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Kevin J. Eckelbarger 1and Craig Young 2
1. Darling Marine Center, University of Maine, Walpole, Maine 04573 and School of Marine Sciences, University of Maine, Orono, Maine 04469, USA
2. Division of Marine Sciences , Harbor Branch Oceanographic Institution, Ft. Pierce, Florida 34946, USA
The ultrastructural features of the ovary and oogenesis have been examined in the neritid gastropod Bathynerita naticoidea, a bathyal species endemic to oil and gas seeps in the Gulf of Mexico. This is the first ultrastructural study of vitellogenesis in any “archaeogastropod”. The ovary is an acinus organ containing oocytes in all stages of oogenesis. Oocytes are closely associated with hypertrophic follicle cells that may play a role in oocyte nutrition. Vitellogenesis is a complex process involving both autosynthetic and heterosynthetic pathways that contribute to the formation of at least three types of yolk bodies. Type I yolk bodies appear to be synthesized autosynthetically through the combined efforts of the Golgi complex and rough endoplasmic reticulum. Type II yolk bodies have an uncertain origin but share many ultrastructural characteristics with mitochondria, suggesting that they may be derived from the latter organelles. Type III yolk bodies appear to form through the heterosynthetic uptake of extra-oocytic precursors via receptor-mediated endocytosis. Oocytes also accumulate lipid droplets and glycogen granules. Vitellogenesis in this species shows similarities with that described previously in a caenogastropod and some Heterobranch (opisthobranchs and pulmonates) species. The ultrastructural features of oogenesis suggest that this species undergoes rapid egg production. The presence of all stages of oogenesis in every ovary examined also suggests that this species could be capable of non-seasonal reproduction.
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