First report of Nematopsis sp. (Apicomplexa: Eugregarinida), in Mytella strigata (Bivalve, Hanley, 1843), comercialized in the host city of COP30, Amazon

Abstract This study investigated the protozoan Nematopsis sp. in the mangrove mussel (Mytella strigata), know in Brazil as “mexilhão-do-mangue”, commercialized at Ver-o-Peso market in Belém, Pará state, Brazil. The purpose of this study was to identify the presence of the parasite and to describe his morphological characteristics. 72 specimens of M. strigata were collected, and the oocysts was analysed by light microscopy, while pathogenicity was assessed throught histological staining. The findings demonstrated a high prevalence (100%) in the foot musculature of the mollusks, characterized by diffuse necrosis and consequent myofibrilar degeneration. The number of oocysts per parasitophore vacuole ranged from 6 to 8, with each oocyst containing a single sporozoite. Based on data obtained through light microscopy and host specificity, the gregarine Nematopsis sp. was morphologically distinct from previously described species. Nonetheless, additional research employing complementary methodologies such as ultrastructural analyses and the use of molecular biology with the use of universal eukaryotic markers such as the rDNA18S gene for phylogenetic analyses will be necessary for the description of a a new species, highlighting it´s significance within the context of COP30 discussions on climate change and environmental health.