A molluscivore is a carnivorous animal that specialises in feeding on molluscs such as gastropods, bivalves, brachiopods and cephalopods. Known molluscivores include numerous predatory (and often cannibalistic) molluscs, (e.g. octopuses, murexes, decollate snails and oyster drills), arthropods such as crabs and firefly larvae, and vertebrates such as fish, birds and mammals. Molluscivory is performed in a variety of ways with some animals highly adapted to this method of feeding. A similar behaviour, durophagy, describes the feeding of animals that consume hard-shelled or exoskeleton bearing organisms, such as corals, shelled molluscs, or crabs.
Description Molluscivory can be performed in several ways:
In some cases, the mollusc prey are simply swallowed entire, including the shell, whereupon the prey is killed through suffocation and/or exposure to digestive enzymes. Only cannibalistic sea slugs, snail-eating cone shells of the taxon Coninae, and some sea anemones use this method. One method, used especially by vertebrate molluscivores, is to break the shell, either by exerting force on the shell until it breaks, often by biting the shell, like with oyster crackers, mosasaurs, and placodonts, or hammering at the shell, e.g. oystercatchers and crabs, or by simply dashing the mollusc on a rock (e.g. song thrushes, gulls, and sea otters). It is hypothesized that human archaic ancestors such as early-Pleistocene Homo erectus on Java were predominantly molluscivorous: stone tool use, pachyosteosclerotic skeleton (slow+shallow diving), much larger brains (seafoods + DHA), fossilisations amid edible mussels (Pseudodon, Elongaria), island colonisations (e.g. Flores), early-Pleistocene intercontinental dispersal along coasts and rivers, enamel damage caused by "oral processing of marine mollusks" (Towle cs 2022 AJPA), ear exostoses (chronic cold-water irrigation), shell engravings (google "Joordens Munro"), etc., google "gondwanatalks verhaegen".
Another method is to remove the shell from the prey. Molluscs are attached to their shell by strong muscular ligaments, making the shell's removal difficult. Molluscivorous birds, such as oystercatchers and the Everglades snail kite, insert their elongate beak into the shell to sever these attachment ligaments, facilitating removal of the prey. The carnivorous terrestrial pulmonate snail known as the "decollate snail" ("decollate" being a synonym for "decapitate") uses a similar method: it reaches into the opening of the prey's shell and bites through the muscles in the prey's neck, whereupon it immediately begins devouring the fleshy parts of its victim. The walrus sucks meat out of bivalve molluscs by sealing its powerful lips to the organism and withdrawing its piston-like tongue rapidly into its mouth, creating a vacuum. Another method, used by octopuses, nautilii and most molluscivoruous sea snails, is to use their radula to drill a hole through the shell, then inject venom and digestive enzymes through the hole, after which the digested prey can be sucked out through the hole. The larvae of glowworms and fireflies are simply small enough to enter the shells of terrestrial snails and begin eating immediately.
In marine mammals
Whales: Sperm whales, pilot whales, Cuvier's beaked whale, Risso's dolphin and species in the genera Mesoplodon, and Hyperoodon and the superfamily Physeteroidea are classified as molluscivores, eating mainly squid. Pinnipeds: Elephant seals, Ross seals and South American fur seals are classed as molluscivores. The walrus eats benthic bivalve molluscs, especially clams, for which it forages by grazing along the sea bottom, searching and identifying prey with its sensitive vibrissae. The walrus sucks the meat out by sealing its powerful lips to the organism and withdrawing its piston-like tongue rapidly into its mouth, creating a vacuum. The walrus palate is uniquely vaulted, enabling effective suction.
In fish Several species of pufferfish and loaches are molluscivores. As many molluscs are protected by a shell, the feeding techniques applied amongst molluscivore fish are highly specialized and usually divided into two groups: "crushers" and "slurpers." Pufferfish tend to be crushers and will use their beak-like teeth to break the shell in order to gain access to the meat inside. Loaches are specialized slurpers, and will make use of their characteristically shaped snout in order to grab hold of, then suck out the animal living inside the shell.
The black carp (Mylopharyngodon piceus) commonly feeds by crushing large molluscs with pharyngeal teeth, extracting soft tissue, and spitting out shell fragments. Four-year-old juveniles are capable of consuming approximately 1–2 kg of molluscs per day. This bottom-dwelling molluscivore was purposely imported into the United States in the early 1970s for use as a food fish and also as a biological control agent for snails—an intermediate host for a trematode parasite in fish reared on fish farms. Two snail-eating cichlids, Trematocranus placodon and Maravichromis anaphyrmis, have been tried as biological control agents of schistosomes in fish ponds in Africa. Redear sunfish (Lepomis micropholus) and bluegill (Lepomis macrochirus) have been used to control quagga mussels (Dreissena bugensis) in the lower Colorado River in the US. The common name of some fish reflects their molluscivorous feeding, for example, the "snail-crusher hap" (Trematocranus placodon), ""red rock sheller" (Haplochromis sp.), "Rusinga oral sheller" (Haplochromis sp.) and "rainbow sheller" (Haplochromis sp.). The redear sunfish is also known as the "shellcracker".
In reptiles Gray's monitor (or "butaan") is well known for its diet, which consists primarily of ripe fruit; however, several prey items are also consumed, including snails. Monitors are generally carnivorous animals, which makes the Gray's monitor somewhat of an exception amongst the varanid family. The prehistoric placodont reptiles is an extinct taxon of marine animals that superficially resembled lizards and turtles, most of whose dentition of peg-like incisors and enormous, molar-like teeth allowed them to prey on molluscs and brachiopods by plucking their prey off of the substrate, and crushing the shells.
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