This was a field-observation study combined with a review of museum collections and published records. The authors examined specimens held by several Swiss natural-history institutions and private collections, then surveyed two dry, south-facing slopes near Zermatt. The first site, at 1,600 metres above sea level, lay just above the railway station; the second, the Ze Bäche site, was at 1,730 metres. Both slopes were dry, well exposed to sunlight and covered with rock-steppe vegetation.

A. roridus is the only European species in its genus and is regarded as a rare, highly localized steppe element with a range extending from southern Sweden through central Europe to the Caucasus and Kazakhstan. In central Europe it is found only at a small number of local sites, especially in the east. Its biology became clearer only recently: a study published in 2015 documented oligophagy within the daisy family and successful rearing on Tanacetum vulgare, with Artemisia vulgaris considered a less certain host.

The review of historical evidence showed that Swiss records are very sparse. A specimen from Schaffhausen, cited in 1883, is preserved in the Museum zu Allerheiligen, while a specimen collected in Zermatt in August 1884 is held by the Natural History Museum of Bern. Later sources repeatedly listed the insect as very rare. A 1990 record near Bargen, south of Schaffhausen, described a dry, nutrient-poor limestone habitat threatened by scrub encroachment; the exact location was 47°47′06.04″ N, 8°36′44.05″ E.

Zermatt supplied the only continuously supported Swiss records over roughly 140 years. Preserved or documented examples came from 1884, 1916, 1931, 1935, 1938, 1957, 1982 and 2023. Two 1982 specimens recorded the site as 1,670 metres above sea level in “prairie artemisia.” The most recent of these series was collected above the Zermatt railway station at Balmen on 20 July 2023, at 46°01′48.19″ N, 7°45′02.60″ E. Other Swiss records included a single specimen from Mergoscia in Ticino in 1973, a report from the Lötschberg southern ramp without surviving voucher specimens, and a record from the Fully area in 2005.

Wormwood was well represented at both surveyed slopes, especially along paths, around deteriorating dry-stone walls and in areas affected by landslides. Adult weevils were found at these disturbed patches, including 12 in total. Because the insects exceed 15 millimetres in length but conceal themselves within dense vegetation, the authors cautioned that they can readily be overlooked. One pupa collected in the field was kept and produced an adult two days later, allowing the study team to observe its subsequent development and behaviour in captivity.

Excavated wormwood plants provided evidence of the previously unconfirmed developmental stages. The first large plants examined contained egg-laying cavities at the root collar below the soil surface, together with one or two young larvae measuring 6–8 millimetres in each root collar or main root. Later plants contained pupae in the upper section of the main root. One pupa was parasitized: a parasitoid larva, identified only as belonging to either Braconidae or Ichneumonidae, had eaten the beetle from within the fully developed pupa and then formed its own pupal case.

Freshly emerged adults were initially bright orange but developed the species’ typical dark coloration with pale scale spots within hours. The beetle began feeding on offered wormwood leaves four days after emergence. Captured adults showed greater activity during mornings and forenoons than during afternoons, evenings or nights. They fed on the leaves and stems of A. absinthium, and multiple copulations were observed. Three apparently older beetles, identified by sparse scaling and partly missing tarsal segments, died before mid-September; the authors considered them likely to have been previous-year adults.

The observations establish Artemisia absinthium as a confirmed host for A. roridus and document the species in dry rock-steppe habitat at elevations approaching 1,700 metres. Because eggs, larvae and newly emerged adults were found in late summer, the authors inferred that development at Zermatt lasts at least two years. They further proposed that facultative double overwintering can occur, first in the egg stage and then as an adult after late-summer emergence, while egg-laying may extend from autumn into early spring. These are interpretations based on limited field and captive observations rather than a continuous multi-year monitoring study.

Subject of Research: First confirmed field development of Adosomus roridus in Artemisia absinthium in Switzerland

Article Title: Das Steppenelement Adosomus roridus (Pallas, 1781) in der Schweiz und erste Dokumentation der Entwicklung in Artemisia absinthium L. ( Coleoptera , Curculionidae )

Article References: Germann, C., & Wartmann, S. (2024). Das Steppenelement Adosomus roridus (Pallas, 1781) in der Schweiz und erste Dokumentation der Entwicklung in Artemisia absinthium L. (Coleoptera, Curculionidae). Alpine Entomology, 8, 147-151. https://doi.org/10.3897/alpento.8.137395

Image Credits: AI Generated

DOI: 10.3897/alpento.8.137395

Keywords: Adosomus roridus, Artemisia absinthium, Swiss weevil, field entomology, host plant, larval development, Zermatt, museum records, rock-steppe habitat, parasitoid, Steppenelement, Adosomus

The Spinose Skipper is no ordinary butterfly. Within Europe it is considered exceptionally localised, known from only a small number of isolated colonies scattered across Serbia, the Republic of North Macedonia, Bulgaria, Romania, Ukraine and southern Russia in the Urals, with more recent discoveries in Greece. Researchers estimate that the species persists at only around 30 sites across its entire European range, a figure that has earned it a designation of Near Threatened on the European Red List of Butterflies. Beyond Europe, its distribution stretches eastwards in a broad arc through Russia’s Altai and Siberia, Kazakhstan, Mongolia and northern China, yet even there it is regarded as uncommon and patchily distributed. This combination of rarity and wide but fragmented range has made every new observation about its biology scientifically valuable.

The mystery centred on the caterpillar’s diet. Because the Spinose Skipper was long classified within the genus Muschampia, and because every other European Muschampia species with a documented lifecycle feeds on plants of the genus Phlomis in the mint family, Lamiaceae, most experts assumed the Spinose Skipper would follow suit. Early fieldworkers in North Macedonia accordingly concentrated their searches on Phlomis plants, inspecting their leaves season after season without success. Over the decades, a confusing scatter of suggestions accumulated in the literature: various authors proposed cinquefoils of the genus Potentilla as likely hosts, while observations from the Volga region of Russia pointed to a species of Marrubium, and a 2019 study in Bulgaria documented eggs and larvae on the wild strawberry Fragaria viridis. The picture was a puzzle with pieces that refused to fit.

