Saw ray

Sawfish is a redirect to this article. For the type species see common sawfish .

Saw ray
The saw ray Pristis pristis in the Georgia Aquarium in Atlanta .
Systematics
Class : Cartilaginous fish (Chondrichthyes) Subclass : Euselachii Subclass : Plate gill (Elasmobranchii) without rank: Stingray (batoidea) Order : Rhinopristiformes Family : Saw ray
Scientific name
Pristidae
Bonaparte , 1838

Sawfish (Pristidae ( Gr .: “Pristis” = saw)), often also called sawfish and to be distinguished from saw sharks , are rays that have a rather elongated, shark-like body. Its most striking feature is the "saw", a cartilaginous protrusion of the head with teeth on the sides, which can make up more than 25% of the total length of the fish. The saw is used to catch prey. To do this, the animals swim in schools of fish and then beat back and forth with the saw in order to subsequently eat the injured victims. It is also used to dig for molluscs and crustaceans in muddy ground . The saw also serves as a sensory organ for electromagnetic signals to track down prey.

features

Sawfish are large rays and reach a length of 2.4 to 5 meters when fully grown, and according to some reports even 6 to 8 meters. Only Pristis clavata remains rather small at 1.40 meters. The body is slightly flattened and shark-like. The tail stalk is very strong, laterally flattened and has lateral keels. The transition from the body to the tail stalk is gradual. The body is covered with small placoid scales. There are no larger spines on the upper side of the body or on the tail stalk. The head is flattened and bears the eponymous "saw", a greatly elongated, flat rostrum , each with a row of sawtooth-like teeth on each side. The teeth sit in deep sockets, keep growing and are replaced by new ones if they are lost. The saw is primarily a sensory organ to track down prey, and is also used to scare away food by poking the ground or to immobilize or kill schooling fish by hitting them wildly. The eyes on the top of the head are well in front of the injection holes . On the underside of the head there are five gill slits on each side, approximately at the level of the middle of the base of the pectoral fin. Gill trap rays are absent. The mouth on the underside of the head is transverse, straight and without pits, folds or similar features. The nostrils lie in front of the mouth, are far apart and are clearly separated from the mouth. The anterior nasal valves are short, not connected to each other, and do not reach the mouth. The jaw teeth are very small, round or oval in shape and without any tips. They sit in 60 or more rows in each jaw, are uniform and not plate-like.

The pectoral fins are relatively small compared to those of other rays and do not grow together with the trunk to form a body disc. They start on the back of the head behind the mouth and end well before the start of the base of the pelvic fin. The pelvic fins are triangular and not divided into two lobes. On the top there are two large and equally large dorsal fins that can be crescent-shaped or triangular. They stand far apart: the first in front of or above the base of the pelvic fin, the second on the caudal peduncle. The caudal fin is large and resembles that of the shark. It is asymmetrical ( heterocerk ), the spine runs upwards in the caudal fin and supports the upper lobe. The lower lobe may be more or less well developed or it may be absent. Sawfish are yellowish, brown, greenish or gray-brown on the upper side, the belly is whitish. There are no drawings or markings of any kind on the body or on the fins.

Saw rays can only be confused with saw sharks (Pristiophoridae), which also have a saw-like rostrum. However, these tend to live in deeper sea regions and temperate latitudes. Their gill openings are on the sides of the head and in front of the pectoral fin bases. Their bodies are less flattened, the saw teeth on the rostrum are smaller and the underside of the rostrum is also covered with a number of small teeth. In the middle of the saw hairostrum there is a pair of long barbels on the sides .

Comparison of saw rays and saw sharks
	Pristis pristis	Japanese saw shark
features	Sawfish (Pristidae)	Saw sharks (Pristiophoridae)
Gills:	ventral (underside of the head)	lateral (head sides)
Barbels :	no barbels	a pair of barbels in the middle of the saw
Teeth on the side of the saw:	same size	alternately small and large
Habitat:	shallow water near the coast	at greater depths of the shelf seas
Size:	medium to large: 1.4 to 7.50 m	relatively small to medium-sized: 60 cm to 1.70 m

Pristis zijsron in the Genoa aquarium

The top and bottom of the rostrum of an Australian saw ray.

Occurrence

Sawfish live in tropical areas of the Atlantic and Indo-Pacific near the coast. Five species live on the northern coast of Australia . Some species also go to the brackish water zones and swim several hundred kilometers in the lower reaches of large rivers in Southeast Asia , New Guinea , Australia and the Amazon . Pristis microdon is known as the freshwater sawfish in Australia. Large populations of Pristis perotteti were known from Lake Nicaragua , where they were likely wiped out by commercial catches in the 1970s. It was not until 2006 that saw rays and the bull shark ( Carcharhinus leucas ) were placed under protection in Nicaragua.

