. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. =O= 4-6 6-8 8-10 10-12 12-16 Snail Size (mm) Figure 3. Size-mediated predator avoidance and death in Phyxella virgata. The upper figure (A) is the percentage of dead snails in each size class (shell length), the lower figure (B) represents the percentage of sur- viving snails in each size class above the waterline, in both predator (darkened circles) and predator-free control (open circles) treatments (n = 4 in both treatments). The error bars are standard errors of the mean. or crawlout was observed in the predator-free con
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. =O= 4-6 6-8 8-10 10-12 12-16 Snail Size (mm) Figure 3. Size-mediated predator avoidance and death in Phyxella virgata. The upper figure (A) is the percentage of dead snails in each size class (shell length), the lower figure (B) represents the percentage of sur- viving snails in each size class above the waterline, in both predator (darkened circles) and predator-free control (open circles) treatments (n = 4 in both treatments). The error bars are standard errors of the mean. or crawlout was observed in the predator-free control aquaria in either species. Of the 315 surviving P. trivolvis, 23 () had some shell damage due to crayfish. The damaged shells were not randomly distributed among the size classes. In the two largest size classes, and of the surviving 10-12 mm and 12-16 mm SL size classes were damaged, respectively. The two smallest (4-6 mm and 6-8 mm SL) size classes had fewer damaged shells than expected ( and , respectively), based on the number of snails originally available in each size class, while the interme- diate (8-10 mm SL) sized class had more damaged shells than expected, (X2 goodness-of-fit test, X2 = , = 4, P < ). In marked contrast, only one out of the 314 surviving P. virgala (in the 8-10 mm SL size class) showed shell damage due to crayfish manipulation. There was no difference in the predation intensity in aquaria housing P. trivolvis or P. virgata; the crayfish con- sumed equal numbers of P. virgata (86) and P. trivolvis Table I The influence l snail size on miwloiii hehavtur in Physella virgata mill Planorbella tnvolvis Variable: % dead Variable: % crawlout P. trivolvix P. virgata P trirohis P. virgala Factor () F F F F Predator presence () ;* ** *** *** Snail size (4, 24) * *** Predator X Size (4,24) * *** The table describes the summary of the ANOVA analyses. Each
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
