Sameer Kumar Pati

The decapod crustacean Barytelphusa cunicularis (Westwood in Sykes, 1836) (Gecarcinucidae) is among the world’s largest freshwater crabs, with both ecological and economic significance. The crab species inhabits diverse aquatic habitats throughout peninsular India, including the Western Ghats. Although commensal associations between invertebrates (including crustaceans) and aquatic insects are widespread, no previous records exist of brachyurans hosting immature chironomids (Diptera: Chironomidae). This study documents the first commensal association between B. cunicularis (Brachyura) and chironomid larvae and pupae, based on field surveys during the dry season in the Kalsubai Harishchandragad Wildlife Sanctuary, Maharashtra. Of 28 crabs examined, 23 harboured chironomid larvae or pupae, most commonly occurring in their subbranchial region, especially in subadults with pre-existing exoskeletal deformities. No infestations were detected in crabs collected during the rainy season or among more terrestrial species, indicating strong seasonal and ecological specificity. Observed deformities in regions where larvae were present appeared to predate their occurrence and were likely related to moulting or environmental stress; there was no evidence that chironomid larvae caused further host damage, supporting a commensal, rather than parasitic, relationship. A potential benefit to the larvae may include passive transport via the host, although this requires further investigation. These findings expand the recognised host range of chironomids and underscore the ecological plasticity of this symbiosis, highlighting the need for further taxonomic and ecological investigation.

Many brachyuran crab species exhibit sexual dimorphism, a defining characteristic marked by morphological differences between males and females, particularly in reproductive structures such as the gonopores, pleon and pleopods. While gynandromorphy — individuals simultaneously exhibiting male and female traits — has been documented in several marine and freshwater crab families, it remains unreported in the family Gecarcinucidae. This study documents the first instance of gynandromorphy in Vela carli (Roux, 1931), a narrowly endemic gecarcinucid species of the Central Western Ghats, India. Crabs of the species were collected from the Silent Valley National Park, Kerala State. Morphological analyses focused on pleon shape, pleopod structure, and presence of female gonopores (vulvae) to characterise sexual dimorphism and gynandromorphic traits. Three subadult gynandromorphs exhibited a unique mosaic of male and female traits. Their pleopod 1 was consistently male-like (uniramous, modified as first gonopod), while the pleopod 2 varied from absent to rudimentary female-like endopods or fully developed second gonopods. Their pleopod 3 was modified as a uniramous gonopod typical of the second gonopod in the largest gynandromorph, whereas pleopods 4 and 5 were absent in all individuals, indicating an incomplete male pleopod set with female-like morphology on pleonal somite 3. Female gonopores were present in all three gynandromorphs but reduced in size relative to adult females. These features suggest early developmental mosaicism as the likely cause as the crab’s habitat was probably free from environmental pollutants. Additionally, adult female sexual characters of V. carli were described in detail for the first time. This discovery fills a critical gap in the understanding of crustacean sexual dimorphism and developmental anomalies, particularly within Gecarcinucidae. The observed phenotypic mosaics highlight complex sexual differentiation mechanisms in freshwater crabs. Given the species’ narrow endemic range and protected habitat, further research on reproductive biology and the ecological consequences of gynandromorphism is essential for conservation.

The west coast of India is home to a diverse range of marine brachyuran crabs, with many species still awaiting discovery and description (Trivedi et al. 2018; Pati et al. 2022a; Valarmathi 2024). ...

A new species of freshwater crab, Ghatiana dhritiarum sp. nov., is described from the central Western Ghats of India in the Uttara Kannada District of the Karnataka State. The new species inhabits water-filled holes of tree trunks and laterite boulders in evergreen forests, with an omnivorous diet. Characterized mainly by a proportionately broad carapace, slender eyestalks, and a medially distinctly curved male first gonopod with a relatively long ultimate article, G. dhritiarum sp. nov. also exhibits other unique morphological features and a distinct coloration in life. This new species can be distinguished from its morphologically closest congener, Ghatiana dvivarna Pati, Thackeray, Bajantri and Hegde, 2022, by differences in the distance between the frontal margin and the anterior margin of the epistome, the relative size of the eyes, the shape of the male first gonopod, and the size of the vulvae, as well as live coloration. This discovery raises the total number of known species in Ghatiana Pati and Sharma, 2014, to 14, including seven species from Karnataka, emphasizing the need for continued exploration, especially in the central Western Ghats region.

The gecarcinucid freshwater crab genera, Travancoriana Bott, 1969, and Vanni Bahir & Yeo, 2007, are known thus far only from the states of Karnataka, Kerala, and Tamil Nadu in southern India, with their species occurring exclusively in the Western Ghats. The taxonomy of these genera is revised using a morphological approach, partly supported by a preceding molecular study, which proved that both genera are polyphyletic, while some species of Vanni s. lat. fit the generic definition of Travancoriana s. lat. In this revision, Travancoriana is restricted to its type species, T. schirnerae Bott, 1969. Five species previously known in Travancoriana are assigned to four new genera: T. charu Bahir & Yeo, 2007 (type species herein designated) and T. pollicaris (Alcock, 1909) to Ponmudiana gen. nov.; T. convexa (Roux, 1931) to Palaniana gen. nov.; T. granulata Pati & Sharma, 2013, to Anamudiana gen. nov.; and T. kuleera Bahir & Yeo, 2007, to Naduganiana gen. nov. The present revision recognises Vanni as comprising four species, including a new species: V. ashini Bahir & Yeo, 2007, V. deepta Bahir & Yeo, 2007, V. gracilis sp. nov., and V. travancorica (Henderson, 1913) (type species). Four species formerly in Vanni are transferred to four new genera: V. giri Bahir & Yeo, 2007, to Idukkiana gen. nov.; V. malabarica (Henderson, 1912) to Santanusus gen. nov.; V. nilgiriensis (Roux, 1931) to Nilgiriana gen. nov.; and V. pusilla (Roux, 1931) to Pusillosa gen. nov., with the designation of a lectotype. Nilgiriana gen. nov. also contains a new species, Nilgiriana paloti sp. nov., described herein. Identification keys are furnished for the known species of Ponmudiana gen. nov., Vanni, and Nilgiriana gen. nov., as well as for the freshwater crab genera of southern India and/or the Western Ghats. Furthermore, a checklist of freshwater crabs of southern India and/or the Western Ghats is provided, which includes their distribution. This study recognises eight new genera and two new species of freshwater crabs, contributing to a better understanding of the diversity and distribution of these important decapod crustaceans, and highlighting the need for continued research into their taxonomy.

