Temperature and Water Flow Effects on the Maturation of Freshwater Sponge Gemmules from Ephydatia fluviatilis

Abstract

Freshwater sponges are benthic aquatic animals, often found fixed to hard substrates in many of Tennessee’s waterways. They are multicellular, non-motile, and heterotrophic invertebrates, collecting nutrients via a process known as filter-feeding and in some cases, an algal symbiont. Sponges may produce sexually or asexually, and this study sought to investigate the cues for asexual reproduction by analyzing the growth of asexual structures called gemmules in the laboratory. Gemmules require specific environmental cues to induce hatching and subsequent growth. Prior to the onset of this study, aquaria were filled and left to incubate for one month in an effort to develop a microbiota and simulate in situ environmental conditions. The choice species for research was Ephydatia fluviatilis, collected from Stewart’s Creek in Smyrna, TN, and stored as refrigerated gemmule samples in the Easson lab. This species was chosen based on previous successful hatching trials in the laboratory. Water circulation and varying temperatures were manipulated to test for their influence on gemmule maturation. These results provide the first experimental data to optimize husbandry conditions for Tennessee's sponges. Temperature and flow independently were statistically significant contributors to the maturation of E. fluviatilis. Fifteen degrees Celsius water temperature contributed to the greatest overall growth area of sponge tissue in the final three of five weeks spent in treatment. Flow also resulted in a greater area of growth at week two alone. Additionally, both temperature and flow had compounding effects on the growth of sponge tissue. This experiment was conducted to be used as a preliminary study to investigate freshwater sponges, and their biotechnical application for water quality monitoring and selective filtration.