Resolving the question required patience of a kind rarely seen in modern ecology. Between 2014 and 2017, researchers conducted repeated field trips to a site near the village of Govrlevo, southwest of Skopje, where healthy populations of the butterfly were known to fly. The surveys spanned early spring to late summer across several years, with visits in May 2014, March and August 2016, and multiple trips in 2017. The breakthrough came on 13 May 2017, when three eggs were finally discovered on a species of Potentilla growing at the site. Crucially, the researchers had not yet seen the Bulgarian findings on Fragaria viridis at the time of their discovery, meaning their independent observation of oviposition on a cinquefoil was untainted by prior expectation, a rare form of scientific replication in field biology.

Identifying the plant itself demanded expert collaboration. A sample collected after females were observed laying eggs was sent to the Faculty of Biology at the University of Belgrade, where Professor Gordana Tomović provisionally identified it as Potentilla detommasii, a cinquefoil species. Notably, several other cinquefoil species grew at the same site, yet the butterfly utilised only this one for oviposition. The chosen plants occupied the driest parts of the habitat, sometimes in large groups and sometimes as isolated individuals, and all three eggs were found on small seedlings bearing just six to eight leaves. This selectivity within a single plant genus hints at a finely tuned chemical or structural relationship between butterfly and host that remains to be explored.

Rearing the immature stages revealed further surprises about the caterpillar’s behaviour. Newly hatched first-instar larvae were placed onto seedlings in carefully constructed rearing containers: plant roots were immersed in water inside plastic bottles, with cotton wool barriers preventing the tiny larvae from drowning, and fine netting over the tops excluding predators while allowing airflow. The plants responded well, producing new roots within a week. Contrary to a previous account from Bulgaria, which described first-instar larvae constructing a characteristic shelter by cutting and folding leaflets, the Macedonian larvae built no shelter at all in their first stage, instead remaining at leaf tips and feeding on small amounts of tissue while leaving the cuticle intact. Only at the second instar did shelter-building begin, with larvae observed folding two leaves together, and later instars went on to construct silken tents.

The caterpillar’s calendar proved equally instructive. As summer heat desiccated the habitat, the host plants entered a summer dormancy that rendered them unsuitable for continued larval development, and the caterpillars responded by entering a summer diapause, a state of suspended development that allows them to survive the inhospitable season. The researchers also attempted to trick the larvae into skipping their winter diapause by exposing them to constant light during later development, but the manipulation failed, confirming that the species is strictly univoltine, producing just one generation per year. This rigid developmental programme, locked to the seasonal rhythm of its host plant, underscores how vulnerable a narrowly specialised insect can be to changes in habitat management and climate.

Perhaps the most far-reaching implication of the discovery concerns butterfly classification. In 2020, a molecular study using nuclear and mitochondrial DNA demonstrated that the Spinose Skipper is not monophyletic with the genus Muschampia, and the species was accordingly moved to the monotypic genus Favria, which sits as sister to the genus Gomalia. The host plant evidence now lines up neatly with the genetics. Every Muschampia species in the Western Palaearctic with a known lifecycle feeds on Phlomis or other Lamiaceae, whereas the Spinose Skipper feeds on plants of the tribe Potentilleae in the rose family, as does its Bulgarian counterpart on Fragaria viridis. Intriguingly, its sister genus Gomalia is morphologically very different, particularly in egg and larval stages, and feeds on Abutilon species in the mallow family, illustrating how quickly host plant associations can diverge even between closely related lineages.

The convergence of independent evidence from two countries makes the conclusion unusually robust. With larvae documented on Potentilla in North Macedonia and on Fragaria viridis, another Potentilleae member, in Bulgaria, the long-standing speculation about the Spinose Skipper’s host plant can finally be laid to rest. The authors suggest that across the species’ vast range, from the Balkans to Mongolia and northern China, different populations likely utilise different Potentilla species or other members of the tribe Potentilleae, a hypothesis that now invites fieldwork across Central Asia. For conservationists, the finding carries practical weight: protecting the Spinose Skipper means protecting its specific cinquefoil host and the dry, drought-prone microhabitats where it grows, knowledge that was simply unavailable before this study.

The story of the Spinose Skipper is a reminder that even in well-studied Europe, fundamental questions about common ecological relationships can persist for generations when species are rare, localised and seasonally fleeting. It took years of targeted searching, a willingness to abandon a plausible but wrong hypothesis about Phlomis, careful plant identification by a specialist botanist, and meticulous captive rearing through every larval instar to close the gap. In the end, the answer was hiding in plain sight on the driest slopes near Skopje, on a seedling cinquefoil with six to eight leaves, and it turned out to be the final piece of evidence confirming that this butterfly never truly belonged in Muschampia at all.

Subject of Research: Host plant and lifecycle ecology of the Spinose Skipper butterfly (Favria cribrellum) in the Republic of North Macedonia

Article Title: The lifecycle and ecology of the Spinose Skipper – Favria cribrellum (Eversmann, 1841) in the Republic of North Macedonia ( Lepidoptera , Hesperiidae )

Article References: Franeta, F., & Gascoigne-Pees, M. (2022). The lifecycle and ecology of the Spinose Skipper – Favria cribrellum (Eversmann, 1841) in the Republic of North Macedonia (Lepidoptera, Hesperiidae). Nota Lepidopterologica, 45, 119-127. https://doi.org/10.3897/nl.45.75723

Image Credits: AI Generated

DOI: 10.3897/nl.45.75723

Keywords: Favria cribrellum, Spinose Skipper, Hesperiidae, Potentilla detommasii, host plant, North Macedonia, butterfly ecology, larval development, diapause, taxonomy, Muschampia, conservation

The research, conducted by a team of Argentine scientists at the National Institute of Agricultural Technology (INTA) and the National University of Tucumán, compared six host fruit species under controlled laboratory conditions: guava and feijoa, both native to South America, and grapefruit, peach, plum, and loquat, all introduced. The team reared fly larvae in each fruit and then measured an unusually comprehensive suite of traits spanning the entire life cycle: how long larvae took to reach pupation, how many pupae survived to adulthood, how large the resulting adults were, how well female ovaries developed, how quickly males reached sexual maturity, and how long adults survived without food.

