Variation or species in aeolid nudibranchs

在一些海栖裸鳃类的种群中发现的“变异”在形态学上进行了研究，必要时也进行了分子学研究。他们有着不同的阴茎。这种差异在保存下来的标本中不易察觉，这应该是它们被认为是单一物种变异的原因。本研究还证明了Facelinella属的不成立，并对樱属中两个相似的种，即学名相同的种，用适当的不同名称进行了描述。这两种风成石的活体标本很容易通过一些外部特征（包括颜色图案）来识别，而当保存这些特征时，这些特征变得模糊，不再用于区分两者。在保存条件下，齿舌形态是区分它们的唯一特征，并对一种日本新记录的气溶胶衣原体Chlamylla acerica的颜色变化进行了研究。除颜色和大小外，外部形态没有差异，内部形态也没有差异，这强烈表明它是一个单一物种的变异。这一点也得到了线粒体COI区DNA比较的支持。通过这些研究，我们发现在活体条件下的外部形态比我们过去期望的物种鉴定提供了更多的信息。这将有助于通过照片和出版数据库来识别物种。目前正在根据生态学对这种变异进行研究。

"Variations" found in the population of some aeolid nudibranchs were examined morphologically, and also molecularly when necessary.Two color morphs of Facelinella quadrilineata were found to be two separate species. They possess very different penes. The difference is not easily detectable in preserved specimens, and this should be the reason why they had been considered to be variations of a single species. This study also proved that the genus Facelinella was invalid.Two similar species of the genus Sakuraeolis, which had been given a same scientific name, were properly described with suitable different names. Alive specimens of the two aeolids were easily identified by a few external characters including color pattern, while when preserved such characters become obscure and no longer useful to distinguish the two. The radular morphology was found to be the only character to distinguish them in preserved condition.Color variation of Chlamylla atypica, an aeolid newly recorded from Japan was also examined. For this aeolid no difference was found in external morphology except for color and size, nor in internal morphology, which strongly suggested that it was to be variation of a single species. This was also supported by comparison of mitochondorial DNA of COI region.With these studies completed with help of this grant-in-aid, it is revealed external morphology in alive condition provides much more information than we used to expect for species identification. This will encourages identification of species by photographs and publishing databases.A widely distributed aeolid with zooxanthellae, Pteraeolidia ianthina, is known to be differ in color among localities. This variation is now under investigation in the light of ecology.