NATURAL HISTORY OBSERVATIONS ON THE BUSYCONINE WHELKS BUSYCON CONTRARIUM (CONRAD) AND BUSYCOTYPUS SPIRATUM (LAMARCK)

Abstract

Several aspects of the natural history of the sympatric busyconine whelks <it>Busycon contrarium</it> and <it>Busycotypus spiratum</it> were examined along the northwest Gulf coast of Florida. Field and laboratory observations were made on feeding rate, crawling speed, size distributions, growth rate and reproduction. The two species were similar in several respects. Both were slow-growing with growth occurring only above 20°C. Modal sizes for both species have markedly declined over the past two decades. Feeding rates and crawling speeds were affected by seasonal temperature changes, being highest at intermediate temperatures. Both species copulate in late autumn to early winter, lay egg capsules in early spring, with hatching beginning in May. One major interspecific difference was observed; the crawling speed of <it>B. spiratum</it> was twice that of <it>B. contrarium</it>. This difference was correlated with the larger foot of <it>B. spiratum</it>.