Manta rays are among the largest rays, with some species reaching a wingspan of over 20 feet. These cartilaginous fish belong to the group known as elasmobranchs, which also includes sharks and skates. Their anatomy is a perfect example of biological adaptation, where the skeletal architecture has been modified to support a specialized diet. This article clarifies the technical composition of their mouth and explains how these massive animals sustain themselves by consuming the ocean’s tiniest organisms.
The Technical Answer Manta Ray Jaw Structure
Manta rays possess the fundamental skeletal architecture that defines a jaw, even though their mouth appears to be a wide, non-biting opening. As elasmobranchs, their skeleton is made entirely of cartilage, rather than bone. This cartilaginous framework includes the mandibular and hyoid arches, which are the evolutionary precursors to the upper and lower jawbones found in other vertebrates.
The head cartilage is lightweight and flexible, a necessary quality for an animal that swims at speed with its mouth open. This framework is highly adapted to support a broad, terminal mouth, which is positioned at the very front of the head, unlike the subterminal mouths of many other rays and sharks. While the skeletal components for a jaw are present, they are greatly reduced and specialized into a funnel-like structure. This mobile cartilaginous frame allows the mouth to open wide, creating a large entrance for water and plankton during feeding, rather than being designed for powerful biting or chewing.
The Filter-Feeding Mechanism
The manta ray’s feeding mechanism is highly specialized for its obligate filter-feeding lifestyle. They sustain themselves primarily on zooplankton, which includes tiny crustaceans and fish larvae, consuming between 20 to 30 kilograms of food each day. They are ram feeders, meaning they must continuously swim forward with their mouths open to push plankton-laden water into their oral cavity.
The most noticeable features assisting this process are the two horn-shaped appendages extending from the head, known as cephalic lobes. These flexible, modified extensions of the pectoral fins uncurl during feeding to funnel the plankton-rich water into the terminal mouth. Once inside the mouth, the water and food pass over a specialized filtering apparatus composed of cascading sheets of gill rakers.
These gill rakers are highly modified into leaf-like filter lobes, not simple sieves. The manta ray utilizes a technique called “ricochet separation,” where food particles are intercepted by the filter lobes and bounce away from the filter pores toward the esophagus. This sophisticated mechanism allows the manta ray to capture plankton much smaller than the physical gaps in the filter, while simultaneously preventing the filter from becoming clogged. The filtered water then flows over the gills to extract oxygen before exiting through the five pairs of gill slits located on the ventral underside of the body.
Manta Rays and Teeth
The presence of a jaw structure naturally leads to the question of whether manta rays possess teeth. Many elasmobranchs, such as sharks, have prominent teeth for predation, but the manta ray’s filter-feeding diet has rendered such structures functionally obsolete.
Manta rays have small, peg-like, vestigial teeth, typically arranged in bands on the lower jaw. These teeth are tiny and are not used for biting, chewing, or processing food. In some species, such as the Oceanic Manta Ray (Mobula birostris), males use these teeth during courtship, gripping the tip of a female’s pectoral wing to stabilize themselves during mating. They are a remnant of their evolutionary past, not a tool for current sustenance.