Scale-eating cichlids use different feeding techniques

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New video footage of scale-eating cichlids from Lake Tanganyika has shown marked differences in the way in which two related species feed.

Takahashi, Moriwaki and Hori studied video footage of Perissodus straeleni and Perissodus microlepis kept in their laboratory and found that the scale-eating techniques used were strikingly different, despite the fish being very closely related.

Their study, which was published in the latest volume of the Journal of Fish Biology, says that Perissodus straeleni presses and shifts its mouth laterally along the body of the prey fish, as the prey attempts to break free.

Perissodus microlepus rotates its body quickly, with both jaws pressed against the flank of the prey, in an attempt to twist the scales free so it can eat them.

The authors said that morphological adaptations in the dentition allow them to feed in a different manner: "Scanning electron microscopy of tooth shapes confirmed that dental morphology clearly differs between the two species: the teeth of P. straeleni are laminar and leaf-shaped with sharp edges along the lateral sides, whereas P. microlepis has thick, broad-based teeth with spine-like points in the upper corners.

"In addition, inspection of tooth condition in wild-caught fishes showed that the ratio of wearing teeth was significantly higher in P. straeleni than in P. microlepis.

"These results indicate that the functional morphology of the teeth plays an important role in their scale-eating actions; in P. straeleni, the sharp edges of the teeth appear to function as blades for scraping while shifting the mouth laterally along the body of the prey, whereas the spine-like projections on the teeth of P. microlepis appear to effectively catch scales while pressing and rotating the mouth, simultaneously wrenching off scales.

"These results clearly demonstrate that the different scale-eating behaviours of the two species are closely associated with the functional diversification of their jaw teeth."

For more information see the paper: Takahashi, R, T Moriwaki and M Hori (2007) - Foraging behaviour and functional morphology of two scale-eating cichlids from Lake Tanganyika. Journal of Fish Biology 70: 1458-1469.