The common sawfish ( Pristis pristis ) is also found in subtropical waters, e.g. B. in the western Mediterranean or in the cooler eastern Pacific from the Gulf of California to Ecuador .

nutrition

Sawfish are slow swimming fish that eat their invertebrates and small fish mainly near the bottom. Schooling fish are killed or injured by quick, side blows with a saw and then eaten.

Reproduction

Sawfish are eilebendgebärend ( ovoviviparous ). You can have more than 20 young. The saw is still soft at birth and only becomes hard when the yolk sac, which was very large at birth , is used up.

Systematics

As early as 1758, the founder of the binary nomenclature Carl von Linné described the first sawfish in his Systema Naturae as Squalus pristis (today Pristis pristis ). The family of saw rays (Pristidae) was established in 1838 by the biologist Charles Lucien Bonaparte . Usually the Pristidae are assigned to an independent order (Pristiformes) within the rays today. Phylogenetically, however, the saw rays are deep within a clade of different genus of fiddle rays . The violin rays become a paraphyletic taxon. The name Rhinopristiformes was given to a new order comprising saw and fiddle rays .

The systematic position of the saw rays within a large fiddle ray clade according to Ashliman et al. (2012)	The internal systematics of saw rays according to Faria et al. (2012)
Stingray (batoidea)    Rajiformes      Electric rays (Torpediniformes)      Trygonorrhinidae       Rhinopristiformes   Rhinobatos      Sawfish (Pristidae)      Glaucostegidae      Rhinidae      Stingray  (Myliobatiformes)	Sawfish (Pristidae)     Anoxypristis   Pointed-head saw ray ( Anoxypristis cuspidata )   Pristis   Pygmy saffron ( Pristis clavata )      Narrow-tooth saw ray ( Pristis pectinata )      Long-comb saw ray ( Pristis zijsron )      Common sawfish ( Pristis pristis )

There are two genera, one of which is monotypical , and five species:

genus		Scientific name	Common name	IUCN status	distribution
Anoxypristis		Anoxypristis cuspidata (Latham, 1794)	Pointed-head saw ray	Severely endangered	Red Sea, Persian Gulf and Indo-Pacific north to southern Japan, south to northern Australia and east to western central Pacific.
Pristis		Pristis clavata Garman , 1906	Dwarf saffron	Severely endangered	Western Indo-Pacific from the Bay of Bengal via Indonesia to eastern, tropical Australia.
		Pristis pectinata Latham , 1794	Narrow-tooth saw ray	Threatened with extinction	Tropical and subtropical Atlantic, possibly also in the Mediterranean.
		Pristis pristis ( Linnaeus , 1758)	Common sawfish	Threatened with extinction	Worldwide in the tropics and subtropics, including the western Mediterranean. In Lake Nicaragua, in West African rivers, in the Congo and in the Zambezi, also in fresh water.
		Pristis zijsron Bleeker , 1851	Long-comb saw ray	Threatened with extinction	Red Sea, Persian Gulf and Indo-Pacific to eastern, tropical Australia.

Tribal history and fossil record

Lebanopristis hiram , a Sclerorhynchid from the Upper Cretaceous Lebanon.

Fossil saw rays appear from the Eocene , including the two recent genera Anoxypristis and Pristis . The genus Propristis , which was found in Eocene deposits in West Africa and North America, is known only in fossil form . A very early sawfish may Peyeria from the Cenomanian of eastern North Africa, but its association with the Pristiden is controversial.

Purely fossil representatives and externally very similar to the saw rays are the so-called pseudo saw rays (Sclerorhynchidae). This group is considered to be the sister group of a clade of saw-rays and other ray families, that is, the saw-rays are probably more closely related to other ray families than to the pseudo-saw-rays and the "saw-ray habitus" has developed independently of each other in both families ( convergent evolution ). The pseudosaws lived from the Upper Cretaceous to the Paleocene and were found mainly in the USA. Specimens of Libanopristis , Micropristis and Sclerorhynchus come from Lebanon .

It is assumed that the saw rays were only able to develop a higher diversity in the Palaeogene because the ecological niche they occupy today was previously occupied by the pseudo saw rays.

Danger

All sawray species are threatened with extinction worldwide and are on the Red List ( IUCN ). They are mainly fished as bycatch , they quickly become entangled in nets with their saw and do not have the opportunity to free themselves. In addition, saws are still collected as trophies and used in traditional Chinese medicine because they are believed to have healing properties. In order to raise awareness of the worldwide endangerment of sawfish species, the American Associations of Zoos and Aquariums and the Sawfish Conservation Society made October 17th Sawfish Day.

