Functional consequences of structural differences in stingray sensory systems. Part I: mechanosensory lateral line canals

Abstract

SUMMARYShort range hydrodynamic and electrosensory signals are important during final stages of prey capture in elasmobranchs (sharks, skates and rays), and may be particularly useful for dorso-ventrally flattened batoids with mouths hidden from their eyes. In stingrays, both the lateral line canal and electrosensory systems are highly modified and complex with significant differences on ventral surfaces that relate to feeding ecology. This study tests functional hypotheses based on quantified differences in sensory system morphology of three stingray species, Urobatis halleri, Myliobatis californica and Pteroplatytrygon violacea. Part I investigates the mechanosensory lateral line canal system whereas part II focuses on the electrosensory system. Stingray lateral line canals include both pored and non-pored sections and differ in branching complexity and distribution. A greater proportion of pored canals and high pore numbers were predicted to correspond to increased response to water flow. Behavioral experiments were performed to compare responses of stingrays to weak water jets mimicking signals produced by potential prey at velocities of 10-20 cm s -1 . Bat rays, M. californica, have the most complex and broadly distributed pored canal network and demonstrated both the highest response rate and greater response intensity to water jet signals. Results suggest that U. halleri and P. violacea may rely on additional sensory input, including tactile and visual cues, respectively, to initiate stronger feeding responses. These results suggest that stingray lateral line canal morphology can indicate detection capabilities through responsiveness to weak water jets. Supplementary material available online at

Functional consequences of structural differences in stingray sensory systems. Part II: electrosensory system

“…An inverse relationship exists between electrosensory anatomy and the importance of vision in pelagic elasmobranchs (Raschi et al, 2001), indicating that pelagic rays may rely more heavily on visual input for locating prey. As with water jets (see part I, Jordan et al, 2009), when 'trick' visual signals were given indicating the presence of food rewards, these rays more aggressively responded to the electric signals. Visual input may be unimportant during the final approach and strike to capture prey (Gardiner and Atema, 2007); however, it may increase attention and responsiveness to the highly directional hydrodynamic and electric signals used in the final stages of capture.…”

“…1 in part I (Jordan et al, 2009)]. Four dipole electrodes, with a 1 cm dipole separation distance, were connected to underwater electric cables (Impulse Enterprise, San Diego, CA, USA) and a 9 V battery source with controls to adjust the current, which was monitored by an ammeter in series (Meterman 35XP, Everett, WA, USA), and a switch to activate one of four electrodes at a time following Kajiura and Holland (Kajiura and Holland, 2002).…”

“…Only initial responses where the ray initiated a right or left turn are included in interspecific comparisons, although rays occasionally made more than one turn to approach the center of the electrode and in some cases they passed over the dipole center and reversed backwards prior to biting. Responses were ranked from 1 to 5 for increasing intensity, where 1=slight pause and 5=bite, as described for water jets in part I (Jordan et al, 2009). No zero response rank was included as rays rarely approached an active electrode without exhibiting a response.…”

Detection of artificial water flows by the lateral line system of a benthic feeding cichlid fish

“…In contrast, artificial stimuli cannot accurately replicate the complexity of stimuli generated by prey, but are controllable, repeatable and quantifiable and are thus amenable to rigorous analysis (e.g. vibrating sphere, Coombs and Janssen, 1990;Coombs et al, 2001;Nauroth and Mogdans, 2009;Mogdans and Nauroth, 2011;piston pump, McHenry et al, 2009;surface waves, Bleckmann, 1980;water jets, Janssen et al, 1990;Montgomery and Skipworth, 1997;Jordan et al, 2009). Both natural and artificial flow stimuli can produce cues for other sensory modalities (e.g.…”

Morfología del sistema mecanosensorial de la línea lateral de Zearaja chilensis (Batoidea: Rajidae)

“…El sistema sensorial en condrictios está conformado por dos sistemas: sistema mecanosensorial de la línea lateral y el sistema electrosensorial (Bleckmann & Hofmann 1999, Montgomery & Bodznick 1999, Jordan 2008, Jordan et al 2009). El sistema mecanosensorial detecta movimientos de agua cercanos a la superficie de la piel, mediante mecanoreceptores que están constituidos por células ciliadas sensoriales cubiertas por una cúpula gelatinosa que se conecta hacia el exterior mediante un sofisticado sistema de canales continuos subepidérmicos (Garman 1888, Roberts 1978, Bleckmann & Hofmann 1999, Maruska 2001, Jordan et al 2009, Shibuya & Tanaka 2012.…”