. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 582 R. B. LOWELL Fissurella lonaifissa Fissurella virescens. FIGURE 2. Lateral (top) and dorsal (bottom) views of tropical eastern Pacific limpet shells. See Figure 1 legend for further information. ate eastern Pacific, measurements were taken for six common species from the west side of San Juan Island, Washington (Lime Kiln Lighthouse, 48°3 I'M, 123°9'W; False Bay, 48°29rN, 123°4rW): Acmaeidae—Collisella digitalis, C. pelta, Notoacmea per- sona, N. scutum, Acmaea mitra; Fissurellidae—Diodora aspera (Fig. 1). In the tropi-
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 582 R. B. LOWELL Fissurella lonaifissa Fissurella virescens. FIGURE 2. Lateral (top) and dorsal (bottom) views of tropical eastern Pacific limpet shells. See Figure 1 legend for further information. ate eastern Pacific, measurements were taken for six common species from the west side of San Juan Island, Washington (Lime Kiln Lighthouse, 48°3 I'M, 123°9'W; False Bay, 48°29rN, 123°4rW): Acmaeidae—Collisella digitalis, C. pelta, Notoacmea per- sona, N. scutum, Acmaea mitra; Fissurellidae—Diodora aspera (Fig. 1). In the tropi- cal eastern Pacific, measurements were taken for six additional common species from the south side of Taboguilla Island: Acmaeidae—Collisella pediculus, Lottia (Scur- ria; Lindberg and McLean, 1981) stipulata; Fissurellidae—Fissurella longifissa, F. virescens; Siphonariidae—Siphonaria gigas, S. maura (Fig. 2). To measure the strengths of these real limpet shells, I used a procedure similar to that used for the shell models. The shells of newly killed limpets were mounted, while still wet, onto one shaft of a Monsanto (type W) tensiometer. As for the shell models, a mm diameter steel hook (in this case, attached to the other shaft of the tensiom- eter) subjected the edge of the shell to a prying force. The force required to break the shell was recorded. Hooks mm and mm in diameter were used for particu- larly small and large shells, respectively (Lowell, 1987); hook diameter had no sig- nificant effect on the force needed to break the shells (Lowell, 1985). To mount the shells securely enough to withstand the force required to break the shell, it was necessary to provide a greater surface area for the glue to attach than the area of the muscle scar. Since the shell model experiment showed that the area of ;st stress in a shell subject to a prying force is at the point of force application at irgin of the shell (see Results), the real shells were moun
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
