The discovery was unexpected. Researchers from the Faculty of Fisheries at Sher-e-Kashmir University of Agricultural Sciences and Technology of Kashmir, together with a colleague from ICAR-Central Institute of Fisheries Education in Mumbai, were conducting a six-month parasitological survey for ectoparasites in Schizothorax species along the River Jhelum. Between February and July 2023, they collected 290 specimens of three native snowtrout species: Schizothorax niger, S. esocinus, and S. curvifrons. Sampling took place at three sites representing different demographic profiles of the valley: Chatabal in Srinagar district, Guree in Anantnag district, and Sopore in Baramulla district, a stretch of river characterized by dense human population and moderate agricultural activity.

Out of all 290 fish examined, only one specimen tested positive for Ichthyobodo necator, and that fish was a Schizothorax niger from the Chatabal site. The overall prevalence was a mere 0.34 percent, rising to 0.95 percent among the 105 S. niger specimens. The infected fish carried eight parasites, giving a mean intensity of 8.00 and a relative density of 0.03. No infections were recorded in any of the fish from the Guree or Sopore sites, and none of the S. esocinus or S. curvifrons specimens harbored the parasite. Such a low prevalence might seem trivial, but for parasitologists it is precisely the kind of signal that matters: it establishes that the parasite is present in the ecosystem and provides a foundation for future ecological and disease-management research in a region where its flagellate protozoan fauna had never been cataloged.

Ichthyobodo necator, formerly known as Costia necatrix, is one of the most widely distributed and clinically important flagellate ectoparasites of freshwater fish worldwide. It was originally described from diseased brown trout alevins cultured in tanks at the College de France in Paris, and it has since been documented across Asia, including Iran, Japan, Singapore, the Philippines, and Sri Lanka. The parasite causes ichthyobodosis, also called costiosis, primarily infecting the skin and gills of fish and capable of producing heavy mortality, a common problem on fish farms. In India, a prevalence assessment in Sambalpur, western Orissa, revealed the occurrence of Costia necatrix on 16 percent of fish farms in that region, with the most affected species being major carps such as Labeo rohita, Catla catla, and Cirrhinus mrigala. Remarkably, the parasite is not confined to freshwater: it has been found in 25 species of marine fish and three species of anadromous salmon across the Pacific and Atlantic Oceans and nearby seas from subarctic to tropical zones, and seawater infections were first discovered in freshwater salmonids transported to the sea, indicating that the parasite is native to freshwater but can survive and flourish in marine environments.

The infected snowtrout in the Kashmir survey showed clinical signs familiar to fish health specialists: lethargy, excessive mucus secretion, and reddish areas indicative of hemorrhage. Under the light microscope, wet mount preparations of skin smears revealed actively motile, small, somewhat comma-shaped trophozoites, with a pair of flagella clearly visible. These microscopic observations set the stage for the study’s most technically revealing work: a combination of classical histopathology and scanning electron microscopy that allowed the researchers to correlate the fine structure of the parasite with the pathological damage in the host tissue.

For histopathology, infected skin samples were fixed in 10 percent neutral buffered formalin, dehydrated through graded ethanol concentrations, cleared with xylene, and infiltrated with molten paraffin wax. Five-micrometer sections were cut, stained with hematoxylin and eosin, and mounted with Canada balsam and DPX mountant for examination at 10X and 40X magnification. The results were striking. The epidermis showed destruction, with vacuoles forming in epidermal cells and significant hyperplasia of the goblet cells, the mucus-secreting cells of the fish skin. Epidermal cells had lost their interlinking cell membranes, and the outer surface layers of the epidermis occasionally appeared to slough off. An inflammatory reaction was evident at the site of parasite attachment. These changes mirror the extensive epidermal destruction and necrosis documented in salmonids infected with Ichthyobodo, including freshwater salmonid juveniles and Japanese flounder, where epidermal hyperplasia and vacuolation are followed by degeneration and sloughing of the skin surface.

Scanning electron microscopy pushed the investigation to an entirely different scale. Infected skin was fixed in 2.5 percent glutaraldehyde and then 1 percent osmium tetroxide, dehydrated through ethanol series, critical-point dried, mounted on aluminum stubs, and sputter-coated with gold before examination with a Gemini SEM 500. The images revealed numerous comma-shaped organisms on the infected skin surface, some clustered together at the same attachment site. The ultrastructure showed exactly how the parasite invades: Ichthyobodo necator attaches to host cells through a specialized attachment disc, and through this disc a cytostome canal, supported by microtubules, penetrates the host cell cytoplasm. The cytostome, the parasite’s feeding apparatus, was clearly visible at a scale bar of one micrometer. Flagellated trophozoites displayed one or two pairs of flagella of unequal length, with the short flagella ending inside a groove and the long flagella extending past the posterior tip of the body. These observations are consistent with earlier ultrastructural studies of the parasite on hatchery-reared salmon parr and on the skin cells of juvenile Atlantic salmon.

The morphological details matter for more than curiosity. The genus Ichthyobodo currently comprises three recognized species: I. necator, I. nitschei from goldfish, and the only identified marine species, I. hippoglossi, which infects Atlantic halibut. Molecular studies using small subunit rDNA sequencing have suggested that I. necator is actually a complex of sibling species, and many unnamed Ichthyobodo species likely remain to be described in cyprinids and other fish. In freshwater, the free-swimming form of I. necator is almost round, while the attached form is pyriform, and the parasite’s shape changes between these states. The distinctive comma-shaped body and smooth attachment disc observed in the Kashmir specimen are consistent with published descriptions of I. necator infecting freshwater fish, which earlier cytological studies reported to possess a smooth cytostome process. However, the authors acknowledge an important limitation: the parasite identity was not confirmed through molecular barcoding, and all clinical and pathological observations rest on a single infected individual, making the findings preliminary and descriptive rather than broadly representative of the parasite’s pathogenicity in S. niger.

