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

Abstract

SUMMARY Elasmobranch fishes (sharks, skates and rays) possess highly sensitive electrosensory systems, which enable them to detect weak electric fields such as those produced by potential prey organisms. Different species have unique electrosensory pore numbers, densities and distributions. Functional differences in detection capabilities resulting from these structural differences are largely unknown. Stingrays and other batoid fishes have eyes positioned on the opposite side of the body from the mouth. Furthermore, they often feed on buried prey, which can be located non-visually using the electrosensory system. In the present study we test functional predictions based on structural differences in three stingray species (Urobatis halleri, Pteroplatytrygon violacea and Myliobatis californica)with differing electrosensory system morphology. We compare detection capabilities based upon behavioral responses to dipole electric signals(5.3–9.6 μA). Species with greater ventral pore numbers and densities were predicted to demonstrate enhanced electrosensory capabilities. Electric field intensities at orientation were similar among these species, although they differed in response type and orientation pathway. Minimum voltage gradients eliciting feeding responses were well below 1 nVcm–1 for all species regardless of pore number and density.

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

“…Montgomery and Skipworth determined that the voltage gradient generated by the weak water jets used in their study could be 1nVcm -1 , which was considered below the electrosensory detection threshold of elasmobranchs (Montgomery and Skipworth, 1997). Kajiura and Holland (Kajiura and Holland, 2002) and part II of the present study (Jordan et al, 2009) have since demonstrated sensitivity well below 1 nV cm -1 for species of sharks and rays; thus, this possibility cannot be ruled out. Unfortunately there was no reasonable way to prevent this byproduct of flow in seawater.…”

Sexual Dimorphism of the Electrosensory System: A Quantitative Analysis of Nerve Axons in the Dorsal Anterior Lateral Line Nerve of the Blue-Spotted Fantail Stingray (Taeniura lymma)

“…To date, no sexual differences have been found in the electrosensitivity of elasmobranchs during prey detection trials [Kajiura and Holland, 2002;Jordan et al, 2009], de- (5 -8) (6 -10) (1,800 -2,520) (3,845 -6,152) (738 -1,230) (6,383 -9,902) Values in parentheses are min-max. Also included is an estimate of the total number of nerve axons, and the observed total number of nerve axons, associated with the dorsal root of the ALLN.…”

Electroreception in the obligate freshwater stingray, Potamotrygon motoro

“…To determine the sensitivity of P. motoro to bioelectric fields, a behavioural assay was employed following methods described in similar studies (Kajiura and Holland 2002;Kajiura 2003;Jordan et al 2009;McGowan and Kajiura 2009). An opaque acrylic plate, 2 m in diameter, was placed on the bottom of a 3785-L fibreglass experimental tank at the FWC laboratory.…”