Exploring the Diversity and Seasonal Dynamics of Aseptate Gregarines in Earthworm: A Preliminary Study in Purulia, West Bengal, India

Aseptate gregarines are frequently observed in annelids, particularly in the seminal vesicles of earthworms. This study investigates the diversity and distribution of gregarines infecting earthworms, along with their seasonal variations, across different regions of the Purulia District in West Bengal. Extensive field surveys were conducted from March 2023 to January 2025 to collect host specimens from various habitats, including forests, agricultural fields, and garden soil. The result revealed a rich diversity of aseptate gregarines across different species of host earthworms. Six different species of parasites were recorded under three different genera, viz. Monocystis Stein, 1848; Nematocystis Hesse, 1909 and Stomatophora Drzhevetskii, 1907. They are Monocystis bengalensis Ghosh, 1923, Monocystis beddardi Ghosh, 1923, Nematocystis sp., Stomatophora diadema Hesse,1909, Stomatophora majumdari Bandyopadhyay et al., 2001, Stomatophora pradhanis Roy Choudhury and Haldar, 1984, respectively. Their different reproductive stages were also observed, and their intensity was noted. Morphometric analysis was employed for parasite identification, and their prevalence. The highest rate of gregarine infection was recorded during the monsoon season, i.e., June-September (96.51%) followed by post-monsoon, i.e., October-November (83.49%), with Monocystis Stein, 1848 being significantly more prevalent than other species. The density of the gregarine’s infective stages is at its maximum during the monsoon may be due to the increased host availability. The precise causes of species-specific seasonal variations in gregarine prevalence need further continuous assessment with additional environmental factors that influence host distribution.