TRANSFER OF SYMBIOTIC BACTERIA IN THE MATURE OOCYTE OF GEODIA-CYDONIUM (PORIFERA, DEMOSPONSGIAE) - AN ULTRASTRUCTURAL-STUDY

The astrophorid Geodia cydonium, an oviparous marine sponge, has small mature oocytes (30-40 mu m) scattered in the mesohyl. The nucleus (8- 9 mu m) is nucleolated and exhibits fine-grained chromatin. The mature oocyte has an irregular surface because of the presence of numerous p seudopodia which protrude into the mesohyl. The most interesting aspec t of the ultrastructural study is represented by the high number of ba cteria which are present in the oocyte cytoplasm and which derive from the mesohyl. The import of the bacteria into the cell occurs by endoc ytosis. Their presence is interpreted as a means of transfer to the ne xt embryo.