. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 336 S. P. LEYS AND B. M. DEGNAN. V Figure 10. Diagram describing the suggested mechanism by which the pigment ring and long posterior cilia allow Reneira sp. larvae to steer away from a light source. (A) As the larva rotates, light from one side of the larva impinges on the base of the cilia closest to the light, but is blocked by the pigment ring from the cilia furthest away from the light. (B) Cilia exposed to the light (arrow) straighten or beat rapidly, depending on the extent of their exposure; those hidden from the lig
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 336 S. P. LEYS AND B. M. DEGNAN. V Figure 10. Diagram describing the suggested mechanism by which the pigment ring and long posterior cilia allow Reneira sp. larvae to steer away from a light source. (A) As the larva rotates, light from one side of the larva impinges on the base of the cilia closest to the light, but is blocked by the pigment ring from the cilia furthest away from the light. (B) Cilia exposed to the light (arrow) straighten or beat rapidly, depending on the extent of their exposure; those hidden from the light by pigment (arrowhead) un- dergo a shadow response and bend over the pigment ring. (C) The indi- vidual response of each cilium to light as the larva rotates causes a graded response taking the larva away from the source of light. Coordination of behavior and cellular differentiation in sponge larvae Cellular differentiation is integral to the behavior of Rc- neira sp. larvae. Five regions of the larva are distinctly differentiated (Fig. 11). The outer ciliated columnar epithe- lial layer of the larva is separated from the cells in the central region by a sheath or band of circumferential cells. A radial or circumferential sheath has been described in many parenchymella larvae as a subepithelial cell layer (Meewis, 1941; Brien, 1973; Woollacott, 1993). Although it has been suggested that the cells in this layer have a secre- tory function (Meewis, 1941), it is equally possible that, in light of the paucity of cell-cell junctions in these larvae, the circumferential subepithelial cells give structural support to the larva during release from the parent and during swim- ming. The cells of the anterior pole are differentiated in Reneira sp. larvae as well. Both the monociliated ciliated flask-shaped cells that occur towards the anterior end of the larva and the large cuboidal cells at the anterior pole have numerous small clear vesicles and may therefore have a secretory functi
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
