Making sense of stingray sensory anatomy

Elasmobranchs (sharks, skates, and rays), can perceive the world around much as we can, through hearing, vision, olfaction (smell), taste, and touch, however, they also are extremely sensitive to water motion and can detect electric fields.  They do this with sophisticated lateral line and electrosensory systems.  My goal in this research was to introduce a more quantitative method for comparing the anatomy of these sensory systems across species and to see if predictions based on evolutionary history or on the ecology (habitat and prey type) of the species were supported.

Lateral line canals

On most fishes, the lateral line consists of a line of tiny pores running down the side of their body.  These pores connect to a main canal where sensory cells are located.  As water flows over their body, pressure changes alter the flow in these canals triggering the sensory hair cells (similar to our inner ear).  In rays, these lateral line canals are spread out over their wings on both sides of their bodies.  Canals in different species differ in layout, type, and branching complexity.  Lateral line canals are shown in blue on the dorsal (top), and ventral (bottom) body surfaces:

Electrosensory system

The ability to detect electric fields is restricted to a relatively small number of species outside of the elasmobranch group.  Its usefulness cannot be underestimated though, because it has re-evolved in several separate groups including other fishes, and even mammals (the platapus)!  The electrosensory system of elasmobranchs consists of small pores on the skins surface, usually distributed on the head, that connect to sensory cells within the body through gel-filled canals.  Once again, on rays, these are dispersed over the body and wings.  Species differ in the number and distribution of these electrosensory pores.  This system is used to detect weak electric fields generated by living things and may also be used for navigation using the Earth's magnetic field.  Elecrosensory pores shown as red dots on the dorsal surface (top) and ventral surface (bottom):

Results

High resolution images and ImageJ software allowed me to make precise measurements of various aspects of these sensory systems.  I found that there were significant differences in the sensory systems of the three species, the round stingray (Urobatis halleri), the bat ray (Myliobatis californica), and the pelagic stingray (Pteroplatytrygon violacea), shown above.  These differences corresponded well with predictions based on feeding ecology and prey type.  From these findings, I was able to make specific predictions about how each species might differ from the others in their detection capabilities From form to function: Stingray sensory superstars.  Please see the link under "Publications" in About Laura for the full story.

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