Meeting Abstract

4.1  Monday, Jan. 4  Follicle Cell Processes in the bull shark Carcharhinus leucas MORGAN, S*; NGUYEN, M; ONOURA, C; TRAN, HT; DAVENPORT, IR; Xavier University of Louisiana; Xavier University of Louisiana; Xavier University of Louisiana; Xavier University of Louisiana; Xavier University of Louisiana idavenpo@xula.edu

Chondrichthyan fishes (sharks, skates, rays and chimeras) are apex predators in the marine environment. As such they have a life history strategy that favors few, but large offspring. The production of large, precocial offspring requires greater maternal input, either in the form of more yolk stored within the egg (lecithotrophy) or by maternal input directly to the embryo (matrotrophy). The progression towards matrotrophy also coincides with the switch from oviparity (egg laying) to that of viviparity (live bearing). Chondrichthyan fishes are a useful model for studying the evolutionary transition from oviparity to viviparity as they have species utilizing all the major steps. These steps include species that produce large externally laid eggs, large eggs retained within the female body cavity, production of uterine milk, oophagy and culminating in the yolk sac placenta. Our interests lie in the evolution of extremely large egg cells, namely the provisioning of these egg cells and in maintaining their structural integrity. Several years ago we showed the presence of a novel, actin-based, tube-like framework that might aid in the evolution of extremely large egg cells in two species of carcharhinid shark, the dusky smoothound Mustelus canis and the Atlantic sharpnose shark Rhizoprionodon terraenovae. We termed these structures, follicle cell processes (FCP). We are continuing to explore the phylogenic distribution of these structures and their ultimate role in oogenesis using light, fluorescence and electron microscopy. In the current study, we demonstrate the presence of FCP in a third species of carcharhinid, the bull shark Carcharhinus leucas.