, Volume 113, Issue 4, pp 527-535

Fish guts as chemical reactors: a model of the alimentary canals of marine herbivorous fishes

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Abstract

The alimentary canals of marine herbivorous fishes are variously composed of a few basic structures strung together in series. We model the structures where digestive processes occur as chemical reactors following the model of Penry and Jumars: the stomach as a batch or continuous-flow stirred-tank (CSTR), the intestine as a plug-flow reactor (PFR), and the hindgut caecum as a CSTR. Other structures, where food is mechanically processed-gill rakers, pharyngeal mills, and muscular stomachs-are classified as gates. The optimality criterion for the model is the digestion of the most nutrient in the least amount of time. With the model we are able to predict gut configuration as a function of nutrient concentration and hypothesize that the guts of herbivorous fishes always have a PFR component and may or may not have a CSTR component. The Penry-Jumars model appears to provide a consistent theoretical framework for four main types of digestive mechanisms in marine herbivorous fishes and offers specific testable hypotheses on the feeding ecology and digestive physiology of four representative species of fish as well as other, still unstudied, herbivorous fishes.

Communicated by M. G. Hadfield, Honolulu
Contribution No. 68 from the Ocean Studies Institute, Long Beach, California 90840, USA