リファレンス
Drilling in the dorid species Vayssierea cf. elegans (Gastropoda: Nudibranchia): Functional and comparative morphological aspects.
Mikhlina, A. L., Tzetlin, A. B., Ekimova, I. A., & Vortsepneva, E. V. (2019). Journal of morphology, 280(1), 119-132.
https://onlinelibrary.wiley.com/doi/full/10.1002/jmor.20922
要旨
The drilling mode of feeding is known from two clades of Gastropoda: Caenogastropoda and Heterobranchia. However, the level of convergence and parallelism or homology among these two lineages is unclear. The morphology of the buccal complex is well studied for drilling caenogastropods, but poorly known for drilling nudibranchs. It is also unclear whether the drilling feeding mechanism is similar between inside gastropods. Accordingly, a comparison between the feeding mechanisms of drilling nudibranchs and caenogastropods can help to understand the evolutional trends inside gastropods. In this study, we redescribe the morphology of the buccal complex of drilling dorid nudibranch Vayssierea cf. elegans, and compare it to that of previous investigations on this species and closely related dorid species. We describe the feeding mechanism of this species based on the obtained morphological and literature data and compare it to the feeding mechanisms described for drilling caenogastropods. The feeding apparatus of Vayssierea cf. elegans corresponds to the general morphology of the dorid buccal complex; that is, it has a similar arrangement of the buccal musculature and pattern of radular morphology. However, there are also adaptations to the drilling feeding mode similar to those found in Caenogastropoda: that is, specialized dissolving glands and lateral teeth with elongated pointed cusps; and even Sacoglossa: the specialized muscle for sucking. The feeding process of Vayssierea cf. elegans includes the same two stages as those described for drilling caenogastropods: (a) the boring stage, which is provided by mechanical and chemical activity, and (b) the swallowing stage.
コメント
オカダウミウシの口器周辺の形態を記載した論文．
オカダウミウシは磯でも簡単に採集できる種であるが，ウズマキゴカイの棲管に穴を開けて中を吸い出すという風変わりな食性を持つ種である．腹足類の中で穿孔を行う種はCaenogastropoda と Heterobranchiaという2グループで見られるが，そのうちCaenogastropoda では良く記載されているもののウミウシを含むHeterobranchiaでは情報が不足していた．そこでこの論文では穿孔を行うウミウシに着目してその口周りの形態を記載して先行研究の知見と比較している． 基本的な形態としてはウミウシの仲間のものを踏襲しているようだが，同時にCaenogastropodに見られる穿孔に特化した形態学的特徴も持ち合わせていたとのことである．機能に応じて離れた系統でも同様の形態が収斂進化したとも言えそうな，面白くてわかりやすい事例だなと思う．
