Tsuchiya Kaori, Hayashi Fumio
Department of Biology, Tokyo Metropolitan University, Minamiosawa 1-1, Hachioji, Tokyo 192-0397 Japan.
Springerplus. 2014 Mar 17;3:144. doi: 10.1186/2193-1801-3-144. eCollection 2014.
Male genitalia in several insect species are asymmetry in right and left shape. However, the function of such asymmetric male genitalia is still unclear. We found that the male genitalia of the damselfly Calopteryx cornelia (Odonata: Calopterygidae) are morphologically symmetric just after emergence but asymmetric after reproductive maturation. Males remove rival sperm stored in the female bursa copulatrix (single spherical sac) and the following spermatheca (Y-shaped tubular sac) prior to their own ejaculation to prevent sperm competition. Males possess the aedeagus with a recurved head to remove bursal sperm and a pair of spiny lateral processes to remove spermathecal sperm. The right lateral process is less developed than the left, and sperm stored in the right spermathecal tube are rarely removed. Experiments involving surgical cutting of each lateral process demonstrated that only the left process functions in spermathecal sperm removal. Thus, males of C. cornelia are left-handed in their sperm removal behaviour at copulation.
在几种昆虫物种中，雄性生殖器的左右形状不对称。然而，这种不对称雄性生殖器的功能仍不清楚。我们发现，豆娘Cornelia calopteryx（蜻蜓目：色蟌科）的雄性生殖器在刚羽化后形态上是对称的，但在生殖成熟后则不对称。雄性在自己射精之前会清除储存在雌性交配囊（单个球形囊）和随后的受精囊（Y形管状囊）中的竞争对手的精子，以防止精子竞争。雄性拥有一个头部弯曲的阳茎以清除交配囊中的精子，以及一对有刺的侧突以清除受精囊中的精子。右侧突比左侧突发育程度低，储存在右侧受精囊管中的精子很少被清除。涉及对每个侧突进行手术切割的实验表明，只有左侧突在清除受精囊精子中起作用。因此，Cornelia calopteryx的雄性在交配时清除精子的行为是“左撇子”。
