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Tooth shape depends on the shark's diet: those that feed on mollusks and crustaceans have dense and flattened teeth used for crushing, those that feed on fish have needle-like teeth for gripping, and those that feed on larger prey such as mammals have pointed lower teeth for gripping and triangular upper teeth with serrated edges for cutting.
The branchial system is typically used for respiration and/or feeding. Many fish have modified posterior gill arches into pharyngeal jaws, often equipped with specialized pharyngeal teeth for handling particular prey items (long, sharp teeth in carnivorous moray eels compared to broad, crushing teeth in durophagous black carp).
Jawless fish and sharks only possess a cartilaginous endocranium, with the upper and lower jaws of cartilaginous fish being separate elements not attached to the skull. Bony fishes have additional dermal bone, forming a more or less coherent skull roof in lungfish and holost fish. The lower jaw defines a chin.
Most fish species with pharyngeal teeth do not have extendable pharyngeal jaws. A particularly notable exception is the highly mobile pharyngeal jaw of the moray eels.These are possibly a response to their inability to swallow as other fishes do by creating a negative pressure in the mouth, perhaps induced by their restricted environmental niche (burrows) or in the air in the intertidal zone. [10]
In fish, barbels can take the form of small, fleshy protrusions or long, cylindrical shaped extensions of the head of a fish. The cylindrical barbel shapes are built on an internal support system that can be made from ossified tissue or from cartilaginous connective tissue that provides a base for blood vessels and myelinated nerves to wrap ...
The Osteostraci (bony armored jawless fish) are generally considered the sister taxon of Gnathostomata. [3] [9] [10] Jaw development in vertebrates is likely a product of the supporting gill arches. This development would help push water into the mouth by the movement of the jaw, so that it would pass over the gills for gas exchange.
A new species of fish has been discovered in the Amazon: a piranha relative with humanlike teeth. The eye-catcher was named after a “Lord of the Rings” villain.
A fish scale is a small rigid plate that grows out of the skin of a fish. The skin of most jawed fishes is covered with these protective scales , which can also provide effective camouflage through the use of reflection and colouration , as well as possible hydrodynamic advantages.