Sensory and behavioral ontogeny of three species of sciaenids and the importance of habitat.

摘要

The sensory and behavioral development of three species of sciaenid larvae with different patterns of habitat use were examined. Atlantic croaker, Micropogonias undulatus, larvae spend the early part of their development offshore, and even after arriving inshore spend relatively little time in seagrass nursery habitats. Red drum, Sciaenops ocellatus, larvae occur inshore throughout most of the larval period and utilize seagrass nursery habitats, although not exclusively. Spotted seatrout, Cynoscion nebulosus, larvae develop entirely inshore and are strongly associated with seagrass nursery habitats. Changes in the visual system were examined by measuring photoreceptor densities, theoretical acuity and theoretical sensitivity of the eye. Changes in the mechanosensory system were examined by counting neuromasts and documenting lateral line canal formation. Behavioral development was assessed by examining response to an anti-predator stimulus. Visual and mechanoreceptive attributes of these three species differed most near the end of the larval period when habitat differences are most pronounced. Atlantic croaker had more visual specializations than the other species with large eyes, more rod (low-light) photoreceptors and higher sensitivity (summation) of photoreceptors. Seatrout had more abundant neuromasts but poorer visual measures relative to the other two species. Red drum were intermediate in sensory morphology, with neuromast numbers that were slightly higher than both species for a portion of the early larval period and visual attributes that were slightly better than seatrout during the late larval period. Use of these sensory systems for anti-predator behavior roughly corresponded to differences in the development of sensory structures, with Atlantic croaker depending most on vision, red drum depending more on mechanoreception, and seatrout depending almost entirely on mechanoreception. Behavioral development also relates to the habitats occupied by each species. Between offshore and deep water habitats after settlement, croaker inhabit primarily open water habitats where vision is unobstructed. Seatrout and red drum inhabit more shallow, structured habitats where seagrass can reduce visual contact between predators and prey and therefore rely more on mechanoreception to detect predators. Thus, development of these three species differs so that sensory capabilities are most appropriate for the habitats that each species predominantly occupies.