolithic revealed by isotopic evidence from Jingtoushan. npj Heritage Science. https://doi.org/10.1038/s40494-026-02986-7

Image Credits: AI Generated

DOI: 10.1038/s40494-026-02986-7

Keywords: Neolithic, stable isotopes, Jingtoushan, rice agriculture, Lower Yangtze Delta, marine diet, bone collagen, subsistence transition, coastal archaeology, ancient diets, Dietary, shift

The research, led by Hannah R. Rigoni of Texas State University together with colleagues from the University of Tennessee and other institutions, set out to answer a question that has puzzled cave biologists for years: how much of the energy flowing through groundwater food webs comes from the sunlit surface, and how much is generated underground by microbes that never see daylight? This question matters because karst aquifers are notoriously fickle. Rainfall can flush organic material into the system in sudden pulses, or it can bypass the aquifer entirely during droughts. If subterranean animals rely too heavily on surface subsidies, their survival hinges on what happens above ground—on land use, urbanization, and the vagaries of weather.

Chemolithoautotrophy—the process by which bacteria and archaea build organic molecules from carbon dioxide using energy harvested from inorganic chemical reactions—thrives wherever reduced compounds such as hydrogen sulfide, methane, iron, or ammonium meet oxygenated water. In karst systems, these compounds can originate from two sources: the slow decomposition of buried organic matter, and the chemical dissolution of minerals like pyrite and gypsum in the bedrock itself. Microbes exploiting these energy sources form the base of a food web that operates entirely in darkness, a phenomenon biologists have documented in sulfidic caves across the globe, from Movile Cave in Romania to the Frasassi Caves in Italy.

To determine whether such chemosynthetic production matters in the Edwards Aquifer, the team sampled groundwater from multiple wells across the Barton Springs segment, capturing not only the water chemistry but also the microbial communities and the fine particulate organic matter—FPOM—that drifts through the system as a potential food source for animals. They combined geochemical measurements with biomass-weighted metabolic profiling, a technique that estimates which metabolic pathways dominate in a microbial community based on the abundance and composition of the organisms present. The results showed clear patterns: wells with distinct geochemical gradients hosted distinct microbial assemblages, and in wells where sulfide was present, the signatures of chemolithoautotrophic metabolism were strongest.

The most striking evidence came from stable isotope analysis. Because chemolithoautotrophic microbes typically produce organic matter with unusually light (depleted) carbon isotope ratios—often below −35 per mil—researchers can trace their contributions through the food web by measuring the isotopic composition of particles and animals. Using Bayesian isotope mixing models applied to the carbon and nitrogen isotope ratios of fine particulate organic matter, the team calculated that chemolithoautotrophic production contributed as much as 44.8 percent of the organic matter in one groundwater well. In sulfidic wells, where heterotrophic microbial activity contributed the least to FPOM, the chemosynthetic signal was clearest.

But when the researchers turned to the animals themselves—the stygofauna, including amphipods, snails, and other invertebrates adapted to life underground—the picture shifted. Bulk carbon isotope ratios of metazoan assemblages were not strongly depleted, failing to show the extreme values that would indicate heavy reliance on chemosynthetic food sources. Bayesian mixing models of animal tissues pointed instead to diets dominated by allochthonous organic matter: the surface-derived material that rains and floods deliver into the aquifer. In other words, even where chemosynthetic microbes were demonstrably producing food, the animals appeared to be eating mostly imported groceries.

Why the disconnect? The authors point to the hydrologic character of the Barton Springs segment. Unlike deep, stagnant aquifers where water may reside for decades or centuries, this portion of the Edwards Aquifer is rapidly recharged. Rainfall over the recharge zone can move through the system in days to weeks, delivering fresh pulses of surface organic matter that overwhelm the slower, steadier production of chemosynthetic microbes. Short groundwater residence times mean that allochthonous food is constantly replenished, giving stygofauna little incentive—or evolutionary pressure—to depend on the in-house production of chemolithoautotrophs. The isotopic signal of chemosynthesis, present in the particulate matter, gets diluted in the diets of animals that feed opportunistically on whatever the latest recharge event delivers.

This finding carries significant implications for conservation. The Barton Springs segment is home to federally listed endangered species, including the Austin blind salamander and Barton Springs salamander, whose populations depend on the quality and quantity of groundwater flowing through the system. If the food web is primarily fueled by surface-derived organic matter, then changes in land use—paved surfaces that alter recharge patterns, agricultural runoff that changes water chemistry, or urban development that reduces the quality of infiltrating water—could ripple through the entire subterranean ecosystem. Conversely, the study shows that chemosynthetic production is not negligible; in certain geochemical settings, it constitutes a substantial fraction of available energy, potentially providing a buffer when surface subsidies falter during droughts.

The research also highlights how much remains unknown about energy flow in groundwater ecosystems worldwide. Karst aquifers underlie roughly 20 to 25 percent of the global land surface and supply drinking water to billions of people, yet the food webs they harbor are among the least studied on the planet. Most previous work on chemolithoautotrophy in subterranean systems has focused on caves with obvious sulfidic springs or sulfur springs, where the chemical energy sources are concentrated and visible. The Edwards Aquifer study demonstrates that even in a rapidly flushed, well-connected karst system—arguably a worst-case scenario for detecting chemosynthetic support—the process is measurable and locally significant.

For the scientists, the next step is to refine the picture with finer-scale sampling: measuring isotope ratios of individual animals and specific food sources, tracking seasonal changes in recharge, and identifying which microbial taxa are responsible for the chemosynthetic production. For now, the study stands as a reminder that the line between sunlit and sunless ecosystems is blurrier than it appears. Deep beneath Austin, microbes are quietly manufacturing food from stone and chemistry, and while the salamanders and shrimp above them may prefer the imported variety, the underground pantry is stocked with homegrown goods as well. Understanding the balance between these two energy pathways may prove essential for protecting one of Texas’s most treasured and vulnerable natural systems as the city above it continues to grow.

Subject of Research: Chemolithoautotrophic microbial production and its contribution to stygofaunal food webs in the Barton Springs segment of the Edwards Aquifer, Texas

Article Title: Chemolithoautotrophic contributions to stygofaunal food webs in the Barton Springs Segment of the Edwards Aquifer, Texas

Article References: Rigoni, H. R., Corrington, C., Hutchins, B. T., Schwartz, B. F., Nowlin, W. H., & Engel, A. S. (2026). Chemolithoautotrophic contributions to stygofaunal food webs in the Barton Springs Segment of the Edwards Aquifer, Texas. Subterranean Biology, 57, 161-208. https://doi.org/10.3897/subtbiol.57.195204

Image Credits: AI Generated

DOI: 10.3897/subtbiol.57.195204

Keywords: Edwards Aquifer, chemolithoautotrophy, stygofauna, karst hydrogeology, stable isotopes, groundwater ecology, microbial communities, Barton Springs, subterranean biology, food webs, organic matter, Texas