Carcharhinus

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Carcharhinus
Blacktip reef shark (Carcharhinus melanopterus)

Blacktip reef shark ( Carcharhinus melanopterus )

Systematics
Subclass : Plate gill (Elasmobranchii)
without rank: Sharks (selachii)
Superordinate : Galeomorphii
Order : Ground Sharks (Carcharhiniformes)
Family : Requiem sharks (Carcharhinidae)
Genre : Carcharhinus
Scientific name
Carcharhinus
Blainville , 1816

The genus Carcharhinus is the most extensive genus of Requiem sharks (Carcharhinidae). It includes over 30 species . The representatives of this group occur in all marine waters of the tropical and temperate latitudes and can also be found in brackish water , for example in front of river mouths, and in fresh water.

Its scientific name is derived from the Greek karcharos , "sharp" and rhis (genitive rhinos ), "nose". They are also namesake of the family of requiem sharks (Carcharhinidae).

features

The Carcharhinus species, usually between one and a maximum of about 4 meters long, have an anal fin and two dorsal fins , the front of which is larger than the rear. The dorsal fins are usually sickle-shaped and upright, in some species they can be more or less rounded. The pectoral fins are also large and sickle-shaped, with the exception of the whitetip deep-sea shark with its very large, wing-like and strongly rounded fins. The beginning of the first dorsal fin is in most species above the pectoral fins or immediately behind the end of the free inner edge of the pectoral fins. A species-specific interdorsal ridge may be present. The anal fin is usually about the same size or slightly larger than the second dorsal fin. The caudal fin has a comparatively small lower and a very large upper lobe.

The back color of most species is gray to gray-brown, rarely also bronze or bluish. The belly can be the same color as the back or be significantly lighter to white. In many species, the tips of the fins show a typical black or white coloring, and drawing patterns can appear on the flanks of the animals.

The snout is long and wide, flattened or pointed. They are also characterized by five gill slits , round eyes with a nictitating membrane and blade-like single-pointed teeth. They differ from the other genera of this family in that they do not have an injection hole and the cutting edges of the upper jaw teeth and (with a few exceptions) those of the lower jaw are always toothed. Other features concern the arrangement and size of the fins in relation to one another.

distribution and habitat

Galapagos shark ( Carcharhinus galapagensis )

The species of the genus Carcharhinus occur worldwide in all temperate to tropical marine areas. There are a number of species that can only be found in narrow coastal areas such as the Australian blacktip shark ( C. tilstoni ) and other species on the Australian coasts or the Caribbean reef shark ( C. perezi ) in the Caribbean; of some types also exist very few copies such as from Pondicherry Shark ( C. hemiodon ) are known of which only 20 copies. There are also a number of cosmopolitan species that can be found in almost all marine areas with the exception of the polar seas, including the whitetip deep-sea shark ( C. longimanus ) and the silky shark ( C. falciformis ).

Most species also live in the area of ​​the coasts, the reef areas and the continental shelf and do not penetrate far into the pelagic . Some species can be found in the bays of freshwater rivers, but only the bull shark ( C. leucas ) regularly invades large river systems in Asia or Africa. Real freshwater sharks such as river sharks (genus Glyphis ) do not exist in this genus. Pronounced deep sea species are exclusively the whitetip deep sea shark and the silk shark.

In the Mediterranean , 10 species of the genus can be found more or less regularly. Some of these species are casual visitors who enter via the Strait of Gibraltar or the Suez Canal. Other species live permanently in the Mediterranean and also give birth to their young here.

Way of life

Carcharhinus species are typically very active and slow to moderate-paced shark species. They are active during the day and at night and, depending on the species, stay close to the surface of the water, especially during the day. As a rule, they are solitary animals, but they can also come together in smaller or larger groups to hunt.

nutrition

Whitetip deep-sea shark ( Carcharhinus longimanus ) accompanied by pilot fish ( Naucrates ductor )

Carcharhinus species, like all requiem sharks, are strong swimmers and predatorily feed on a variety of fish including other sharks, octopus , crustaceans , turtles and marine mammals such as seals, and the occasional seabird . There are no outspoken food specialists, the species-specific food spectrum depends primarily on the size and the marine region as well as on whether the animals hunt in the open water or on the bottom.

In particular, the large sharks such as the whitetip deep-sea shark and the silky shark, but also sharks of other genera such as the blue shark ( Prionace glauca ), the tiger shark ( Galeocerdo cuvier ) or the great white shark ( Carcharodon carcharias ), are not picky about the choice of prey and on the hunt they attack all possible prey animals of suitable size (opportunistic predators). The wide range of food available allows these species to cope with almost any marine habitat. Correspondingly, however, they can also be potentially dangerous for swimmers and divers, since they also regard them as prey.

