Ecology, Paleobiology and Evolutionary Constraint in the Octopus
Abstract:Packard (1972) proposed that the evolution of the coleoid cephalopods was largely a response to competition and predation from vertebrates in the Mesozoic. While recent paleontological discoveries necessitate modifying this scenario, it remains true that the shell-less condition, streamlined body form, visual acuity, closed circulatory system, and denning, body patterning and other complex behaviors help octopuses avoid their teleostean predators and persist in shallow, nearshore environments. There is currently no experimental evidence that teleost-octopod competition is important in shallow marine communities. However, field studies suggest an inverse relationship between predatory fishes and octopus population density. Where predatory fishes are absent, in a semi-isolated marine lake in the Bahamas, octopuses are two orders of magnitude more abundant than in Caribbean coastal communities. Octopuses are the top carnivores in the lake, where a constraint of morphological and behavioral evolution becomes important: dens are the limiting resource. Living in dens is also an evolutionary imperative in Caribbean coastal communities, but dens are plentiful and predation is limiting. Predation in the geologic past molded morphologies and behaviors well-suited to current, high-predation environments. These features become ecological constraints when the usual limitation of heavy predation pressure is lifted. I suggest using a modified version of Packard's scenario to organize and guide future research on octopus ecology and ethology.
Document Type: Research Article
Publication date: 1991-09-01
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