The results, published in Frontiers in Insect Science, revealed that host species significantly affected every single trait measured. Guava, a native host and one of the fruits most heavily infested by this species in nature, supported the fastest larval development of all six fruits, with larvae pupating in just about 13 days. Grapefruit, by contrast, stretched development to nearly 30 days. Peach and feijoa fell in between at roughly 16 days, with loquat and plum taking around 19 to 21 days. On the surface, guava looks like the ideal nursery—fast development is generally considered a hallmark of host quality, because larvae that linger face greater exposure to predators, parasitoids, pathogens, and the vagaries of weather.

But the adult stage told a very different story. Flies reared in guava emerged as smaller adults, with shorter wings, reduced ovary development, and lower resistance to starvation. Females from guava also showed a higher proportion of atrophied, non-functional ovaries. Meanwhile, the exotic stone fruits—peach and plum—consistently produced the largest adults with the best-developed ovaries and the highest overall performance across multiple traits. Plum also conferred the greatest starvation tolerance, meaning that flies raised in this introduced host could survive longest without food. Loquat generally produced the poorest outcomes, yielding the smallest females, the smallest ovaries, and delayed male sexual maturation, although it did confer relatively good starvation resistance.

Some of the patterns were genuinely counterintuitive. Grapefruit, which forced the slowest larval development, nonetheless produced males that began their sexual calling behavior—the pheromone-releasing courtship display—earlier than males from any other host. Grapefruit females also showed no ovarian atrophy at all, and adult emergence from grapefruit was among the highest recorded. Feijoa, the other native Myrtaceae tested, behaved similarly to guava in supporting rapid development, but it had the lowest pupal survival of any fruit, with only about 17 percent of pupae reaching adulthood, even as it accelerated male sexual maturation. Each fruit, in other words, was a bundle of benefits and costs rather than a simple ranking of good and bad hosts.

To integrate these multidimensional results, the researchers built a heatmap of standardized trait values and performed a principal component analysis combining the biological data with published nutritional profiles of each fruit from the USDA nutrient database. The first two principal components explained roughly 71 percent of the total variance, and the analysis confirmed visually what the individual statistics implied: no fruit species sat at the optimum for all traits. Peach and plum overlapped almost completely in the PCA space, indicating similar nutritional and life-history profiles, while guava, grapefruit, and loquat each occupied distinct positions associated with different combinations of nutrients and performance outcomes.

The nutritional analysis added an intriguing layer of complexity. Guava had the highest protein, lipid, fiber, carbohydrate, and mineral content of all six fruits—on paper, it should have been the best host. Yet apart from fast development, guava performed poorly on nearly everything else. The authors suggest several non-exclusive explanations. Guava pulp contains phenolic compounds and tannins, potent anti-nutritional defenses that force developing larvae to divert metabolic energy into detoxification rather than growth. The ratio of sucrose to total phenolics in guava is dramatically lower than in peach, imposing a much heavier chemical burden. Guava’s high ash content may also disrupt osmotic balance and reduce nutrient absorption efficiency. Whatever the precise mechanism, the lesson is clear: macronutrient content alone cannot predict host quality, and the evolutionary history between insect and plant matters in ways that simple chemistry tables miss.

Perhaps the most provocative implication concerns the so-called mother-knows-best hypothesis, which holds that female insects preferentially oviposit on hosts that maximize their offspring’s fitness. Field surveys have long suggested that A. fraterculus predominantly infests native fruits, and guava and feijoa are among the most heavily attacked species in nature. Yet in the laboratory, these native hosts did not deliver superior offspring performance. The study’s authors are careful to note the caveats: laboratory conditions exclude many ecological factors—temperature fluctuations, desiccation risk, natural enemies, seasonal constraints—that shape host suitability in the real world, and field infestation levels are not always a direct proxy for female preference. Still, the results point toward a decoupling between where these flies lay their eggs and where their offspring actually thrive, a mismatch documented in other phytophagous insects as well.

One possible resolution, the researchers propose, is that different hosts are advantageous at different times. In temperate Argentina, native and exotic fruits ripen in different seasons, and a slow-developing larva inside a grapefruit may actually benefit when temperatures drop—citrus pulp stays moist for weeks and could even allow larvae to overwinter in place, a strategy documented in the Mediterranean fruit fly. Early-season hosts might favor rapid reproduction, while late-season hosts might enhance survival and stress tolerance. Under this view, no host is universally optimal because the demographic needs of the population shift across the year, and the very notion of a single best fruit dissolves into a seasonal mosaic of partial advantages.

Beyond its evolutionary interest, the work carries practical weight. A. fraterculus is actually a cryptic species complex, infests more than 177 reported host plant species, and triggers stringent quarantine restrictions that complicate fruit exports from South America. Understanding which hosts produce larger, more fecund, more stress-tolerant adults—and which merely produce fast ones—can improve predictions of pest population dynamics and sharpen integrated management strategies, from monitoring programs to sterile insect technique campaigns that depend on producing high-quality mass-reared flies. The study also flags clear priorities for future research: behavioral assays of oviposition preference paired with biochemical analyses of fruit chemistry, including secondary metabolites that current nutritional databases do not capture. For now, the message for anyone modeling this pest is sobering and liberating at once: the fruit fly’s world is not a ladder of better and worse fruits, but a landscape of trade-offs in which every host wins something and loses something else.

