Sand tiger shark
| Sand tiger shark | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
Sand tiger shark ( Carcharias taurus ) |
||||||||||||
| Systematics | ||||||||||||
|
||||||||||||
| Scientific name of the family | ||||||||||||
| Carchariidae | ||||||||||||
| Johannes Müller & Henle , 1838 | ||||||||||||
| Scientific name of the genus | ||||||||||||
| Carcharias | ||||||||||||
| Rafinesque , 1810 | ||||||||||||
| Scientific name of the species | ||||||||||||
| Carcharias taurus | ||||||||||||
| Rafinesque, 1810 |
The sand tiger shark ( Carcharias taurus ), also simply called sand tiger , is a shark that occurs almost worldwide in tropical, subtropical and warm-temperate seas.
Appearance
With the sand tiger sharks, the females reach a maximum length of 3.2 meters. The males stay smaller with a maximum body length of 2.6 meters. In general, adult animals are 2 to 2.2 meters in length. Outwardly, the sexes hardly differ. They have a pointed, flattened snout and small eyes in relation to the body. They don't have a nictitating membrane to protect their eyes. The long, pointed teeth are pointed strongly forward. The sand tiger sharks are perfectly adapted to the sea sand bottom thanks to the color of the top and the pattern. Characteristic are the yellow to dark red spots on the elongated, strong, yellowish body, which become paler with age. The ventral side is white. The two dorsal fins, of which the front one is offset relatively far back, are of the same size.
Way of life
Sand tiger sharks prefer to live individually in shallow water layers near the coast or near coral and rock reefs in areas further away from the coast, where they mainly feed on fish . Occasionally, larger groups can be found that come together during the seasonal migration of the stocks, during the breeding season or to hunt. Due to the lack of a swim bladder , they are constantly in motion in a leisurely manner of swimming in order to avoid sinking into deeper water layers. However, they are the only species of shark to have the ability to store swallowed air in their stomachs so that the stomach acts as a kind of swim bladder. This enables them to float motionless in the water. During the day they often stay in caves where they sleep in a suspended manner. When swimming, the sand tiger sharks always have their mouths slightly open so that the sharp, long teeth are visible. That gives them a dangerous appearance. However, they are not aggressive.
nutrition
At night the sand tiger sharks go hunting. They mainly prey on medium-sized fish such as mackerel , hake , herrings , blue fish or wrasse . In addition to these medium-sized bony fish, there are also smaller sharks, rays , large squids and crustaceans such as larger crabs or lobsters on the menu. In daylight they can only be seen occasionally while eating. Sometimes sand tiger sharks hunt in small groups. First a large school of prey fish is surrounded, then the sand tiger sharks attack their prey together.
Reproduction
Female sand tiger sharks reach sexual maturity at a length of about two meters. As with most sharks, the males bite the female during courtship and mating. The female sharks protect themselves with a much thicker skin. When they bite, the male sand tiger sharks lose some teeth that fall to the sea floor. On the basis of sand tiger shark teeth found in the respective area, it can later be proven that it was a mating site.
Up to 25 egg cells are formed in the paired ovaries and are fertilized in the associated fallopian tubes. The seedlings hatch at an early stage of development. On the belly side there is a large yolk sac, from which the seedlings feed first. When this is consumed, the young animals are about 18 centimeters in size and already have sharp teeth. In the young animals there is a prenatal cannibalism . Only one young animal grows in a gestation period of eight to twelve months in each of the two uterine sacs. During the gestation period, the two oldest young animals feed on the yolk of the unfertilized eggs and later on the other hatching embryos. The mother animal then produces further (unfertilized) eggs, which serve to feed the young animals until they are born. When they are born, they will be one meter long and weigh 20 kilograms.
distribution
The range of the sand tiger sharks is wide. They can be found in the temperate as well as in the subtropical and tropical zones. It occurs in the western Atlantic from the Gulf of Maine over the Caribbean and the Gulf of Mexico to Brazil and Patagonia in the south of Argentina . In the east Atlantic they are common off the coasts of Morocco , in the Mediterranean , off the Canary Islands to the Gulf of Guinea . There are other occurrences off the east coast of South Africa in the Indian Ocean and in the Red Sea . Larger populations of sand tiger sharks also live off Australia , Korea and Japan .
Systematics
The scientific names of species and genus were introduced in 1810 by the American polymath Constantine S. Rafinesque-Schmaltz . As Terra typica was Sicily specified. Eugomphodus (Gill, 1861) is a synonym of the genus Carcharias , Carcharias griseus (Ayres, 1843) is a synonym description of the species.
In 1878, another species of the genus Francis Day described the Indian sand tiger shark ( Carcharias tricuspidatus ) on the basis of a skin that has since been lost . It should occur in the northern Indian Ocean , on the coasts of India and Pakistan , possibly also in Indonesia , Vietnam , Australia , the Philippines and on the coast of northern China . A rounder snout and the lack of lip furrows were named as differences to the sand tiger shark. It should be 3.7 meters long, according to unreliable information from the first person describing it, even 6.1 meters long. While this shark was still treated as an independent species by Compagno in 1984 and was also included in representations based on it, such as the fishbase with the indication that it is possibly a synonym of Carcharias taurus , it appears in the version of the Sharks published in 2004 of the World by Compagno et al. no longer open. Thus the genus Carcharias is probably monotypical .
