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Blue shark
The blue shark (Prionace glauca), also known as the great blue shark, is a species of requiem shark in the family Carcharhinidae which inhabits deep waters in the world's temperate and tropical oceans. It is the only species of genus Prionace. Averaging around 3.1 m (10 ft) and preferring cooler waters, the blue shark migrates long distances, such as from New England to South America. It is listed as Near Threatened by the IUCN.
Although generally lethargic, they can move very quickly. Blue sharks are viviparous and are noted for large litters of 25 to over 100 pups. They feed primarily on small fish and squid, although they can take larger prey. Some of the blue shark's predators include the killer whale and larger sharks like tiger sharks and the great white shark. Their maximum lifespan is still unknown, but it is believed that they can live up to 20 years. They are one of the most abundant pelagic sharks, with large numbers being caught by fisheries as bycatch on longlines and nets.
The earliest fossil teeth of this species are known from the Miocene of Sri Lanka. Other fossil teeth of this species are known from the Miocene and Pliocene of Chile, Italy, and possibly Belgium.
The blue shark is an oceanic and epipelagic shark found worldwide in deep temperate and tropical waters from the surface to about 350 m (1,150 ft). In temperate seas it may approach shore, where it can be observed by divers; while in tropical waters, it inhabits greater depths. It lives as far north as Norway and as far south as Chile. Blue sharks are found off the coasts of every continent, except Antarctica. Its greatest Pacific concentrations occur between 20° and 50° North, but with strong seasonal fluctuations. In the tropics, it spreads evenly between 20° N and 20° S. It prefers water temperatures between 12 and 20 °C (54–68 °F), but can be seen in water ranging from 3.9 to 31 °C (39.0–87.8 °F). Records from the Atlantic show a regular clockwise migration within the prevailing currents.
Blue sharks are light-bodied with long pectoral fins. Like many other sharks, blue sharks are countershaded: the top of the body is deep blue, lighter on the sides, and the underside is white. The male blue shark commonly grows to 1.82 to 2.82 m (6.0 to 9.3 ft) at maturity, whereas the larger females commonly grow to 2.2 to 3.3 m (7.2 to 10.8 ft) at maturity. Large specimens can grow to 3.8 m (12 ft) long. Occasionally, an outsized blue shark is reported, with one widely printed claim of a length of 6.1 m (20 ft), but no shark even approaching this size has been scientifically documented. The blue shark is fairly elongated and slender in build and typically weighs from 27 to 55 kg (60 to 121 lb) in males and from 93 to 182 kg (205 to 401 lb) in large females. Occasionally, a female in excess of 3 metres (10 ft) will weigh over 204 kg (450 lb). The heaviest reported weight for the species was 391 kg (862 lb). However, anecdotal claims exist for the species to exceptionally reach 800–900 kg (1,800–2,000 lb) in weight, though these are not verified. The blue shark is also ectothermic and it has a unique sense of smell.[citation needed]
The five senses that blue sharks share with other members of the Carcharhinidae family are vision, hearing, lateral line, chemoreception, and electroreception. These senses allow them to perceive and react to a variety of biotic or abiotic stimuli in their immediate environment and across a different range of spatial scales.
The well-developed eyes of blue sharks exhibit interspecific variations in their eye structure, which are characteristic of adaptations for vision in a variety of light environments, from the brightly lit surface waters to the darkness of the deep sea. The lateral position of the eyes in the head allows a cyclopean visual field of 360° in the vertical plane and between 308° and 338° in the horizontal plane.
The morphology of the inner ears of blue sharks is similar to that of other gnathostomes. It consists of a membranous labyrinth that is made up of three semicircular canals that are filled with fluid and arranged orthogonally, as well as three otolithic organs, which are the sacculus, utriculus, and lagena. These sharks are most sensitive to frequencies below roughly 100 Hz, but they can hear sounds up to roughly 1000 Hz.
