Abstract
The dispersal of marine larvae determines the level of connectivity among populations, influences population dynamics, and affects evolutionary processes. Patterns of dispersal are influenced by both ocean currents and larval behavior, yet the role of behavior remains poorly understood. Here we report the first integrated study of the ontogeny of multiple sensory systems and orientation behavior throughout the larval phase of a coral reef fish—the neon goby, Elacatinus lori. We document the developmental morphology of all major sensory organs (lateral line, visual, auditory, olfactory, gustatory) together with the development of larval swimming and orientation behaviors observed in a circular arena set adrift at sea. We show that all sensory organs are present at hatch and increase in size (or number) and complexity throughout the larval phase. Further, we demonstrate that most larvae can orient as early as 2 days post-hatch, and they swim faster and straighter as they develop. We conclude that sensory organs and swimming abilities are sufficiently developed to allow E. lori larvae to orient soon after hatch, suggesting that early orientation behavior may be common among coral reef fishes. Finally, we provide a framework for testing alternative hypotheses for the orientation strategies used by fish larvae, laying a foundation for a deeper understanding of the role of behavior in shaping dispersal patterns in the sea.
Highlights
The dispersal of marine larvae determines the level of connectivity among populations, influences population dynamics, and affects evolutionary processes
Analysis of the morphology of the sensory organs in E. lori indicated that the ontogenetic trajectories of each of the sensory systems are unremarkable in comparison to those in other fishes, but some functional inferences could be made
The mechanosensory lateral line system is comprised of 22 diamond-shaped neuromast receptor organs located in the epithelium of the head and trunk (Fig. 1b: 0 dph), and neuromast number increases gradually throughout the larval phase
Summary
The dispersal of marine larvae determines the level of connectivity among populations, influences population dynamics, and affects evolutionary processes. There is empirical evidence that the late-stage larvae of many marine fishes have strong swimming abilities[4,5,6,7,8] and can orient their movements[9,10,11,12,13] in response to one or more types of sensory c ues[14,15,16,17,18,19,20] This suggests that the behavior of late-stage larvae plays an active role in determining their ultimate dispersal trajectories[21]. To our knowledge, no empirical studies have simultaneously evaluated the ontogeny of multiple sensory systems, swimming abilities, and orientation behaviors throughout the larval phase due to the challenges faced in collecting or rearing an ontogenetic series of any reef fish species. The extent of larval dispersal in E. lori 36, which is relatively restricted compared to other species[40,41,42], combined with the observation that their swimming abilities improve throughout development[8], suggests that the behavior of E. lori larvae may actively influence their dispersal trajectories
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