SEX STEROID-METABOLISM IN THE ANTARCTIC PTEROPOD CLIONE ANTARCTICA (MOLLUSCA, GASTROPODA)

The ability of the antarctic pteropod Clione antarctica (Mollusca: Gas tropoda) to synthesize sex steroids from radiolabeled steroid precurso rs was examined in individuals sampled near the end of their observed reproductive season from McMurdo Sound, Antarctica. The precursors, H- 3-progesterone and 3H-androstenedione, were absorbed and subsequently metabolized to produce several progestin and androgen metabolites, inc luding 5 alpha-pregnane-3,20-dione, 3 beta-hydroxy-5 alpha-pregnan-20- one, 3 beta-hydroxy-4-pregnen-20-one, 5 alpha-androstane-3,17-dione, 3 beta-hydroxy-5 alpha-androstan-17-one (androsterone), and 3 beta-hydr oxy-5 alpha-androstan-17-one (epiandrosterone). Synthesis or accumulat ion of testosterone and estradiol was not observed. At least 2 unident ified, water-soluble progestin metabolites were synthesized, as well a s an unidentified esterified steroid. The metabolic accumulation of th ese steroidal compounds indicates that C. antarctica can produce poten tially bioactive steroids. The activity of steroid metabolic enzymes i n a polar species further indicates the universal capacity of inverteb rates from various geographic regions to metabolize biologically relev ant steroids.