Ganges shark
Ganges shark Temporal range: Miocene-recent[1]
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Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Chondrichthyes |
Subclass: | Elasmobranchii |
Subdivision: | Selachimorpha |
Order: | Carcharhiniformes |
Family: | Carcharhinidae |
Genus: | Glyphis |
Species: | G. gangeticus
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Binomial name | |
Glyphis gangeticus (J. P. Müller & Henle, 1839)
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Glyphis gangeticus inhabits the Ganges-Hooghly River system | |
Synonyms | |
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The Ganges shark (Glyphis gangeticus) is a
Taxonomy
Formerly the Borneo river shark (Glyphis fowlerae) and the Irrawaddy river shark (Glyphis siamensis) were considered to represent two other species in the genus Glyphis. They have recently been reclassified as G. gangeticus based on genetic studies, and their scientific names are treated as synonyms.[4]
The Borneo river shark is known only from the Kinabatangan River in Borneo. It can reach a length of 78 cm (31 in). Only 13 specimens are known to science, all collected in 1996. Expeditions in 2010 and 2011 failed to find any, and while fishermen recognised the shark, they have not been seen for many years.[4]
The Irrawaddy river shark is known only from a single museum specimen originally caught at the mouth of the
A possibly
Physical appearance
G. gangeticus is a little-known species that is yet to be adequately described.[8] Its size at birth is 56 to 61 cm (22 to 24 in), growing to an estimated 178 cm (70 in) at maturity, with a maximum size of about 204 cm (80 in).[9] The size at birth or maturity is unknown for any other Glyphis species.[6]
A typical requiem shark in its external appearance, it is stocky, with two spineless
Its snout is broadly rounded and much shorter than the width of its mouth. The mouth is long, broad, and extends back and up towards the eyes.[3]
Its eyes are minute, suggesting that it may be adapted to turbid water with poor visibility, such as occurs in the Ganges River and the
The upper teeth have high, broad, serrated, triangular cusps and the labial furrows are very short. The lower front teeth have long, hooked, protruding cusps with unserrated cutting edges along the entire cusp, but without spear-like tips and with low cusplets on feet of crowns. The tooth row counts are 32–37/31–34.[10]
Diagnostic features
G. gangeticus can be identified by the first few lower front teeth, which have cutting edges along entire cusp, giving the cusps a claw-like shape, and low cusplets. Also, a second dorsal fin that is about half the height of first dorsal is distinct to this species.[11]
Distribution
The Ganges shark, as its name suggests, is largely restricted to the rivers of eastern and northeastern India, particularly the
In theory, G. gangeticus could occur in shallow marine estuaries; however, no marine records of the species have been verified to date. Originally, the species was assigned a wide range in the Indo-West Pacific, but this was found to be mostly based on other species of requiem sharks, particularly members of the genus Carcharhinus.[9]
Most literature records and specimens labelled as this species are in fact bull sharks (Carcharhinus leucas) or other carcharhinid species. An extensive 10-year search produced only a few specimens, caught in 1996 in the Ganges River.[14]
Habitat and ecology
G. gangeticus is known to inhabit only freshwater, inshore marine, and estuarine systems in the lower reaches of the Ganges-Hooghly River system. Their feeding habits are mostly unknown. The shark's small eyes and slender teeth suggest that it is primarily a fish-eater and is adapted to turbid water.
Reproduction
It is probably
Possibility of migration
Some researchers consider G. gangeticus to be amphidromous, covering more than 100 km (62 mi) in both directions.[16] However, this is not thought to be for breeding, as the case in anadromous and catadromous species.[17] The presence of newborn individuals in the Hooghly River suggests that the young may be born in fresh water.[11]
A specimen photographed in 2011 by natural history journalist Malaka Rodrigo at Negombo fish market in Sri Lanka prompted researcher Rex de Silva to speculate on whether the species could occasionally be carried south of its normal range by ocean currents. However, only the head of the shark appears in the photo. Leading shark expert Leonard Compagno emphasised the need to check the dentition and the dorsal fin proportions to confirm the specimen as G. gangeticus, stating that it could also be one of the four other named species.[18]
Specimens
G. gangeticus was originally known only from three 19th-century museum specimens, one each in the
One female specimen was recorded at Sassoon Docks in Mumbai, India in February 2016, measuring 266 cm (105 in) total length. It was caught in the Arabian Sea.[20]
Molecular biology
Glyphis species, like other sharks, exhibit a very slow rate of genetic change. This makes them even more vulnerable to becoming extinct, as they are unable to adapt to the rapid and extreme changes caused by humans to their environment.[6]
As only a few specimens exist, naturally little material available is for genetic sampling. However, two websites list records for G. gangeticus:
The Barcode of Life Data Systems (BOLDS) Stats website[21] lists one record:
Public Records: 0
Specimens with Barcodes: 1
Species With Barcodes: 1
The NCBI Taxonomy database has one record of mitochondrial genetic material (1,044 base pairs of linear DNA):
Glyphis gangeticus bio-material GN2669,[22] reported in a 2012 paper on DNA sequencing in shark and ray species.[23]
Conservation
G. gangeticus is one of 20 sharks on the
Major threats
River sharks are thought to be particularly vulnerable to habitat changes. The Ganges shark is restricted to a very narrow band of habitat that is heavily affected by human activity. Overfishing, habitat degradation from
The single Irrawaddy river shark specimen stems from an area of intensive
Conservation actions
In 2001, the Indian government banned the landing of all species of chondrichthyan fish in its ports. However, shortly afterwards, this ban was amended to cover only 10 species of chondrichthyans. These, including G. gangeticus, are protected under Schedule I, Part II A of the
Human interaction
The Ganges shark is widely feared as a ferocious man-eater,[28] but most of the attacks attributed to it are probably the result of confusion with the bull shark Carcharhinus leucas.[10] This is likely because bull sharks are known to travel long distances into freshwater systems and may co-exist in the same waters as the Ganges shark. Since little is known about the behaviour of genuine freshwater river sharks, and since G. gangeticus is critically endangered, contact with humans is very rare.[29]
The biological differences between the Ganges shark and bull shark also point to a lower likelihood of attacks on humans by the Ganges shark. G. gangeticus has much narrower, higher, upper teeth and slender-cusped, less heavily built lower teeth than C. leucas. Such small sharp teeth are more suitable for fish-impaling, and less useful for dismembering tough mammalian prey than the stout teeth of the bull shark.[11]
Etymology
Glyphis: from Greek glyphe, means "carving".[30]
See also
References
- ^ P. E. P, Deraniyagala (1969). "A Miocene vertebrate faunule from the Malu member of Ceylon". Spolia Zeylanica.
