Histological studies of the ovaries of two tropical portunid crabs, portunus pelagicus (l.) and scylla serrata (f.)

Abstract

The histology of ovaries of adult crabs, Portunus pelagicus and Scylla serrata, were studied and compared using light microscopy. In general, the histological features, the steps of oogenetic cells and the stages of ovarian development appear similar in the two species. The ovary possesses three to four lobes, and each lobe is divided into lobules. A thick capsule surrounds the ovarian lobes and its extensions cover and separate each lobule. The lobule is composed of follicles, each containing a cluster of oocytes at different steps within the confinement of connective tissue trabeculae. There are five steps of oogenetic cells, i.e., oogonia (Og) and four steps of oocytes (Oc1, Oc2, Oc3, Oc4). Og are the earliest germ cells and are located in the center of each lobule. They divide mitotically and move into each follicle where they become Oc1. Oc2rapidly increase in size, exhibits a clockface nucleus and basophilic cytoplasm. Oc2possess larger nuclei, non-condensed chromatin, a prominent nucleolus and are intensely basophilic. Oc1and Oc2are previtellogenic and do not contain yolk granules. Oc3are larger in size, with a slate grey cytoplasm and contain a few yolk granules. Oc4are fully mature oocytes, in possession of completely dispersed chromatin in the nucleus and a very prominent nucleolus. The cytoplasm is eosinophilic due to the presence of numerous yolk granules. The Periodic acid-Schiff reaction and Sudan black stains suggest that Oc4also contain large amounts of glycoprotein and lipid in their cytoplasm. The ovarian cycle is divided into four stages, i.e., spawn-spent (stage I), proliferative (stage II), pre-mature (stage III) and mature (stage IV). Each stage contains different cellular associations: stage I is characterized by the reconfiguration of connective tissue scaffold, plus remnants of unspawned oocytes; stage II contains numerous dividing Og and a few Oc1; stage III contains primarily Oc1, Oc2, Oc3; and stage IV contains mostly Oc4and small clusters of Og. © 2007 Taylor & Francis Group, LLC.