Meeting Abstract
The cranial canals of the salmonid mechanosensory lateral line system are well-developed in adults and contain more neuromast receptor organs than in other teleost fishes. Larvae (fry) emerge from the gravel after the yolk is absorbed, up to several months post-fertilization. We hypothesize that the comparatively long larval stage of salmonids, during which neuromasts can increase in number, explains adult LL morphology. An ontogenetic series of hatchery-reared brook trout (Salvelinus fontinalis) was used to describe the ontogeny and distribution of neuromasts from day-of-hatch (alevin, larvae), through the larval period, to 6 months post-hatch (parr, juveniles). SEM and histology showed that although all neuromasts sit on the skin surface, two distinct groups are evident even in young larvae: presumptive canal neuromasts (PCNs; which become enclosed in canals) and superficial neuromasts (SNs; which remain on the skin). SN and PCN number increase during the long larval period before PCNs are enclosed in bony canals. In addition, PCNs appear before SNs and then increase in size at similar rates so that PCNs tend to be larger than SNs. PCNs and SNs are both oval-shaped (but demonstrate variation in length:width ratio) with a central sensory strip containing sensory hair cells. These changes in neuromast number and morphology likely affect their sensitivity to water flows, which is especially important in high flow environments. During the early vulnerable stages of brook trout life history, such morphological changes are predicted to have important impacts on behavioral role, and ultimately survival. Funding: NSF Graduate Research Fellowship and a URI Enhancement of Graduate Research Award to AEJ.
