. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 402 N. W. BLACKSTONE AND L. W. BUSS. 40 80 AGE(DAYS) 120 Figure 4. Two colonies from each of 3 crosses (5x8, circles; 12 x 7, squares; and 3x4, triangles; the crosses are designated as in Table IV) were grown beyond 50 days on glass cover slips and measured for shape (perimeter/y area). Lines connect values for each colony: 2 colonies reached the edges of the cover slips in 12 X 7 > 3 X 4). The biological basis of shape The results presented show a strong correlation between measures of peripheral stolon development and p
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 402 N. W. BLACKSTONE AND L. W. BUSS. 40 80 AGE(DAYS) 120 Figure 4. Two colonies from each of 3 crosses (5x8, circles; 12 x 7, squares; and 3x4, triangles; the crosses are designated as in Table IV) were grown beyond 50 days on glass cover slips and measured for shape (perimeter/y area). Lines connect values for each colony: 2 colonies reached the edges of the cover slips in 12 X 7 > 3 X 4). The biological basis of shape The results presented show a strong correlation between measures of peripheral stolon development and pcrim- eter/^area in Hydractinia. Previous work (McFadden et 1984; Yund, 1987; Buss and Grosberg, 1990) suggests that peripheral stolon development is correlated with competitive ability in Hydractinia. Thus, shape as mea- sured by perimeter/}'area will show a similar correlation. Further, Podocoryne shows more irregular shapes than Hydractinia and thus greater peripheral stolon develop- ment; this result agrees with its competitive dominance over Hydractinia in laboratory studies (McFadden, 1986). The correlations of shape with competitive ability can make measures of shape useful to biologists, but clearly shape differences are not causally related to competitive ability (see discussion below). Rather, shape, competitive ability, and peripheral stolon development are likely cor- related consequences of the underlying dynamics of growth in these hydroids. Shape measures bear a clearly interpretable relation- ship to these growth dynamics. Examining Figure 1 suggests that perimeter/Marea will measure the degree to which stolons extend from a central ring stolon or network of ring stolons. Stolons encase the gastrovascular canals; the combined actions of stolons and, in particular, muscular polyps drive the gastrovascular fluid through the canals and nourish the colony (see Schierwater et in press). Since the gastrovascular system is closed, peripheral sto- lons are ess
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
