Delivery and Storage of Sperm at First Mating of Female Chionoecetes opilio (Brachyura: Majidae) in Relation to Size and Morphometric Maturity of Male Parent

Abstract

ABSTRACT Virgin female Chionoecetes opilio were paired with males, in a noncompetitive laboratory setting, less than 12 h after molting to maturity. The quantity of sperm that females received and stored was measured as ejaculate weight and number of sperm cells. Females copulated 1-4 times prior to spawning; the first and second intromissions lasted an average of 34.4 and 37.7 min, respectively. On the whole, the weight of ejaculate and number of sperm cells did not differ between the left and right spermathecae. The number of sperm cells received or stored in spermathecae was independent of male and female carapace widths. Morphometrically mature (large claw) males transmitted an estimated 10.8 x 106 sperm cells to each spermatheca, and an estimated 2.1 x 106 sperm cells from each spermatheca were used to fertilize the first egg clutch (≈ 70 sperm cells per oocyte). Females did not extrude eggs when fewer than 1.9 x 105 sperm cells were delivered to at least one spermatheca, resulting in a ratio of <7 sperm cells per oocyte. A median of 10.2 x 106 and 8.7 x 106 sperm cells were stored per spermatheca by females that extruded eggs after mating with morphometrically immature (small claw) and morphometrically mature males, respectively. The ratio of number of sperm cells to ejaculate weight was significantly greater in stored ejaculates from morphometrically immature males than in those from morphometrically mature males. Both male morphs mated successively with 5 different females over a period of 14-33 days, with no significant change in the weight of ejaculate or the number of sperm cells stored by females after spawning.