ИСТИНА

Species of the order Desmoscolecida are characterized by unusual appearance with prominent cuticular main ring covered with rough concretions. Most authors considered the concretions as a product of secretory activity. Riemann & Riemann (2010) basing on observations on behaviour of live desmoscolecoids conclude that concretions are mineral particle accumulations. Goal of this study is evaluation of both hypotheses of the cuticle structure as well as obtaining new data on other desmoscolecoid strucrures. Main subject is Tricoma albimaris Decraemer & Tchesunov, 1996 sampled in the sublittoral zone of the White Sea, Northern Russia; and additional Quadricoma sp. from Pacific deep sea. Methods are TEM and SEM microscopy, SEM detection of element composition. Results. Covering over the main rings looks as confused accumulations of irregular amorphous platelets or granules of various shape and size. No glands or any cells with secretory activity were revealed in the subcuticular epidermis. Analysis of element composition reveals clear peaks of silicium, aluminium, and iron that indicates the concretions are mineral accumulations resembling clay. The hypothesis of Riemann & Riemann (2010) is thus supported. Other results: large vesicular amphids are covered with thin cuticle which similar to the body cuticle and bears concretions. So-called ocelli known in most desmoscolecoid species incl. deepsea species are ovoid bodies with concentric striation and without evident sensory structures. The project is by grant RFBR N 12-04-00781.