Developmental changes of the oocyte and its enveloping layers, inmicropercops swinhonis(Pisces: Perciformes)

Abstract

In the goby Micropercops swinhonis, the development of its egg's enveloping layers could be divided into 4 stages. In the earliest developmental period, stage I, there is a simple oocyte surrounded by a layer of squamous follicular cells. Stage II corresponds to the yolk vesicle stage of vitellogenesis. Here the initial follicular layer has become bilaminar with the retention of its outer squamous cell layer and the acquisition of an inner cuboidal cell layer just over the zona radiata. The number and size of the cuboidal cells increases throughout this stage. Stage III corresponds to the yolk granule stage of true vitellogenesis. Here the cuboidal cells begin to be replaced by columnar cells. As the oocyte grows, the columnar cells increase in size. The columnar cells produce cytoplasmic neutral mucins and by the end of this stage their cytoplasm has been filled with this mucin. In stage IV a single layer of squamous cells still remained as the outer follicular layer of the oocyte. The secretory activity...