Identification of Isolated and in situ Freshwater Sponge Spicules of Eastern Tennessee

Abstract

Of the 9K known species of sponges, less than 300 are freshwater (FW) and fewer than 35 are known from North America. Last surveyed in 1943 in Tennessee [1], only 4 species of freshwater sponges were identified, all form the Reelfoot Lake region of northwestern Tennessee. Sponges contain skeletal elements called spicules. Spicules of freshwater sponges are siliceous. Three forms of spicules, megascleres, microscleres and gemmoscleres, are recognized. Spicule shapes and sizes are quite varied and their use for differentiating species is well established [2]. Asexual reproductive resting stages known as gemmules are produced in response to adverse environmental conditions. The protective surface layer of a gemmule is composed of gemmoscleres. Of the three spicule types gemmoscleres are the most importance taxonomically.