瘤背石磺的胚胎和幼虫发育

Embryonic and larval development of Onchidium struma

在水温27～29℃、气温27～31℃和海水盐度为16的环境条件下人工孵化瘤背石磺的卵块,根据早期发育的形态变化将其划分为胚胎发育(包括卵裂期、囊胚期、原肠期、卵内担轮幼虫、卵内面盘幼虫)和幼虫发育(包括开口期、大面盘幼虫、附着期、匍匐幼虫)两个阶段。受精卵发育至卵内担轮幼虫需要51h,胚胎发育89h后变态为卵内面盘幼虫,第7天面盘幼虫孵化出卵,直径增大1倍;第23天幼虫变态为匍匐幼虫,虫体直径为受精卵的4倍。分析认为,瘤背石磺的胚胎发育具备典型的不等全裂、螺旋卵裂特征,幼虫为典型的腹足纲面盘幼虫形态;温度对胚胎发育时间影响显著而充气可以加速幼虫孵化出卵;面盘幼虫需要有适宜的潮间带环境和饵料(如底栖硅藻)才可以正常附着变态。

<Abstrcat>Egg masses of Onchidium struma are artificially hatched at water temperature 27-29℃, atmospheric temperature 27-31℃ and brackish water salinity 16. Based on the morphological change, early development can be divided into 2 stages: embryonic development (including cleavage, blastula, gastrula, egg-trochophora and egg-veliger) and larval development (including weaning stage, big veliger, settlement stage and creeping larvae). The fertilized egg developing into egg-trochophora takes 51 hours, and into egg-veliger 89 hours. On the 7^(th) day, veliger hatched out from egg capsule, its diameter doubled. On the 23^(th) day, creeping larvae were formed, its length was 4 times than fertilized egg's. It was suggested that embryo of Onchidium struma show typical molluscan development of a holoblastic cleavage and spiral cleavage pattern, and the larva have the appearance of characteristic gastropod veligers; temperature affect embryonic development remarkablely, also, aerated process can accelerate larvae hatch; only with inter-tidal environment and optimal food (such as benthic diatoms) could creeping larvae live through settlement stage.