, Volume 9, Issue 2, pp 87-101

Scale-eating in characoids and other fishes

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Synopsis

Scale-eating is known for several unrelated fish groups, but few data are available on the habits of most species. General habits and feeding behavior of some lepidophagous characoids are presented and compared to other scale-eating species. The diversity of morphology, habits, and behavior of scale-eating fishes is great, and few patterns are shared by the specialized scale-eaters. Except for modified teeth, no morphological characteristic permits identifying a fish as a specialized lepidophage. Hunting tactics consist mainly of ambush, stalking, or disguise (aggressive mimicry). Scale-removal may be accomplished by a jarring strike with the snout, generally directed at the prey's flank, or by biting or rasping. The mode of scale-removal seems to reflect primarily the disposition of the jaws and the teeth. Scales are swallowed directly if taken in the mouth; if not, they are gathered as they sink, or picked up from the bottom. Scale-eating is probably a size-limited habit. Specialized scale-eaters rarely exceed 200 mm, most ranging near 120 mm. Some species eat scales only when young; most take other food items in addition to scales. Scale-eating habits probably arose from trophic or social behaviors. These are not mutually exclusive and, indeed, may have acted together during the evolution of lepidophagy. Suggested trophic origins include scraping epilithic algae, modified piscivory, and necrophagy. Social origins include intra- and interspecific aggressive behavior during feeding.