砂海螂(Mya arenaria Linnaens)幼体与稚贝发育的初步研究

在人工培育条件下,砂海螂(Mya arenaria Linnaens)幼体与稚贝的发育过程,根据其形态与行为生物学特征,可分为五个时期:浮游期幼体、第一变态期幼体、两营期幼体、第二变态期幼体和稚贝。 浮游期幼体包括担轮幼体、D形面盘幼体、壳顶期幼体,历时约5天,第一变态期幼体足发达,出现平衡囊和鳃原基,但仍营浮游生活,历时约5天。两营期幼体的外套膜后方部分愈合,开始形成水管,(?)营浮游和匍匐爬行两种生活方式,且以浮游为主,历时约10天。第二变态期幼体出现眼点,面盘萎缩,几乎完全营匐匐生活,历时约4天。稚贝初期在出水管的先端出现可伸缩、透明的膜状管,随着发育,此管逐渐萎缩消矢。稚贝期历时约45天.形成幼时时.足丝消失,完全转入埋栖生活。

Larval and Post-larval Development of the Clam, Mya arenaria Linnaens

According to the morphology and behavior the postembryonic development of the clam, Mya arenaria , under the cultivated condition could be devided into 5 stages; planktonic, first metamorphic, double living, second metamorphic and postlarval stages. The planktonic stage containing trocophora, veliger and umber larvae lasts about 5 days. The first metamorphic stage lasts about 5 days. The feet of the larvae are well developed and the statocysts and gillbuds are present. The larvae are still planktonic. The double living stage lasts about 10 days. The larvae are facultative with planktonic as dominant. The posterior part of the mantle is partially fused and the siphone formation begins. The second metamorphic stage lasts about -1 days. The velums atrophy and the larvae are almost completely creeping. At the early days of the postlarval stage a contractile membranous tube is present at the anterior end of the siphone and then atrophies along with the development. This stage lasts for 45 days. After young clams are formed the byssus disappear and the animals are completely burrowing.