Stingrays are cartilaginous fish known for their flattened bodies and whip-like tails, primarily inhabiting the ocean floor in tropical and temperate waters. Jellyfish are gelatinous, free-swimming invertebrates that drift through the water column. These two distinct groups occupy different ecological niches, raising questions about their potential interaction in the marine food web. This article examines the typical stingray diet and whether these bottom-dwellers consume jellyfish.
Stingrays and the Consumption of Jellyfish
Whether stingrays eat jellyfish depends entirely on the specific species. For the majority of bottom-dwelling (benthic) stingrays, jellyfish are not a standard part of their diet. These rays primarily forage in the sand and mud, where jellyfish are rarely found. Furthermore, the gelatinous composition of jellyfish provides low nutritional value compared to hard-shelled prey, making them an inefficient food source for most predators.
One notable exception is the pelagic stingray (Pteroplatytrygon violacea), a species that lives in the open ocean rather than on the seafloor. This free-swimming ray preys upon other pelagic, or open-water, organisms. The diet of the pelagic stingray includes planktonic crustaceans, small fish, jellyfish, and squid, making it an opportunistic feeder in the water column. Unlike its benthic relatives, this ray has adapted to consume free-swimming prey rather than crushing hard shells.
Adaptations for a Crustacean and Mollusk Diet
Most stingrays possess a unique anatomy highly specialized for a diet of bottom-dwelling invertebrates. Their mouths are located on the underside of their disc-shaped bodies, perfectly positioned for feeding directly on the substrate. The typical diet consists of bivalves (clams and oysters), crustaceans (crabs and shrimp), and marine worms.
The stingray’s jaw structure is powerful, designed for crushing, despite their skeletons being made of cartilage rather than bone. Instead of pointed teeth, the mouths of many benthic stingrays contain flat, plate-like dental structures. These dental plates are designed to crush the robust, calcified shells of mollusks and other armored prey.
To locate hidden meals, stingrays rely on electroreception. They use specialized sensory pores called the Ampullae of Lorenzini, located near the mouth, to detect the faint electrical signals emitted by prey buried beneath the sand. Once prey is located, the ray employs a strategy often referred to as “tenting.”
The ray presses its pectoral fins against the seafloor and raises its head, generating a strong suction force beneath its body. This suction mechanism pulls the prey and sediment directly into its mouth. The ray then either swallows the prey whole or uses its dental plates to crush the shells. This feeding strategy is optimized for harvesting hard-shelled items from the sea floor, which contrasts with the soft, free-floating nature of a jellyfish.
Predators That Target Jellyfish
While most stingrays bypass jellyfish, other marine animals have evolved specific adaptations to consume this gelatinous prey. Leatherback sea turtles (Dermochelys coriacea) are recognized jellyfish predators. These turtles have specialized, backward-pointing papillae lining their throats, which help them grip and funnel slippery jellyfish while expelling excess water.
The Ocean Sunfish (Mola Mola) is another significant consumer of jellyfish, eating substantial amounts of various gelatinous organisms. Certain seabirds, such as fulmars, have also been observed consuming jellyfish by pecking at the inner tissues to avoid the stinging tentacles. Even the colossal Whale Shark, a filter feeder, inadvertently includes jellyfish in its diet as it strains plankton from the water. These predators possess protective features, specialized mouth structures, or a size advantage that allows them to withstand the jellyfish’s stinging nematocysts.