Growth and development of the veliger larvae and juveniles of Polinices pulchellus (Gastropoda: Naticidae)

Abstract

Adult Polinices pulchellus were collected from the field and held in aquaria under ambient conditions. Egg collars laid by P. pulchellus were cultured at 14°C and 20°C and larval development after hatching was documented photographically. Planktotrophic Polinices pulchellus veligers hatched from egg collars cultured at 20°C after nine to ten days and after 14 to 15 days at 14°C. Veligers spent most of their time close to the water surface and began feeding within one hour of hatching. Repeated attempts to raise larvae to metamorphic competency at 14°C were unsuccessful. Morphological changes, most notably in the colour and size of the velum and foot, were observed in larvae raised at 20°C. During the first 25 days of larval development the velum broadened and bifurcated into four velar arms, the distal regions of which acquired a deep red coloration. By day 40 the foot had increased considerably in size and the degree of black pigmentation. By day 45 pediveligers were competent to metamorphose to the juvenile stage. Exposure to sediment from the adult habitat induced metamorphosis, larvae lost their vela and became benthic juveniles. Within three days of metamorphosis, juvenile snails drilled the bivalve Lasaea adansoni (∼2 mm), later drilled Cerastoderma edule (∼4 mm), and displayed cannibalistic behaviour. Larvae survived for ∼6 months in the absence of a suitable settlement cue.