Sexual reproduction of Cinachyra tarentina (Porifera, Demospongiae)

The sexual reproductive cycle of the Tetractinomorpha Spirophorida Cinachyr a tarentina was studied mainly using light microscopy on samples collected in South Italy over a 2-year period. Some aspects of the egg morphology wer e observed using transmission electron microscopy. Each year, young oocytes in previtellogenesis appeared in May and coexisted with growing oocytes. Y ork-filled eggs a ere present in June and July. Oogenesis preceded spermato genesis which occurred only in June. Cinachyra tarentina is an oviparous sp ecies having small eggs ranging from 40 to 50 mu m in diameter which are sc attered in the mesohyl and have a nucleolated nucleus surrounded by dictyos omes of the Golgi apparatus. Growing oocytes and yolk-filled eggs have an i rregular surface because of the presence of numerous pseudopodia which prot rude into the mesohyl. Even though apparently gonochoric individuals were m ostly observed, the rare specimens with sperm clusters and young oocytes pr oved the occurrence of successive hermaphroditism as an underlying mechanis m. Some aspects of the reproductive biology of C. tarentina are compared wi th that of other Tetractinomorpha.