Fractal morphology of mechanosensory lateral-line canals in Stichaeidae

The marine teleost family Stichaeidae shows considerable variation in the morphology of mechanosensory lateral-line canals across its six subfamilies, 38 genera, and 82 species. Some species have reduced cephalic canals and no trunk canals, others have a full cephalic canal system and a single trunk canal that extends the length of the body, and others have complex, branched cephalic canals and multiple trunk canals with branching. In this study, fractal techniques are used to quantify the complexity of lateral-line systems of 21 species of Stichaeidae, representing all six subfamilies and the full range of mechanosensory system configurations within the family. The fractal dimension, D, ranged from 0.9769 in Bryozoichthys lysimus, which has reduced cephalic canals and lacks trunk canals, to 1.5704 in Phytichthys chirus, which has a complex cephalic canal network and multiple, complexly branching trunk canals. Species with more complex cephalic and trunk canals had higher values of D. The error associated with repeatedly measuring the same individual multiple times was consistently low, suggesting that fractal analyses is an accurate and precise method for quantifying the complexity of mechanosensory lateral-line canals. Such information may benefit studies of mechanosensory system evolution and function.