The Evolutionary Significance of Intra-cohort Cannibalism in Larvae of a Xeric-inhabiting Salamander: An Inter-cohort Comparison
2005
COHEN, MIRIAM | Pelem, Raṿit | SHARON, RAKEFET | IFRACH, HADAS | YEHESKELY-HAYON, DANIELLA | WARBURG, MICHAEL R.
Cannibalistic behaviour in seven Salamandra salamandra infraimmaculata half-sib cohort larvae (each born to a single female and at the same time) and in juveniles was studied under different food and density conditions. The level of cannibalistic behaviour (tails bitten off or larvae eaten) changed as the larvae grew, from a low level during the first week to a peak at five weeks, regardless of differences in mass between the experimental larvae. No cannibalistic behaviour was observed in post-metamorphic salamanders even if they were cannibalistic as larvae. Significant differences in levels of cannibalism were found among different cohorts. Whereas in one cohort only 7% of the larvae were cannibalistic, in another, the cannibalism level peaked at 70% thereby indicating a possible maternal effect. However, cannibalistic behaviour in salamander larvae was apparently not related to the mother's age. The effect of food and density on cannibalism seems to be indirect or of secondary importance. Thus, cannibalism level was similar when food was scarce or when fed ad-libitum, whereas larvae offered a high level of food were significantly more cannibalistic. This could indicate that an optimum food level triggers cannibalism. When food becomes abundant the need for cannibalism ceased to persist. Under xeric conditions, ponds dry out rapidly; consequently rapid development through cannibalism results in earlier metamorphosis essential for this species' survival because of the limited time for dispersal of juveniles.
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