Context makes the discovery more consequential. The River Jhelum, the largest and longest river in Kashmir, supports an average annual fish yield of approximately 20.5 kilograms per hectare, but it faces mounting challenges from human encroachment and pollution. Over the past decade, the native Schizothorax population has become susceptible to a range of parasites spanning protozoans, platyhelminthes, nematodes, and acanthocephalans, and the fish population has been steadily declining. Previous research in the valley has shown that pathogenic invasion becomes more likely when water quality changes, and that rising eutrophication of lakes drives parasite infections in schizothoracine fishes. Pollution stress may have direct or indirect effects on parasite prevalence, which raises questions about whether environmental degradation of the Jhelum is creating conditions favorable for flagellate pathogens like Ichthyobodo to establish themselves in the river’s fish communities.

The researchers argue that the finding contributes not only to knowledge of parasite diversity in the Kashmir Himalayas but also serves as a foundation for future research on the ecology, biology, and management of the region’s freshwater ecosystems. They call for monitoring and surveillance programs to assess the long-term implications of Ichthyobodo infection on the health and sustainability of S. niger populations in the River Jhelum, and for further studies to explore the parasite’s life cycle, transmission dynamics, and host-parasite interactions. For a food fish that is widely distributed and highly valued across Kashmir, the appearance of a parasite capable of causing heavy mortality in fish farms is a warning worth heeding. Whether I. necator remains a rare curiosity in the Jhelum or becomes an emerging threat to the valley’s iconic snowtrout may depend on how quickly science and conservation efforts respond to this first, microscopic glimpse of the parasite in Himalayan waters.

Subject of Research: First report of Ichthyobodo necator, a flagellate protozoan parasite, in Schizothorax niger from the River Jhelum in the Kashmir Himalayas, India

Article Title: First report of Ichthyobodo necator, a flagellate protozoan parasite, in Schizothorax niger from the River Jhelum in the Kashmir Himalayas, India

Article References: Shafi, I., Wali, A., Shah, F. A., Iqbal, G., Dar, S. A., & Sofi, N. A. (2026). First report of Ichthyobodo necator, a flagellate protozoan parasite, in Schizothorax niger from the River Jhelum in the Kashmir Himalayas, India. Frontiers in Aquaculture, 5, Article 1846130. https://doi.org/10.3389/faquc.2026.1846130

Image Credits: AI Generated

DOI: 10.3389/faquc.2026.1846130

Keywords: First, report, Ichthyobodo, necator, flagellate, protozoan, parasite, Schizothorax, niger, River, Jhelum, Kashmir

The research focused on the ventrointermediate nucleus of the thalamus, or Vim, the canonical target for Essential Tremor deep brain stimulation. Chronic high-frequency stimulation of this nucleus and its neighboring subthalamic region modulates a distributed network, notably the cortico-ponto-cerebello-rubro-thalamo-cortical circuit, which has long been implicated in the generation of pathological oscillations. Although the clinical benefit of Vim stimulation is well established, the precise neuronal mechanisms underlying the improvement remain incompletely deciphered, and the contribution of bi-hemispheric modulation is particularly unclear. Ipsilateral effects, in which stimulation of one thalamus influences tremor on the same side of the body, have been reported but are not always apparent, hinting that the two hemispheres do not operate as independent, mirrored modules.

To probe this hemispheric organization, the team developed a data-driven probabilistic mapping approach that linked simulated stimulation volumes, known as Volumes of Tissue Activated, to symptom improvement and side effects for each hemisphere separately. Unlike conventional probabilistic studies that pool data from both sides by mirroring one hemisphere onto the other, this framework preserved the spatial identity of each hemisphere, allowing genuine inter-hemispheric comparisons. The investigators retrospectively analyzed intraoperative stimulation data collected between 2008 and 2017 at the University Hospital Clermont-Ferrand in France, where all 23 patients underwent bilateral Vim lead implantation under local anesthesia. The left hemisphere was systematically explored and implanted first, with the right hemisphere following approximately one hour later, a consistent surgical sequence that provided a natural experimental contrast between a naïve hemisphere and one already carrying an implanted electrode.

The intraoperative exploration itself was remarkably dense. Using rigid semi-microelectrodes with a contact diameter of 0.5 millimeters, the surgeons tested stimulation positions in one-millimeter increments along trajectories averaging 14 millimeters in length, one central track optimized for the Vim and Forel’s field H, and a secondary track two millimeters away, mostly posterior, exploring the ventrocaudal nucleus of the thalamus in search of paresthesia. At each position, the stimulation current was increased from 0.2 to 3 milliamperes in 0.2-milliampere steps, and the physician rated tremor improvement on a five-point Likert scale converted into linear percentage data. In total, 605 stimulation spots were tested, corresponding to an average of twelve sites per hemisphere per patient, and 696 stimulation tests were recorded. Among these, roughly 23 percent elicited side effects, with paresthesia being the most common, followed by dysarthria, oculomotor disturbances, vegetative symptoms, and pyramidal signs.

Each stimulation spot was then categorized according to its therapeutic window, defined as the difference between the minimum current inducing clinical improvement and the threshold at which side effects occur, combined with the presence or absence of side effects at the upper stimulation limit. Six categories emerged, ranging from clinically unusable sites where stimulation immediately induced side effects or produced no effect at all, to the optimal category 3, considered the clinical sweet spot, characterized by a therapeutic window of at least 1.5 milliamperes and no side effects. This categorization framework, combined with the probabilistic volumes, provided a refined, clinically relevant lens for understanding where stimulation produces benefit, where it produces harm, and where the two effects spatially converge or diverge.

The computational pipeline behind the probabilistic maps was equally sophisticated. Patient-specific brain conductivity models were generated from individual anatomical MRI scans, assigning tissue classes of cerebrospinal fluid, gray matter, and white matter with distinct but isotropic conductivities. Electric field simulations were run for each patient and each tested stimulation setting, and the resulting field meshes were thresholded at 0.2 volts per millimeter to obtain the Volumes of Tissue Activated. A total of 696 VTAs were computed, 381 in the left hemisphere and 315 in the right, and these were transformed using a non-linear approach to a group-specific MRI template aligned to the anterior commissure-posterior commissure plane, enabling group-level statistical analysis. The voxels associated with significant improvement were selected using a Bayesian one-sample t-test with a null hypothesis that improvement was less than 75 percent, a threshold chosen as clinically relevant, and a Bayes factor of 10 as the significance criterion, comparable to a p-value of 0.01. The side effect volumes were computed with a binomial test, since the information was binary, and corrected for multiple comparisons using the False Discovery Rate.