Subject of Research: Effects of host fruit species on larval development and adult life-history traits of the polyphagous pest Anastrepha fraterculus

Article Title: No single host is optimal: effects of fruit species on development and adult performance in Anastrepha fraterculus (Diptera: Tephritidae)

Article References: Pacelli, F., Ruiz, M. J., Devescovi, F., Nussenbaum, A. L., Garbalena, M. S., Bachmann, G. E., Milla, F. H., Vera, M. T., & Segura, D. F. (2026). No single host is optimal: effects of fruit species on development and adult performance in Anastrepha fraterculus (Diptera: Tephritidae). Frontiers in Insect Science, 6, Article 1832786. https://doi.org/10.3389/finsc.2026.1832786

Image Credits: AI Generated

DOI: 10.3389/finsc.2026.1832786

Keywords: Anastrepha fraterculus, Tephritidae, fruit flies, host plant use, life-history trade-offs, larval development, ovary development, sexual maturation, starvation resistance, polyphagy, pest management, entomology

The work describes a formal model intended for integration into ALMaSS, the Animal Landscape and Man Simulation System, a long-established platform that simulates farms, fields, weather and wildlife at one-metre resolution across landscapes of typically ten by ten kilometres. Every moth in the new model exists as an individual digital agent with its own age, size, location and accumulating pesticide burden. Because each insect responds to its own simulated surroundings, the model can capture the kinds of chance events and spatial quirks that simpler, population-average assessments miss entirely. The choice of species was deliberate: N. pronuba is the type species of the enormous moth family Noctuidae, is widespread across its native Palearctic range, has become invasive in North America, and unusually for an insect, enjoys a rich historical literature on its biology, much of it from a doctoral study published in 1956.

A core technical achievement of the paper is the standardisation of how temperature drives development. The authors fitted Lobry–Rosso–Flandrois thermal performance curves, a mathematical form borrowed from microbial growth modelling, to decades-old laboratory data for eggs, larvae and pupae. Each curve is defined by four parameters: minimum, optimum and maximum developmental temperatures, and the growth rate at the optimum. For eggs, the fitted optimum came out at roughly 26 degrees Celsius with development failing above 29 degrees; larvae peaked near 29 degrees but died reliably at 27.5 degrees in the older survival experiments; pupae tolerated warmer conditions up to a 35-degree ceiling. Because the fitted curves estimated minimum development temperatures poorly, the team truncated them conservatively, assuming no development below 6 degrees for eggs and larvae and 7 degrees for pupae, values consistent with direct observation.

The larval data reveal an ecological subtlety with real consequences for pesticide exposure. Early laboratory work showed that first-instar caterpillars are active during the day, second instars are intermediate, and instars three through seven become strictly nocturnal, avoiding even moonlight. The final instar burrows beneath the soil surface, making it effectively invisible to any spray drifting overhead. In the model, larvae of instars one to six are therefore assumed to be above ground only between dusk and dawn when temperatures permit, while seventh-instar larvae remain protected below the surface. Since overspray is most likely during daylight hours when machinery operates, this behavioural rhythm substantially shapes which life stages encounter chemicals and when.

Adult behaviour is reconstructed from a patchwork of studies. Flight-mill experiments show N. pronuba can fly more than eleven kilometres, placing it at the top of the dispersal range measured among noctuids, and mark-release-recapture studies report mean movements of 867 metres between recaptures. The model gives each adult a daily dispersal distance drawn from a distribution between 100 metres and the 11-kilometre maximum. Energy budgets were scaled from sphinx moth physiology: a feeding weight of about 0.48 grams and a 21 percent weight loss over a maximum flight translate into an assumed daily nectar intake of roughly 86 microlitres. Foraging itself follows a deliberately neutral stochastic design, with moths moving toward high nectar concentrations along directed random walks, a placeholder until real foraging strategies can be characterised.

Reproduction is governed by photoperiod. Historical work identified a critical day length of around fifteen hours for triggering ovarian activation, suggesting females aestivate through high summer before breeding. The model assigns each female her own threshold drawn from a narrow Gaussian distribution, then allots her a total egg complement sampled from a skewed beta distribution averaging 1,323 eggs, reflecting laboratory figures of roughly 1,000 to 1,500 eggs laid in three to five batches. Egg numbers are split into batches using a broken-stick model constrained to match observed cluster sizes. Oviposition sites are chosen among patches of herbaceous vegetation, with attractiveness scaled to patch area, reflecting evidence that nocturnal, scent-oriented moths favour large habitat patches in ways diurnal butterflies do not.

Mortality comes from many directions, and the model treats them explicitly. Parasitoid wasps are represented as their own agents with functional responses combining search efficiency and handling time, following an approach already validated for a white butterfly model. Above certain densities, disease transmission and larval cannibalism impose additional spatially dependent mortality, while temperature-dependent survival curves capture the sharp thermal limits documented in the laboratory: at 25 degrees only 7 percent of larvae survived to maturity, and none at 27.5 degrees. Soil moisture adds another constraint, with larvae and pupae surviving best at 4 to 8 percent moisture and dying at extremes, represented by a symmetrical super-Gaussian function. Management is included bluntly: all soil cultivation kills non-adult stages, and complete vegetation removal is likewise assumed lethal, assumptions the authors flag for calibration against field data.

Pesticides enter the simulation through three separate pathways. Dietary exposure accumulates when adults drink contaminated nectar or larvae eat contaminated leaves. Contact exposure occurs when a moth crosses a treated surface, with uptake calculated from the pesticide load per square metre, the body area in contact and an absorption parameter. Overspray applies only when a spray event or drift coincides with a moth present in the field and not sheltered in soil. All three routes feed a single body-burden value per individual, which decays daily. In this first iteration, toxicology is deliberately simple: once the burden exceeds a threshold, the moth faces a daily probability of death. The authors acknowledge that sublethal effects, which in real moths can impair navigation, reduce fecundity and even harm offspring, remain outside the current framework.

The team is unusually candid about what the model cannot do. It excludes evolutionary responses such as resistance development, pheromone communication and social information, fine-scale microhabitat refugia within the one-metre grid, and the daily rhythms of nectar production that some flowers show. Extreme weather events, which can cause catastrophic mortality beyond anything captured in smooth laboratory-derived curves, are not represented. Nor does the model track interactions with competing herbivores or the indirect effects of pesticides eliminating preferred host plants. The authors position the tool accordingly: it is designed for comparing relative pesticide risks across landscape scenarios, identifying which life stages are most vulnerable, and testing whether spatial refugia could sustain populations, not for forecasting exact moth numbers or extinction probabilities.

