File:American malacological bulletin (1987) (17968620458).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

View Book Page: Book Viewer
About This Book: Catalog Entry
View All Images: All Images From Book
Click here to view book online to see this illustration in context in a browseable online version of this book.

Text Appearing Before Image:
McMAHON AND WHITEHEAD: SHELL VARIATION IN ANCYLUS 113 between these two variables (Table 4). Of two different Co. Donegal river populations of An- cylus fluviatilis (Glennaddragh River and Croleavy Lough Outlet) collected at upstream and downstream locations, significant variation occurred in the mean shell CaC03 con- tent of individuals of approximately the same range of SL be- tween adult generations of the upstream (site 31R) and downstream Croleavy Lough Outlet collections (site 32). The mean shell CaC03 content of individuals from the downstream site (mean CaC03 content = 0.981) proved significantly greater than that of those from the upstream site (mean CaC03 content = 0.972) when tested by a Student's t-test (P < 0.05) (Zar, 1974) (Table 5). Significant differences also occurred between the means of all three morphmetric ratios of the 1984 juvenile generations collected at upstream and downstream sites on the Glennaddragh River (Table 5). Comparisons of shell mor- phometries of adult individuals could not be made for the Glennaddragh River as adults were not present in the upstream population sample (site 30) (Table 1). Students t-tests indicated that the mean AL/AW ratio was significantly lower and the mean AL/SH , and AW/SH ratios significantly higher (P 0.5) in Croleavy Lough Outlet (Table 5). Student's t-test also revealed significant differences between the mean shell CaC03 contents and shell mor- phometric ratios of populations of Ancylus fluviatilus collected at the same sites in different years. Of the six populations for which collections were repeated, the mean shell CaC03 contents of three populations differed significantly (P < 0.05) between 1982 and 1984. Mean shell CaC03 content was greater in adult limpets taken in 1982 (collection 3) than in those taken in 1984 (collection 23R) from the same site in an unnamed stream in Cashel, Co. Donegal, while the mean shell CaC03 contents of individuals taken in 1982 at both the Glen River, Straboy, Co. Donegal (collection 6) and an un- named stream in Derrylahan, Co. Donegal (collection 8) were significantly less than those of adults taken at the same sites in 1984 (collections 26R and 28R, respectively) (Table 6). In all cases the differences in mean SL and growth rate of these populations between 1982 and 1984 were negligible (Tables 1 and 2), thus, allometries of shell CaC03 content or weight could not account for these morphometric differences in shell mineral content. Of the six recollected populations, a significant dif- 4.5 o o O LXJ I CO O) E 4.0;- 3.5 3.0 2.5 2.0 1.5 -.44
Text Appearing After Image:
o°M O35 ,23 0.3 0.4 0.5 0.6 0.7 mm AL / 30 DAYS Fig. 5. Allometry of estimated population shell CaC03 weight (mg) of a standard 4.5 mm AL individual in relation to estimated annual shell growth rate in Irish Ancylus fluviatilis. The y axis is mg shell CaC03 weight estimated for a standard individual from least squares linear regres- sion equations relating mg shell CaC03 weight to aperture length for each population sampled. The x axis is annual population shell growth rate in mm aperture length per 30 days (mm AL/30 Days). Open circles are the estimated shell CaC03 weights of a standard 4.5 mm AL individual for each population as indicated by adjacent collection numbers (see Tables 1 and 2). Standard errors about each estimate were smaller than point diameter in all cases. The solid line represents the best fit of a significant least squares linear regression as follows: Shell CaC03 weight (mg) = 1.55 + 2.98 (mm AL/30 Days) (r = 0.477, n = 26, F = 7.06, P < 0.001).

Note About Images