Mexistenasellus floridensis sp. n., the first stenasellid isopod discovered from the Floridan aquifer (Crustacea, Isopoda, Asellota)

Mexistenasellus floridensis sp. n. is described from Hole in Wall Cave, Jackson County, Florida. The discovery of this unique isopod nearly doubles the range of the Family Stenasellidae in North America, which was previously known from Oaxaca, Mexico to southern Texas, USA. This is the first stenasellid reported swimming in the water column of a cave, a curious finding for an isopod that belongs to a group that is generally more adapted to inhabiting interstitial spaces. Mexistenasellus floridensis occurs syntopically with the subterranean asellid Caecidotea putea. Both species have been observed swimming in the water column, although neither has apparent anatomical adaptations for swimming as compared to the natatory pereopods of Remasellus parvus, an asellid that occurs in caves in Alachua, Madison and Wakulla counties, Florida.