Experimental evidence for a suction-biting performance tradeoff in Mesoamerican cichlids

Tradeoffs can occur when multiple functions are shared by a single mechanical system, where changes to the system that improve the performance of one function necessarily lead to a decrease in performance of a second function. The teleost oral jaws are a complex mechanical system, and a multifunction tradeoff is thought to exist between the opposing functions of suction-based and biting-based feeding. We experimentally measured suction- and biting-based feeding performance across 10 heroine cichlid species spanning a range of ecomorphological diversity to test for the presence of a suction-biting tradeoff. We found an inverse relationship between suction-based and biting-based feeding performance across species, as well as significant relationships between performance and morphological features of the oral jaws, where larger oral-jaw gape and greater protrusion were associated with improved suction-feeding and decreased benthic-feeding performance. We observed a fivefold range among species in biting rates during benthic-feeding trials, with a twofold range observed among benthic-feeding specialists, and propose that diversity in the properties of attached prey has generated diversity among biting-based specialists reliant on high-force bites versus those reliant on high biting rates.