Development of the planktotrophic veligers and plantigrades ofStrombus pugilis(Gastropoda)

Abstract

The organogenesis, histogenesis and growth of larvae of the fighting conch Strombus pugilis (Linne´ , 1758) were studied over a period of 30 d after hatching in laboratory culture. Early development of S. pugilis was examined by light and scanning electron microscopy. Rearing was conducted at 27+ 1 8C. Veligers were reared at 200 larvae l 21 in 4-l containers. Larvae were fed with the microalgae Isochrysis galbana and Nanochloropsis oculata at a concentration of 1,000 cell l 21 . The protoconch at hatching measured 212+ 12.14 mm in length and the shell reached 1,100+ 29.11 m m2 9 d after hatching. Development characteristics are described from hatching to settlement. Newly hatched veligers possess two velar lobes, a larval shell consisting of 1.5 whorls, eyespots and a single right tentacle. Late veligers (5-d old larvae) have four velar lobes and two shell whorls and the left tentacle appears. Pediveligers show a functional adult heart at 11 d. Crawling behaviour and settlement were observed from 27 to 31 d. Plantigrades were observed after 29 d, when a functioning proboscis is observed and the velar lobes are lost. This study will facilitate the identification of gastropod larval shells in the plankton and of juveniles in the meiobenthos and will aid aquaculture of Strombus species.