Ultrastructure of secondary body cavity in polychaetes of the family Phyllodocidae (Polychaeta, Annelida). 1. Polychaetes without developed bloody system [Russian]

摘要

Five species of polychaetes of the family Phyllodocidae (Phyllodoce groenlandica (Oerst.), Ph. maculata (L.), Eteone longa (Fabricius), Eulalia bilineata (Johnston), E. viridis (L.)) and some nectochaeta of the same family were studied. All the species studied are similar in morphology. Two unclear turuli represent dorsal longitudinal muscles; two distinct one, ventral longitudinal muscles. The entire circular musculature is absent. Dissepiments, being incomplete, are presented on the ventral side of the body and formed by muscle cells. Coelothelium is absent; coelomocytes were not found. Coelomic lining consists of simple myoepithelium, cells of which form differently developed appendages. Most numerous, developed and branched appendages are in large animals: Ph. groenlandica and Ph. maculata. Visceral and parietal cells of small phyllodocides have smaller appendages. Myoepithelium of nectochaeta forms no extensions. Large mesoderm cells need larger surface, through which exchange with coelomic fluid takes place. Small cells need smaller surface contact with coelomic fluid. The size of myoepithelial cells depends on the animal's size. The necessary surface area is provided by cytoplasmic appendages. Thus, the degree of developing the cytoplasmic appendages, their number, and branching are adaptive features.