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

• Published in: Parasitology international Vol. 84; p. 102408
• Main Authors: Jithila, P.J., Devi, A.R. Sudha, Prasadan, P.K., Abaunza, P.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.10.2021
• Subjects: Aplocheilus lineatus; Histopathology; Parasitic castration; Seasonal variation; Tetracotyle wayanadensis; Western Ghats; Western Ghats; Tetracotyle wayanadensis; Histopathology; Seasonal variation; Aplocheilus lineatus; Parasitic castration
• ISSN: 1383-5769; 1873-0329
• DOI: 10.1016/j.parint.2021.102408

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. •Tetracotyle wayanadensis metacercaria is a potential parasitic castrator of the freshwater fish, Aplocheilus lineatus.•Metacercarial infection in the ovary of fish revealed severe necrosis and degeneration of oocytes and follicular atresia.•Oocytes were damaged. Vitelline envelope appeared thin. Yolk globules lost their integrity. Size of oocytes was reduced.•Infection showed seasonal variation. Highest prevalence and mean abundance were in monsoon and mean intensity in winter.•Tetracotyle wayanadensis infected fish showed behavioural changes related to feeding activities