Comparative study of the diaphragm (gular membrane) in Terebelliformia (Polychaeta, Annelida)статья
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Дата последнего поиска статьи во внешних источниках: 18 июля 2013 г.
Аннотация:The structure and location of the diaphragm (gular membrane) was studied in five families of Terebelliformia:
Terebellidae, Trichobranchidae, Pectinariidae, Ampharetidae and Alvinellidae, using dissections, histology, and
scanning and transmission electron microscopy. Position, shape, and structure of the diaphragm differ in these taxa.
In Terebellidae and Pectinariidae the diaphragm is straight. In Trichobranchidae, Ampharetidae and Alvinellidae it
is funnel-shaped. Diaphragm possesses two contractile sacs in Terebellidae and Pectinariidae, one in Alvinellidae
and none at all in Trichobranchidae. The relative size and form of the sacs varied. Representatives of the family
Ampharetidae have one or two sacs or none at all. Four kinds of the diaphragm can be distinguished: strait with two
sacs, funnel-shaped with two sacs, funnel-shaped with one sac, funnel-shaped without sacs. In some Alvinellidae,
the diaphragm is fenestrated, while in all other taxa it is continuous. The wall of the sacs is more muscular than
the wall of the remaining diaphragm. The diaphragm is attached to the body wall at different levels: between the
third and fourth segments in pectinariids or between the fourth and fifth in terebellids, ampharetids, alvinellids
and trichobranchids. In most cases, the diaphragm contains two coelothelial layers with a well-developed extracellular
matrix in between, and one or two muscle layers. The maximum development of the muscle fibres occurs
in Terebellidae; probably related to the length of buccal tentacles. Significance of morphological and ultrastructural
peculiarities of the diaphragm is discussed.