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In elasmobranchs (sharks and rays) the spiracle bears a small pseudobranch that resembles a gill in structure, but only receives blood already oxygenated by the true gills. [7] The function of the pseudobranch is unknown, but it is believed that it supplies highly oxygenated blood to the optic choroid and retina and may have baroreceptor ...
The thresher sharks have an extreme example of this tail in which the upper lobe has evolved into a weapon for stunning prey. Bottom-dwelling sharks such as catsharks and carpet sharks have tails with long upper lobes and virtually no lower lobe. The upper lobe is held at a very low angle, which sacrifices speed for maneuverability.
The speartooth shark has a streamlined, rather robust body with a short, wide head. The snout is flattened, with large nostrils divided into incurrent and excurrent openings by large, triangular flaps of skin. The eyes are small and equipped with nictitating membranes (protective third eyelids). The sizable, arched mouth has very short furrows ...
The whitetip reef shark (Triaenodon obesus) is a species of requiem shark, in the family Carcharhinidae, and the only member of its genus.A small shark that does not usually exceed 1.6 m (5.2 ft) in length, this species is easily recognizable by its slender body and short but broad head, as well as tubular skin flaps beside the nostrils, oval eyes with vertical pupils, and white-tipped dorsal ...
Marks made by cookiecutter sharks have been found on a wide variety of marine mammals and fishes, and on submarines, undersea cables, and human bodies. It also consumes whole smaller prey, such as squid. Cookiecutter sharks have adaptations for hovering in the water column, and likely rely on stealth and subterfuge to capture more active prey ...
The bonnethead (Sphyrna tiburo), also called a bonnet shark or shovelhead, [3] is a small member of the hammerhead shark genus Sphyrna, and part of the family Sphyrnidae.It is an abundant species in the littoral zone of the North Atlantic and the Gulf of Mexico, is the only shark species known to display sexual dimorphism in the morphology of the head, and is the only shark species known to be ...
The sandbar shark is one of the largest coastal sharks in the world, and is closely related to the dusky shark, the bignose shark, and the bull shark. Its dorsal fin is triangular and very high, and it has very long pectoral fins. Sandbar sharks usually have heavy-set bodies and rounded snouts that are shorter than the average shark's snout.
It is likely that most captured sharks survive to be returned to the water alive, as this species can tolerate being out of water for an extended period of time. From 1988 to 1991, there was a New Zealand shark liver fishery and reported catches of draughtsboard sharks were 74–540 tons per year. After the fishery was discontinued, catches ...