Life cycle and larval ultrastructure of two Mediterranean Poecilosclerida species sharing habitat

<p>8th World Sponge Conference (September 20th-24th, 2010–Girona, Spain)</p> <p><em>Hemimycale columella</em> and <em>Crella elegans</em> are both poecilosclerid sponges and share habitat in the western Mediterranean sublittoral. Both are thick encrusting species, pale orange to pink at the surface, covered by round densely distributed pore-sieves, and hermaphrodites. Furthermore, the larval release–of a typical parenquimella–of the two species occurs at the beginning of autumn in the study area. Due to this phenotypic convergence of the genera Hemimycale and Crella, species fro the Pacific and red Sea species have been misidentified in the past. To gain knowledge on the possible interactions of these two species, we investigated their timing of gamete and larva production, their reproductive investment, and some ultrastructural aspects of gametes and larvae for both species. In <em>C. elegans</em>, oocytes are produced from June to July, embryos start to be formed in July and larvae are abundant in September-October. In <em>H. columella</em>, oocytes were present from July to September, embryos appeared in September and coexisted with mature larvae in October. No reproductive elements were found in any of the two species from November on. The larval ultrastructure shows distinct features in both species, with notably higher collagen density in <em>C. elegans</em>.