ИСТИНА

Kamptozoa is a small group of invertebrate animals with unclear phylogenetic position. The investigation of kamptozoan integument ultrastructure can help to understand its relationships. It is known that Kamptozoan cuticle belongs to microvillous type and contains layers of crossing proteinaceous fibers. The cuticle ultrastructure on different parts of zooid body and stolon still haven't been investigated in detail. In this research the cuticle ultrastructure of two colonial species Barentsia discreta (Busk, 1886) and Pedicellina cernua (Pallas, 1774) was investigated. It is shown that the cuticle structure strongly differs on different parts of zooid and stolon. The cuticle of atrial cavity is a thin fibrous layer similar in structure with cuticle of Lophophorata, Echinodermata, Archyannelida and larval stages of many invertebrates. The cuticle of this type probably isn't able to provide reliable mechanical protection of integument because of its small thickness and friable consistency, but it doesn't prevent from metabolism with environment. The cuticle of calyx, stalk and stolon has two main layers: finest external osmiophylic layer and fibrous layer. In the rigid parts of colony (peduncle of B. discreta and stolon of both species) the cuticle has additional homogeneous layers. Thick fibers of cuticle in middle and lower parts of calyx form regular tiers. Each tier consists of two systems of obliquely placed fibers directed at an angle to each other that are demarcated by the fibers going in apical-basal direction. The cuticle of Kamptozoa is penetrated by epidermal microvilli that end with expanded tips formed capitate swellings on the cuticle surface. The formations similar to capitate swellings are described in cuticle of many Annelida. In general the cuticle structure of colonial Kamptozoa is very close to annelid cuticle structure. This study was supported by the President's Grant for the state support of leading science schools (NSh-1801.2014.4).