The results revealed a pronounced asymmetry between the two hemispheres. In the first implanted, left hemisphere, the Probabilistic Volume of Improvement was confined to the infero-posterior part of the Vim, reaching the subthalamic tegmental fields traversed by rubro-thalamo-cortical fibers, while the Probabilistic Volume of Side Effects sat above, posterior, and lateral to it, spanning both the Vim and the ventrocaudal nucleus. In the second implanted, right hemisphere, the improvement and side effect volumes overlapped substantially, intersecting the Vim and the ventrocaudal nucleus in their intermediate parts. The volume of the improvement region in the right hemisphere reached 457 cubic millimeters, about twelve times larger than the 37 cubic millimeters in the left, while the side effect volume followed the opposite trend to a lesser extent, at 388 cubic millimeters in the left versus 285 cubic millimeters in the right. Stimulation spot clusters, identified using a density-based spatial clustering algorithm, confirmed these differences, with optimal positions in the left hemisphere distributed more medially and inferiorly than in the right, and the clusters in the right hemisphere occupying the intermediate and superior parts of the Vim.

The interpretation the authors offer is that the first lead implantation produces a transitory, tangible lesioning effect, a reversible phenomenon linked to the mechanical and electrical perturbation of the tissue during exploration and implantation. This quasi-experimental lesioning of the left hemisphere achieved near-complete tremor suppression within a larger, functionally undifferentiated central region of the right Vim, encompassing both anti-tremor and side effect-related areas. When the surgeons subsequently explored the right hemisphere, the stimulation map they encountered was no longer that of a naïve thalamus but of one already functionally rearranged by the contralateral implantation. The confined area of improvement revealed in the initially explored hemisphere widened the contralateral improvement volume, resulting in the overlap between improvement and side effect regions that characterizes the second hemisphere. This expansion likely accounts for the masking of hemisphere-specific lesion effects when data from both hemispheres are averaged, a practice common in probabilistic mapping studies.

The findings also resonate with pioneering stereotactic work from the 1960s, in which the improvement volume of the first implanted hemisphere corresponds to the camptotomy site, while the overlay of improvement and side effect volumes in the second hemisphere corresponds to both the thalamo-capsular and the relay-nuclei sites. The left improvement volume is clearly related to the cortico-ponto-cerebello-rubro-thalamic pathway, whereas the right combined volume is more related to the cortico-thalamic and thalamo-cortical systems, and both are also related to the cortico-subthalamic fibers. These anatomical relationships fit within the broader circuits implicated in Essential Tremor syndrome, including the cerebellar and thalamic relay systems whose dysfunction generates the pathological oscillations that stimulation suppresses. The colocation of Vim neuron clumps and fiber pathways in the second hemisphere may explain why the improvement and side effect volumes converge there, since the same stimulation current activates both relay neurons and passing fibers.

The clinical implications of this work are potentially far-reaching. The authors suggest that the large probabilistic volume in the second explored hemisphere should be considered when positioning the deep brain stimulation lead, given that the deeper contacts may be effective, mirroring the improvement volume of the first hemisphere once the transitory lesioning effect wears off. During chronic stimulation, both electrodes exert contra- and ipsilateral effects that should incorporate the geometric and functional modifications of stimulation revealed by this study. A possible development could be the application of novel chronic stimulation strategies, such as interleaved interhemispheric multi-energy and multi-contact stimulations, in which stimulation intensity alternates between hemispheres, with one receiving a conventional therapeutic amplitude while the contralateral hemisphere simultaneously receives a lower amplitude, followed by periodic switching. Future prospective studies with randomized first hemisphere implantation could further investigate whether the lesioning effect is truly hemisphere-independent or whether lateralized functional markers exist across the extended tremor circuitry. The retrospective design and limited sample size of 23 patients warrant caution, though the high density of stimulation spots per patient and the robustness of the Bayesian statistical approach mitigate some of these concerns. As the understanding of bi-hemispheric modulation deepens, the decoupling of first and second hemisphere analyses in acute intraoperative effects may become a standard consideration, not only for Essential Tremor but potentially for other movement disorders such as Parkinson’s disease and dystonia, where the interplay between lesioning and stimulation effects could similarly shape the spatial organization of clinical benefit.

Subject of Research: Intraoperative asymmetry of thalamic stimulation mapping in Essential Tremor: specificity of first hemisphere implantation and transitory lesioning effect

Article Title: Intraoperative asymmetry of thalamic stimulation mapping in Essential Tremor: specificity of first hemisphere implantation and transitory lesioning effect

Article References: Bucciarelli, V., Vogel, D., Coste, J., Chaix, R., Hemm, S., & Lemaire, J.-J. (2026). Intraoperative asymmetry of thalamic stimulation mapping in Essential Tremor: specificity of first hemisphere implantation and transitory lesioning effect. Frontiers in Neurology, 17, Article 1893911. https://doi.org/10.3389/fneur.2026.1893911

Image Credits: AI Generated

DOI: 10.3389/fneur.2026.1893911

Keywords: Intraoperative, asymmetry, thalamic, stimulation, mapping, Essential, Tremor, specificity, first, hemisphere, implantation, transitory

The story begins on 12 August 2024, when researchers sampling along the French shoreline at Evian-les-Bains collected multiple samples representing different lake substrates using a Surber net with a 500 micrometre mesh and a 20 by 25 centimetre aperture. The site itself is a study in human-modified shorelines: a vertical quay wall runs along the water’s edge, the substrate is composed primarily of boulders and cobbles partially covered by quagga mussels, zebra mussels and bryophytes, and short sections of riprap intermittently reinforce the bank. Water depth at the base of the shoreline ranges from roughly one to 1.5 metres, and the lakebed slopes moderately for about 80 metres offshore, where it reaches six to seven metres before dropping away steeply.

Crucially, the two amphipod specimens that would make history were not dredged from deep soft sediments but plucked from a bryophyte sample growing on rocks at a water depth of just 0.2 metres, within the wave-splash zone where riparian bryophytes typically occur in Lake Geneva. These mosses, such as Orthotrichum species, are essentially riparian plants that tolerate periodic submersion rather than truly aquatic species like Fontinalis, and their development is generally absent or very limited below the wave-splash zone. This narrow, mossy ribbon along the shore turned out to be exactly the kind of habitat C. trichiatus finds congenial, a detail that may reshape how biologists think about where alien amphipods hide in lakes.

