Kubota Shin
Seto Marine Biological Laboratory, Field Science Education and Research Center, Kyoto University, Shirahama, Wakayama 649-2211, Japan.
Zoolog Sci. 2012 Aug;29(8):481-3. doi: 10.2108/zsj.29.481.
Circadial spawning times of medusa of the bivalve-inhabiting hydrozoans Eugymnanthea japonica Kubota and Eutima japonica Uchida are confirmed to be morning (possibly sunrise) for the former species and night for the latter. Eugymnanthea, with small, short-lived, univoltine medusae, seems to have evolved from a form similar to Eutima japonica, with larger, longer-lived, multivoltine medusae; the morning spawning of medusae in Eugymnanthea may therefore be a newly evolved trait. Medusa release from polyps and spawning of medusae are not synchronous in Eugymnanthea japonica. This non-synchrony may represent an evolutionarily transitional state leading to the most advanced state, synchrony of these two reproductive events, as in certain other ephemeral hydrozoan medusae.
栖息于双壳贝类的水螅虫类日本优美水母（Kubota）和日本真蒂水母（Uchida）的昼夜产卵时间已得到确认，前者为早晨（可能是日出时），后者为夜晚。优美水母具有小型、寿命短、一年生的水母，似乎是从类似于日本真蒂水母的形态进化而来，后者的水母体型更大、寿命更长、多世代生；因此，优美水母早晨产卵可能是一个新进化出的特征。在日本优美水母中，水螅体释放水母和水母产卵并不同步。这种不同步可能代表一种进化过渡状态，通向像某些其他短暂水螅虫类水母那样的这两种生殖事件同步的最先进状态。
