Winged hammerhead shark
| Winged hammerhead shark | ||||||||||||
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Eusphyra blochii , illustration from 1889 |
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| Systematics | ||||||||||||
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| Scientific name of the genus | ||||||||||||
| Eusphyra | ||||||||||||
| Gill , 1861 | ||||||||||||
| Scientific name of the species | ||||||||||||
| Eusphyra blochii | ||||||||||||
| ( Cuvier , 1816) |
The wingtip hammerhead shark ( Eusphyra blochii ) belongs to the family of hammerhead sharks (Sphyrnidae). In this hammerhead species, the very pronounced widening of the head, the cephalofoil , is particularly noticeable, as its extension corresponds to about half the body length.
anatomy
The wingtip hammerhead is one of the comparatively small species of hammerhead shark with a maximum body length of 186 centimeters, with the average length being around 120 and 140 centimeters. It is characterized by a particularly broad cephalofoil , which, with a width of 40 to 50 percent of the body length, is significantly wider than that of all other hammerhead sharks. It is also very narrow and has greatly enlarged nostrils on the front, where the distance is 1.1 to 1.3 times the length of the nostril diameter, while in all other species it is 7 to 14 times the length of the nostril diameter . The eyes are located on the side at the end of the cephalofoil and are round or almost round.
The front dorsal fin attaches over the base of the pectoral fins and is therefore a little further forward than other hammerheads.
distribution
The wingtip hammerhead shark is found in tropical waters of the Pacific Ocean and the Indian Ocean (between latitudes 31 ° N and 20 ° S) mainly near the coast of the continental shelf . The distribution area extends from the Red Sea over the entire South Asian coast of the Indian Ocean to northern China and Japan as well as the entire Indo-Pacific region of Southeast Asia to the north coast of Australia .
Reproduction
The wingtip hammerhead is viviparous . The young talent in the uterus of the mother animal approach and feeds to birth a yolk sac - placenta . The gestation period is about 11 months, the females then give birth to between six and nine young. Rival fights have been observed between pregnant female sharks. Since the shark is characterized by an extremely broad head even as a young animal, the two head wings lie against the body before birth and only unfold after birth.
Systematics
Originally it was assumed that the broadening of the head developed gradually, with the spade-nosed shark ( Scoliodon laticaudus ) being regarded as a sister species to the hammerhead sharks within the requiem sharks . According to this idea, the shovel-nose hammerhead was the most original type of hammerhead, while the wingtip hammerhead with its very large cephalofoil was considered a strongly derived species.
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Relationships among hammerheads according to Compagno 1988
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Relationships among hammerheads according to Lim et al. 2010
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On the basis of phylogenetic investigations of morphological and molecular biological characteristics ( isoenzymes and mitochondrial DNA ) it could be proven that the wingtip hammerhead is the most primitive species within the hammerheads and within the genus Sphyrna the species with a very large cephalofoil (great hammerhead, Smooth hammerhead and bow-forehead hammerhead) are to be regarded as particularly original. The position of the species with particularly expansive cephalofoil was also confirmed by further investigations in 2010.
This suggests that within the hammerheads the large species with a large cephalofoil represent the original state and the smaller species with the narrower heads are derived from them. Regarding height, Lim et al. 2010 due to their kinship hypothesis and the distribution of the species that the most primitive hammerheads were large species, from which both the smaller wingtip hammerhead and the smaller Sphyrna species are derived.
Danger
The wingtip hammerhead has been classified as endangered in the IUCN Red List since 2016 .
Individual evidence
- ^ A b c d Leonard Compagno, Marc Dando, Sarah Fowler: Sharks of the World. Princeton University Press, Princeton 2005 ISBN 0-691-12072-2 , pp. 322-323.
- ↑ a b c d L.JV Compagno: Sharks of the Order Carcharhiniformes. Princeton University Press 1988.
- ↑ a b c Douglas D. Lim, Philip Motta, Kyle Mara, Andrew P. Martin: Phylogeny of hammerhead sharks (Family Sphyrnidae) inferred from mitochondrial and nuclear genes . In: Molecular Phylogenetics and Evolution . tape 55 , no. 2 , 2010, p. 572-579 .
- ↑ a b Mauro José Cavalcanti: A Phylogenetic Supertree of the Hammerhead Sharks (Carcharhiniformes: Sphyrnidae) . In: Zoological Studies . tape 46 , no. 1 , 2007, p. 6–11 ( zoolstud.sinica.edu.tw [PDF; 171 kB ]).
- ↑ Eusphyra blochii in the Red List of Threatened Species of the IUCN 2016. Posted by: Smart, JJ, Simpfendorfer, CA, 2015. Accessed July 11, 2016th
literature
- Leonard Compagno , Marc Dando, Sarah Fowler: Sharks of the World. Princeton University Press , Princeton 2005 ISBN 0-691-12072-2 , pp. 322-323.
- Leonard J. V. 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. Volume 4, FAO Rome 1984; Pp. 538-547. 92-5-101383-7. ( Family Sphyrnidae Gill, 1872 )
Web links
- Eusphyra blochii on Fishbase.org (English)
- Eusphyra blochii. In: Shark Foundation.