Unionicola
Unionicola is a genus of freshwater arachnids, belonging to the family Unionicolidae. The genus was described in 1842 by Samuel Stehman Haldeman. The genus has cosmopolitan distribution. Most "Unionicola" are associated with mollusks, but "Unionicola crassipes" and "Unionicola minor" are associated with sponges of family Spongillidae. The association with mussels can be described as symbiotic. There is evidence that mites consume host tissue and can be associated with reduced host fitness, although the causal direction of the latter remains unclear. Species include the following: