Neuroendocrine effects on ovarian development in the crab Thalamita crenata Latreille studied in vitro

Abstract

The inhibition of ovarian maturation by a hormone produced in the eyestalk has been repeatedly demonstrated in many species of crustaceans. However, the discovery of an ovary stimulating factor in the thoracic ganglion has been recent and confined to two species of fresh water crabs, Potamon dehaani and Paratelphusa hydrodromous. The current investigation has disclosed the presence of a similar hormonal factor in the thoracic ganglion of a littoral crab, Thalamita crenata Latreille. Studies of these two factors and their effects on the maturation process were conducted by using the organ culture method in conjunction with in vivo experimentations. In the ill vitro studies ovarian explants were cultivated in a medium composed of Pantin's crab saline and Medium 199 without serum (Baltimore Biological Laboratories). This medium was effective in promoting growth in the germinative zone and of the interstitial cells of these explants. Growth was indicated by the presence of cells undergoing cell division and by the increased number of interstitial cells. The proliferation of these cells, especially those in the germinative zone, indicated that this aspect of oocyte development in vitro was independent of any hormonal factors. Maintenance of young oocytes was demonstrated in cultivation of explants with the culture medium. However, the addition of brain extracts to the medium showed that the brain may be involved in promoting growth in these oocytes. Older oocytes undergoing cytoplasmic changes such as vesicle formation ,and yolk deposition were not maintained in the culture medium. When the medium was supplemented with an extract of the thoracic ganglion, maintenance of these oocytes, notably those undergoing yolk deposition, was demonstrated. However, further growth was not induced. Extracts of the brain did not affect the oocytes in this stage of development. Parallel in vivo studies in which extracts of the thoracic ganglia were injected into normal females revealed the presence of a stimulating factor. This factor not only maintained vitellogenesis, but also initiated it. Eyestalk replacement studies verified the presence of an inhibitory factor in the eyestalks. This inhibitor, directly or indirectly, suppressed vitellogenesis. It is concluded that an ovarian stimulating factor is found in the thoracic ganglion. This substance initiates and maintains vitellogenesis. Earlier stages in the development of the oocytes are not affected by this thoracic ganglionic factor.