Tetracotyle wayanadensis (Trematoda: Digenea) metacercaria - A potential parasitic castrator of the freshwater fish Aplocheilus lineatus (Valenciennes, 1846): A histopathological and temporal variation study in the South Western Ghats, India.

Parasitic castration is a phenomenon where the parasite blocks or reduces the host reproductive output. This study explored the impact of Tetracotyle wayanadensis infection on the reproductive performance of the freshwater fish Aplocheilus lineatus. Heavily infected A. lineatus showed slow and sluggish movements with reduced food intake and feeding activities. Histopathological observations of the ovary revealed severe necrosis and degeneration of previtellogenic and vitellogenic oocytes and follicular atresia. The oogonial nests were absent; chromatin nucleolar oocytes irregularly shaped and vacuolated. Perinucleolar oocytes have a vacuolated appearance with the hypertrophied highly columnar follicular cells invading them. Vitellogenic oocytes had a shrunken appearance with folded zona radiata; yolk globules broken down into smaller granules together with vacuolar degeneration of the ooplasm. The hypertrophied highly columnar follicular cells invaded the early vitellogenic oocytes to phagocytize the degenerating material. Zona radiata was found broken and liquefaction of yolk globules was evident with advancement in follicular atresia. Seasonal variation of parasitic infection has also been studied. Metacercaria infecting the vital organs showed seasonal variation with the highest values for prevalence and abundance during monsoon and mean intensity during winter. The lowest values for these descriptors were documented during the post-monsoon period.

Description of a new species of freshwater crab of the genus rcithelphusa Pati amp; Sudha Devi, 2015 (Decapoda: Brachyura: Gecarcinucidae) from the Western Ghats, Kerala, India.

A new species of the hitherto monotypic gecarcinucid freshwater crab genus, Arcithelphusa Pati Sudha Devi, 2015, is described from the Western Ghats, in the Wayanad district of Kerala, India. Arcithelphusa tumpikkai sp. nov. can be easily distinguished from the only congener, A. cochleariformis Pati Sudha Devi, 2015, mainly by its relatively broader carapace, the presence of a short flagellum on the exopod of the third maxilliped, and the relatively less stout male first gonopod, with a sharply bent and relatively long terminal segment. The diagnosis for Arcithelphusa is emended to include the new species, which can be useful in distinguishing it from the closely related genus Cylindrotelphusa Alcock, 1909. The state of Kerala now has 38 species of gecarcinucid crabs, including the present new species.

Spiralothelphusa gibberosa, a new freshwater crab (Brachyura: Gecarcinucidae) from Thrissur district, Kerala, India.

A new species of freshwater crab, Spiralothelphusa gibberosa n. sp. is described from rice fields near Kizhoor in Thrissur district of Kerala in southern India. The new species is easily differentiated from its congeners by its first male pleopod (G1), which has a long, less strongly twisted terminal segment and distal portion of subterminal segment in addition to a setose hump on the outer margin of the non-twisted portion. Key to the species of the genus Spiralothelphusa Bott, 1968, is provided. We recognized S. wuellerstorfi (Heller, 1862), as a new record to Maharashtra based on specimens wrongly identified as S. hydrodroma (Herbst, 1794), by Pati & Sharma (2014).