ヨメガカサ<i>Cellana toreuma</i> (Reeve) の環境と介殻の變異

Abstract

Cellana toreuma (Reeve) is a very common Japanese littoral limpet which is distributed from Hokkaidô to Ryûkyû. The present paper deals with its shell variations in relation to its environments, especially to the level of its habitat and to the roughness of the coastal waves to which it is exposed. The variations in question were studied by determining two ratios, namely, Length/Height (L/H) and Length/Breadth (L/B) of the shell with the following results: - 1. The value of L/B is larger in the high water limpet than in the low water one and that of L/H is smaller in the former than in the latter. 2. When we compare limpets which live at high level, exposed to rougher waves with those which are found at equal level but on calmer shore, it is found that the value of L/H is smaller in the former than in the latter, but the reverse is the case with that of L/B. In other words, the shell is more highly spired and more circular at rough water than at calm water. 3. For this reason, we can hardly find the difference due to the level of the habitat of those limpets which are not subjected to rougher waves. 4. The limpet that rows on a rough surface of the rock has rough shell and the one that grows on a smooth surface has smooth shell. Since the lower the level, the rougher the rock-surface, the low water limpets are, generally saying, roughly sculptured and the, high water ones smoothly.