Tropical freshwater sponges develop from gemmules faster than their temperate-region counterparts

Abstract

Gemmules are asexual reproductive structures, with internal cells that migrate through an opening in the process of germination, and start to differentiate to form a functional sponge. They have been used as models to understand the physiology and biology of freshwater sponges, but these studies were carried out only in a restricted group of sponges from the temperate region. Therefore, detailed studies describing the developmental stages of freshwater sponges, especially belonging to other lineages and localities, are still necessary to understand how the sponges are formed from gemmules. Here, we describe the development during gemmule germination of two neotropical freshwater sponges, Radiospongilla inesi and Heteromeyenia cristalina. We classified the development of both species in five stages based on phenotypic characteristics. Differences in the developmental stages between the studied species were observed, suggesting that development is species specific. Moreover, when comparing the development of the tropical freshwater sponges with their temperate counterparts, we found differences in the timing of the stages, especially in the formation of the juvenile sponge. Therefore, the tropical species have a similar, but faster development.