Linking functional morphology and feeding performance in larvae of two coral-reef fishes

Abstract

Despite the well acknowledged phenomenon that the biology of marine teleost fish larvae is much different from that of juvenile and adult conspecifics, very little is known about the changes in design of the feeding apparatus as larvae develop from hatching through metamorphosis. Furthermore, our understanding of the consequences of these developmental changes for feeding performance is very limited. In this study, we examined the relationship between the development of the feeding apparatus and feeding performance in larvae of Amphiprion ocellaris and Pseudochromis fridmani using cluster analysis, multi-dimensional scaling (nMDS), and canonical correspondence analysis (CCA). Several patterns emerge from our analyses. First, the state of development of the feeding apparatus increased in complexity through ontogeny, from a simple, hyoid-driven system at the onset of exogenous feeding to a more complex feeding system involving all adult functional elements of the cranium just prior to metamorphosis. Although the feeding apparatus converged to the hyoid-opercular-mandible linkage state around metamorphosis in both species, P. fridmani had a lesser developed hyoid-mandible linkage system relative to A. ocellaris at the onset of first-feeding. Second, first-feeding larvae fed on smaller, less elusive zooplankton. In contrast, larvae that survived beyond the first-feeding stage fed on more diverse prey types, including larger, more elusive zooplankton. Third, intra- and inter-specific variation in the development of the feeding apparatus is associated with variation in feeding performance. The post-hatch developmental trajectory in both species showed a pattern consistent with stage (i.e., ontogenetic state)-specific shifts in morphology and performance. Furthermore, the number of developmental transitions in both feeding functional morphology and feeding performance differ between species that exhibit contrasting incubation periods.