Labrid cleaner fishes show kinematic convergence as juveniles despite variation in morphology

Cleaning, a dietary strategy in which mucus or ectoparasites are removed and consumed off other taxa, is performed facultatively or obligately in a variety of species. We explored whether species in the Labridae (wrasses, parrotfishes) of varying ecological specialization employ similar mechanisms of prey capture. In investigating feeding on attached prey among juveniles of 19 species of wrasses, we found that patterns of biting in wrasses are influenced by the interaction between the maxilla and a feature of the premaxilla which we term the maxillary crest. Premaxillary motion during biting appears to be guided by the relative size of the crest. In many cases, this results in a 'premaxillary bite' wherein the premaxillae rapidly move anteroventrally to meet the lower jaws and deliver a protruded bite. Cleaners in the Labrichthyini tribe, however, exhibited reduced or absent maxillary crests. This coincided with a distinct kinematic pattern of prey capture in these labrichthyine cleaners, coupled with some of the fastest and lowest-excursion jaw movements. Although evidence of kinematic specialization can be found in these labrichthyines (most notably in the obligate cleaners in Labroides), we found that facultative cleaners from other lineages similarly evolved reductions in excursions and timing. Convergence in feeding kinematics is thus apparent despite varying degrees of cleaning specialization and underlying morphological features.