- ^ . Retrieved 10 November 2022.
- ^ S2CID 35379347.
- ^ PMID 26460025.
- ^ Froese, Rainer; Pauly, Daniel (eds.) (2009). "Glyphis siamensis" in FishBase. November 2009 version.
- ^ a b c d e f Martin, R. A. "The Mysterious, Endangered River Sharks (Glyphis spp.)". ReefQuest Centre for Shark Research. Retrieved 10 December 2012.
- ISBN 978-0-691-12072-0.
- S2CID 52833147.
- ^ a b c Compagno, L. J. V. (2005). 'Ganges shark Glyphis gangeticus'. In: Fowler, S.L., Cavanagh, R.D., Camhi, M., Burgess, G.H., Cailliet, G.M., Fordham, S.V., Simpfendorfer, C.A. and Musick, J.A. (eds). Sharks, rays and chimaeras: the status of the Chondrichthyan fishes. Gland, Switzerland, and Cambridge, UK.: IUCN Species Survival Commission Shark Specialist Group, IUCN. pp. 305–306.
- ^ a b c d Compagno, L. J. V. (1984). "FAO Species Catalogue. Vol. 4. Sharks of the world. An annotated and illustrated catalogue of shark species known to date. Part 2 - Carcharhiniformes". FAO Fisheries Synopsis. 125 (4/2): 251–655. Retrieved 6 December 2012.
- ^ a b c "Glyphis gangeticus". Marine Species Identification Portal. Retrieved 6 December 2012.
- ^ "Glyphis gangeticus". Carnivora forum. Retrieved 6 December 2012.
- ^ a b Adamson, Allan (21 April 2018). "Rare River Shark Species Not Seen In A Decade Found On Sale In A Fish Market". Tech Times. Retrieved 22 April 2018.
- ^ Compagno, L. J. V. (2002). 'Freshwater and estuarine elasmobranch surveys in the Indo-Pacific region: threats, distribution and speciation'. In: S.L. Fowler, T.M. Reed and F.A. Dipper (eds) Elasmobranch Biodiversity, Conservation and Management; Proceedings of the International Seminar and Workshop, Sabah, Malaysia, July 1997. Gland, Switzerland and Cambridge, UK: IUCN SSC Shark Specialist Group.
- ^ Roberts, T. R. (2005). 'Debunking the mythology of the so-called freshwater shark of the Ganges. Glyphis gangeticus (Elasmobranchii, Carcharhinidae)'. In: 7th Indo-Pacific Fish Conference. Howard International Hotel, Taipei, Taiwan. Academica Sinica, Taipei, Taiwan. Taipei, Taiwan: Ichythological Society of Taiwan.
- ^ Hărșan, R.; Petrescu-Mag, I. V. (2008). "Endangered fish species of the world – a review". AACL Bioflux. 1 (2): 193–216.
- ^ Riede, K. (2004). 2004 Global register of migratory species - from global to regional scales. Final Report of the R&D-Projekt 808 05 081. Bonn, Germany: Federal Agency for Nature Conservation. p. 329.
- ^ de Silva, Rex I. (May–August 2011). "Does the Ganges shark Glyphis gangeticus stray to Sri Lanka?". Bombay Natural History Society. 108 (2): 136.
- ISBN 9782831703350.
- PMID 29611178.
- ^ "Glyphis gangeticus". Barcode of Life Data Systems. Retrieved 6 December 2012.
- ^ "Glyphis gangeticus". NCBI. 31 July 2012. Retrieved 10 December 2012.
- S2CID 83264478.
- )
- .
- ^ Schedule I, Part II A, Indian Wildlife Protection Act 1972. Government of India Ministry of Environment and Forests. 2006.
- ^ S.A. Hussain and Ruchi Badola (ed.). "Aquatic Fauna of Ganga River: Status and Conservation. Ganga Aqualife" (PDF). Conservation Monitoring Centre, Wildlife Institute of India, Dehradun.WII-GACMC (2017) Pp 120,124
- ^ Coppleson, V. M. (1962). Shark Attack. Sydney, Australia: Angus and Robertson.
- PMID 22429712.
- ^ "Common names of Glyphis gangeticus". Fish base. Retrieved 10 December 2012.