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The shared trait of breathing via gills in bony fish and cartilaginous fish is a famous example of symplesiomorphy. Bony fish are more closely related to terrestrial vertebrates, which evolved out of a clade of bony fishes that breathe through their skin or lungs, than they are to the sharks, rays, and the other cartilaginous fish. Their kind ...
The spiracle is often located towards the top of the animal allowing breathing even while the animal is mostly buried under sediments. [5] As sharks adapted a faster moving lifestyle some became obligate ram ventilators , breathing exclusively by forcing water through their gills by swimming; among these are requiem sharks and hammerhead sharks ...
Each gill is supported by a cartilaginous or bony gill arch, [1] which helps to maintain the gill's surface area. Bony fish (osteichthyans, mostly teleost ray-finned fish) have four pairs of arches, cartilaginous fish (chondrichthyans) have five to seven pairs, and the more basal jawless fish ("agnathans") have up to seven.
Osteichthyes (/ ˌ ɒ s t iː ˈ ɪ k θ iː z / ost-ee-IK-theez), [2] also known as osteichthyans or commonly referred to as the bony fish, is a diverse superclass of vertebrate animals that have endoskeletons primarily composed of bone tissue.
Many bony fishes have an internal organ called a swim bladder, or gas bladder, that adjusts their buoyancy through manipulation of gases. In this way, fish can stay at the current water depth, or ascend or descend without having to waste energy in swimming. The bladder is only found in bony fishes.
The gill arches of bony fish typically have no septum, so the gills alone project from the arch, supported by individual gill rays. Some species retain gill rakers. Though all but the most primitive bony fish lack spiracles, the pseudobranch associated with them often remains, being located at the base of the operculum.
When they swim, water flows into the mouth and across the gills. Because these sharks rely on this technique, they must keep swimming in order to respire. Bony fish use countercurrent flow to maximize the intake of oxygen that can diffuse through the gill. Countercurrent flow occurs when deoxygenated blood moves through the gill in one ...
Bony fish can be further divided into those with lobe fins and those with ray fins. Lobe fins have the form of fleshy lobes supported by bony stalks which extend from the body. [ 16 ] Lobe fins evolved into the legs of the first tetrapod land vertebrates, so by extension an early ancestor of humans was a lobe-finned fish.