Even so, the implications are considerable. Because the model is modular, parameterised primarily from N. pronuba but adaptable to other noctuids with similar life histories, it could become a template for assessing an entire guild of night-flying pollinators that current regulatory schemes ignore. Developmental patterns proved strikingly consistent across noctuid species, from pest species such as Helicoverpa armigera to wild relatives, suggesting the framework can be retuned with modest new data. A striking correlation strengthens that case: across noctuid species, fecundity and flight distance are strongly and positively related, hinting at a predictable axis of life-history variation the model can exploit. For the first time, regulators weighing a spray programme will be able to ask not only what happens to bees by day, but what unfolds among the moths that take over the same fields at night, and to do so with a tool whose assumptions, strengths and blind spots are stated in full.

Subject of Research: Agent-based modelling of Noctua pronuba for pesticide risk assessment in European agricultural landscapes

Article Title: The Formal Model for Noctua pronuba ( Lepidoptera , Noctuidae ) representing a typical agricultural-landscape night-flying moth species for pesticide risk assessment

Article References: Topping, C. J., & Pettersson, L. B. (2025). The Formal Model for Noctua pronuba (Lepidoptera, Noctuidae) representing a typical agricultural-landscape night-flying moth species for pesticide risk assessment. Food and Ecological Systems Modelling Journal, 6, Article e165232. https://doi.org/10.3897/fmj.6.165232

Image Credits: AI Generated

DOI: 10.3897/fmj.6.165232

Keywords: Noctua pronuba, ALMaSS, agent-based model, pesticide risk assessment, nocturnal pollinators, thermal performance curves, agricultural landscape, Lepidoptera, ecotoxicology, larval development, dispersal, Noctuidae

The challenge of describing crab larvae is far greater than it might appear. Brachyuran crabs, the true crabs, are among the most diverse and ecologically significant groups within the Decapoda, playing pivotal roles in marine and coastal ecosystems as scavengers, predators, and prey. Yet their early lives unfold as planktonic larvae that drift with the currents, and identifying these tiny creatures is notoriously difficult. Of the roughly 430 crab species recorded in the Western Indian Ocean, only about 125, or 29 percent, have had their larvae described at all. In the Gulf of Aden, the knowledge gap is even more pronounced, with research historically focused on adult crab biodiversity or, at best, on descriptions of the first larval stage gleaned from plankton samples. Complete larval sequences, which require rearing living larvae through every molt in the laboratory, remain rare prizes.

The genus Metopograpsus, belonging to the family Grapsidae, comprises seven species, of which two have been recorded from Yemeni coastal waters of the Gulf of Aden: M. thukuhar and M. messor. Before this study, complete larval development had been described for only two members of the genus, M. latifrons and M. frontalis, both typically passing through five zoeal stages before reaching the megalopa, with total development periods ranging from 25 to 38 days. Comprehensive reviews have highlighted the scarcity of detailed larval descriptions across the family, with fewer than 30 species documented across 41 studies. The difficulty is partly practical: the very small larvae of some Metopograpsus species are notoriously hard to feed in captivity, which is why many earlier studies stopped at the first zoeal stage.

The Yemeni team’s breakthrough began with two ovigerous females, crabs carrying eggs, collected by hand from a mangrove habitat in Mukalla on 25 July 2017. The specimens were transported to the Faculty of Environmental Sciences and Marine Biology at Hadhramout University, where they were held in laboratory aquaria until hatching. Around 500 larvae emerged on 1 August 2017. The researchers then distributed the larvae in groups of 50 into one-litre containers holding 800 millilitres of seawater, maintained at a salinity of 35 parts per thousand and a temperature of 27 degrees Celsius under a 12-hour light and dark cycle. The earliest stages were fed rotifers, while later stages received a mixed diet of rotifers and freshly hatched Artemia nauplii, with the water changed every other day. Over a period of 30 days, the larvae progressed through five distinct zoeal stages, each of which was carefully preserved, dissected, and described.

The laboratory work demanded considerable technical precision. Ten larvae from each stage were fixed in 70 percent ethanol and shipped to the Marine Sciences Laboratory at King Abdulaziz University for detailed examination. There, specimens were dissected under a WILD stereomicroscope and cleared in polyvinyl lactophenol for approximately 24 hours to render internal and external structures visible. Observations were made with an Olympus BH-2 compound microscope equipped with differential interference contrast optics, and illustrations were prepared with a camera lucida to preserve accurate proportions. The researchers recorded a suite of morphometric parameters for each stage, including rostrum dorsal length, cephalothorax length and width, furcal length, basal telson length, and pleon length, measuring ten individuals per stage with a calibrated ocular micrometer to the nearest 0.01 millimetre.

The resulting descriptions reveal a larva that grows steadily in complexity. The first zoea measures about 0.87 millimetres from the tip of the rostral spine to the tip of the dorsal spine, with a rounded cephalothorax, sessile eyes, and a forked telson bearing three pairs of stout spinulate setae. Its antennule carries four aesthetascs of unequal size, the sensory structures larvae use to probe their environment, while the antenna lacks a differentiated endopod and exopod. By the fifth zoea, the animal has grown to a rostrum dorsal length of about 1.60 millimetres, its antennule has become biramous with eleven aesthetascs, the mandible has developed a palp bud, the third maxillipeds have elongated, and the pereiopods, the future walking legs and claws, have grown substantially. Between these endpoints, the scaphognathite, the setose gill-bailing blade of the maxilla, expands from four marginal plumose setae in the first stage to thirty by the fifth, a tidy illustration of how larval feeding and respiratory machinery scales with body size.

