Saw sharks

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Saw sharks
Japanese saw shark (Pristiophorus japonicus)

Japanese saw shark ( Pristiophorus japonicus )

Systematics
Subclass : Euselachii
Subclass : Plate gill (Elasmobranchii)
without rank: Sharks (selachii)
Superordinate : Squalomorphii
Order : Sawshark-like
Family : Saw sharks
Scientific name of the  order
Pristiophoriformes
Berg , 1958
Scientific name of the  family
Pristiophoridae
Bleeker , 1859

The family of saw sharks (Pristiophoridae) forms a family of sharks , which in turn consists of two genera , Pliotrema and Pristiophorus . Without close relatives, they simultaneously form one of the eight orders of the sharks, the saw-shark-like (Pristiophoriformes).

distribution

The species known so far live mainly in the western Atlantic , near Cuba , Florida and the Bahamas , in the southwest Indian Ocean near South Africa and in the western Pacific from Australia to Japan .

features

Saw sharks form one of the most peculiar groups of sharks and their outer shape with the elongated, saw-blade-like rostrum can easily lead to confusion with the saw- rays , which, however , are counted as rays and from which the saw-sharks differ by the two barbels on each side of the saw and by the fact that the gill slits are not on the underside of the body. The flat saw is alternately set with large and small teeth, which are regularly replaced. Most species are no longer than one and a half meters, the largest with a maximum length of 140 centimeters is Warren's six-gill sawshark . Like angel sharks , saw sharks have two stingless dorsal fins , no anal fin and large injection holes .

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

Way of life

Saw sharks feed on small fish, crustaceans and cuttlefish and reproduce ovoviviparously (oviparous). Much about their behavior and their living conditions has not yet been researched.

The long rostrum is used to search for food, which is equipped with barbels and other sensory organs and can therefore perceive movements and probably also electrical fields and chemical impressions in the sea floor. The prey is tracked down with a saw, dug up and probably also partly killed. In addition, the saw is also used by some saw sharks against attackers and other species.

Systematics

Long-nosed saw shark ( Pristiophorus cirratus )
Short-nosed saw shark ( Pristiophorus nudipinnis )

The saw sharks are divided into two genera , one of which contains three and the other seven species formally described . The genera differ in the number of gill openings and in the structure of the teeth. Pliotrema has six gill slits, the larger rostral teeth are serrated, and the teeth are reinforced by transverse elevations. In Pristiophorus , the teeth are smooth, the large rostral teeth remain smaller, there are only five gill slits.

Compagno et al. (2005) mention - in addition to the one Pliotrema species - eight Pristiophorus species, of which four had not yet been formally described at this point in time. Three of these species have now been described : the Tropical Saw Shark in 2008 , the Dwarf Saw Shark off the coast of East Africa in 2011 and, most recently, the Philippine Saw Shark in 2013 . In contrast, the "East Australian saw shark", which was formerly known informally by the IUCN under the name " Pristiophorus peroniensis ", is probably identical to the long-nosed saw shark ( Pristiophorus cirratus ). In March 2020, two new species of the genus Pliotrema were described, which are no longer monotypical.

Genera and species

Individual evidence

  1. ^ Leonard Compagno, Marc Dando, Sarah Fowler: Sharks of the World. Princeton Field Guides, Princeton University Press, Princeton and Oxford 2005; Pp. 131-136, ISBN 0-691-12072-2 .
  2. ^ A b Gordon K. Yearsley, Peter R. Last, William T. White: A new species of sawshark, Pristiophorus delicatus sp. nov. (Pristiophoriformes: Pristiophoridae), from northeastern Australia. In: PR Last, WT White, JJ Pogonoski: Descriptions of New Australian Chondrichthyans. CSIRO Marine and Atmospheric Research Paper No. 022. 2008, pp. 23–38, PDF (complete volume, 13 MB).
  3. ↑ DA Ebert, GM Cailliet: Pristiophorus nancyae , a New Species of Sawshark (Chondrichthyes: Pristiophoridae) from Southern Africa. Bulletin of Marine Science. Vol. 87, No. 3, 2011, pp. 501-512, doi: 10.5343 / bms.2010.1108 .
  4. ↑ David A. Ebert, Hana A. Wilms: Pristiophorus lanae sp. nov., a new sawshark species from the Western North Pacific, with comments on the genus Pristiophorus Müller & Henle, 1837 (Chondrichthyes: Pristiophoridae). Zootaxa . Vol. 3752, No. 1, 2013, pp. 86-100, doi: 10.11646 / zootaxa.3752.1.7 .
  5. ↑ a b Simon Weigmann, Ofer Gon, Ruth H. Leeney, Ellen Barrowclift, Per Berggren, Narriman Jiddawi, Andrew J. Temple: Revision of the sixgill sawsharks, genus Pliotrema (Chondrichthyes, Pristiophoriformes), with descriptions of two new species and a redescription of P. warreni Regan. PLOS ONE , March 2020, doi: 10.1371 / journal.pone.0228791

literature

Web links

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