. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. HYDROBIA MORPHOLOGY AND SYSTEMATICS 211 whorls are seen. The convexity of whorls is greatly variable in a population, from slight to pronounced; sutures are correspondingly shallow to moderately deep. The length of the body whorl is greater than that seen in H. truncata, less than that seen in H. salsa (Fig. 9). The umbilical opening is rimate to moderately open. The shell length ranges from to mm, depending on the population ; given all whorls, the length of the largest specimens ranges from to mm. The s
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. HYDROBIA MORPHOLOGY AND SYSTEMATICS 211 whorls are seen. The convexity of whorls is greatly variable in a population, from slight to pronounced; sutures are correspondingly shallow to moderately deep. The length of the body whorl is greater than that seen in H. truncata, less than that seen in H. salsa (Fig. 9). The umbilical opening is rimate to moderately open. The shell length ranges from to mm, depending on the population ; given all whorls, the length of the largest specimens ranges from to mm. The shells of the seven populations are compared for five variables (Table I). Considering size alone (column 1), specimens of H. truncata from Salt Pond are the largest. However, as seen, absolute size varies considerably among populations of a species. Accordingly, the species cannot be simply identified on the basis of size. Specimens of H. salsa have the widest shell per size (column 2). Again, there is considerable variation among populations of a species. There is a clear difference between H. truncata (all populations), and H. salsa and H. tottcni in length of body whorl per size (column 3). There is a difference between H. truncata, and H. salsa and H. totteni in length of aperture per size (last column). Considering the above descriptions and Table I, there is much more similarity between shells of H. totteni and H. salsa than between either of these and H. truncata. Further differences among populations and species are seen in Figures 8-10. The ratio of length of body whorl is plotted against length of the last three whorls for shells of six populations (Figs. 9, 10). The regression for pooled data from the six populations was highly significant (P = ) yielding a formula of y = to Considering each population separately, the regression was 02 /A A ;. FIGURE 8. Analysis of shells from five populations involving the relationship of the width of the 4
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
