A hydrodynamic antenna: novel lateral line design in the tail of myliobatid stingrays

Eagle rays, cownose rays, and manta rays (family Myliobatidae) have a
slender tail that can be longer than the animal’s body length, but its
function and structure are unknown. Using histology, immunohistochemistry,
and 3D imaging with micro-CT scans, we describe the anatomy and function
of the tail of Rhinoptera bonasus, the cownose ray. The tail is an
extension of the vertebral column with unique morphological
specializations. Along the tail after the barb, vertebral centra are
absent, and neural and hemal arches fuse and form a solid mineralized
structure that we termed caudal synarcual which imparts passive stiffness
to the tail, reducing bending. Two lateral lines extend along both sides
of the tail. The lateral lines are composed of a main canal connected to
an extensive network of tubules, which extends and ramifies toward the
dorsal and ventral tail surfaces and opens to the surrounding water via
small pores. A remarkable continuous neuromast is located within each main
canal. The complex lateral line sensory system in the myliobatid ray tail
supports the hypothesis that the tail of myliobatids functions like a
hydrodynamic sensory antenna extending posterior to the body and may play
an important role in their behavioral and functional ecology.