It turns out that, like the antennas on an insect or crustacean, a ray uses its tail to sense its environment. The inside of a myliobatid stingray tail is remarkably complex, the scientists learned. It has a caudal synarcual, or a specialized adaptation of the ray’s skeletal near the back, which keeps the tail stiff and thereby minimizes the sound of water as it goes about sensing its surroundings.
“Cownose rays are active swimmers living in a diversity of environments where background noise can be high; for example, noise produced by waves near the surface or during swimming (signals associated with high frequencies),” the authors write. “The filtering capacities of the lateral line system of the tail could improve the signal-to-noise ratio, avoiding overstimulation of the canal neuromasts.”
Yet despite this stiff core, the tail’s tissue is also pockmarked with tiny holes that link to the fish’s lateral line canal, a system of sensory organs that fish and amphibians often use analogous to a human’s central nervous system. In the cownose ray, the lateral line runs the length of the tail and branches off to pores in the fish’s skin, which they likely use to process information about their environment.
By contrast, most aquatic vertebrates have a lateral line that is streamlined near the animal’s tail and only becomes complex near their head. This would help them both bury themselves to avoid predators and sense the location of the bivalves upon which they prey.
“The complex lateral line mechanosensory system in the tail of R. bonasus supports the hypothesis that the tail functions like a hydrodynamic sensory antenna and may play an important role in their behavioural and functional ecology,” the authors conclude.
