Ultrastructural study of the jaw structures in two species of Ampharetidae (Annelida, Polychaeta)статья
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Дата последнего поиска статьи во внешних источниках: 18 июля 2013 г.
Аннотация:Two species of jaw bearing Ampharetidae (
Adercodon pleijeli
(Mackie 1994) and
Ampharete
sp. B) were investigated in order to describe the microanatomy of the
mouth parts and especially jaws of these enigmatic polychaetes. The animals
of both studied species have 14–18 mouth tentacles that are about 30
μ
m in
diameter each. In both species, the ventral pharyngeal organ is well developed
and situated on the ventral side of the buccal cavity. It is composed of a ventral
muscle bulb and investing muscles. The bulb consists of posterior and anterior
parts separated by a deep median transversal groove. In both species, the
triangular teeth or denticles are arranged in a single transversal row on the
surface of the posterior part of the ventral bulb just in front of its posterior
edge. There are 36 denticles in
Adercodon pleijeli
and 50 in
Ampharete
sp. B.
The height of the denticles (6–12
μ
m) is similar in both species. Each tooth is
composed of two main layers. The outer one (dental) is the electron-dense
sclerotized layer that covers the tooth. The inner one consists of long microvilli
with a collagen matrix between them. The thickness of the dental layer ranges
from 0.95 to 0.6
μ
m. The jaws of the studied worms may play a certain role in
scraping off microfouling. The fine structure of the jaws in Ampharetidae
is very similar to that of the mandibles of Dorvilleidae, the mandibles and the
maxillae of Lumbrineridae, Eunicidae and Onuphidae, and the jaws of other
Aciculata. This type of jaw is characterized by unlimited growth and the absence
of replacement. The occurrence of jaws in a few smaller Ampharetidae is
considered as an apomorphic state.