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

Abstract

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 pseudopodia which protrude into the mesohyl. The most interesting aspect of the ultrastructural study is represented by the high number of bacteria which are present in the oocyte cytoplasm and which derive from the mesohyl. The import of the bacteria into the cell occurs by endocytosis. Their presence is interpreted as a means of transfer to the next embryo.