Gonadal Cycle, Gametogenesis and Energy Allocation in Two Sympatric Mid Shelf Sea Stars with Contrasting Modes of Reproduction

The goniasterid sea stars Anthenoides piercei and Tosia parva were collected 19 times over a 30-month period from a rhodolith substrate (90 m depth) in the northern Gulf of Mexico. Size frequency distributions of both sea stars indicated little evidence of annual recruitment. Cumulative population size distributions were unimodal and skewed towards larger body sizes, with a mean size of 57.3 g wet weight (R = 8.5 cm) in A. piercei and 6.1 g wet weight (R= 2.1 cm) in T. parva. Both species exhibited annual gonadal growth cycles. Anthenoides piercei produces small eggs (130 μm diameter) which are spawned during the fall and early winter and presumably develop into planktotrophic larvae. Tosia parva produces much larger lecithotrophic eggs (600 μm diameter) which are spawned during the summer months. It is unknown whether these lecithotrophic embryos are brooded as in the congener T. australis. An inverse relationship between the gonadal and pyloric cecal indices was apparent in both species during 1989. However, organ index reciprocity was less evident during the subsequent 16 months. The energetic composition of the mature ovaries of A. piercei (26.7 kJ˙g^–1 dry weight) was lower than that of T. parva (31.1 kJ˙g^–1 dry weight). This was attributable to higher lipid levels in the ovaries of T. parva than in A. piercei (54.7 vs. 25.9% dry weight). Nonetheless, the relative allocation of energy to the mature ovaries was similar in both species.