Identité du crabe d'eau douce Indochinamon beieri (Pretzmann, 1966), avec la description d'un nouveau genre et de quatre nouvelles espèces du nord-est de l'Inde (Decapoda, Brachyura, Potamidae). L'identité précise du crabe d'eau douce potamidé, Indochinamon beieri (Pretzmann, 1966), est établie, diagnostiquée et illustrée après examen du matériel type provenant du Myanmar. La diagnose/description de l'espèce et les mentions ultérieures étaient basées sur un spécimen mal identifié et illustré, probablement du Nagaland dans le nord-est de l'Inde, ce qui a semé une confusion importante parmi les carcinologues, qui se sont référés à différents taxons sous le nom d'I. beieri. Deux de ces taxons du nord-est de l'Inde sont présentés ici comme de nouvelles espèces d'un nouveau genre, Capitamon n. gen., i.e., C. mizoramense n. gen., n. sp. du Mizoram et C. clarki n. gen., n. sp. probablement du Nagaland. Capitamon n. gen. comprend également deux nouvelles espèces, à savoir C. capitatum n. gen., n. sp. (espèce type) de l'Arunachal Pradesh et du Nagaland, et C. meitei n. gen., n. sp. de Manipur. Indochinamon manipurense (Alcock, 1909) est également attribué à Capitamon n. gen. car il possède les caractéristiques du nouveau genre. Capitamon n. gen. est ainsi connu par cinq espèces nominales du nord-est de l'Inde, tandis que I. beieri est limité à sa localité type au Myanmar, les signalisations indiennes précédentes se révélant erronées. À l'exclusion de I. manipurense, Indochinamon Yeo & Ng, 2007, contient désormais 42 espèces. Une clé d'identification des espèces de Capitamon n. gen. est fournie.

A new species of gecarcinucid freshwater crab, Ghatiana dvirupa sp. nov., is described herein from the Kali Tiger Reserve of the Uttara Kannada district, Karnataka state, India. The Kali Tiger Reserve is a protected area, which is situated in the Central Western Ghats. The new species superficially most resembles Ghatiana sanguinolenta Pati, Thackeray & Pawar, 2023, from Karnataka but can easily be distinguished mainly by its ultimate article of the male first gonopod, which is distally gently curved inwards against the gently outwardly curved distal portion of the ultimate article in the latter species. Ghatiana dvirupa sp. nov. is also compared with the remaining species of the genus from Karnataka and some morphologically related species from Maharashtra. The difference in colour in life has been noticed between males and females of G. dvirupa sp. nov.; as such the common name of the new species is proposed as “Mr. and Mrs. Ghat Crab”. Ghatiana Pati & Sharma, 2014, is now known for 13 species, all from the Western Ghats of India. Karnataka currently possesses six species of Ghatiana, and many new species are yet to be described.

Ghatiana sanguinolenta sp. nov. is recognized herein as the twelfth species of the gecarcinucid genus Ghatiana Pati & Sharma, 2014, and the fifth species of the genus from the Karnataka state. This new species of freshwater crab is currently known only from the type locality, which is situated in the Central Western Ghats of India. Ghatiana sanguinolenta sp. nov. can be immediately distinguished from congeners by the outwardly curved ultimate article of the male first gonopod and the dark blood-red colour in life.

A new genus and new species of gecarcinucid freshwater crab, Aradhya placida gen. et sp. nov., is recognized from the northern part of the Central Western Ghats of India. The new genus is diagnosed, and the new species from the Uttara Kannada district of Karnataka state, is described herein. The new genus most resembles Arcithelphusa Pati & Sudha Devi, 2015, Cylindrotelphusa Alcock, 1909, Rajathelphusa Raj, Kumar & Ng, 2021, and Pavizham Raj, Kumar & Ng, 2022, in having an ovate, relatively narrow and deep carapace, with the front narrow as compared to other Indian gecarcinucid genera. Aradhya gen. nov. is nevertheless separated from those genera by the characters in the carapace, epigastric and postorbital cristae, external orbital angle, cervical grooves, third maxilliped, chelipeds, male thoracic sternites/sternopleonal cavity/pleon, male second gonopod, and especially by the elongated male telson and the stouter ultimate article of the male first gonopod.

Vela bandhavya sp. nov., a new species of gecarcinucid crab is described from the Central Western Ghats, Uttara Kannada district, Karnataka state, India. The new species can be immediately distinguished from three other species of Vela Bahir & Yeo, 2007, mainly by its short male sternopleonal cavity and a relatively shorter distal article of the male first gonopod. The diagnosis of Vela is revised to accommodate the new species, and an illustrated identification key is provided for all four species. An anomalous adult male crab, with a pair of pleopods on the pleonal somite 5 in addition to the male gonopods, is also reported.