But the most scientifically valuable findings are the features that set M. thukuhar apart from its relatives. Across all five zoeal stages, the cephalothorax completely lacks lateral spines, a trait shared so far only with M. messor among described species of the genus and not reported in the others. The dorsal spine, meanwhile, bears simple setae, a feature previously documented in the genus only in M. messor from the Red Sea. The antenna lacks an exopod entirely. The researchers also confirmed that the first zoea displays the seven characters considered typical of grapsid larvae, including a 2,2 setal arrangement on the maxillar endopod, a 2,2,2,2 pattern on the basis of the first maxilliped, an endopodal setal pattern of 0,1,5 on the second maxilliped, and an elongated telson base longer than the furcal arms. Together with the absence of lateral spines, the second maxilliped pattern helps distinguish M. thukuhar and M. messor from all other members of the genus.

These details matter because larval morphology is a powerful tool for untangling crab systematics. Comparisons with the larvae of M. messor revealed near-identical development, differing only in the number of setae on the scaphognathite of the second zoea, ten versus eleven, and the basial setae of the maxillule in the third zoea, seven versus eight. Contrasts with M. latifrons and M. frontalis were sharper: M. latifrons, for example, develops a lateral cephalothorax spine by the second zoeal stage, and M. frontalis shows a sixth pleonite fused to the telson in early stages. The team also noted discrepancies in older descriptions of M. maculatus, now generally regarded as a junior synonym of M. latifrons, suggesting that some reported larval differences may reflect intraspecific variation, rearing conditions, or incomplete early descriptions rather than true species distinctions. Combined with molecular studies of adults, the larval evidence supports placing Metopograpsus in its own well-separated subfamily, the Metopograpsinae, within the Grapsidae.

The study also carries a cautionary note for plankton-based surveys. Earlier work in Pakistani waters reported the first zoea of M. thukuhar among planktonic decapod larvae, but the researchers point out that the illustrated specimen appears more closely related to M. messor, underscoring how easily these larvae can be misidentified without laboratory-reared reference material. Reliable diagnostic characters, such as setae on the dorsal spine, the number of antennular setae, and the precise setation of the maxillule, maxilla, and first maxilliped basis, now provide a firm basis for identifying M. thukuhar larvae collected at sea. Accurate larval identification, in turn, underpins studies of larval dispersal, population connectivity, and the thermal physiology of early-stage crabs, topics of growing urgency as coastal waters warm.

For the Gulf of Aden, a region where mangrove ecosystems face mounting environmental pressure, the first complete larval description of M. thukuhar is more than a taxonomic milestone. It establishes a foundation for future ecological and conservation research on grapsid crabs, whose larvae link mangrove nurseries to open-ocean currents. By revealing which features define this species from its earliest days, the Yemeni team has given marine scientists a new lens on a hidden chapter of coastal life, and a reminder that even familiar crabs can keep their most intimate secrets until someone takes the trouble to raise them, one delicate molt at a time.

Subject of Research: Laboratory rearing and morphological description of the five zoeal stages of the mangrove crab Metopograpsus thukuhar from the Gulf of Aden

Article Title: Morphological description of the zoeal stages of Metopograpsus thukuhar (Owen, 1839) (Decapoda: Brachyura: Grapsidae) reared under laboratory conditions

Article References: Al Haj, A. E., Pyar, H., Al Aidaroos, A. M., Sas, A. A., & Al-Gahwari, Y. A. (2026). Morphological description of the zoeal stages of Metopograpsus thukuhar (Owen, 1839) (Decapoda: Brachyura: Grapsidae) reared under laboratory conditions. Discover Animals, 3(1), Article 91. https://doi.org/10.1007/s44338-026-00240-9

Image Credits: AI Generated

DOI: 10.1007/s44338-026-00240-9

Keywords: Metopograpsus thukuhar, zoea, larval development, Grapsidae, Brachyura, Gulf of Aden, mangrove crab, crab larvae, morphology, laboratory rearing, Yemen, marine biodiversity

Crown-of-thorns outbreaks are not a new phenomenon. Four major outbreaks have swept the Great Barrier Reef since the 1960s, and rising densities detected near Lizard Island suggest a fifth is now underway. What drives these population explosions has long divided researchers, with three broad hypotheses on the table: bottom-up boosts in larval food supply, top-down release from predation on juveniles and adults, and natural population fluctuations. None of these mechanisms is mutually exclusive, but the new study, led by Frances Patel of the Australian Institute of Marine Science together with colleagues at the University of Otago, homes in on the first of them with unusual precision—asking not just whether food matters, but when and for how long.

The researchers conducted five experiments in total, using separate larval cohorts spawned from broodstock collected from mid-shelf reefs near Townsville between 2022 and 2025. All rearing was performed at the National Sea Simulator in Townsville in an automated flow-through feeding system that held food concentrations at tightly controlled levels, a marked improvement over daily manual feeding setups used in most previous crown-of-thorns larval studies. Larvae were fed mixtures of the algae Dunaliella sp. and Tisochrysis lutea at either satiating high food levels—0.6 to 1.7 micrograms of chlorophyll a per litre, corresponding to 2,205 to 3,405 algal cells per millilitre—or limiting low food levels of 0.12 to 0.44 micrograms chlorophyll a per litre. Crucially, these concentrations mirror real conditions: the high food levels match those measured on mid-shelf reefs after nutrient pulses from upwelling or river runoff, while the low levels resemble typical surface waters on the Great Barrier Reef outside flood events.

The first set of experiments tested a long-standing but unverified idea: that crown-of-thorns larvae might harbor photosynthetic microbial symbionts capable of supplementing their nutrition through light-driven metabolite transfer. Such associations have been documented in coral larvae and in larvae of the tropical sea star Mithrodia clavigera, and a microbial study had suggested that crown-of-thorns larvae contain bacteria potentially capable of photosynthesis. If true, light could act as a nutritional lifeline for larvae drifting through the food-poor waters that characterize much of the reef. The result was emphatically negative. Larvae raised under a 12-hour light and 12-hour dark cycle performed no better—or worse—than larvae raised in complete darkness, at both food levels. Food concentration alone drove development: 57 to 62 percent of high-food larvae had reached the brachiolaria stage by day seven, compared with just 5 to 9 percent under low food, and by day fifteen roughly 80 percent of high-food larvae had progressed to mid or late brachiolaria versus about 1 percent of low-food larvae. Settlement success under high food reached 46 to 50 percent, with no influence of light, while no larvae settled at all under low food conditions.

