Lucky Nahid Sultana, Ihara Ryo, Yamaoka Kosaku, Hori Michio
Department of Zoology, Division of Biological Science, Graduate School of Science, Kyoto University, Sakyo, Japan.
Zoolog Sci. 2012 May;29(5):286-92. doi: 10.2108/zsj.29.286.
Behavioral laterality is widely found among vertebrates, but has been little studied in aquatic invertebrates. We examined behavioral laterality in attacks on prey shrimp by the cuttlefish, Sepia lycidas, and correlated this to their morphological asymmetry. Behavioral tests in the laboratory revealed significant individual bias for turning either clockwise or counterclockwise toward prey, suggesting behavioral dimorphism in foraging behavior. Morphological bias was examined by measuring the curvature of the cuttlebone; in some the cuttlebone was convex to the right (righty), while in others, the cuttlebone was convex to the left (lefty). The frequency distributions of an index of cuttlebone asymmetry were bimodal, indicating that populations were composed of two types of individuals: "righty" and "lefty." Moreover, an individual's laterality in foraging behavior corresponded with the asymmetry of its cuttlebone, with righty individuals tending to turn counterclockwise and lefty ones in the opposite direction. These results indicate that cuttlefish exhibit behavioral dimorphism and morphological antisymmetry in natural populations. The presence of two types of lateral morph in cuttlefish provides new information on the relationship between antisymmetric morphologies and the evolution of individual laterality in behavioral responses in cephalopods. The implications of these findings for the interpretation of ecological meaning and maintenance mechanisms of laterality in cuttlefish are also discussed.
行为偏侧性在脊椎动物中广泛存在，但在水生无脊椎动物中却鲜有研究。我们研究了乌贼（Sepia lycidas）攻击猎物虾时的行为偏侧性，并将其与乌贼的形态不对称性相关联。实验室行为测试显示，个体在转向猎物时存在显著的顺时针或逆时针偏向，这表明在觅食行为中存在行为二态性。通过测量乌贼骨的曲率来检测形态偏向；有些乌贼骨向右凸出（右型），而另一些则向左凸出（左型）。乌贼骨不对称指数的频率分布是双峰的，这表明群体由两种类型的个体组成：“右型”和“左型”。此外，个体在觅食行为中的偏侧性与其乌贼骨的不对称性相对应，右型个体倾向于逆时针转向，而左型个体则相反。这些结果表明，乌贼在自然种群中表现出行为二态性和形态反对称性。乌贼中两种类型的侧化形态的存在为头足类动物中反对称形态与个体行为反应中偏侧性进化之间的关系提供了新信息。我们还讨论了这些发现对解释乌贼偏侧性的生态意义和维持机制的影响。
