Comparative Morphology of Microsclere Structure in Spongilla alba, S. cenota, and S. lacustris (Porifera: Spongillidae)

The microscleres of the fresh-water sponges Spongilla alba, S. cenota, and S. lacustris were studied using scanning electron microscopy. The purpose of the investigation was to determine if microsclere structure among the three species is distinctive and if variations exist among specimens of S. lacustris from different geographical areas; the microscleres among the three species were distinct. Spongilla alba can be distinguished from S. cenota and S. lacustris by microscleres having blunt tips composed of four, small, recurved spines and by the distribution of simple, curved spines and complex, burr-like spines on the microscleres. Spongilla cenota can be distinguished from S. lacustris by the presence of burr-like complex spines with smooth pedicels increasing in length toward the middle of the spicule, and by the distribution of these spines. Spongilla alba and S. cenota were more similar to each other than they were to S. lacustris, but S. cenota had more features in common with S. lacustris than did S. alba. Microscleres of S. lacustris showed considerable variation, and specimens from different geographic areas could not be separated consistently based on spicule structure. In no case did variations in spicules of S. lacustris approach the distinctiveness of features among recognized species.