WILMOT, A.*; DIDIER, D.; WEBB, J.: Morphology of the Lateral Line Canals of the Head in Chimaerid Fishes (Family Chimaeridae)

Most living chimaeroid fishes have a unique lateral line canal system consisting of open canals that appear as grooves on the head and trunk. Members of the Family Chimaeridae possess a unique canal morphology in which lateral line canals at the anterior of the head are enlarged with wide dilations along the length of the canal and at canal junctions. This characteristic is phylogenetically significant at the familial level. In an effort to explore the potential significance of this character at lower taxonomic levels a survey of 10 species of chimaerid fishes, 4 species of Chimaera and 6 species of Hydrolagus, were studied. Canal distribution and terminology was standardized and canal dilations were counted. The number of calcified rings supporting the canal between dilations was counted in cleared and stained specimens. Scanning electron microscopy and paraffin histology were used to examine morphology and development of lateral line canals in embryos and juveniles as well as determine the location of the neuromast organs within the canals. Number of lateral line canal dilations is highly correlated to the size of the specimen and appears to have no significant taxonomic value; however, the pattern of lateral line canals on the head and the morphology of the calcified rings are useful for distinguishing species. This detailed morphological study provides new characters for identification of species of chimaeroid fishes.