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Blue shark
The blue shark (Prionace glauca), also known as the great blue shark, is a species of requiem shark in the family Carcharhinidae which inhabits deep waters in the world's temperate and tropical oceans. It is the only species of genus Prionace. Averaging around 3.1 m (10 ft) and preferring cooler waters, the blue shark migrates long distances, such as from New England to South America. It is listed as Near Threatened by the IUCN.
Although generally lethargic, they can move very quickly. Blue sharks are viviparous and are noted for large litters of 25 to over 100 pups. They feed primarily on small fish and squid, although they can take larger prey. Some of the blue shark's predators include the killer whale and larger sharks like tiger sharks and the great white shark. Their maximum lifespan is still unknown, but it is believed that they can live up to 20 years. They are one of the most abundant pelagic sharks, with large numbers being caught by fisheries as bycatch on longlines and nets.
The earliest fossil teeth of this species are known from the Miocene of Sri Lanka. Other fossil teeth of this species are known from the Miocene and Pliocene of Chile, Italy, and possibly Belgium.
The blue shark is an oceanic and epipelagic shark found worldwide in deep temperate and tropical waters from the surface to about 350 m (1,150 ft). In temperate seas it may approach shore, where it can be observed by divers; while in tropical waters, it inhabits greater depths. It lives as far north as Norway and as far south as Chile. Blue sharks are found off the coasts of every continent, except Antarctica. Its greatest Pacific concentrations occur between 20° and 50° North, but with strong seasonal fluctuations. In the tropics, it spreads evenly between 20° N and 20° S. It prefers water temperatures between 12 and 20 °C (54–68 °F), but can be seen in water ranging from 3.9 to 31 °C (39.0–87.8 °F). Records from the Atlantic show a regular clockwise migration within the prevailing currents.
Blue sharks are light-bodied with long pectoral fins. Like many other sharks, blue sharks are countershaded: the top of the body is deep blue, lighter on the sides, and the underside is white. The male blue shark commonly grows to 1.82 to 2.82 m (6.0 to 9.3 ft) at maturity, whereas the larger females commonly grow to 2.2 to 3.3 m (7.2 to 10.8 ft) at maturity. Large specimens can grow to 3.8 m (12 ft) long. Occasionally, an outsized blue shark is reported, with one widely printed claim of a length of 6.1 m (20 ft), but no shark even approaching this size has been scientifically documented. The blue shark is fairly elongated and slender in build and typically weighs from 27 to 55 kg (60 to 121 lb) in males and from 93 to 182 kg (205 to 401 lb) in large females. Occasionally, a female in excess of 3 metres (10 ft) will weigh over 204 kg (450 lb). The heaviest reported weight for the species was 391 kg (862 lb). However, anecdotal claims exist for the species to exceptionally reach 800–900 kg (1,800–2,000 lb) in weight, though these are not verified. The blue shark is also ectothermic and it has a unique sense of smell.[citation needed]
The five senses that blue sharks share with other members of the Carcharhinidae family are vision, hearing, lateral line, chemoreception, and electroreception. These senses allow them to perceive and react to a variety of biotic or abiotic stimuli in their immediate environment and across a different range of spatial scales.
The well-developed eyes of blue sharks exhibit interspecific variations in their eye structure, which are characteristic of adaptations for vision in a variety of light environments, from the brightly lit surface waters to the darkness of the deep sea. The lateral position of the eyes in the head allows a cyclopean visual field of 360° in the vertical plane and between 308° and 338° in the horizontal plane.
The morphology of the inner ears of blue sharks is similar to that of other gnathostomes. It consists of a membranous labyrinth that is made up of three semicircular canals that are filled with fluid and arranged orthogonally, as well as three otolithic organs, which are the sacculus, utriculus, and lagena. These sharks are most sensitive to frequencies below roughly 100 Hz, but they can hear sounds up to roughly 1000 Hz.