Pumping Water or Producing Larvae? Oscula Occlusion during the Reproductive Period of the Sponge Svenzea zeai

摘要

The sponge Svenzea z e a i (Demo s p o n g i a e : Halichondrida), a common inhabitant of the Caribbean Sea, is known to brood the largest larvae recorded in sponges all year round (Rützler et al. 2003). In June 2008, we observed several specimens of S. zeai in the Bahamian islands of Little San Salvador (~10% of observed colonies) and Plana Cay (~80%) with some or all oscula partially or totally occluded by a thin veil (Fig. 1A). All sponges that exhibited closed oscula were brooding embryos (Fig. 1B), but not all brooding sponges had occluded oscula. The development of the veil appeared to interfere with water flow through the osculum, suggesting a reduction in water circulation throughout the sponge. We subsequently analyzed the oscular rims using transmission electron microscopy (TEM) and observed that the sponge mesohyl in the rim of the veil was occupied by a cell type (~30% of the section surface) filled with inclusions that had a granular content. Our observations suggest that the contents of these vesicles were continuously being released and were forming the mucus material of the veil (Fig. 1C).