The sand tiger shark belongs to the order of the mackerel shark-like (Lamniformes) and was placed there in the family of sand sharks (Odontaspididae), to which the eponymous shark genus Odontaspis also belongs. As various studies on the mackerel shark systematics and cartilage fish systematics have shown, the sand tiger shark is not particularly closely related to Odontaspis . The closest relatives of the sand tiger shark, the shortfin mako (Lamnidae), including the well-known white shark ( Carcharodon carcharias ) is one, and the basking shark (Cetorhinidae) while Odontaspis together with the thresher sharks (Alopiidae), the megamouth (Megachasmidae) and the crocodile shark (Pseudocarchariidae) forms a clade within the mackerel shark-like.
In order to get back to monophyletic families, the Carchariidae family was revalidated in November 2019, which was introduced as Carchariae in 1838 by the German anatomists and zoologists Johannes Müller and Jakob Henle . The sand tiger shark is the only type of Carchariidae while only the genus Odontaspis remains with the Odontaspididae.
Sand tiger shark and human
Sand tiger sharks are enormously threatened in their populations. Because of the risk of confusion with the distantly similar looking tiger shark ( Galeocerdo cuvieri ) from the family of Requiem sharks (Carcharhinidae), it is held responsible for attacks on bathers and divers that have not been proven. The tiger shark, like the sand tiger shark, often invades coastal waters and snaps at anything that moves, including people. This was followed by heavy hunting of the sand tiger sharks, which in 1974 meant that they had to be legally protected in certain distribution areas, for example in the Cod Grounds Commonwealth Marine Reserve off Queensland and New South Wales in Australia and also in the territorial waters of the United States . They are classified as endangered by the IUCN .
In Japan, the meat of the sand tiger shark is in great demand. The sand tiger sharks are mostly caught with baited longlines. The fins are used for the shark fin soup and the cod liver oil as oil. By -catch in trawl nets used for fishing for bony fish, is another threat. Further large decimations of the stocks are being driven by sport fishermen who hunt sand tiger sharks with harpoons and explosive projectiles ( power heads ). Off the coasts of Australia there was a reduction in the population of up to 95 percent between 1950 and 1990. In other areas, such as off Florida , the species has almost completely disappeared. It is feared that it will become extinct in certain areas of distribution.
supporting documents
- ↑ Constantine S. Rafinesque-Schmaltz: Caratteri di Alcuni Nuovi Generi e Nuove Specie di Animali e Piante della Sicilia. Palermo (1810)
- ↑ Carcharias taurus in the Catalog of Fishes (English)
- ↑ Carcharias in the Catalog of Fishes (English)
- ↑ a b Leonard JV Compagno: Sharks of the world An annotated and illustrated catalog of shark species known to date Part 1 - Hexanchiformes to Lamniformes . FAO SPECIES CATALOG Full PDF Carcharias tricuspidatus
- ↑ Sand tiger shark on Fishbase.org (English)
- ↑ Deborah L. Bowden, Carolina Vargas-Caro, Jennifer R. Ovenden, Michael B. Bennett & Carlos Bustamante: The phylogenomic position of the gray nurse shark Carcharias taurus Rafinesque, 1810 (Lamniformes, Odontaspididae) inferred from the mitochondrial genome. Mitogenome Announcement, 2015, doi: 10.3109 / 19401736.2015.1089486
- ↑ Gavin JP Naylor, Janine N. Caira, Kirsten Jensen, Kerri AM Rosana, Nicolas Straube, Clemens Lakner: Elasmobranch Phylogeny: A Mitochondrial Estimate Based on 595 Species. Page 38 in Jeffrey C. Carrier, John A. Musick, Michael R. Heithaus: Biology of Sharks and Their Relatives (Marine Biology). Publisher: Crc Pr Inc, 2012, ISBN 1-4398-3924-7 . DOI: 10.1201 / b11867-4
- ↑ Kenshu Shimada: Phylogeny of lamniform sharks (Chondrichthyes: Elasmobranchii) and the contribution of dental characters to lamniform systematics. Paleontological Research, 9 (1): 55-72 (2005). doi: 10.2517 / prpsj.9.55
- ↑ Nicholas R. Stone and Kenshu Shimada: Skeletal Anatomy of the Bigeye Sand Tiger Shark, Odontaspis noronhai (Lamniformes: Odontaspididae), and Its Implications for Lamniform Phylogeny, Taxonomy, and Conservation Biology. Copeia 107 (4), 632-652, (2019). doi: 10.1643 / CG-18-160
Web links
- Sand tiger shark on Fishbase.org (English)
- Carcharias taurus in the endangered Red List species the IUCN 2008 Posted by: D. Pollard, A. Smith, 2000. Retrieved on January 2 of 2009.