. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 218 N. A. KNOTT ET AL. orientations and, as a result, induction of passive flow may be more constrained. Yet many marine habitats, both inter- tidal and subtidal. experience water movement that can be predictable in both direction and strength (Wainwright and Dillion, 1969; Denny, 1988). In such habitats, there is the potential for unstalked ascidians to use dynamic pressure for assisted feeding, but this has not yet been demonstrated. The Bernoulli effect and viscous entrainment (Day, 1974; Vo- gel. 1978, 1994; Kott, 1989)
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 218 N. A. KNOTT ET AL. orientations and, as a result, induction of passive flow may be more constrained. Yet many marine habitats, both inter- tidal and subtidal. experience water movement that can be predictable in both direction and strength (Wainwright and Dillion, 1969; Denny, 1988). In such habitats, there is the potential for unstalked ascidians to use dynamic pressure for assisted feeding, but this has not yet been demonstrated. The Bernoulli effect and viscous entrainment (Day, 1974; Vo- gel. 1978, 1994; Kott, 1989) may also enable unstalked ascidians to induce passive flow from external water move- ment by positioning their exhalant siphons higher above the substratum than their inhalant siphons (Vogel. 1974, 1977; Allanson et 1992). P\nra stolonifera (Heller, 1978) is the common solitary ascidian found on intertidal rocky shores along the east coast of Australia (Kott, 1985). This unstalked ascidian has its inhalant siphon directed horizontally and its exhalant siphon higher and directed vertically (Fig. I; Day, 1974; Kott, 1985). Furthermore, casual observations suggested that the inhalant siphons of these ascidians were usually directed into the oncoming waves. We predicted that this arrangement and orientation of the siphons would induce passive flow through the ascidian. To evaluate whether P. stolonifera induces passive flow from the movement of water over intertidal shores, we investigated four questions; (1) whether the ascidian was nonrandomly oriented. (2) whether the arrangement of the ascidian's siphons was capable of inducing passive flow. (3) whether the orienta- tion of the ascidian affects the magnitude of passive flow, and (4) whether its orientation into the flow increases its feeding rate on the rocky shore. Materials and Methods Field orientation We surveyed the orientation of Pynra stolonifera at six rocky shores covering a wide range of wave exposures and orien
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
