Smrithy Raj

A new genus and species of gecarcinucid freshwater crab, Kasargodia sheebaen. gen., n. sp., is described from the Ranipuram Hill Station in the central Western Ghats, India. This new genus is distinguished from Vanni Bahir & Yeo, 2007 and Travancoriana Bott, 1969 by several key features: the antennal article 4 is elongated, being notably longer than wide (as opposed to quadrate to subrectangular in Vanni and Travancoriana); the suborbital margin is almost smooth (rather than distinctly granular); the terminal and subterminal articles of the male first gonopod are not clearly demarcated by sutures (clearly separated in the other genera); the short male second gonopod (shorter than the male first gonopod) is relatively stout, with a short distal article that is not flagelliform (more slender, elongated, flagelliform distal article in the other genera); and the basal antennal article in the new genus is distinctly elongated, with a constricted median part (subquadrate in Vanni and more similar to the condition in Travancoriana). The relatively stout male second gonopod with a short distal article in Kasargodian. gen., is an unusual feature, shared with genera such as Barytelphusa Alcock, 1909, Cylindrotelphusa Alcock, 1909, and Barusa Pati & Yeo, 2022. Unlike the new genus, the male first gonopod in these genera have the terminal and subterminal articles clearly demarcated by sutures.

A new species of gecarcinucid freshwater crab Pilarta vaman sp. nov. is described from Gavi, Southern Western Ghats, Kerala, Southern India. The new species differs from P. anuka Bahir & Yeo, 2007, by its more quadrate carapace with an extremely shallow cervical groove that is almost undiscernible, as well as the proportionately longer terminal article and more convex outer margins of the subterminal article of the male first gonopod; from P. aroma Pati, Rajesh, Raj, Sheeja, Kumar & Sureshan, 2017, by its low subtruncate inner angle of the carpus of the cheliped, and the narrower proximal part of the subterminal article and shape of the terminal article of the male first gonopod; and from P. punctatissima Pati, Rajesh, Raj, Sheeja, Kumar & Sureshan, 2017, by the carapace and the surfaces of the chela being weakly punctate, the male pleonal somite 6 has the lateral margins gently concave and the overall male first gonopod being more elongate.

Aim: The aim of this study was to understand the interplay between local and regional factors as drivers of population physiological diversity in a tropical freshwater crab species. Location: Western Ghats, south‐west India. Taxon: Barytelphusa cunicularis, Brachyura, Crustacea. Methods: We applied an integrative approach combining population genetics and whole animal physiology, using the tropical freshwater crab Barytelphusa cunicularis as our model species. We tested for effects of population location (e.g., latitude, altitude), season (as a proxy for rainfall and water temperature) and/or warming on indices of whole animal respiratory physiology (metabolic rate, MO ₂ ) and hypoxic performance (P _crit , i.e., the PO ₂ at which routine MO ₂ can no longer be sustained) in five widely distributed populations of this species. We also generated population genetic data (mtDNA COI and nDNA histone H3 sequences) to determine the extent of any population genetic structuring and/or cryptic species diversity present to verify that we were investigating a single species. Results: Despite a high level of genetic structuring between the different populations of B. cunicularis examined, the genetic distances observed were consistent with intra‐ and not interspecific differences in freshwater crabs. Populations varied in the diversity of the physiological (MO ₂ ) responses observed. There were significant effects of season and population on respiration in response to temperature and P _crit in response to acute hypoxia. Main Conclusions: We conclude that local environmental factors are important in shaping physiological diversity between populations in tropical freshwater species and systems. This highlights the need to include population‐level responses in any projections we make on how biodiversity will respond to ongoing and future environmental changes, including those caused by climate change.

An integrative taxonomic study on the gobioid fishes of Ashtamudi Lake (a Ramsar Site), Kerala, India revealed the occurrence of 12 species representing 10 genera, including three species of the genus Oxyurichthys. The Arrowfin goby, Oxyurichthys tentacularis, considered as the mainstay of gobioid fisheries in the Lake for over 40 years, represents a clear case of misidentification of O. ophthalmonema. Combined morpho-molecular analysis confirmed, for the first time, the occurrence of Oxyurichthys omanensis in the Indian subcontinent, and from anywhere outside its type locality in the Gulf of Oman. Three additional new records are presented: Exyrias puntang from mainland India, Paratrypauchen microcephalus from the West coast of India, and Istigobius diadema from the southwest coast of India. Intensive region-wise studies, particularly along the western coast of India, are required to better understand the diversity and distribution of estuarine and freshwater gobies.

Understanding the dynamics between native and invasive species in aquatic ecosystems is crucial for effective conservation and management. This study investigates the diet composition and niche overlap of the native paradise fish (Pseudosphromenus dayi) and the introduced three-spot gourami (Trichopodus trichopterus) in a coastal wetland in Kerala, India. Through a comprehensive diet analysis, the study aims to reveal trophic dynamics and potential competition between these coexisting species. A substantial diet overlap of 0.73 indicates significant resource sharing, particularly in detritus, plant matter, Chlorophyta, insect remains, Cyanophyta, and Crustacea, highlighting a pronounced interaction between the paradise fish and three-spot gourami. Abundant resources in the wetland likely alleviate interspecific competition, facilitating the coexistence of both species. The presence of microplastics in the gut of both species signals increased human intervention and plastic pollution in the watershed and wetland. These findings underscore the importance of considering dietary preferences and ecological behaviours in assessing interactions between native and invasive species. Effective management strategies are crucial to mitigate potential competition and maintain the ecological integrity of wetland habitats. Continuous monitoring of invasive freshwater fishes is recommended for early detection and the implementation of management plans to address potential threats.

Purpose Specimens of Elthusa from trashfish of the Indian SW coast were described as a new parasitic cymothoid, Elthusa nemo sp. nov., (Crustacea: Isopoda). Later, the branchial cavity of the Blotchfin dragonet Callionymus filamentosus Valenciennes, 1837 were documented as its micro- and macro-habitat (host). Methods Fresh/live specimens of unidentified cymothoid samples were collected from the trash fishes obtained from Neendakara (08°30.0′ N 76°53.30′ E) fish landing centre, Kollam district, Kerala state, southwest coast of India. After a long search for the host species, we recovered the isopod from the branchial cavity of the deep-sea fish Callionymus filamentosus Valenciennes, 1837 (Callionymiformes: Callionymidae). The new species is described and illustrated based on ovigerous females. Results Elthusa nemo sp. nov., has the following sets of combinations of characters: body slightly twisted, elongated, dorsal surfaces smooth, nearly twice as long as greatest width; pleon short, ~ 14% body length, 0.8 times as wide as pereon maximum width; widest at pleonite 2 and narrowest at pleonite 1; only pleonite 1, laterally overlapped by pereonite 7 posterolateral expansion and coxa 7; presence of appendix masculina on pleopod 2; uropods 0.8 times as the length of pleotelson; antenna with two plumose setae on article 4. Conclusion Elthusa nemo sp. nov., is the sixth species of the genus known from Indian waters.