Identifying amphipods is notoriously fiddly work, and the researchers leaned on precise anatomical characters to separate their specimens from the lake’s other crustacean residents. The genus Chaetogammarus can easily be distinguished from Gammarus and Dikerogammarus by the morphology of the third uropod and the first and second urosome segments. In both Dikerogammarus and Chaetogammarus, the inner ramus of the third uropod is very short, whereas it is well developed in Gammarus. Furthermore, Chaetogammarus and Gammarus lack the paired dorsal protuberances bearing spines on the first and second urosome segments, a characteristic feature of Dikerogammarus species. Among Chaetogammarus species, C. trichiatus is characterized by a third uropod densely covered with recurved setae, and even in females these recurved setae are at least densely developed at the apex of the third uropod, separating it from the related C. ischnus.

Because morphological identification alone left some uncertainty, the two specimens were checked with molecular techniques in 2025. Total genomic DNA was extracted using a BioSprint 96 extraction robot following a non-destructive protocol that enables post-extraction morphological study of the specimens. A 181 base-pair portion of the mitochondrial cytochrome c oxidase subunit I gene, the workhorse barcode for animal identification, was amplified using the LCO1490 and CO1-CFMRb primers. The polymerase chain reaction mix, prepared in 25 microlitre volumes, included template DNA, both primers, dNTP solution, buffer containing magnesium chloride, bovine serum albumin, GoTaq G2 DNA Polymerase and sterile water. Optimized conditions involved an initial denaturation at 95 degrees Celsius for five minutes, followed by five cycles with annealing at 45 degrees and 35 cycles with annealing at 50 degrees, each with 30-second denaturation and 45-second extension steps, and a final extension at 72 degrees for seven minutes. Purification and Sanger sequencing were carried out commercially.

The molecular verdict was unambiguous. Both sequences were identified as C. trichiatus, clustering in a single clade with reference sequences of the species from the Barcode of Life Data System with 100 percent support. The two specimens, bearing GBIF codes GBIFCH00967050 and GBIFCH00967051, are now housed in the Department of Zoology of the Naturéum in Lausanne, Switzerland, their exoskeletons well preserved after the soft tissues were used for sequencing. Morphology and molecules had spoken with one voice: a new alien species had been documented in Lake Geneva.

The native distribution of C. trichiatus extends across the Ponto-Caspian region, including the lagoons and estuarine habitats of the northwestern Black Sea, as well as the Azov Sea, their deltas and the coastal lakes of Bulgaria and Romania. The species was first reported as an alien in Germany in 1996 and has since spread throughout the Danube basin and several catchments in northeastern France, probably via the Main-Danube Canal. In Switzerland it has been recorded in the Rhine basin since 2003 and, more recently, in the Aare basin in 2025. It has also turned up in the upper Dnieper River in Belarus and the Oder catchment in Central Europe. What makes the animal such a successful colonizer is a potent biological toolkit: a relatively short life cycle and generation time, brood protection, an omnivorous feeding strategy and high ecological plasticity, including the ability to tolerate broad salinity gradients.

Yet the species is only infrequently recorded in lake environments and is generally considered more closely associated with large rivers, where it occupies habitats ranging from artificial riprap structures to gravel banks, mud, roots and stony substrates. Records from the lower and middle French Rhone River suggest an ongoing expansion, with occurrences reported downstream of Lyon at several sites between 2017 and 2022 in the main river channel and two active secondary channels, indicating a slow and progressive upstream colonization of the Rhone basin prior to the Lake Geneva detection. Nevertheless, because the species has not been recorded in the French Upper Rhone, it is unlikely that its arrival in the lake originated from upstream dispersal through the French Rhone corridor. The absence of records from the littoral zone of the lake’s western basin, despite more than ten years of regular monitoring, further supports this. According to earlier research, proximity to ports is a key predictor of the distribution of several Ponto-Caspian invasive species, including C. trichiatus, making human-mediated transport, perhaps via recreational boats, the most plausible explanation.

The finding also carries a warning for the lake’s existing community. In Lake Geneva, non-native crustaceans now constitute almost the entire amphipod fauna, with native Gammarus pulex and Gammarus fossarum progressively displaced by the killer shrimp Dikerogammarus villosus and only rarely found in surveys. The present detection suggests that C. trichiatus can coexist with related crustaceans already present in the lake, such as D. villosus and Chelicorophium curvispinum, but its establishment may lead to future changes in community structure. Competitive interactions are likely within the bryophyte mats covering riprap and cobble habitats, potentially affecting populations of C. curvispinum and Dikerogammarus species, as well as other bryophyte-associated macroinvertebrates like insect larvae and small gastropods. Those deeper soft substrates and macrophytes where the other species also occur, generally in lower numbers, may provide alternative refuges that limit the impact of competition. Beyond Lake Geneva, the record raises the possibility of further colonization of other peri-alpine and mountain lakes, a particular concern for alpine lakes supporting glacial relict populations of the native amphipod Gammarus lacustris, where introduced species could threaten conservation-important populations.

Practically speaking, the discovery should change how surveys are interpreted and conducted. Small individuals of C. trichiatus may easily be mistaken for Gammarus species when examined only in lateral view, particularly during routine sorting of lake samples, so careful examination of the third uropod is essential, while the dense recurved setae on that appendage allow separation from C. ischnus. Re-examination of preserved material could determine whether the species had been present in Lake Geneva before its first detection in 2024, and targeted monitoring near the lake’s major ports may prove especially valuable for early detection of newly introduced exotics. The identification key provided by the authors should facilitate routine recognition during macroinvertebrate surveys and reduce the risk of future misidentifications. For now, a mossy strip of shoreline at Evian-les-Bains has delivered a reminder that Europe’s invasion frontiers run not only down its great rivers but across its treasured lakes, one small crustacean at a time.

