Skates are cartilaginous fish, recognized by their flattened bodies and wing-like pectoral fins, belonging to the same subclass as sharks and rays. They are primarily benthic organisms, meaning they spend most of their lives on the seafloor, inhabiting marine environments from shallow coastal waters to the deep ocean. This bottom-dwelling lifestyle dictates their feeding strategy, which focuses almost entirely on prey found in or on the sediment.
Primary Food Sources
The diet of most skates is composed of bottom-dwelling invertebrates, reflecting their habitat. Crustaceans form a large portion of their food intake, with species like crabs and shrimp being commonly consumed. Smaller skates often target softer-bodied crustaceans such as amphipods, while larger species can crush hard-shelled crabs.
Mollusks, including clams, snails, and bivalves, also represent a significant food source. Their feeding apparatus is well-suited for crushing the protective shells of these animals. Polychaete worms, which often live buried within the sand or mud, are another common item on the skate menu.
As skates grow larger, their diet often incorporates small, bottom-dwelling fish, also known as teleosts. Examples of fish prey include sand eels or small gobies, captured as the skate glides over the seabed. The inclusion of fish often signifies a shift in the skate’s trophic role, positioning the largest individuals as higher-level predators.
Specialized Hunting and Feeding Adaptations
Skates employ sophisticated sensory tools to locate prey that is often hidden beneath the sand. Their most notable adaptation is the Ampullae of Lorenzini, a network of specialized electroreceptors visible as small pores around the head and on the underside of their body. These organs detect the faint electric fields generated by the muscle contractions of living prey, allowing the skate to pinpoint buried animals even when vision is obstructed. The ability to sense these electrical signals gives skates a distinct advantage for hunting infaunal invertebrates.
The skate’s mouth is positioned ventrally, on the underside of the body, which is perfectly adapted for sweeping up prey from the ocean floor. Their jaws are powerful, and their teeth are typically small, blunt, and arranged in crushing plates. This dental structure is ideal for breaking the hard exoskeletons of crustaceans and the shells of mollusks.
To extract prey from the sediment, skates often utilize powerful suction. By rapidly expanding their oral cavity, they generate a negative pressure that quickly pulls buried invertebrates out of the sand and into their mouth. This combination of electroreception to locate the prey and a powerful vacuum to extract it makes the skate an efficient benthic predator.
Dietary Shifts and Habitat Influence
A skate’s diet changes significantly throughout its life, a phenomenon known as an ontogenetic dietary shift. Juvenile skates typically begin consuming smaller, less mobile, and softer-bodied invertebrates like tiny amphipods and small worms. This focus on smaller prey matches their limited body size and less developed crushing power.
As the skate increases in size and maturity, its feeding capabilities expand, leading to a shift toward larger prey items. Adult skates can successfully hunt and consume larger crustaceans, such as adult crabs, and increasingly rely on small fish as a primary energy source. This transition results in the largest skates occupying a higher trophic level than their juvenile counterparts.
The specific marine environment a skate inhabits also influences its diet by determining the local prey availability. Skates living in shallower coastal areas may feed on different species than those residing in the deep ocean, which may target deep-sea crustaceans or cephalopods. This highlights that skates are generally opportunistic feeders, consuming the most abundant and accessible prey species within their immediate habitat.