File:American malacological bulletin (1987) (18129965466).jpg

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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HORNBACH AND COX: ENVIRONMENTAL INFLUENCES IN PISIDIUM 61 Table 5. Median survival times for Pisidium casertanum of shell lengths < 1.2 mm from either Riopel Pond (RP) or Farriers Pond (FP) maintained under conditions of varying water hardness. Numbers in parentheses are standard errors. RP FP Number of Median Survival Number of Median Survival Water Individuals Time Individuals Time Hardness at start of (days) at start of (days) Experiment Experiment Very Soft 23 136.5 (34.1) 75 213.8 (10.8) Soft 39 45.7 (21.6) 108 227.7 (13.5) Hard 35 293.6 (39.1) 84 397.9 (31.5) Very Hard 17 217.5 (30.9) 70 257.5 (12.4) Pond* 31 542.9 (23.2) 137 615.0 (175.6) * - a control series that consisted of water from the pond of origin, i.e. pond water for clams from RP was water from RP and pond water for clams from FP was water from FP. Table 6. Allele frequency for 10 presumptive loci for 4 enzyme systems of Pisidium casertanum from Farriers Pond (FP) and Riopel Pond (RP). Nei's identity (I) was calculated from the frequency data. N is the number of individuals analyzed. Abbreviations follow Horn- bach ef al. (1980a) and Werth (1985). RP Enzyme Locus Popula- Allele I N System tion Frequency a b c PEP 1 FP RP 0.75 1.00 0.25 0 0.949 20 20 2 FP RP 1.00 1.00 0 0 1.000 20 20 3 FP RP 0.45 0 0.50 1.00 0.05 0.741 20 20 PGI 1 FP 0.25 0.75 0.316 20 RP 1.00 0 20 2 FP RP 1.00 1.00 0 0 1.000 20 20 EST 1 FP 1.00 0.00 1.000 27 RP 1.00 0.00 29 FP 1.00 0.00 1.000 27 2 RP 1.00 0.00 29 3 FP RP 0.44 1.00 0.55 0.00 0.625 27 29 PGM 1 FP 1.00 0.00 1.000 7 RP 1.00 0.00 9 2 FP RP 1.00 1.00 0.00 0.00 1.000 7 9
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200 400 600 800 TIME (DAYS) 1000 Fig. 8. Survivorship curves for Pisidium casertanum taken from two ponds (RP = Riopel Pond; FP = Farriers Pond) and reared in waters of various hardnesses. genotypic variation is consistent with the observed phenotypic variation (Berven ef al., 1979). The transfer experiments were too short to allow for the examination of environmental in- fluences on growth although variations in survivorship pat- terns did appear to have an environmental component since clams transferred from FP to RP had a decrease in survivor- ship while those transferred from RP to FP generally had an increased survivorship (Table 3), especially when consider- ing smaller (younger) clams. Since young clams from RP transferred to FP have survivorship rates less than those from FP and since those transferred from FP to RP also have lower survivorship than those from RP this could be a case of max- imizing selection (Berven ef al., 1979) where the phenotype is maximized in all cases. The data on survivorship and growth, however, are merely suggestive in this area and not conclusive. Despite the fact that environment seems to play a role in accounting for differences in life histories displayed by

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