Subject of Research: First record of the Ponto-Caspian amphipod Chaetogammarus trichiatus in Lake Geneva

Article Title: First record of the Ponto-Caspian amphipod Chaetogammarus trichiatus (Martynov, 1932) (= Echinogammarus trichiatus ) ( Crustacea , Gammaridae ) in Lake Geneva

Article References: Marle, P., Stoffel, C., & Renahy, S. (2026). First record of the Ponto-Caspian amphipod Chaetogammarus trichiatus (Martynov, 1932) (= Echinogammarus trichiatus) (Crustacea, Gammaridae) in Lake Geneva. Alpine Entomology, 10, 163-168. https://doi.org/10.3897/alpento.10.207817

Image Credits: AI Generated

DOI: 10.3897/alpento.10.207817

Keywords: invasive species, amphipods, Lake Geneva, Ponto-Caspian, DNA barcoding, freshwater ecology, biodiversity, First, record, amphipod, Chaetogammarus, trichiatus

Flatfishes are among the most strikingly asymmetrical vertebrates on Earth. During development, one eye migrates across the top of the skull so that both eyes and coloration end up on a single side, while the other side remains eyeless and pale. Currently, 826 species across 19 families are recognized as valid. In most flatfish families, eye position is fixed: families such as Paralichthyidae, Bothidae, and Scophthalmidae have both eyes on the left side, while families such as Pleuronectidae, Poecilopsettidae, and Samaridae have both eyes on the right. In contrast, members of Psettodidae, considered the most primitive flounders, naturally occur in roughly equal proportions with eyes on either side, and within Citharidae eye orientation varies at the generic level.

For decades, reversed individuals—those with eyes on the side opposite to their family’s norm—had never been documented in the family Bothidae, as summarized by researchers in 1964 and 1983. The family was long regarded as the most specialized group within the order Pleuronectiformes, with pronounced left-right differences such as a lateral line developed only on the eyed side and a much longer pectoral fin on the eyed side than on the blind side. This high degree of asymmetry led scientists to consider that the lower the level of specialization, the more likely inversion phenomena are to occur. Reversal was reported most frequently in Paralichthyidae and Pleuronectidae, families with fixed eye positions but lower degrees of asymmetrical development.

That assumption has now been shaken. In recent years, three reversed bothid specimens have been found and reported in the genera Chascanopsetta, Parabothus, and Crossorhombus. The two new specimens from Taiwan, belonging to Engyprosopon maldivense and Engyprosopon grandisquama, represent the first records of the reversed condition among members of their genus. Moreover, both show reversed internal organs—a condition known as situs inversus—making them the third and fourth records of visceral inversion in the entire family Bothidae.

The first specimen, a male Engyprosopon maldivense measuring 82.3 millimeters in standard length, was collected off Ke-Tzu-Liao Fishing port in Kaohsiung, southern Taiwan, in February 2024. The second, a female Engyprosopon grandisquama measuring 51.4 millimeters, was collected from the same waters in May 2024. Both were preserved in the Pisces Collection of the National Museum of Marine Biology and Aquarium in Pingtung, Taiwan. Detailed examination, including digital radiographs taken in collaboration with the Hokkaido University Museum in Japan, allowed researchers to compare the reversed individuals with normal specimens collected from the same location.

The reversed Engyprosopon maldivense was identified based on several diagnostic features: the absence of blotches on the caudal fin, no serrations on the inner gill rakers, biserial upper-jaw teeth, a wide interorbital width, 44 lateral-line scales, and 0 + 9 gill rakers. Its meristic and morphometric data generally agree with those of normal sinistral specimens, with only minor differences such as a slightly larger lower eye and slightly different jaw and pelvic-fin proportions. The reversed Engyprosopon grandisquama was identified by a pair of black blotches on the caudal fin, 40 lateral-line scales, 0 + 7 gill rakers, and a distinctive interorbital width. In both specimens, the liver is situated on the eyed side and a large part of the stomach on the blind side—a complete reversal of visceral organ positions compared with normal individuals.

Previously, reversed specimens in the family Bothidae were extremely rare, with only three reported cases. The rarity is possibly due to their low commercial value, which results in a low chance of detecting an inversion. Bothidae and Samaridae are generally small, contain few species important to fisheries, and are mostly discarded or used as feed for other fish. In contrast, reversal is most commonly reported in Pleuronectidae and Paralichthyidae, which contain many species important to fisheries. Abnormal individuals with both eyes on the opposite side are easily discovered during the distribution process of these fish, and when processed into dried fish, many individuals of the same species are lined up, making inverted individuals highly conspicuous. From this, it can be speculated that the observed frequency of inverted individuals is due to differences in the chances of discovery rather than true biological differences among families.

The genetic basis of reversal has been demonstrated through crossbreeding experiments in the starry flounder Platichthys stellatus, conducted by Policansky in 1982. In Japanese populations, 100 percent of individuals have both eyes on the left side, whereas in American populations 50 percent have both eyes on the right and 50 percent on the left. Crossbreeding experiments between left-eyed males and females and between right-eyed males and females revealed that inverted individuals appeared at a rate of approximately 13 to 18 percent in both cases, confirming that the appearance of inversion is caused by heredity. The survival percentage of inversions occurring in nature is thought to be significantly lower than that observed in experimental results.

Reproduction in Bothidae may impose additional constraints on reversed individuals. It is known that reproductive behavior involves males and females overlapping away from the seabed. If the position of the genital pores is reversed, there would be a disadvantage during mating, which could explain a geographical bias in the frequency of reversal similar to that seen in Platichthys stellatus, where the dextral type occurs predominantly on the American side and the sinistral type on the Japanese side.

The discovery of inverted individuals in three genera and four species of the family Bothidae has called into question the long-held idea that the family was too specialized for reversal to occur. The two new specimens from Taiwan suggest that the reversed condition in Bothidae may be more common than previously thought, and that the observed rarity reflects sampling bias rather than evolutionary constraint. As more specimens are examined and more collections are made in understudied waters, scientists may find that reversed flatfishes are quietly swimming throughout the world’s oceans, waiting to be noticed.

