. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 146 STEPHEN C. BROWN COLLAPSE OF RIM Pro* Para M Dist ParaM. DISK SHAPE Prox Para M Dist Para M Remoter M RETRACTION OF RIM Ant CircM Post Rod M SPHERICAL Obi Para M AntCirc M Ant RadM Trans M PostCrcM AXIAL DISPLACEMENT Promoter M Obi ParaM AXIAL DISPLACEMENT Remotor M Prox Para M FIGURE 12. Proposed muscle action during pump cycle, see text for details; periods of muscle shortening indicated by broad lines; maintenance of maximal contraction, narrow lines; active or passive resistance to elongation, dashed lines; passive e
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 146 STEPHEN C. BROWN COLLAPSE OF RIM Pro* Para M Dist ParaM. DISK SHAPE Prox Para M Dist Para M Remoter M RETRACTION OF RIM Ant CircM Post Rod M SPHERICAL Obi Para M AntCirc M Ant RadM Trans M PostCrcM AXIAL DISPLACEMENT Promoter M Obi ParaM AXIAL DISPLACEMENT Remotor M Prox Para M FIGURE 12. Proposed muscle action during pump cycle, see text for details; periods of muscle shortening indicated by broad lines; maintenance of maximal contraction, narrow lines; active or passive resistance to elongation, dashed lines; passive elongation, omitted. this phase. It is not possible to state, however, whether the proximal parapodial muscles resist being stretched by actively maintaining tonus, or by simply being elongated to their maximum length. Contraction of the remoter muscles appears to be responsible for inflating the lateral (parapodial) margin and keeping it closely pressed against the inner margin of the tube during the power stroke ( in the extended "disk shape" configuration). [For any muscle set to cause such marginal inflation, its contraction must force coelomic fluid from the main cavity into the peripheral region without simultaneously reducing the circumference of the segment. Close inspection of Figure 11 reveals that during the latter phases of the recovery stroke, the posterior wall rapidly loses its hemispherical compound curvature and assumes a more flattened shape. The volume of the coelomic fluid "lost" from the main cavity consequent upon this configuration change is the likely source of fluid required to inflate the parapodial margin. The criss-crossing slips of the remoter muscles are the only fibers whose shortening can accomplish this shape change in the main cavity]. The final shape of the margin, however, cannot be determined solely by the remoter muscles. The integument in this region is likewise too thin and elastic to maintain such a shape by itsel
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
