Gustafson et al. Upon settlement into soft sand or muddy substrata, juveniles burrow as much as 3 feet below the surface. C. costata in Virginia have been observed to spawn from May to September. In Florida and throughout the warmer regions of its range, the gonads of C. costata tend to remain ripe year-round, except during June through August, the months of prime spawning . In C. costata , a brief trochophore stage follows fertilization, with D-stage veliger larvae developing within the first 24 hours.
Eggs have a limited amount of yolk, which requires that larvae begin to feed after the first day.
In larval growth trials, optimum shell length increase occurred at 30 C over the entire 16-day larval period. In growth trials, optimum shell length increase for C. costata larvae occurred at a salinity of 20 ppt . Filtered water, waste products, and gametes are passed out the excurrent siphon. C. costata competes with other sessile filter feeders such as the hard clam, Mercenaria mercenaria . It is also likely to compete with suspension feeders such as bryozoans and some species of polychaete worms.