Subject of Research: Marine Biology

Article Title: First records of two reversed flatfishes, Engyprosopon maldivense and Engyprosopon grandisquama ( Actinopterygii , Pleuronectiformes , Bothidae ), from Taiwan, northwestern Pacific Ocean

Article References: Amaoka, K., Hо, H.-C., & Su, Y. (2026). First records of two reversed flatfishes, Engyprosopon maldivense and Engyprosopon grandisquama (Actinopterygii, Pleuronectiformes, Bothidae), from Taiwan, northwestern Pacific Ocean. Acta Ichthyologica et Piscatoria, 56, 431-439. https://doi.org/10.3897/aiep.56.207218

Image Credits: AI Generated

DOI: 10.3897/aiep.56.207218

Keywords: flatfish, Engyprosopon, Taiwan, situs inversus, Bothidae, reversal, marine biology, First, records, reversed, flatfishes, maldivense

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The discovery of a melanistic Asia Minor Dwarf Racer on the Anatolian mainland carries weight that extends well beyond a single unusual specimen. Until this record, every published observation of a dark morph in Eirenis modestus came from small islands scattered across the eastern Aegean: the Yassıca and Sarıot islets off Muğla Province, Kastellorizo in the Dodecanese, and most recently Symi. Islands are evolutionary laboratories in the classic sense, and repeated reports of melanism from insular populations naturally invite speculation about founder effects, genetic drift, or local adaptation to island conditions. A mainland specimen complicates that narrative. It demonstrates that the capacity for melanistic coloration is not confined to isolated island gene pools but is present, at least occasionally, within continental populations where the species is presumably most abundant and most genetically diverse.

The specimen itself was a young individual, as indicated by its modest snout-vent length of 155 millimeters, well below the maximum total length of roughly 600 millimeters reported for the species. This matters for interpreting its appearance. In many snake species, the dark pileus mark and nuchal collar that characterize E. modestus fade with age, and pattern expression can change substantially between juveniles and adults. The greyish-white scales scattered across the neck region of this specimen, fading rapidly toward midbody, suggest that the animal was in the process of transitioning from juvenile patterning toward adult coloration, with melanistic pigmentation overriding the typical light brown or grey dorsal ground color. The progressive darkening of the ventral scales toward the tail is also noteworthy, since ventral coloration is often less variable than dorsal patterning and can provide useful comparative characters in studies of chromatic anomalies.

The pholidotic data collected from the specimen serve an important function beyond simple species identification. Because melanism can dramatically alter the external appearance of a snake, researchers must rule out the possibility that an unusually dark individual belongs to a different, naturally dark species. The scale counts recorded here, including seventeen dorsal scale rows at midbody, a single preocular and two postocular scales, seven supralabials on each side, eight sublabials, 161 ventral scales, and 72 subcaudal scales, all fall within the documented ranges for E. modestus and distinguish it from other small Eirenis species that occur in southern Anatolia. This careful morphological verification is what elevates the record from an interesting photograph to a scientifically defensible range extension for the melanistic morph itself.

The biogeographic pattern emerging from the combined records deserves closer attention. All known melanistic individuals of this species, including the new mainland specimen, have been found in localities characterized by relatively high humidity and Mediterranean or coastal climatic influence. Çağman and Demre sit on the southwestern Anatolian coast, an area of mild winters, hot summers, and substantial atmospheric moisture influenced by the Mediterranean Sea. The island records from Kastellorizo, Symi, and the Muğla islets share similar maritime climates. This clustering is consistent with the predictions of Gloger’s rule, the observation, first formalized in the nineteenth century and refined by later comparative work, that animals inhabiting warm and humid environments tend to deposit more dark eumelanin pigment than those in arid or cold regions. The mechanistic basis of Gloger’s rule remains debated, but leading explanations include the role of melanin in feather or scale structural integrity under humid conditions, enhanced protection against feather-degrading or skin-colonizing microorganisms, and improved background matching against the darker, more vegetated substrates typical of humid habitats.

The alternative explanation, thermal melanism, holds that darker individuals gain a heating advantage in cool climates because dark surfaces absorb solar radiation more efficiently, allowing faster warming and higher equilibrium body temperatures. This hypothesis has received substantial empirical support in some groups. Comparative phylogenetic analyses of Eurasian vipers have found evidence consistent with darker coloration evolving in cooler environments, and similar patterns have been reported for elapid snakes. Field studies of polymorphic populations have also documented potential fitness consequences of melanism, including higher growth rates, improved body condition, longer daily activity periods, and enhanced locomotor performance in dark individuals, all of which could translate into meaningful survival and reproductive advantages under certain climatic regimes.

However, the evidence for thermal melanism is not universal, and recent broad-scale analyses have complicated the picture. A meta-analysis covering polymorphic terrestrial snake species found that the prevalence of melanism correlated more strongly with annual precipitation than with temperature, lending support to the idea that moisture-related selection, in the spirit of Gloger’s rule, may be the more important driver of dark morph distributions at large geographic scales. The same analysis noted that melanistic snakes appear to be encountered more frequently in coastal regions and on islands than in mainland populations, a pattern that the present record only partially fits. The Çağman–Demre locality is coastal, but it lies on the mainland rather than an island, which weakens any argument that insularity itself is the primary driver of melanism in this species. Instead, the shared climatic profile of all recorded localities points toward humidity or related environmental variables as the more plausible common factor.

Predation pressure introduces a further layer of complexity that any adaptive explanation must address. The typical coloration of E. modestus, a light brown or grey dorsum with a darker collar and pileus, presumably functions as crypsis against the pale, rocky, and sparsely vegetated substrates the species inhabits. A uniformly black snake moving across light limestone or sun-bleached soil may be considerably more conspicuous to visually oriented predators, including birds of prey, mammals, and larger reptiles. In island populations, reduced predator communities are sometimes invoked to explain the persistence of conspicuous color morphs, since relaxed predation pressure can allow otherwise disadvantageous phenotypes to persist. The mainland record raises the question of whether predation regimes in coastal southwestern Anatolia are similarly permissive, or whether the melanistic morph survives there despite, rather than because of, its conspicuousness. Without data on predator communities and predation rates at these localities, this remains speculative, but it represents a testable dimension of the phenomenon.