Reproduction

Young blacktip reef shark on the beach

The species of the genus are viviparous and form a yolk sac placenta ( placental viviparous ). Depending on the species and the size of the mother, the females give birth between one and about 15 young animals. The gestation periods differ depending on the species, region and population and can be between 9 and 24 months. The very slowly growing animals reach sexual maturity at a length which, depending on the species, is around one to two meters, whereby the sexually mature females are usually somewhat longer and older.

Systematics

There are 36 species in the genus. The differentiation of the species is often very difficult because the main defining features such as the relative body proportions and the shape of the placoid scales change in the course of ontogeny . In addition, in some species there is a clear sexual dimorphism in terms of color and tooth shape. Another important distinguishing feature is the number of vertebrae , which means that an unambiguous determination to distinguish between externally very similar species is only possible through a combination of external and internal characteristics. Often the regional occurrence or behavior of the animals helps with the determination.

The night sharks (formerly Hypoprion ), which were previously listed as a separate genus, are now assigned to this genus. The genus Carcharhinus contains the following 36 species:

Small blacktip shark ( Carcharhinus limbatus )

The genus Carcharhinus is very likely to be paraphyletic with regard to the blue shark ( Prionace glauca ), so it should include it. According to a molecular biological study in 2008, the shark is the sister species of the great nosed shark ( C. altimus ) and the silk shark ( C. falciforum ), which are grouped in the middle of the genus.

Humans and Carcharhinus species

Silky shark ( Carcharhinus falci )

Within the genus Carcharhinus there are a number of very large shark species that can also be found regularly in coastal areas. Accordingly, many of the species are classified as potentially dangerous for humans, including the silky shark, the bull shark and the whitetip deep sea shark. There have been a number of documented cases of attacks by these species on swimmers, divers and boats, as well as others where they are suspected of being attackers.

see also: → Danger to people from sharks

Many Carcharhinus however TYPES are on the Red List of endangered species of the IUCN as endangered to critically endangered species. The high pressure caused by fishing in a large part of the sharks' distribution areas is given as a source of danger . They are mainly caught as bycatch in deep-sea fishing with longlines and trawls. The large fins of the deep sea species are also very popular as the basis of the well-known shark fin soup , the carcasses are disposed of after removal. Due to the very imprecise data on deep-sea fishing, there are hardly any concrete catch figures or information on population sizes and changes.

supporting documents

  1. ^ Excursus on opportunistic predators in the species portrait tiger shark , de Maddalena & Bänsch 2005; Page 2007
  2. ↑ a b William T. White: A redescription of Carcharhinus dussumieri and C. sealei, with resurrection of C. coatesi and C. tjutjot as valid species (Chondrichthyes: Carcharhinidae). Zootaxa 3241: 1-34 (2012)
  3. ↑ William T. White & Simon Weigmann: Carcharhinus humani sp. nov., a new whaler shark (Carcharhiniformes: Carcharhinidae) from the western Indian Ocean. Zootaxa 3821 (1): 71-87 (2014)
  4. ^ William T. White, Peter M. Kyne and Mark Harris. 2019. Lost before Found: A New Species of Whaler Shark Carcharhinus obsolerus from the Western Central Pacific known only from Historic Records. PLoS ONE. 14 (1): e0209387. DOI: 10.1371 / journal.pone.0209387
  5. ^ Mine Dosay-Akbulut: The phylogenetic relationship within the genus Carcharhinus. In: Comptes Rendus Biologies. 331, 2008, p. 500, doi : 10.1016 / j.crvi.2008.04.001 .

literature

  • LJV Compagno : Sharks of the world. An annotated and illustrated catalog of shark species known to date. Part 2. Carcharhiniformes. FAO Species Catalog for Fishery Purposes Vol. 4. FAO Rome 1984. ISBN 92-5-101383-7 ( Complete PDF )
  • Leonard Compagno, Marc Dando, Sarah Fowler: Sharks of the World. Princeton Field Guides, Princeton University Press , Princeton and Oxford 2005; Pages 288-308. ISBN 978-0-691-12072-0
  • Alessandro de Maddalena, Harald Bänsch: Sharks in the Mediterranean , Franckh-Kosmos Verlags-GmbH, Stuttgart 2005; Pages 176-203. ISBN 3-440-10458-3
  • Ralf M. Hennemann: Sharks and rays worldwide. Jahr-Verlag, Hamburg 2001; Pages 119–149. ISBN 3-86132-584-5 .

Web links

Commons : Carcharhinus  - collection of images, videos and audio files
  • Carcharhinus on Fishbase.org (English)
  • Welt Online AFP / mcz: Unequal Parents - Hybrid Sharks Discovered for the First Time in the World, January 3, 2012; Welt Online Ulli Kulke: Hybrid Sharks - The end of the biological concept of species seems near, from January 4, 2012; Zeit Online AFP: Evolution - Australian researchers find hybrids of two shark species, from January 3, 2012