Yusa Yoichi, Takemura Mayuko, Miyazaki Katsumi, Watanabe Tetsuya, Yamato Shigeyuki
Faculty of Science, Nara Women's University, Kitauoya-nishi, Nara 630-8506, Japan.
Biol Bull. 2010 Jun;218(3):259-65. doi: 10.1086/BBLv218n3p259.
In the lepadomorph barnacle Octolasmis warwickii, individuals are often found attached to the scutum of conspecifics living externally on the crab hosts. To test whether these conspecific-attached individuals are dwarf males, as are known to occur in other suborders of barnacles, we compared the pattern of attachment, size-frequency distribution, and reproductive status of the conspecific-attached (Con-A) and crab-attached (Crab-A) individuals. Con-As were smaller than Crab-As. There was a positive relationship between the body size of Crab-As and the number of individuals on them. Con-As had longer penises than Crab-As of the same body size, and their testes were better developed. The four largest Con-As examined were brooding eggs. These results indicate that Con-As of O. warwickii are dwarf males, with a potential to become hermaphroditic. This represents the first known example of coexistence of males and hermaphrodites in the suborder Lepadomorpha. The mating group size of O. warwickii was smaller than in its hermaphroditic congeners but larger than in barnacles with dwarf males and females, which supports the current theories that group size is important for the evolution of sexuality patterns in barnacles.
在茗荷科藤壶沃氏八腕藤壶（Octolasmis warwickii）中，常发现个体附着在寄居在蟹宿主外部的同种个体的盾板上。为了测试这些附着在同种个体上的个体是否如在藤壶其他亚目中已知的那样是矮雄，我们比较了附着在同种个体上（Con-A）和附着在蟹上（Crab-A）的个体的附着模式、大小频率分布和生殖状态。Con-A个体比Crab-A个体小。Crab-A个体的体型与附着在其上的个体数量之间存在正相关关系。相同体型的Con-A个体比Crab-A个体的阴茎更长，且其睾丸发育得更好。所检查的四个最大的Con-A个体正在孵卵。这些结果表明，沃氏八腕藤壶的Con-A个体是矮雄，具有变为雌雄同体的潜力。这代表了茗荷亚目中已知的首例雄性和雌雄同体共存的例子。沃氏八腕藤壶的交配群体规模比其雌雄同体的同类物种小，但比有矮雄和雌体的藤壶大，这支持了当前的理论，即群体规模对藤壶性别模式的进化很重要。
