Mature males produce ripe sperm when they reach lengths of approximately 118 mm. Females mature at lengths of approximately 135 - 140 mm. Gonadal development in females can be judged by ovary color. Undeveloped ovaries are opaque and white in color. Developing ovaries appear yellow, a stage which may last 1 - 2 months. Ripe ovaries are an olive color, and may remain so until fully spent (generally in less than 1 month). Spent ovaries quickly develop to the yellow stage within a few days, and will ripen again within 2 - 3 months (King 1948; Brown and Patlan 1974).Spawning behavior in P. setiferus
is initiated by an increase in offshore bottom water temperatures during spring (Whitaker 1981). In the Carolinas, spawning occurs from May through September (Williams 1955), while further south in the Gulf of Mexico, spawning occurs from March through September. Williams (1965) and Joyce (1965) each reported only one spawning period for P. setiferus
. However, Gunter (1950) suggested spring and fall spawning periods in Texas waters.Spawning occurs as far as 9 km from the shore, in water depths of at least 9 m (Whitaker 1983b), with females discharging eggs directly to the water column without brooding them as is common in other crustaceans. During copulation, which occurs between hard-shelled individuals, the male attaches a spermatophore to the thelycum of a female. Spermatozoa are released simultaneously with eggs from the female, with fertilization occurring in the water column. Eggs are opaque with a blue-tinged chorion (Linder and Cook 1970) and measure approximately 0.19 - 0.20 mm in diameter. Eggs sink to the bottom of the water column as they are released, and hatch within 10 - 12 hours into planktonic nauplii larvae that measure approximately 0.3 mm in length. Between 500,000 to 1 million eggs are released per spawn.