World Library  
Flag as Inappropriate
Email this Article

Irrawaddy river shark

Article Id: WHEBN0006785104
Reproduction Date:

Title: Irrawaddy river shark  
Author: World Heritage Encyclopedia
Language: English
Subject: Carcharhinidae, Broadfin shark, Scoliodon, WikiProject Sharks/Watchlist, Ganges shark
Collection:
Publisher: World Heritage Encyclopedia
Publication
Date:
 

Irrawaddy river shark

Irrawaddy river shark
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Chondrichthyes
Subclass: Elasmobranchii
Superorder: Selachimorpha
Order: Carcharhiniformes
Family: Carcharhinidae
Genus: Glyphis
Species: G. siamensis
Binomial name
Glyphis siamensis
(Steindachner, 1896)
Occurrences of the Irrawaddy river shark
Synonyms

Carcharias siamensis Steindachner, 1896

Glyphis siamensis (Irrawaddy river shark) is a species of requiem shark, belonging to the family Carcharhinidae, known only from a single museum specimen originally caught at the mouth of the Irrawaddy River in Myanmar. A plain gray, thick-bodied shark with a short rounded snout, tiny eyes, and broad first dorsal fin, the Irrawaddy river shark is difficult to distinguish from other members of its genus without anatomical examination. Virtually nothing is known of its natural history; it is thought to be a fish-eater with a viviparous mode of reproduction. The International Union for Conservation of Nature (IUCN) has assessed this species as Critically Endangered, as its distribution is extremely limited and suffers heavy fishing pressure and habitat degradation.

Contents

  • Taxonomy 1
  • Distribution and habitat 2
  • Description 3
  • Biology and ecology 4
  • Human interactions 5
  • References 6

Taxonomy

The only known specimen was collected in the 19th century and described as Carcharias siamensis by Austrian ichthyologist Franz Steindachner, in Annalen des Naturhistorischen Museums in Wien (volume 11, 1896).[1][2] However, subsequent authors doubted the validity of this species, regarding it as an abnormal bull shark (Carcharhinus leucas), until in 2005 shark systematist Leonard Compagno recognized it as distinct member of the genus Glyphis.[3]

Distribution and habitat

The Irrawaddy river shark is found in the delta of the Irrawaddy River near Yangon, Myanmar, apparently inhabiting brackish water in a large, heavily silt-laden river lined with mangrove forests.[1]

Description

The sole specimen is a 60 cm (24 in) long immature male, suggesting an adult length of 1–3 m (3–10 ft). Like other river sharks, its body is robustly built with a high back that slopes down to a broadly rounded snout shorter than the mouth is wide. The eyes are minute, and the nares are small and widely spaced. The mouth contains 29 tooth rows in the upper and lower jaws, and has short furrows at the corners. The upper teeth are broad, triangular, and upright, with serrated margins, while the lower teeth at the front are more finely serrated with a pair of small cusplets at the base.[3][4]

The first dorsal fin is broad and triangular, originating over the rear pectoral fin bases with its free rear tip ending in front of the pelvic fin origins. The second dorsal fin is half as tall as the first, and there is no ridge between the dorsal fins. The trailing margin of the anal fin has a deep notch. The coloration is a plain grayish brown above and white below, without conspicuous fin markings. This shark most closely resembles the Ganges shark (G. gangeticus), but has more vertebrae (209 versus 169) and fewer teeth (29/29 versus 32–37/31–34).[3][4]

Biology and ecology

The small teeth of the Irrawaddy river shark suggests that it mainly preys on fish, while its small eyes are consistent with the extremely turbid water in which it hunts. Reproduction is presumably viviparous, with the young sustained by a placental connection, as in other requiem sharks.[3]

Human interactions

Intensive artisanal fishing, mainly gillnetting but also line and electrofishing, occurs in the stretch of river where the sole Irrawaddy river shark specimen was caught. Habitat degradation poses a further threat to this shark, including water pollution and the clearing of mangrove trees for fuel, construction materials, and other products. This shark may be naturally rare, which along with its highly restricted range, probable overfishing, and loss of habitat, has led the International Union for Conservation of Nature (IUCN) to list it as Critically Endangered. Despite fishing and scientific surveys in the area, no more Irrawaddy river sharks have been recorded in the hundred-plus years since the first.[1]

References

  1. ^ a b c d Barnett, L.A.K., K.L. Quaranta, D.A. Ebert, W.T. White and L.J.V. Compagno (2008). Glyphis siamensis. In: IUCN 2008. IUCN Red List of Threatened Species. Retrieved November 11, 2009.
  2. ^ Froese, Rainer and Pauly, Daniel, eds. (2009). "Glyphis siamensis in FishBase. November 2009 version.
  3. ^ a b c d Martin, R.A. spp.)GlyphisThe Mysterious, Endangered River Sharks (. ReefQuest Centre for Shark Research. Retrieved on November 11, 2009.
  4. ^ a b Compagno, L.J.V., M. Dando and S. Fowler (2005). Sharks of the World. Princeton University Press. p. 309–311.  
This article was sourced from Creative Commons Attribution-ShareAlike License; additional terms may apply. World Heritage Encyclopedia content is assembled from numerous content providers, Open Access Publishing, and in compliance with The Fair Access to Science and Technology Research Act (FASTR), Wikimedia Foundation, Inc., Public Library of Science, The Encyclopedia of Life, Open Book Publishers (OBP), PubMed, U.S. National Library of Medicine, National Center for Biotechnology Information, U.S. National Library of Medicine, National Institutes of Health (NIH), U.S. Department of Health & Human Services, and USA.gov, which sources content from all federal, state, local, tribal, and territorial government publication portals (.gov, .mil, .edu). Funding for USA.gov and content contributors is made possible from the U.S. Congress, E-Government Act of 2002.
 
Crowd sourced content that is contributed to World Heritage Encyclopedia is peer reviewed and edited by our editorial staff to ensure quality scholarly research articles.
 
By using this site, you agree to the Terms of Use and Privacy Policy. World Heritage Encyclopedia™ is a registered trademark of the World Public Library Association, a non-profit organization.
 



Copyright © World Library Foundation. All rights reserved. eBooks from World Library are sponsored by the World Library Foundation,
a 501c(4) Member's Support Non-Profit Organization, and is NOT affiliated with any governmental agency or department.