Аннотация:Eubranchus rupium is a common nudibranch species in the White Sea. The representatives of the species are drill-feeders and feed on colonial hydroids of genus Obelia. E. rupium has a planktonic larva – veliger, which settles on the Obelia colony then metamorphoses. The juvenile individuals may be subdivided into six categories according to their external morphology. We called these categories post-larval stages, where the first stage appears after the settlement and metamorphosis of the veliger and the sixth stage is represented by a fully matured adult individual. All the stages inhabit Obelia colony and may be found together. Beginning from the first stage the juveniles switch to the drilling feeding mode, which is characteristic for adult individuals. Here, we study the morphology of the buccal complex in different post-larval stages of ontogenetic development of Eubranchus rupium.
The general morphology of post-larval stages’ buccal complexes was studied by confocal laser scanning microscopy and scanning electron microscopy. The general morphology of adult molluscs’ buccal complex was studied by confocal laser scanning microscopy, light microscopy and scanning electron microscopy. The 3D-reconstruction of the buccal complex of the adult specimen was constructed as well.
According to our data, even the first post-larval juvenile stage has similar groups of buccal muscles and the radula and the jaws of similar morphology as the adult individuals. During body growth, the size of buccal complex proportionally increases. Unlike nudibranchs of the genus Dendronotus young specimens of Eubranchus rupium have the same feeding objects and the same feeding mode as the adult ones; that is why the radula in small ones is the same as in adults. As the buccal armature in young and mature animals is identical, the buccal musculature should be the same in juvenile and adult specimens.
The study was funded by RFBR according to the research project № 18-34-00251.