Sullivan Charles H, Maugel Timothy K
Biol Bull. 1984 Oct;167(2):378-389. doi: 10.2307/1541284.
Embryos of the marine mud snail Ilyanassa obsoleta undergo early development within an egg capsule. After about a week of encapsulation, embryos hatch by releasing a chemical substance that removes the plug found at the apex of a capsule. However, the mechanism of action of this hatching substance remains poorly understood. To study how the hatching substance functions, we examined the composition of the egg capsule, particularly the plug region, to determine what the "substrate" of the hatching substance might be. We have also examined the formation and organization of the egg capsule to determine the origin and identity of the regions of a capsule that the hatching substance must remove. The results show that the Ilyanassa egg capsule is organized into four layers, the outer three of which are composed of protein and carbohydrate. Portions of the two inner layers of the capsule wall extend into the capsule apex and form the plug, which is dissolved by the hatching substance. The isolated capsule plug region contains three major glycoproteins resolved on sodium dodecyl sulfate-polyacrylamide gels. Therefore, the hatching substance may be a protease similar in action to the enzymes released by many other embryos at hatching.
海生泥蜗牛（Ilyanassa obsoleta）的胚胎在卵囊中经历早期发育。在被包裹大约一周后，胚胎通过释放一种化学物质来孵化，这种化学物质会移除位于卵囊顶端的塞子。然而，这种孵化物质的作用机制仍知之甚少。为了研究孵化物质的功能，我们检查了卵囊的组成，特别是塞子区域，以确定孵化物质的“底物”可能是什么。我们还研究了卵囊的形成和组织结构，以确定孵化物质必须移除的卵囊区域的起源和特征。结果表明，Ilyanassa卵囊由四层组成，其中外层的三层由蛋白质和碳水化合物构成。囊壁的两层内层部分延伸到卵囊顶端并形成塞子，该塞子会被孵化物质溶解。分离出的卵囊塞子区域在十二烷基硫酸钠-聚丙烯酰胺凝胶上可分辨出三种主要的糖蛋白。因此，孵化物质可能是一种蛋白酶，其作用类似于许多其他胚胎在孵化时释放的酶。
