脉红螺早期发育的观察

在实验室条件下对脉红螺Rapana venosa早期个体发生及其发育过程进行了研究.结果表明：脉红螺的发育属间接发生型,其胚胎发育包括卵裂、囊胚、原肠胚、膜内担轮幼虫和膜内面盘幼虫;幼虫发育包括面盘幼虫、后期面盘幼虫和匍匐幼虫,匍匐幼虫经变态后发育为稚螺;在水温为21 ～22℃的条件下,受精卵需18 ～20 d发育至膜内面盘幼虫,经20～ 26 d后,面盘幼虫逐渐破膜而出;脉红螺面盘幼虫具有1对眼点和1对平衡囊,面盘呈双叶状,后期面盘幼虫的面盘中部开始凹陷,并逐步加深成4叶,呈蝶状,足发达,幼虫既能浮游又能爬行,随着进一步的生长发育,逐渐转入匍匐生活,成为稚螺.

Observation on early development of snail Rapana venosa

The incubation, embryonic and larval development were observed in snail Rapana venosa in a laboratory in this study. The indirect early development of the snail was divided into embryonic development including cleav- age, blastula, gastrula, trochophore, and intra-membrane veliger, and larval development composed of veliger, late veliger and crawling larvae ,which were metamorphosed into juveniles. It took about 18-20 d for the develop- ment from the fertilized egg to intra-membrane veliger and the veligers were hatched in 20-26 d at temperature of 21-22 ℃. The veligers had a pair of eyes, a pair of statoliths and bi-lobed velum, and the late veligers showed a velum with four-lobed like a butterfly, and the well-developed foot. The larvae swam and crept freely, and grew rapidly and gradually turned into crawing juveniles.