The second set of experiments manipulated the timing of food availability. Larvae were switched between high and low food regimes five days after the onset of feeding, at seven days post-fertilisation. Larvae given high food early and then switched to low food still developed far better than larvae given low food early and then switched to high food. By day eleven, 88 percent of larvae kept on constant high food had reached mid to late brachiolaria stages, compared with 67 percent of the high-to-low group, 26 percent of the low-to-high group, and only 1 percent of larvae on constant low food. This asymmetry reveals a striking developmental plasticity with a clear message: food encountered early in larval life matters far more than food delivered later. Larvae that started well partially recovered when conditions improved, but they never caught up with siblings that had a strong start.

The third experiment delivered the study’s most consequential result by quantifying exactly how many days of high food are needed. Larvae exposed to one to three days of high food showed modest benefits, with 17 to 37 percent reaching advanced stages. But at four days of high food—a threshold response—more than 70 percent of larvae reached mid to late brachiolaria, essentially matching larvae raised on high food for the entire nine-day experiment. Settlement, however, required a slightly longer window: fewer than 1 percent of larvae exposed to only one or two days of high food settled, around 6 percent settled after three to four days, and 34 to 69 percent settled after five to nine days of high food exposure. In other words, a bloom lasting roughly four to five days at the start of the larval phase is sufficient to push most larvae onto a fast developmental track and to lift settlement rates to levels comparable with permanent abundance.

The physiological logic behind this sensitivity lies in the energetics of early development. Crown-of-thorns larvae at about two days old develop a functional gut and begin feeding, but maternal resources in the egg are depleted by the late bipinnaria stage. Marine invertebrate larvae carry lipids as their dominant energy reserve, yet accumulating carbohydrates during the bipinnaria stages may fuel the protein-rich brachiolaria phase and metamorphosis that follow. Previous work on related sea stars has shown that well-fed larvae establish higher carbohydrate concentrations during early development, and that later starvation does not necessarily compromise settlement if early nutrition was adequate. The authors suggest two possible outcomes from the pulse-feeding experiments: larvae that received high food in their first five days accumulated sufficient energy reserves to fuel complete development regardless of later nutrition, while larvae that started on low food accrued inadequate reserves that later abundance could not repay.

These results mesh tightly with what is known about phytoplankton dynamics on the Great Barrier Reef during the seastar’s spawning season. Intense rainfall events push nutrients into coastal waters through river runoff, while intrusions of nutrient-rich upwelled water fertilize deeper layers where larvae have recently been found at depths of up to 30 metres. Phytoplankton can double in abundance one to two times per day, allowing blooms to develop rapidly and persist for days to weeks. One recorded bloom lasting five days reached the reef corridor between Cairns and Lizard Island—the so-called outbreak initiation zone. That duration sits squarely within the four-to-five-day window the new experiments identify as sufficient to dramatically boost larval development, suggesting that even a single episodic bloom coinciding with spawning could amplify the number of larvae surviving to settlement.

The study also carries implications for how reef managers think about water quality. Nutrient enrichment from catchment runoff has long been suspected of feeding crown-of-thorns outbreaks, but the mechanistic link has been difficult to demonstrate because larvae are notoriously hard to sample in the wild. By showing that the critical nutritional window is narrow, early, and quantitatively defined, the research makes the bottom-up hypothesis testable against environmental monitoring data: blooms of sufficient concentration and duration overlapping the spawning season become a concrete, observable trigger to look for. Shorter larval development times may also increase larval retention near source reefs, a process previously proposed to contribute to primary outbreak initiation.

Important caveats remain. Laboratory settlement rates cannot be translated directly into recruitment success, because newly settled juveniles face heavy predation and other mortality in the field, and nutritional carryover effects into the juvenile stage may not be visible at settlement. The light experiments were also conducted under aquarium conditions that may lack the diverse natural microbial communities needed to establish photosynthetic symbionts, so the authors caution that the symbiont question warrants further study with larvae from natural environments. Still, the core conclusion stands: light does not rescue food-limited larvae, but a brief, well-timed pulse of phytoplankton abundance can transform larval fortunes. In the seasonal rhythm of the Great Barrier Reef, where floods and upwelling punctuate an otherwise nutrient-poor sea, those transient windows of plenty may be precisely what turns an ordinary spawning season into the beginning of an outbreak.

Subject of Research: Effects of light and short-term phytoplankton food pulses on larval development and settlement of the coral-eating crown-of-thorns seastar (Acanthaster cf. solaris)

Article Title: Does light and short-term high food availability enhance larval success in the coral eating crown-of-thorns seastar (Acanthaster cf. solaris)?

Article References: Patel, F., McDowell, E., Bastin, L., Gomez Cabrera, M., Lamare, M., & Uthicke, S. (2026). Does light and short-term high food availability enhance larval success in the coral eating crown-of-thorns seastar (Acanthaster cf. solaris)?. Coral Reefs. https://doi.org/10.1007/s00338-026-02962-4

Image Credits: AI Generated

DOI: 10.1007/s00338-026-02962-4

Keywords: crown-of-thorns seastar, Acanthaster cf. solaris, Great Barrier Reef, phytoplankton blooms, larval development, larval settlement, nutrient enrichment, upwelling, river runoff, coral reef decline, population outbreaks, developmental plasticity

The research, led by Andreas Tsipourlianos and Katerina A. Moutou of the University of Thessaly in Greece, together with João C. R. Cardoso and Deborah M. Power of the University of the Algarve in Portugal, focused on two fish species of enormous commercial importance in Mediterranean aquaculture: the gilthead seabream (Sparus aurata) and the European seabass (Dicentrarchus labrax). These species are evolutionarily close relatives, yet they occupy ecologically distinct niches, making them an ideal comparative pair for dissecting how genome history and ecological lifestyle interact to shape the genetic architecture of core metabolism. Both species also possess well-annotated reference genomes, a prerequisite for the kind of rigorous comparative genomics the team undertook.

