Meeting Abstract
P1.31 Monday, Jan. 4 Follicle Cell Processes in the sandbar shark Carcharhinus plumbeus MORGAN, S; NGUYEN, M; ONOURA, C*; RICHARDSON, T; TRAN, HT; DAVENPORT, IR; Xavier University of Louisiana; Xavier University of Louisiana; Xavier University of Louisiana; Xavier University of Louisiana; Xavier University of Louisiana; Xavier University of Louisiana idavenpo@xula.edu
Elasmobranch fishes (sharks, skates and rays), are among the dominant predators in the marine environment. Apex predators typically have low fecundity but to compensate produce large, precocial offspring. Producing larger offspring requires more maternal input i.e. increasing the amounts of yolk stored within the egg (lecithotrophy), or by supplementary nutrition supplied to the developing embryo from the mother (matrotrophy). Lecithotrophy has finite limits as the egg is a single cell and thus is confined by physical properties; the egg has to maintain its physical integrity. There is also the question of how to get vast amounts of nutrients to these large egg cells. To produce very large offspring the mother needs to supply additional nutrition to the developing embryo throughout gestation. In elasmobranchs this is achieved in a variety of ways including the secretion of uterine milk, oophagy and ultimately the evolution of the yolk sac placenta. Our interests are in the production of large egg cells; in elamobranchs they can reach 10 cm in diameter. In recent years we have indicated the presence of a novel, actin-based, tube-like framework embedded in the zona pellucid. This framework may well aid in the production of these extremely large egg cells. This framework has so far been described in two species of carcharhinid, 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 phylogentic distribution of these structures and their ultimate role in oogenesis. We have found FCP in a fourth species of carcharhinid, the sandbar shark Carcharhinus plumbeus.
