Durophagy
Durophagy is the eating behavior of
In the order
Teleost fish (Teleostei)
Many teleosts, like the Atlantic wolffish, exhibit durophagous behaviour and crush hard prey with their jaws and teeth. Other fish use of their pharyngeal teeth, with the aid of their protrusible mouth for enabling the grabbing of prey to draw it into their mouth. The pharyngeal jaws found in more derived teleosts are more powerful, with left and right ceratobranchials fusing to become one lower jaw and the pharyngeal branchial fusing to create a large upper jaw that articulates with the neurocranium. They have also developed a muscle, the hypertrophied pharyngeal, to crush prey with help from the molariform pharyngeal teeth. This allows for the consumption of hard-shelled prey.[8][9]
Triggerfish (Balistidae)
Triggerfish have jaws that contain a row of four teeth on either side, the upper jaw containing an additional set of six plate-like pharyngeal teeth. Triggerfish do not have jaw protrusion and there are enlarged jaw adductor muscles for extra power to crush the protective shells and spines of their prey.[8]
Cichlids (Cichlidae)
Mollusk shells can be crushed to expose soft parts of the prey to digestive juices or the soft parts can be removed from the shell. Species that crush shells are defined by their large and greatly thickened pharyngeal bones. These bones have flat-crowned teeth and along with their dorsal fellows drawn by powerful muscles, create a crushing mill. The jaws are less derived as they are for just for picking up relatively large objects.[10][11]
The second method
Chondrichthyans
Within the
Horn sharks (Heterodontiformes)
Horn sharks have molariform teeth. The anterior teeth are pointed and are used for grasping while the posterior teeth are molariform and are used for crushing. Horn sharks feed primarily on limpets, bivalve molluscs and blue crabs.[8]
Bonnethead shark (Sphyrna tiburo)
The
Chimeras (Holocephali)
Chimeras (Holocephali) have pavement teeth that are flat, hexagonal in shape and interconnect to form an even dental plate. There is the presence of calcified strengthened cartilaginous jaws, calcified struts within the jaws and a lever 'nutcracker' system that amplifies the force of the jaw adductor muscles. The fusion of the palatoquadrate and mandibular symphysis, a restricted gape and asynchronous activation of the jaw adductors are key elements in the 'nutcracker' model of jaw-crushing ability. Chimeras use their pavement teeth for grinding molluscs, gastropods and crabs.[8]
Myliobatidae
Eagle (Aetobatus narinari) and cow-nose (Rhinoptera javanica) rays
In eagle (
Myliobatis and Aetobatus
In Myliobatis and Aetobatus, anteroposterior ridges of the basal plate extend from the posterior margin of the tooth and these interdigitate with those of the succeeding tooth and also form a shelf on which the body of the neighboring tooth rests. The dentition of the bat ray (Myliobatis californica) is made up of a series of seven files of crushing teeth. The central hexagonal plate is very wide, taking up about half the width of the occlusal surface and it is flanked by three lateral files of smaller teeth on each side, the outermost being pentagonal. The crushing surface formed by the teeth of the upper jaw is more curved than that of the lower jaw.[12]
Birds
Shorebirds commonly consume bivalves and snails which are low in chitin but the calcium carbonate shell makes up a large portion of their weight. Bivalves and snails are largely consumed whole by ducks and wading birds. The molluscivores that swallow snails or bivalves whole have large well-modularized gizzards for crushing the strong shells. The gizzard of red-necked stints and red knots is more than ten times larger than the proventriculus. The size of the gizzard is adaptable in these shore birds, becoming atrophied when soft food items like worms are consumed and increasing in size and muscularity following prolonged consumption of snails, cockles or mussels. The production of chitinase for the hydrolysis of chitin is important for birds that consume mollusks.[13]
Marine mammals
Sea otters (Enhydra lutris)
Sea otter molars are broad, flat, multi cuspid teeth and the carnassial are also modified for crushing. Both the temporalis and masseter muscles are well developed, creating a strong bite force. The teeth are extremely broad and carnassial are highly molarized. Captured prey is manipulated with the forepaws or is held temporarily in loose skin pouches in the armpits. For larger, heavier-shelled prey, otters will sometimes exhibit tool-use behavior, breaking open sea urchins and mussels with a false stone used as an anvil. Sea otters can also bite sea urchins and mussels open using their strong jaws and teeth. Adults can crush most of their food items but youngsters have not yet developed powerful enough jaws. Therefore, young otters require the assistance of a tool or stone. Tools may also be used when the molluscs are too large to be crushed in the jaws.[14][15]
Mammals
Monkeys
All mangabeys appear to be durophagous and possess relatively thick molar enamel and expanded premolars, dental adaptations for processing hard foods. Their diet consists of Sacoglottis gabonensis seeds. These seeds can remain on the ground for months without rotting. With hard-object feeding, Mangabeys needed selection to favour thick molar enamel and flattened molars for crushing seeds.[16]
Giant panda
The giant panda is mainly a herbivore despite its short, relatively unspecialized digestive tract that is characteristic of carnivores. Giant pandas lack microbial digestion in their rumen or caecum that is typical of most herbivores for breaking down cellulose and lignin in plant cell walls. Therefore, Giant Pandas need to get their nutrients from the cell contents and fraction of hemicellulose they can break down. The panda subsists mainly on bamboo and does so with modifications of their jaws. Pandas show elaboration of the crushing features of the dentition. The molars are broad, flat, multi cuspid teeth and are the main grinding surface. Jaw action is not a simple crushing one but rather a definite sideways grinding. Panda jaws have a large zygomatico-mandibularis muscle, which is responsible for the sideways movement of the jaw. The glenoid is very deep, preventing back and forth movement of the jaw.[15][17]
Bamboo represents a predictable food source which is seasonally abundant. Pandas are able to subsist on it despite its low nutritive content. Pandas do this by moving large quantities through the digestive tract in a short period of time. They also reduce their energy expenditures by resting and only remaining active to feed, and they don't have a hibernation period, allowing them to have more foraging time. They chose security over uncertainty, indicated by their bamboo eating adaptations.[17]
Hyaenids
Bone-crushing eating habits appear to be associated with stronger teeth, as seen is in
Wolverine (Gulo gulo)
The wolverine has jaws and teeth that are extremely powerful and together with its scavenging habits, have earned the wolverine the name "hyena of the north". The wolverine is an effective scavenger, capable of cracking heavy bones and shows the same adaptations in the jaw as the hyenas do. The sagittal crest projects well above the area of attachment of the neck muscles, and in a large animal it extends back far behind the level of the condyles to provide attachments for the relatively enormous temporalis muscles, creating a powerful bite force.[17]