Hatching of an estuarine crab : characterization, activity, and putative role of a caseinolytic protease

本文报道了河口蟹Sesarma haematocheir（akate-gani）的蚤状幼体在0.5 - 1 h内从雌蟹体内同步孵化。孵化的三个方面进行了研究：酪蛋白分解活性，胚胎包膜结构的形态变化，和环境因素。孵化水（即，在其中孵化出带状疱疹的过滤培养基）含有酪蛋白分解蛋白酶，并且该蛋白酶的分子量通过凝胶过滤来估计。透射电子显微镜显示，信封（1.8 μ m厚）是由三个不同的layrs：外（E1），厚中间（E2），和薄内（E3）layr。外两层，结构上的信封的主要组成部分，在孵化过程中没有形态上的改变，但内层（E3）的孵化前11小时和3小时之间明显改变，这表明它的消化。胚胎被膜分离物的测定和形态学观察也表明，被膜被孵化水消化。低水温对卵孵化时间有显著影响，且对离体胚胎的影响远大于附着胚胎。盐度是无效的。本文还讨论了消化E3层的孵化机理。

The zoeas of an estuarine crab Sesarma haematocheir (akate-gani) hatch synchronously within 0.5 - 1 h from a female. Three aspects of hatching were studied : caseinolytic activity, morphological changes of the embryonic envelope structure, and environmental factors. Hatch water (i.e., the filtered medium in whcih zoeas have hatched) contains a caseinolytic protease, and the molecular weight of this protease was estimated on gel filtration. Transmission electron microscopy shows that the envelope (1.8 mum thick) is composed of three distinct layrs : an outer (E1), thick middle (E2), and thin inner (E3) layr. The outer two layrs, that are structurally the main components of the envelope, were not morphologically altered during hatching, but the inner layr (E3) was clearly altered between 11 h and 3 h before hatching, suggesting its digestion. The assay with isolates of the embryonic envelopes and morphological observations also suggested that the envelope is digested by the hatch water. The time of hatching was strongly affected by low water temperatures, and their effects were much stronger to the embryos detached from the female than female-attached embryos. Salinity was ineffective. Mechanisms of hatching based on the digestion of this (E3) layr has been discussed.