. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. LUNULE FUNCTION IN MELLITA 565 CURRENT INDUCED FLOW. FIGURE 3. Illustration of flow tank experiment results. Schematic cross-section through the sand dollar shows water moving up through the lunule in response to a current. RESULTS Lunule growth analysis The population measured for lunule growth exhibited an allometric relation for the length of the two lateral and two posterior lunules (Fig. 1). The anal lunule showed a non-significant allometric trend in the same direction (Fig. 2). The slopes of the regression lines are s
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. LUNULE FUNCTION IN MELLITA 565 CURRENT INDUCED FLOW. FIGURE 3. Illustration of flow tank experiment results. Schematic cross-section through the sand dollar shows water moving up through the lunule in response to a current. RESULTS Lunule growth analysis The population measured for lunule growth exhibited an allometric relation for the length of the two lateral and two posterior lunules (Fig. 1). The anal lunule showed a non-significant allometric trend in the same direction (Fig. 2). The slopes of the regression lines are shown with the Bonferroni confidence intervals on the figures. The allometric relationships suggest that the lunules grow more rapidly than does the body. We feel confident that this is a real developmental pattern and not an artifact of adult size distribution, because sand dollar growth appears to be highly indeterminate. There is at least a two- or three-fold range in adult size (personal observation) and there is no reason to believe that large adults are the same age as small adults. There may be no functional significance in the allometric trend alone, but the allometry raises the possibility that the functional importance of the lunules differs as body size changes. Flow tank experiment The flow tank study illustrates an unusual property of the lunule: When an appreciable current (8 cm/sec or more) was passed over the sand dollar, water from the sand beneath the lunule was drawn up through the lunule (Fig. 3). This was probably due to a combination of Bernoulli effect and viscous entrainment, what Vogel (1977) has called "induced ; Although the process occurred to a small extent at very low current speeds, at higher speeds—above about 8 cm/sec— a significant stream of dye appeared in a few seconds. Field experiments We found strikingly little difference in the burrowing speed of five sand dollars before and after plugging their lunules: The mean time fo
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
