Meeting Abstract
The ecomorphology of the mechanosensory lateral line (LL) system of teleost fishes with reference to the flow regimes that they inhabit is not well understood. The canal neuromasts (CN) and superficial neuromasts (SN) of the LL system occur in varying proportions among species. Several authors have documented relatively high numbers of CNs and low numbers of SNs in adult salmonids (Order Salmoniformes), which is unusual among teleosts. Brook trout (Salvelinus fontinalis), a commercially important species, is routinely raised in hatcheries and are available for study. Here we describe the morphology and distribution of the cranial CNs and SNs in alevin and fry to determine when the relative numbers of CNs and SNs observed in adults are established. An ontogenetic series (0-52 days post-hatch, dph; n=13 spec.; from wild-caught parents) were prepared for SEM. Length, width, and area of presumptive CNs (PCNs) and SNs were determined. By 14 dph (yolk sac still present), PCN and SN morphologies have diverged, with larger, oval PCNs and smaller, round SNs. By 45 dph (after feeding has begun), preopercular PCNs have begun to sink into a canal groove. Multiple PCNs are also found in each of the other canal series: supraorbital (n=12), infraorbital (n=10), preopercular (n=6), and mandibular (n=8). However, only 5 lines of SNs are present on the head; SN number is relatively low, especially when compared to that in stomiiforms (another group of basal euteleosts), and otophysans (e.g., zebrafish, tetras, goldfish), which have 100’s of SNs and tend to live under low flow conditions. The high number of cranial CNs may be related to their life in flowing water and the functional significance of this will be discussed.