Movie

• Sawfish - Neptune's Forgotten Children. Documentation, 2008, 43 min., Director: Florian Guthknecht, production: Bayerischer Rundfunk, summary by arte . Documentation on sawfish on the north coast of Australia and a project to save them from extinction.
• The laughing sawfish painted on the tower of U96 was made famous by the movie Das Boot .

swell

literature

• LJV Compagno, PR Last: Order Pristiformes. Pristidae. Sawfishes . P. 1410-1417 in: KE Carpenter, VH Niem (Ed.): FAO species identification guide for fishery purposes. The living marine resources of the Western Central Pacific. Volume 3. Batoid fishes, chimaeras and bony fishes part 1 (Elopidae to Linophrynidae). FAO , Rome 1999 ( PDF 469 kB)
• Kurt Fiedler: Textbook of Special Zoology, Volume II, Part 2: Fish. Gustav Fischer Verlag, Jena 1991, ISBN 3-334-00339-6 .
• Joseph S. Nelson : Fishes of the World. John Wiley & Sons, 2006, ISBN 0-471-25031-7 .
• Barbara E. Wueringer, Lyle Squire Jr., Shaun P. Collin: The biology of extinct and extant sawfish (Batoidea: Sclerorhynchidae and Pristidae). Reviews in Fish Biology and Fisheries, Vol. 19, No. 4, 2009, pp. 445-464, doi : 10.1007 / s11160-009-9112-7

Individual evidence

1. ↑ ^{a b} Neil C. Aschliman, Mutsumi Nishida, Masaki Miya, Jun G. Inoue, Kerri M. Rosana, Gavin JP Naylord: Body plan convergence in the evolution of skates and rays (Chondrichthyes: Batoidea). In: Molecular Phylogenetics and Evolution. Volume 63, No. 1, April 2012, pp. 28-42. doi: 10.1016 / j.ympev.2011.12.012 .
2. ↑ 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 43 in Jeffrey C. Carrier, John A. Musick, Michael R. Heithaus: Biology of Sharks and Their Relatives (Marine Biology). Publisher: Crc Pr Inc, 2012, ISBN 1-43983-924-7 .
3. ^ ^{A b} Vicente V. Faria, Matthew T. McDavitt, Patricia Charvet, Tonya R. Wiley, Colin A. Simpfendorfer & Gavin JP Naylor: Species delineation and global population structure of Critically Endangered sawfishes (Pristidae). Zoological Journal o the Linnean Society, Vol 167, Issue 1, 2012, DOI: 10.1111 / j.1096-3642.2012.00872.x
4. ↑ Anoxypristis cuspidata on Fishbase.org (English)
5. ↑ Anoxypristis cuspidata at the IUCN (English)
6. ↑ Pristis clavata on Fishbase.org (English)
7. ↑ Pristis clavata at the IUCN (English)
8. ↑ Pristis pectinata on Fishbase.org (English)
9. ↑ Pristis pectinata at the IUCN (English)
10. ↑ Pristis pristis on Fishbase.org (English)
11. ↑ Pristis pristis at the IUCN (English)
12. ↑ Pristis zijsron on Fishbase.org (English)
13. ↑ Pristis zijsron at the IUCN (English)
14. Jump up ↑ Jürgen Kriwet: The systematic position of the Cretaceous sclerorhynchid sawfishes (Elasmobranchii, Pristiorajea). Pp. 57-73 in: G. Arratia, A. Tintori (Eds.): Mesozoic Fishes 3 - Systematics, Paleoenvironments and Biodiversity. Publishing house Dr. Friedrich Pfeil, Munich 2004, ISBN 3-89937-053-8
15. ↑ Henri Cappetta: Sclerorhynchidae nov. fam., Pristidae et Pristiophoridae: un exemple de parallélisme chez les Sélaciens. Comptes rendus hebdomadaires des séances de l'Académie des sciences. Série D, Sciences naturelles. Vol. 278, No. 1, 1974, pp. 225-228 ( gallica.bnf.fr )
16. ^ Karl Albert Frickhinger: Fossil Atlas of Fish , Mergus-Verlag, Melle 1999, ISBN 3-88244-018-X
17. ↑ Tonya Wiley: International Sawfish Day is October 17. ourpositiveplanet.com, October 8, 2019, accessed August 23, 2020

Web links

Commons : Saw Ray  - Collection of images, videos and audio files

• Sawfish on Fishbase.org (English)
• Sawfish - Neptune's Forgotten Children (Part 1 of 3) TV show by BR , (Part 2 of 3) , (Part 3 of 3) .