Meeting Abstract
The fins of fishes are innervated with sensory nerves and specialized endings capable of providing feedback on the environment. Here we describe the morphology and distribution of a newly identified sensory ending in the pectoral and pelvic fins of two distantly related damselfish (Pomacentrus coelestis and Chromis viridis) that vary in their substrate association (rubble vs live coral specialist). Immunolabeling with a general neuronal marker revealed an extensive and precisely organized network of sensory fibers, a subset of which terminate in these newly identified bulbous endings. Although the physiology of these endings has yet to be determined, their anatomy suggests that they may be involved in taste perception. Located at or in close proximity to the epidermal surface, these receptors are small (~15 µm diameter) and are found primarily in the distal half of the fin. Despite differences in habitat and fin function, the general innervation patterns between the pectoral and pelvic fins were similar in both species. Along a given ray, endings exhibit stereotypical branching patterns with receptors linearly orientated to one another along the proximodistal axis of the fin. The leading and trailing edges of the paired fins exhibit the highest receptor densities with the distance between receptors ranging from 50 – 100 µm. As receptor density influences sensitivity and the ability to discriminate separate stimuli, the increased density observed along the edges of the paired fins suggests their importance as focal points for stimulus detection as the fins move through the water. In addition to further examining the function of these receptors, we aim to compare variation in the distributions of these receptors among fins and to other species known to exhibit chemosensory abilities via fins.
