Borneo shark
| Borneo shark | |
|---|---|
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Scientific classification 
| |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Chondrichthyes |
| Subclass: | Elasmobranchii |
| Subdivision: | Selachimorpha |
| Order: | Carcharhiniformes |
| Family: | Carcharhinidae |
| Genus: | Carcharhinus |
| Species: | C. borneensis
|
| Binomial name | |
| Carcharhinus borneensis (Bleeker, 1858)
| |
| |
| Present (dark blue) and possible historical (light blue) range of the Borneo shark[2][3] | |
| Synonyms | |
|
Carcharias borneensis Bleeker, 1858 | |
The Borneo shark (Carcharhinus borneensis) is a
anal fin
origin.
Almost nothing is known about the natural history of the Borneo shark. It is
viviparous like other requiem sharks; the females bear litters of six pups, which are provisioned through gestation by a placental connection. The International Union for Conservation of Nature last assessed this species as Critically Endangered
. While an extant population has since been found, the Borneo shark continues to merit conservation concern given its highly limited range within heavily fished waters.
Taxonomy and phylogeny
Dutch
ichthyologist Pieter Bleeker originally described the Borneo shark as Carcharias (Prionodon) borneensis in an 1858 issue of the scientific journal Acta Societatis Regiae Scientiarum Indo-Neêrlandicae. He based his account on a newborn male 24 cm (9.4 in) long, caught off Singkawang in western Kalimantan, Borneo.[4] Later authors have recognized this species as belonging to the genus Carcharhinus.[5] Before 2004, only five specimens of the Borneo shark were known, all of them immature and collected before 1937.[2] In April and May 2004, researchers from Universiti Malaysia Sabah discovered a number of additional specimens while surveying the fishery resources of Sabah and Sarawak.[3]
The
spottail shark (C. sorrah), creek whaler (C. fitzroyensis), whitecheek shark (C. dussumieri), hardnose shark (C. macloti), and Pondicherry shark (C. hemiodon).[7] The Borneo shark resembles the sharpnose sharks (Rhizoprionodon) in certain traits, for example the enlarged pores by its mouth. Nevertheless, other aspects of its morphology firmly place it within Carcharhinus.[3]
Description
The Borneo shark is slim-bodied, with a long, pointed snout and oblique, slit-like nostrils preceded by narrow, nipple-shaped flaps of skin. The eyes are rather large and circular, and equipped with nictitating membranes. The corners of the sizable mouth bear short, indistinct furrows, and immediately above are a series of enlarged pores that are unique within the genus. There are 25–26 upper and 23–25 lower tooth rows. The upper teeth have a single, narrow, oblique cusp with strongly serrated edges, and large cusplets on the trailing side. The lower teeth are similar, but tend to be more slender and finely serrated. The five pairs of gill slits are short.[3][5]
The
dermal denticles are small and overlapping, each with three horizontal ridges leading to marginal teeth. This species is slate-gray above, darkening towards the tips of the dorsal fins and upper caudal fin lobe; some specimens have irregular rows of small, white blotches, which may be an artifact of handling. The underside is white, which extends onto the flanks as a vague pale band. There are faint, lighter edges on the pectoral, pelvic, and anal fin trailing margins. The largest known specimen measures 65 cm (26 in) long.[3][5]
Distribution and habitat
All recent specimens of the Borneo shark have been collected solely from fishery landing sites at
inshore waters in northwestern Borneo.[3][8] Of the five earlier specimens, four came from Borneo and one from Zhoushan Island in China, hinting at a wider historical distribution. This species was also recorded from Borongan in the Philippines in 1895, and Java in 1933; these records cannot be substantiated and there have been no subsequent sightings from these areas.[3]
Biology and ecology
viviparous like other requiem sharks, with the developing embryos provisioned by the mother through a placental connection formed from the depleted yolk sac. The litter size is six, and the pups are born at close to 24–28 cm (9.4–11.0 in) long. From the available specimens, the length at sexual maturity can be surmised to be under 55–58 cm (22–23 in) in males and under 61–65 cm (24–26 in) in females.[3][9]
Human interactions
The
artisanal and commercial fishing.[3] It is caught by line gear and used for meat, though it has minimal commercial significance.[8]
References
- ^ . Retrieved 24 May 2023.
- ^ a b c Dulvy, N.K., Bin Ali, A., Derrick, D., Dharmadi & Fahmi. (2021). "Carcharhinus borneensis". p. e.T39367A124407121.
{{cite web}}: CS1 maint: multiple names: authors list (link) - ^ ISBN 978-1-921605-57-4.
- ^ Bleeker, P. (1858). "Twaalfde bijdrage tot de kennis der vischfauna van Borneo. Visschen van Sinkawang". Acta Societatis Regiae Scientiarum Indo-Neêrlandicae. 5 (7): 1–10.
- ^ ISBN 92-5-101384-5.
- ^ Garrick, J.A.F. (1982). Sharks of the genus Carcharhinus. NOAA Technical Report, NMFS CIRC 445.
- ISBN 0-691-08453-X.
- ^ ISBN 978-1-921605-59-8.
- ^ ISBN 978-3-89937-132-1.
External links
Media related to Carcharhinus borneensis at Wikimedia Commons