Seasonal rainfall drives temporal niche partitioning in the helminth community of scorpion mud turtle (Kinosternon scorpioides) from Marajó Island.

The alternation between wet and dry seasons in tropical regions can dramatically affect parasite infection dynamics by influencing larval survival, intermediate-host density, definitive-host foraging behaviour, and host immune function. Freshwater chelonians are excellent models for studying parasite-host ecology. Their longevity, site fidelity, and dietary breadth make them valuable sentinel species for aquatic ecosystem health. Here, we identified the gastrointestinal helminth fauna of scorpion mud turtle (Kinosternon scorpioides) from Marajó Island and evaluated seasonal effects on parasite community dynamics. We observed a 71% reduction in parasite load during the dry season and substantial compositional shifts, in addition to species-specific responses: Spiroxys figueiredoi exclusively during floods and Nematophila grandis peaking during dry periods. Parasite species with flexible transmission pathways may thrive while specialists decline. Kinosternon scorpioides and its parasites function as sentinels, and monitoring helminth community composition could more accurately track ecosystem health than measuring host abundance alone.