ИСТИНА

Mooreonuphis stigmatis as typical for Onuphidae (Eunicida) has a complex jaw apparatus consisting of ventral mandibles and dorsal maxillae. The replacement of maxillae apparatus in different stage of ontogeny of M. stigmatis was studied by light, scanning and transmission microscopy. Mandibles are not replaced trough all the life. M. stigmatis has three generations of maxillae based on general morphology. The first one appear in 4 chaetiger larvae and consist of asymmetric MX1, fused caudally in a carrier-like structure, symmetric MX2 and MX3. The left MX1 is much bigger then right one with numerous small denticles on the edge. MX2 are solid with denticles. MX3 are pair of small irregular shaped plates. The second generation of maxillae appears in 13–18 juveniles and similar to adult jaw. MX1 are paired sickle-like insignificantly asymmetric structures with a few denticles. The carrier-like structure paired. MX2 and MX3 are symmetric with denticles. The adult maxillae are typical for Onuphidae and observed in juveniles that are released to the environment. They consist of four paired maxillae and one unpaired MX3. MX1 are solid sickle-like structures with smooth edge connected by symmetry carrier-like part. MX2 are massive symmetric with danticles. The left elongated MX3 well developed and carry danticles. MX4 are oval plates and MX5 are small irregular shaped plates. The maxillae replacement occurs in different ontogeny stage (from 13 to 18 chaetegers larvae) and independent of number of chaetegers in different hatches. The studies of general and fine morphology of jaw in different stages showed that the maxillary elements formed by layer of gnatoblasts with short microvilli and one gnatoblast formed one denticle of maxillae.