Chelatrematidae n. fam., a new family of digenetic trematodes from the South Western Ghats, India, erected on the basis of morphological and molecular studies.

On the basis of the morphological characterization of Chelatrema neilgherriensis Manjula & Janardanan, 2006 recovered from the freshwater fish Barilius gatensis (Valenciennes, 1844) in the Wayanad region of the Western Ghats, the diagnostic features of the genus Chelatrema Gupta & Kumari, 1973 have been modified. Based on the phylogenetic analysis of C. neilgherriensis and comparative morphology studies relative to members of other families of Gorgoderoidea Looss, 1901, this genus is placed in a new family Chelatrematidae n. fam. The studies revealed the molecular and morphological closeness of Chelatrema with Paracreptatrematina limi Amin & Myer, 1982, and the latter is transferred to this new family. Hence the new family Chelatrematidae n. fam. comprises the genera Chelatrema and Paracreptatrematina.

Distribution of different species of metacercariae in two freshwater fishes: Haludaria fasciata (Teleostei: Cyprinidae) and Pseudosphromenus cupanus (Teleostei: Osphromenidae).

Information on the distribution and abundance patterns of trematodes are essential to reveal the ecology of host-parasite interactions. The Western Ghats of India, a biodiversity hotspot, is rich in freshwater fish diversity and endemism. Though there are several studies on various other aspects of fish ecology, studies on their parasitic fauna is meager. The objective of the present study is to explore the distribution and infection patterns of metacercariae of five species of trematodes in the freshwater fishes, Haludaria fasciata and Pseudosphromenus cupanus. The infection parameters were analyzed for each host and CART model was applied to analyze the environmental factors affecting parasite distribution patterns. All species of metacercariae showed an over-dispersed aggregate distributions. The classification tree models indicated that among the environmental factors considered, differences in host locality was the most influential factor in both fishes, followed at a greater distance by the factor seasonality. The parasite communities exhibited temporal and spatial differences in the infection pattern in response to seasonal and locational variations.

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 Tetracotyle wayanadensis n. sp. (Digenea: Strigeidae) metacercaria infecting six species of freshwater fishes from Western Ghats, India.

Tetracotyle wayanadensis n. sp. (Digenea, Strigeidae) infecting different organs of six species of freshwater fishes, Haludaria fasciata (eye, buccal cavity), Amblypharyngodon melettinus (eye, buccal cavity), Aplochelus lineatus (operculum, heart, mesenteries), Pethia conchonius (brain), Parambassis thomassi (muscles, mesenteries) and Lepidocephalus thermali (mesenteries) collected from water bodies in the Wayanad region of the Western Ghats is described and illustrated. Tetracotyle wayanadensis n. sp. is new to the genus and is separated from its congeners on the basis of differences in morphology and morphometry. The present paper also describes the prevalence, intensity, mean abundance and sites of infection of the parasite in each host. The prevalence of infection of T. wayanadensis n. sp. in Haludaria fasciata is 7.5%, intensity of infection is 2.66 and mean abundance is 0.2; in Amblypharyngodon melettinus 10%, 6 and 0.6; in Aplochelus lineatus 12.2%, 6.2 and 0.76; in Pethia conchonius 7.14%, 5 and 0.36; in Parambassis thomassi 100%, 2 and 2; in Lepidocephalus thermali 10%, 2 and 0.2 respectively.