The genetic basis of melanism in E. modestus is entirely unknown, and this gap limits interpretation of the current record. In other reptile groups, melanism can arise through single-gene mutations with strong phenotypic effects, through polygenic variation, or through developmental plasticity. If melanism in this species is controlled by a simple recessive allele, for example, it could persist at low frequencies in mainland populations through a balance of mutation, drift, and selection, appearing only rarely as homozygous individuals. Alternatively, if the trait is polygenic, its expression might vary continuously and be more sensitive to environmental conditions. Distinguishing between these possibilities would require controlled breeding experiments or population genomic sampling, neither of which has yet been attempted for this species. The absence of any published estimate of melanism frequency within E. modestus populations is a related obstacle; without baseline frequency data from both mainland and island sites, it is impossible to determine whether the mainland record represents a genuinely rare event or simply the first documented instance of a more widespread phenomenon.

The collection circumstances of the specimen also merit comment. The animal was found beneath a flat stone at approximately half past five in the afternoon on the ninth of May, consistent with the species’ known behavior of sheltering under cover objects during daylight hours and emerging at twilight to forage. Its diet in the region consists primarily of terrestrial arthropods, particularly beetles, orthopterans, and centipedes, with occasional small lizards taken as prey. This crepuscular and largely invertebrate-based ecology means that E. modestus is not a strongly heliothermic species in the way that basking vipers or lacertid lizards are, which may weaken the expected advantage of thermal melanism in this lineage. A snake that spends much of its active period under cover or foraging in shaded microhabitats gains less from rapid solar heating than one that basks openly, and this ecological context could help explain why the moisture-related hypothesis appears more consistent with the observed geographic pattern of melanism in this species.

From a broader biogeographic perspective, the Anatolian mainland is the center of abundance for E. modestus, with three nominal subspecies distributed across western, central, and southern Türkiye and neighboring regions. The nominate subspecies E. m. modestus occupies Armenia, Azerbaijan, eastern Georgia, southern Russia, and northwestern Iran, while E. m. semimaculatus occurs in central and western Anatolia and E. m. cilicius in southern Türkiye. The Çağman–Demre locality falls within the range of E. m. cilicius, the southern Anatolian subspecies, adding a taxonomic dimension to the record. Populations from southern Anatolia and parts of the Aegean are known to exhibit variable rows of dark blotches on the anterior body, particularly within E. m. semimaculatus, suggesting that the species already possesses considerable latent variation in dark pigmentation. It is plausible that melanism represents an extreme expression of this existing variation, rather than an entirely novel mutation, though this hypothesis has not been tested.

Future research directions follow naturally from these observations. Systematic sampling across the Anatolian mainland and adjacent islands, ideally with standardized survey effort, would allow researchers to estimate the true frequency of melanistic individuals in different populations and test whether frequency correlates with humidity, temperature, insularity, or substrate characteristics. Genetic sampling of both melanistic and typically colored individuals from the same populations would clarify the inheritance pattern of the trait. Radiotelemetry or thermal imaging studies could directly measure whether melanistic individuals achieve different body temperatures from normally colored conspecifics under natural conditions, providing a field test of the thermal advantage hypothesis at the intraspecific level. Finally, experimental approaches using clay model snakes or artificial prey could quantify differential predation on dark versus light morphs in coastal and inland habitats, addressing the predator-mediated selection component of the puzzle. Each of these avenues would transform a growing collection of anecdotal records into a genuine test of the ecological and evolutionary forces shaping color variation in this understudied species.

In the meantime, the Çağman–Demre record stands as a reminder that even well-documented species in relatively accessible regions can still yield surprises. The Asia Minor Dwarf Racer is not rare, and much of its range lies within areas frequented by herpetologists, yet melanistic individuals have now been documented only a handful of times across more than three decades of published literature. Whether this reflects genuine rarity of the morph, insufficient survey effort directed at detecting it, or a combination of both remains an open question. Continued documentation of additional cases, particularly from the mainland where the species is most abundant, will be essential for building the dataset needed to evaluate the geographic distribution, frequency, and adaptive significance of melanism in this small but biogeographically interesting colubrid.

Subject of Research: …

Article Title: A melanistic Eirenis modestus (Martin, 1838) from the Anatolian mainland: first record outside island populations

Article References: A melanistic Eirenis modestus (Martin, 1838) from the Anatolian mainland: first record outside island populations. (n.d.). https://doi.org/10.3897/caucasiana.5.e204607

Image Credits: AI Generated

DOI: 10.3897/caucasiana.5.e204607

Keywords: melanistic, Eirenis, modestus, Martin, Anatolian, mainland, first, record, outside, island, populations, scientific research

Red algae are overwhelmingly marine: only about ten percent of the group occurs in freshwater, and those species are stenovalent, meaning they tolerate only a narrow range of environmental conditions. They favour rivers with running water, where they colonise rocks exposed to turbulent flow. This ecological pickiness makes some of them rare, restricted to specific habitats, and unable to survive in anthropised areas. Roughly seventy percent of freshwater red algae belong to the order Batrachospermales, whose members typically form macroscopic uniaxial gametophytes with whorled branches that give a bead-like appearance, or a pseudoparenchymatous thallus with a mucilaginous or cartilaginous consistency. Most have a heteromorphic triphasic life history comprising a sporophyte known as the Chantransia stage, a gametophyte, and a carposporophyte phase.

Molecular phylogenetics based on two markers now places the entire order in a single family, the Batrachospermaceae, with 21 genera including Lemanea and Paralemanea. The two genera have an intricate taxonomic history that culminated in their separation as distinct genera. Mitochondrial genome work has corroborated that split: Paralemanea species possess the largest genomes and most extensive intergenic regions sequenced to date within the Batrachospermales, and they are the only taxa in the order to contain introns, which are absent in all other members, including the sister genus Lemanea.

Morphologically, the genera are distinguished by a handful of diacritical characters. Lemanea carries spermatangia arranged in circular papillae at the nodes, has T- or L-shaped ray cells abutting the cortex, and a main axis without cortication. Paralemanea instead has spermatangia arranged in rings around the nodes, simple ray cells organised in two layers — a proximal layer that does not touch the outer cortex and a distal, generally Y-branched layer connected to the cortex — and cortical filaments surrounding the axial filaments. Some Paralemanea species also lack stalks. In Italy, reports of both genera are scarce and scattered, and in Sicily only three records of Lemanea exist, all referring to Lemanea fluviatilis. No Paralemanea species had ever been published for the island.

