Opening and slow closing movements
(Fig. 408–409) of the valves are governed by
fluctuations in pressure within the meta coelomic
body cavity and are generated by
contraction of the lateral muscle layers of the
body, which are composed of circulo-longitudinal fibers. This body cavity functions
as a single, fluid-filled chamber, although
partially divided by a gastric parietal
band and, with the coelomic canal of the
pedicle, acts as a fluid reservoir in the hydraulic
system. This system that opens the
valves performs the same function as the
elastic hinge ligament of the molluscs and
the diductor muscles of articulated brachiopods.
Quick closure is obtained by the contraction
of the anterior and posterior adductor
muscles. Scissor Like movements of the
valves occur by contraction of the well developed,
oblique muscles. This complex
body musculature sustains the unique, infaunal
mode of life of these brachiopods.
Opening and slow closing movements(Fig. 408–409) of the valves are governed byfluctuations in pressure within the meta coelomicbody cavity and are generated bycontraction of the lateral muscle layers of thebody, which are composed of circulo-longitudinal fibers. This body cavity functionsas a single, fluid-filled chamber, althoughpartially divided by a gastric parietalband and, with the coelomic canal of thepedicle, acts as a fluid reservoir in the hydraulicsystem. This system that opens thevalves performs the same function as theelastic hinge ligament of the molluscs andthe diductor muscles of articulated brachiopods.Quick closure is obtained by the contractionof the anterior and posterior adductormuscles. Scissor Like movements of thevalves occur by contraction of the well developed,oblique muscles. This complexbody musculature sustains the unique, infaunalmode of life of these brachiopods.
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