Rivest Brian R
Biol Bull. 1984 Dec;167(3):543-554. doi: 10.2307/1541408.
The Pacific nudibranch Palio (= Polycera) zosterae and the Atlantic P. dubia copulate in a manner different from that of most nudibranchs. Nudibranchs are hermaphroditic and normally copulate reciprocally, with the intromittant organ of one inserted in the vaginal opening of the other. P. zosterae and P. dubia lack a complete vaginal duct. Copulation is usually reciprocal but involves the piercing of the body wall by a barbed, eversible penial cirrus. If the cirrus injects exogenous sperm into the body wall or the haemocoel, the sperm are phagocytosed by blood cells. If the cirrus penetrates the gonad, exogenous sperm may be injected into a spermatogenic acinus. After traveling down the hermaphroditic duct to the anterior reproductive organs, these sperm presumably are sorted from endogenous sperm and stored in the receptaculum seminis. The organization of the reproductive system in Palio differs markedly from that in members of the closely related genus Polycera.
太平洋裸鳃类动物帕利奥（=多角海牛属）zosterae和大西洋的P. dubia的交配方式与大多数裸鳃类动物不同。裸鳃类动物是雌雄同体的，通常相互交配，一方的插入器官插入另一方的阴道口。P. zosterae和P. dubia没有完整的阴道管道。交配通常是相互的，但涉及到有倒刺的、可外翻的阴茎触须刺穿体壁。如果触须将外源精子注入体壁或血腔，精子会被血细胞吞噬。如果触须穿透性腺，外源精子可能会被注入生精腺泡。这些精子沿着雌雄同体管道下行到前部生殖器官后，大概会与内源精子分离并储存在贮精囊。帕利奥的生殖系统结构与亲缘关系密切的多角海牛属成员明显不同。