During field surveys from May to early July 2022 at two sites along the Alcantara River — Passo Mojo at 547 metres above sea level and Monte San Nicola at 400 metres, both in the territory of Castiglione di Sicilia — the team found numerous thalli referable to Lemanea and Paralemanea. The river flows eastwards between the Nebrodi and Peloritani mountains on its northern side and the volcano Etna on its southern side, and over millennia it has slowly eroded Etna’s hard lava rocks, creating rapids, waterfalls and narrow deep canyons alternating with typical riffle-run stretches. Samples were taken to the Laboratory of Phycology at the University of Catania, fixed in four percent formaldehyde or preserved in water and ethanol, and examined under an Olympus BX 40 microscope for the vegetative and reproductive characters needed to separate genera and species. Representative thalli were dried and deposited in the CAT herbarium, algae section, of the University of Catania.

The specimens collected at Monte San Nicola matched Lemanea fucina, a species with no previous reports anywhere in Italy. Its thalli formed light to dark green tufts about 10 to 13 centimetres long, stalked and gradually narrowing toward the base, with many branches and often secondary ones, while false branches appeared rarely where the thallus had broken off. Nodes and internodes were easily distinguished. The nodal basal portion measured 524 to 714 micrometres, the nodal median portion 643 to 809 micrometres and the nodal apical portion 619 to 786 micrometres, while the internodal portions ranged from 405 to 524 micrometres basally, 476 to 524 micrometres medially and 430 to 476 micrometres apically, giving a nodal-internodal ratio of 1.4 to 1.6. The central axial cell lacked a cortex and bore T-shaped ray cells, visible in both cross and longitudinal sections. The thalli were monoecious, with spermatangial papillae distributed in circular patches on the nodes and carposporophytes borne on the inner portion of the cortex. Carposporangia arranged in chains measured 35 to 40 micrometres long with a diameter of 20 to 30 micrometres. The Chantransia stage was not found.

Ecologically, L. fucina was found exclusively at Monte San Nicola, a natural site with rapids formed by erosive processes, where it colonised the surfaces of volcanic rocks within microhabitats such as concavities shaped by high-energy turbulent flow, which provided optimal substrates for thallus attachment. Only a few thalli were observed within a community dominated by P. catenata. Associated taxa included the cyanobacterium Nostoc and the macroalgae Cladophora and Vaucheria, which were abundant in areas with lower hydrodynamic stress and during the summer, when reduced river discharge produced less turbulent conditions and the subsequent desiccation of L. fucina.

Paralemanea catenata, by contrast, turned up at both sites. Its thalli formed turfs arising from a perennial basal crust, roughly 2 to 17 centimetres tall, with uniaxial, pseudoparenchymatous, unstalked, dark green and slightly curved upright axes lacking true branches, though young branches developed where axes were broken, forming the so-called false branches. The nodal basal portion varied between 381 and 520 micrometres, the nodal median between 596 and 820 micrometres and the nodal apical between 320 and 636 micrometres, while internodal portions measured 212 to 380, 437 to 540 and 400 to 485 micrometres respectively, with a nodal-internodal ratio of 1.3 to 1.4. The central axis was composed of numerous cortical filaments with radial cells in two layers, the proximal one not touching the outer cortex and the distal one Y-shaped and connected to it. The monoecious thalli bore spermatangial sori in narrow, sometimes interrupted nodal rings, and carposporangia in chains of 25 to 30 micrometres in length and 20 to 25 micrometres in diameter. Crucially, the reddish to brownish Chantransia stage was observed in several thalli, growing near the base of the gametophyte with alternating or unilateral branching, and in one case was seen producing juvenile gametophytes from its filaments.

At Monte San Nicola, P. catenata shared its habitat with L. fucina, while at Passo Mojo, an artificial water bridle, it colonised vertical surfaces beneath a small waterfall at the end of the concrete bridle. In early July, as river capacity decreases and rock surfaces dry, the thalli desiccate but the species persists as a perennial crust on the substrates. At both sites it formed extensive populations covering several square metres, becoming the physiognomic dominant, especially in areas more exposed to the flow. During summer, Cladophora and Vaucheria formed mosaic-like assemblages on surfaces colonised by P. catenata, growing between or above its thalli, and in some instances completely overgrew the basal crusts following the senescence of the gametophytes.

The findings extend the known European ranges of both species further south than previously reported, with P. catenata’s only prior Italian record coming from the Listi stream in Aspromonte, southern Italy. Interestingly, the carposporangia of both Sicilian species were smaller than literature values. The study also underscores how taxonomic ambiguity in the Batrachospermaceae — where diagnostic characters can vary with thallus age and maturity, and repeated revisions have left the same species described under different synonyms, as with L. fucina and L. mamillosa — complicates identification. Ecologically, the contrast is telling: L. fucina was restricted to the natural, low-anthropisation site, while P. catenata tolerated the more human-affected Passo Mojo, suggesting a broader ecological tolerance. The presence of carposporangia in both species may indicate healthy populations in non-anthropised stretches of the Alcantara. Because Lemanea and Paralemanea require turbulent water, climate change scenarios predicting reduced precipitation and river flow could favour competitively advantaged taxa such as Cladophora and Vaucheria at their expense, making sensitive freshwater red algae valuable early-warning indicators for the conservation and monitoring of river habitats under growing anthropogenic pressure.

Subject of Research: Botany

Article Title: First record of Lemanea fucina Bory in Italy and Paralemanea catenata (Kützing) Vis & Sheath ( Batrachospermaceae , Rhodophyta ) in Sicily (Italy)

Article References: Pagana, I., Di Stefano, M., Alongi, G., Cristaudo, A., & Emma, G. (2026). First record of Lemanea fucina Bory in Italy and Paralemanea catenata (Kützing) Vis & Sheath (Batrachospermaceae, Rhodophyta) in Sicily (Italy). Italian Botanist, 22, 51-63. https://doi.org/10.3897/italianbotanist.22.196629

Image Credits: AI Generated

DOI: 10.3897/italianbotanist.22.196629

Keywords: freshwater red algae, Batrachospermaceae, Lemanea fucina, Paralemanea catenata, Alcantara River, Sicily, biogeography, First, record, Lemanea, fucina, Bory