How rays use their sensory abilities to hunt for prey

In a new research, a team of scientists explored the sensory abilities of rays in order to find how the marine animals scout for food on the seafloor, in spite of their eyes being on the top of their head.
 
According to a report in the Natural History Magazine, the research was carried out by Laura K Jordan, of the University of California, Los Angeles, and two colleagues, who studied the case of the bat ray Myliobatis californica, which lives off the coast of California.
 
An earlier theory regarding the ability of the rays in detecting prey was that they sense the jets of water that buried clams sometimes expel.
 
For confirming this theory, the team simulated clam jets at the bottom of a large tank, and then watched the effect on wild-caught bat rays.
 
The rays did indeed stop over the jets to bite at their source.
 
They sensed the jets through their undersides, which are equipped with a well-developed lateral line system-the series of pores and canals that enables all fishes to detect water movements.
 
Jordan's team also tried the trick with two other ray species that don't eat clams.
 
Their lateral line systems are much less complex, and they responded to the jets less than half as often as did the bat rays.
 
The team also studied the rays' sensitivity to the electrical fields that all living organisms (including buried clams) produce-a sensory specialty of sharks and rays.
 
All three species bit enthusiastically at dipole electrodes the scientists hid at the bottom of the tank, but the bat rays may have set a new record by detecting signals weaker than 0.1 nanovolt per centimeter, which is less than a billionth of the electrical field generated between the poles of an AA battery.