MORPHOLOGY OF THE MECHANOSENSORY LATERAL-LINE SYSTEM IN THE ATLANTIC STINGRAY, DASYATIS-SABINA - THE MECHANOTACTILE HYPOTHESIS

The biological function of anatomical specializations in the mechanose nsory lateral line of elasmobranch fishes is essentially unknown. The gross and histological features of the lateral line in the Atlantic st ingray, Dasyatis sabina, were examined with special reference to its r ole in the localization and capture of natural invertebrate prey. Supe rficial neuromasts are arranged in bilateral rows near the dorsal midl ine from the spiracle to the posterior body disk and in a lateral posi tion along the entire length of the tail. All dorsal lateral line cana ls are pored, contain sensory neuromasts, and have accessory lateral t ubules that most likely function to increase their receptive field. Th e pored ventral canal system consists of the lateral hyomandibular can al along the disk margin and the short, separate mandibular canal on t he lower jaw The extensive nonpored and relatively compliant ventral i nfraorbital, supraorbital, and medial hyomandibular canals form a cont inuous complex on the snout, around the mouth, and along the abdomen. Vesicles of Savi are small mechanosensory subdermal pouches that occur in bilateral rows only along the ventral midline of the rostrum. Supe rficial neuromasts are best positioned to detect water movements along the transverse body axis such as those produced by tidal currents, co nspecifics, or predators. The pored dorsal canal system is positioned to detect water movements created by conspecifics, predators, or possi bly distortions in the flow field during swimming. Based upon the stin gray lateral line morphology and feeding behavior, we propose the Mech anotactile Hypothesis, which states that the ventral nonpored canals a nd vesicles of Savi function as specialized tactile mechanoreceptors t hat facilitate the detection and capture of small benthic invertebrate prey. (C) 1998 Wiley-Liss, Inc.