. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 0 FLOW VELOCITY INCREMENTS Figure 6. Percentage of crabs feeding passively over a range of con- stant velocity flows. Each constant flow velocity indicated on the x axis was maintained for 10 min. All crabs fed only actively from 0 to cm s~'. An increasing percentage of crabs switched from active to passive feeding over the range of to cm s~'. At flows of cm s~' and above, all crabs fed exclusively in the passive mode. of feeding-fan movements. Thus, a distinct peak on the powe
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 0 FLOW VELOCITY INCREMENTS Figure 6. Percentage of crabs feeding passively over a range of con- stant velocity flows. Each constant flow velocity indicated on the x axis was maintained for 10 min. All crabs fed only actively from 0 to cm s~'. An increasing percentage of crabs switched from active to passive feeding over the range of to cm s~'. At flows of cm s~' and above, all crabs fed exclusively in the passive mode. of feeding-fan movements. Thus, a distinct peak on the power spectrum curve indicates a dominant activity rate, or frequency (on the A axis directly below the peak), that characterizes a distinct feeding mode. For both the left and right fans, two dominant power spectrum peaks rep- resent the distinct activity rates of active and passive feed- ing. Several peaks between the active and passive peaks represent intermediate frequency behaviors that occurred during the transition from active to passive feeding. Discussion Not all suspension feeders are able to switch between active and passive modes. The switch may increase feeding efficiency in at least several ways. First, passively feeding crabs are able to depend on an external ambient current to deliver suspended food particles to feeding structures; they therefore do not spend their own metabolic energy to pump water past food-capturing structures. They are also able to orient their feeding appendages optimally with respect to current direction. Baumiller (1988) demon- strated that fluid flux through a concave model filter (a concave-shaped mesh) oriented perpendicular to the flow with the concave side facing upstream was greater than fluid flux through a similarly positioned planar mesh. Spielman and Goren (1968) showed that particle capture efficiency depends on the orientation of filter fibers. These facts together offer an explanation for the consistent pas- sive-feeding orientat
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
