A comparison of lateral line morphology of blue cod and torrentfish: two sandperches of the family Pinguipedidae

Parapercis colias (blue cod) and Cheimarrichthys fosteri (torrentfish) are two members of the family Pinguipedidae. They reside in habitats with different background levels of hydrodynamic activity and differ in their feeding ecology. The peripheral morphology of the mechanosensory lateral line system was investigated in each species. The torrentfish is the only freshwater member of this otherwise exclusively marine family. It resides in turbulent fast flowing habitats and feeds nocturnally on stream drift. Torrentfish have many superficial neuromasts and a simple unbranched canal system. In comparison the blue cod resides in sub-tidal slow flowing habitats, is a diurnal predator and has relatively few superficial neuromasts and a well-developed branching canal system. For these two species the background level of hydrodynamic activity does not appear to be the dominant selection pressure on lateral line morphology, in the case of the torrentfish in particular it is more compelling to view lateral line morphology in the light of environmental pressures that have favoured the evolution of nocturnal feeding.