Morphogenesis and fine structure of the developing jaws ofMooreonuphis stigmatis (Onuphidae, Annelida)статья
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Дата последнего поиска статьи во внешних источниках: 8 августа 2017 г.
Аннотация:The morphology of the jaw apparatus of Mooreonuphis stigmatis was studied at different stages of devel-opment using light and electron microscopy as well as 3D reconstruction techniques. Three generationsof maxillary apparatuses were identified. The first (larval) type of maxillae was found in juveniles thathave from 4 up to 15 chaetigers. They are formed by short microvilli and have no capacity for continuousgrowth, as they are completely replaced by the subsequent generation of jaws. The second (juvenile)type of maxillae appears in individuals that have from 10 to 18 chaetigers. They are fully penetrated bylong microvilli and have a layer of collagen fibrils in the basicuticle. The third (adult) type of maxillae isfound in worms that have at least 92 chaetigers. These maxillae have long microvilli that penetrate theintermediate layer of the basicuticle but do not reach the thick collagen layer. The mandibles and twogenerations of maxillae (adult and juvenile) have the capacity for continuous growth. Previously, it wasthought that different types of jaw structures are characteristic of different annelid taxa (for example,Dorvilleidae, Adercodon, etc.). Our data suggest that all three types of structures are found during devel-opmental changes of the jaws in one species. The similarity between the larval maxillae of M. stigmatisand maxillary apparatus of Dorvilleidae supports the progenetic origin of the latter. The features of finemorphology suggest that the larval maxillae of Onuphidae have more chances to be fossilized than theadult maxillae. Consequently, the larval maxillae of labidognath Eunicida could be better represented infossil material, while the calcified adult maxillae have a lower preservation capacity.