Despite the acknowledged phenomenon that the biology of marine-fish larvae is considered different from that of juvenile and adult conspecifics, very little is known about the morphological and biomechanical changes that occur to the feeding apparatus of as they develop from hatching through metamorphosis. Moreover, our understanding of the consequences of these developmental changes for feeding performance and prey selectivity is limited. Starvation is often implicated as a leading cause of mortality during pelagic larval development. Since mortality during this life history stage is known to influence recruitment success and subsequent population dynamics of marine fishes, there is still a need to understand the processes that influence feeding success in marine-fish larvae. In this study, the relationship between the development of the feeding apparatus and feeding performance was examined in ten species of marine-fish larvae.

All ten species exhibited increased skeletal complexity through their development from developing cranial elements, articulations, and musculoskeletal linkages. 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 in all species around metamorphosis, the relative contribution of skeletal elements to the functional feeding apparatus was different among species. Four developmental transitions of the feeding apparatus were found in all species except in Amphiprion ocellaris, which exhibited only three transitions. Most species initiated first feeding during the the initial hyoid stage, characterized by rudimentary development of the hyoid apparatus and overall low neurocranium complexity. The complete hyoid stage typically occurred 3 days post hatching (dph), and was characterized by expansion of the cerato and epihyal cartilage, and increasing skeletal complexity. The initial opercular series stage exhibited ossification and separation of the upper and lower jaws, initial ossification of the opercular series and overall amassment of cranial elements until reaching the complete opercular series, which consisted of the full adult arrangement of the feeding apparatus. Amphiprion ocellaris exhibited more pronounced functional-morphological features of the feeding apparatus characteristic of the first feeding stage in the remaining nine species. The first feeding stage of these nine species was identified as the initial hyoid stage, characterized by rudimentary hyoid and suspensorium development, and a near total lack of other skeletal elements. Pseudochromis fridmani and Abudefduf saxatilis exhibited initial development and expansion of the palatine-quadrate cartilage, and Gobiesox strumosus exhibited relatively more robust cleithrum and pectoral fin development during the first feeding stage. Development of the feeding apparatus continued through metamorphosis to the adult arrangement although the relative contribution of skeletal elements varied throughout development.

This study showed high and variable levels of prey selectivity among species of marine-fish larvae. Among the species that consumed 35–90 and 91–270 μm zooplankton, calanoid copepods were the dominant prey type consumed. Still, there were high levels of prey selectivity within these broad prey types. Many species of marine-fish larvae appear to be generalist feeders capable of consuming a broad range of prey types. Rotifers and Artemia are novel prey types to most species of marine-fish larvae. Consumption of these prey types suggests adaptability in prey selectivity, but morphological features among these two prey type consumers was not noticed.