Teleost fishes carry a particularly rich evolutionary legacy in their DNA. Like all vertebrates, their ancestors experienced two rounds of whole-genome duplication deep in evolutionary time. Then, roughly 350 million years ago, the lineage that gave rise to modern teleosts underwent a third, teleost-specific genome duplication. These events doubled and redoubled the genetic raw material available to fish ancestors, creating thousands of duplicate gene pairs. Most duplicates are eventually lost, silenced by mutation, or repurposed for new functions. But some are retained, and understanding why certain duplicates persist while others vanish is one of the central questions in genome evolution. OXPHOS genes, with their tight dosage requirements and dual-genome coordination, represent an especially demanding test case for theories of duplicate retention.

Using comparative genomics across euteleost lineages, the researchers identified 23 multi-copy OXPHOS gene families in the gilthead seabream and 21 in the European seabass. This means that for a substantial number of the genes encoding the respiratory machinery, both fish carry more than one copy, or paralogue, in their nuclear genomes. Critically, the team was able to trace the origin of most of these duplicated families back to the teleost-specific genome duplication, demonstrating that this ancient genomic upheaval left a durable imprint on one of the most conserved metabolic pathways in biology. The finding challenges any assumption that core energy genes are immune to the effects of genome doubling.

Why would an organism keep two copies of a gene whose product must be produced in precise stoichiometric proportions to assemble a functional respiratory complex? The researchers tested a hypothesis that has gained traction in evolutionary biology: duplicate retention reflects a balance between dosage constraints, which favor keeping both copies active at reduced levels to maintain the correct overall output, and functional divergence, which allows one copy to specialize in a new context, tissue, or developmental stage. To examine this balance in action, the team turned to a life stage where energy demand is at its most extreme: early larval development.

Fish larvae are biological sprinters. Within days of hatching, they must grow rapidly, develop organs, begin swimming and feeding, and reorganize their metabolism from the yolk-dependent state of the embryo to the self-fueling physiology of a free-living organism. Mitochondrial energy production is central to every one of these transitions, and any disruption to OXPHOS function during this window can be lethal. This makes early development an ideal natural experiment for asking whether duplicated OXPHOS genes do the same work or different work.

The transcriptomics analysis revealed that paralogous OXPHOS genes do not behave uniformly. Some paralogues showed stable, coordinated expression patterns across development, consistent with the dosage-balance model: both copies contribute to maintaining the required output of the respiratory complexes. Others displayed a strikingly different behavior, being expressed only at specific developmental stages, suggesting that they have acquired stage-specific regulatory roles. This split personality among duplicates, with some copies serving as dosage partners and others as developmental specialists, provides direct evidence that functional diversification has shaped the OXPHOS repertoire of these fish since the teleost genome duplication.

The implications extend beyond evolutionary theory. Aquaculture is one of the fastest-growing food production sectors in the world, and gilthead seabream and European seabass are cornerstone species of Mediterranean fish farming. Larval survival is a persistent bottleneck in hatchery production, and energy metabolism is a key determinant of whether a larva successfully navigates the vulnerable early stages of life. By mapping which OXPHOS paralogues are deployed at which developmental moments, the study lays a molecular foundation for understanding, and potentially improving, larval performance under farming conditions. Genes that are switched on during critical developmental transitions could serve as markers of metabolic health or as targets for nutritional and environmental optimization.

The work also speaks to a broader question in biology: how do the mitochondrial and nuclear genomes, which are inherited in different ways and evolve at different rates, maintain their intricate partnership across hundreds of millions of years? Duplicated nuclear OXPHOS genes add another layer of complexity to this coevolutionary dance. If one nuclear copy diverges in function or expression, the mitochondrial components with which it interacts must remain compatible. The retention patterns documented in seabream and seabass suggest that this negotiation has produced a flexible but carefully balanced system, one in which redundancy provides resilience and specialization provides developmental precision.

Funding for the study came from the European Union through the H2020 PerformFISH project, which aims to integrate innovative approaches for competitive and sustainable performance across the Mediterranean aquaculture value chain, along with Portuguese national funds from the Foundation for Science and Technology. Larval samples were supplied by the Hellenic Centre for Marine Research in Crete, whose certified aquaculture facilities enabled the controlled developmental work underpinning the transcriptomic analysis. As the first comprehensive survey of OXPHOS paralogue evolution in euteleosts, the study opens a window onto how ancient genome doublings continue to echo through the metabolism of modern fish, and it suggests that the duplicated genes left behind by those events are not evolutionary leftovers but active, functionally relevant players in the energy economy of development. For a pathway as fundamental as oxidative phosphorylation, that flexibility may be exactly what allowed teleosts, the most diverse group of vertebrates, to radiate into nearly every aquatic habitat on the planet.

Subject of Research: Evolution and retention of duplicated oxidative phosphorylation genes in euteleost fishes

Article Title: Evolution and retention of oxidative phosphorylation paralogues in euteleosts: insights from gilthead seabream and European seabass

Article References: Tsipourlianos, A., Cardoso, J. C. R., Angelakopoulos, R., Kotoula, A., Power, D. M., Mamuris, Z., & Moutou, K. A. (2026). Evolution and retention of oxidative phosphorylation paralogues in euteleosts: insights from gilthead seabream and European seabass. BMC Genomics. https://doi.org/10.1186/s12864-026-13338-x

Image Credits: AI Generated

DOI: 10.1186/s12864-026-13338-x

Keywords: oxidative phosphorylation, OXPHOS, gene duplication, teleost genome duplication, gilthead seabream, European seabass, mitochondria, larval development, comparative genomics, transcriptomics, gene retention, aquaculture