アコヤガイ増殖に関する研究-IV : 貝殻外形の雌雄差について

概要

論文の詳細を見る
Sexual difference in the external shape of the shell of the pearl oyster Pinctada martensii has been investigated. The materials used for this investigation were 3 or 4-years old bivalves, which were collected at the coast of Hiwasa, Tokushima Prefecture. The dimensions in the length of shell (L), in the height of shell (H) and in the length of hinge line (hi) were measured respectively as shown in Fig. 1. The sexes were determined anatomically, being exactly ascertained their gonads. As the result of measurement, Fig. 2 indicates the frequency polygon of each sex, in the dimensions of L/H×100 and hi/H×100. The distributions are supposed to be normal frequency curves (Table 1). The curves of the relative growth (L/H) are shown in Fig. 3. In these two figures, the male type of shell is not clearly different from the female one. On the other hand, the three types of shell (L>H, L<H and L=H types) are distinguished without regard to both sexes, as shown in Fig. 4. And, in these three types, the percentages for the male shells are always higher than those for the female ones (Table 2). Therefore, it is difficult to distinguish the sexual difference in the external shape of the shell.