Title: American malacological bulletin
Identifier: americanmal4519861987amer (find matches)
Year: 1983 (1980s)
Authors: American Malacological Union
Subjects: Mollusks; Mollusks
Publisher: (Hattiesburg, Miss. ?) : (American Malacological Union)
Contributing Library: Smithsonian Libraries
Digitizing Sponsor: Biodiversity Heritage Library

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112 AMER. MALAC. BULL 5(1) (1987)
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0.90- '0.2 0.3 0.4 0.5 mm AL / 30 DAYS 0.6 Fig. 4. Interpopulation variation in the population mean shell calcium carbonate content (mg CaC03/mg total shell weight) (y axis) in relation to annual population shell growth rate in mm aperture length per 30 days (mm AL/30 Days) (x axis) for Irish Ancylus fluviatilis. Open circles are mean shell calcium content values of each population for which collection sites are indicated by adjacent numbers (see Tables 1 and 2). Vertical bars are standard errors of the means. No significant correlation (P > 0.5) existed between mean population shell calcium car- bonate content and growth rate (see Table 4 for regression parameters). were larger than 4.5 mm Al yielding erroneous estimations of the shell CaC03 weight of a standard individual) proved to be significantly linearly correlated with annual population growth rate (mm AL/30 days) (a = 1.55, b = 2.98, n = 26, r = 0.477, F = 7.06, P < 0.05) (Fig. 5). Both the population mean shell AL/AW and AW/SH ratios of a standard 4.5 mm AL individual were significantly (P < 0.005) linearly correlated with shell growth rate when ratio and growth rate data were transformed into common logarithms (Table 4). The AL/AW ratio decreased markedly with increasing population shell growth rate (r = 0.638, F = 19.881, n = 31, P < 0.001) (Table 4) such that populations characterized by high shell growth rates tended to consist of individuals with rounder shell apertures of greater relative area (Fig. 6). The population mean AW/SH ratio of a stan- dard 4.5 mm AL individual was highly positively correlated with annual population shell growth rate (r = 0.530, F = 11.329, n = 31, P 0.5). Initially this result ap- peared rather incongruous as the AL/SH ratio, like the AW/SH ratio, is a measure of shell steepness or elevation. It might be presumed that if the AW dimension increases relative to SH in individuals from faster growing populations, then AL should also display a proportionate increase in relation to SH. However, AL decreases relative to AW in individuals from faster growing populations (Fig. 6, Table 4). This decrease in AL relative to AW in individuals from very fast growing populations results in a disproportionate decrease in the AL/SH ratio compared to the AW/SH ratio. Therefore, mean AL/SH ratios of faster growing populations did not increase as population growth rates surpassed 0.5 mm AL/30 days (Fig. 8), resulting in a statistically insignificant relationship

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