Zoology 117 (2014) 95–103 Contents lists available at ScienceDirect Zoology j our na l ho me pa g e: www. elsevier.com/locate/zool Behavioral responses of batoid elasmobranchs to prey-simulating electric fields are correlated to peripheral sensory morphology and ecology Christine N. Bedore ∗ , Lindsay L. Harris, Stephen M. Kajiura Department of Biological Sciences, Florida Atlantic University, 777 Glades Road, Boca Raton, FL 33431, USA a r t i c l e i n f o Article history: Received 10 May 2013 Received in revised form 18 August 2013 Accepted 1 September 2013 Available online 16 November 2013 Keywords: Electroreception Electrosensory system Batoids Cownose ray Yellow stingray a b s t r a c t Electrosensory pore number, distribution, and sensitivity to prey-simulating electric fields have been described for many shark species. Electrosensory systems in batoids have received much less atten- tion. Pore number and distribution have yet to be correlated to differences in sensitivity. However, pore number, pore distribution and sensitivity have been linked to behavior, diet, and morphology and follow species-specific trends. We report here that cownose rays have a greater number of pores than the yellow stingray, most of which are concentrated on the anterior ventral surface for both species. However, yellow stingrays have a broader arrangement of pores on both their dorsal and ventral surfaces than the cownose rays. Yellow stingrays demonstrated a median behavioral sensitivity to weak electric fields of 22 nV cm -1 and are among the most highly sensitive batoids studied to date. Cownose rays are less sensitive than all other elasmobranch species with a median sensitivity of 107 nV cm -1 . As reported in previous studies, a higher pore number did not result in greater sensitivity. Cownose rays are benthopelagic schooling rays and may benefit from reduced sensitivity to bioelectric fields when they are surrounded by the bioelectric fields of conspecifics. Yellow stingrays, on the other hand, are typically solitary and bury in the substrate. A greater number of pores on their dorsal surface might improve detection of predators above them. Also, increased sensitivity and a broader distribution of pores may be beneficial as small prey items move past a buried ray. © 2013 Elsevier GmbH. All rights reserved. 1. Introduction The ability to detect weak bioelectric fields has evolved inde- pendently in several vertebrate lineages (Bullock et al., 1983; Czech-Damal et al., 2012). The most renowned and most sensitive group known to use electroreception is the elasmobranch fishes, the sharks, skates, and rays (Bullock et al., 1983). The elasmobranch electrosensory system is composed of receptor cells that line the lumen of a bulbous ampulla, which leads to a canal filled with a conductive glycoprotein gel that terminates as a pore on the sur- face of the skin (Hueter et al., 2004). These pores are the interface between the seawater environment and the internal environment of the animal. The receptors detect a voltage gradient between the pore and the reference potential at the receptor cell. The pores are distributed in species-specific arrangements on the head of sharks ∗ Corresponding author. Present address: Biology Department, Duke University, Box 90338, Durham, NC 27708, USA. Tel.: +1 919 684 7188. E-mail addresses: christine.bedore@duke.edu, bedorech@gmail.com (C.N. Bedore). and on the dorsal and ventral body surfaces of skates and rays (Raschi, 1986; Kajiura et al., 2010). Pore distribution has been correlated with habitat, diet, mor- phology, and lifestyle (Raschi, 1986; Raschi and Mackanos, 1987; Kajiura, 2001; Jordan, 2008; Wueringer and Tibbets, 2008; Kajiura et al., 2010; Wueringer et al., 2011, 2012), but neither pore distribu- tion nor pore number have been correlated to sensitivity (Kajiura, 2001; Kajiura and Holland, 2002; Jordan et al., 2009). Nonetheless, pore number and distribution may still contribute to behavioral responses to bioelectric fields, perhaps by providing an increase in spatial resolution. For example, Raschi (1986) correlated high pore densities in skates with diets composed of immobile infaunal invertebrates and hypothesized that high pore densities increase spatial resolution during prey localization. Additionally, broad dis- tributions of pores across dorsal and ventral surfaces of skates were correlated with generalized diets of mobile infaunal and epiben- thic invertebrates, as well as with mobile pelagic prey like squid and teleosts (Raschi, 1986). These broad distributions are thought to expand the electrosensory search area so that prey farther from the mouth can be more easily detected. The batoid order Myliobatiformes exhibits a wide range of mor- phologies, lifestyles, habitats, and diets (Fig. 1), which may correlate 0944-2006/$ – see front matter © 2013 Elsevier GmbH. All rights reserved. http://dx.doi.org/10.1016/j.zool.2013.09.002