Observations on the egg capsules and hatchlings of the knobbed whelk, Busycon carica (Gmelin, 1791) in coastal Georgia

Despite the commercial importance and abundance of knobbed whelks on the east coast of the United States, very little life history information exists for juveniles in the egg capsule and the first few critical weeks post hatching. As a result, various intertidal sandy-mud flats around Wassaw Sound, Georgia were monitored from early April 2001 when copulating and egg-laying whelks were first observed to early June 2001 when most egg capsules had opened and the hatchlings had begun to disperse. During this spawning event, egg strings were collected, the length of the embryonated (mean = 339.86 mm) and unembryonated (mean = 199.67 mm) portions were measured, and the number of embryonated capsules per string (mean = 89.76) was determined. The middle section of the embryonated portion comprised the largest capsules (mean height = 22.12 mm, mean width = 31.11 mm, mean thickness = 6.03 mm) and had the highest number of encapsulated embryos with an average of 46 (up to 99). Egg strings were also hatched in the laboratory with the intention of examining the effects of diet (meat, macroalgae, and microalgae) and temperature (20, 25, and 30 degree C) on the growth and survival rates of newly hatched juveniles. Optimum growth and survival conditions resulted in those reared on a meat diet in aquaria maintained at 20 degree C.