Tawny nurse shark

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Tawny nurse shark
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Chondrichthyes
Subclass: Elasmobranchii
Subdivision: Selachimorpha
Order: Orectolobiformes
Family: Ginglymostomatidae
Genus: Nebrius
Species:
N. ferrugineus
Binomial name
Nebrius ferrugineus
(
Lesson
, 1831)
Range of the tawny nurse shark
Synonyms

Ginglymostoma muelleri Günther, 1870
Ginglymostoma rueppellii Bleeker, 1852
Nebrius concolor Rüppell, 1837
Nebrius doldi Smith, 1953
Nebrodes concolor ogilbyi Whitley, 1934
Nebrodes macrurus Garman, 1913
Scyllium ferrugineum Lesson, 1831
Scymnus porosus Ehrenberg, 1871

The tawny nurse shark (Nebrius ferrugineus) is a species of carpet shark in the family Ginglymostomatidae, and the only extant member of the genus Nebrius.

It is found widely along

pectoral fins
. The maximum recorded length of the tawny nurse shark is 3.2 m (10 ft).

eggs produced by the mother while inside the uterus
. The litter size may be as small as one or two, based on the large size of near-term embryos.

Compared to the nurse shark, the tawny nurse shark has a more placid disposition and will often allow divers to touch and play with it. However, it should be accorded respect due to its powerful jaws and sharp teeth. This species is caught by

fishmeal. It is also esteemed as a game fish off Queensland, Australia, and is known for its habit of spitting water in the faces of its captors. The International Union for Conservation of Nature (IUCN) has assessed the tawny nurse shark as Vulnerable, with subpopulations in several areas already diminished or extirpated
.

Taxonomy and phylogeny

Early illustration of a tawny nurse shark from Fauna of British India (1889).

The tawny nurse shark was first described by French naturalist

René-Primevère Lesson as Scyllium ferrugineum, based on a 1.4 m (4 ft 7 in) long specimen from New Guinea. His short account was published in 1831 in Voyage au tour du monde, sur la corvette La Coquille. A more detailed description, along with an illustration, was published by German naturalist Eduard Rüppell in 1837 as Nebrius concolor, based on a specimen from the Red Sea. Both names were retained, often in separate genera (Ginglymostoma and Nebrius respectively), until they were synonymized by Leonard Compagno in 1984. Compagno recognized that the tooth shape differences used to separate these species were the result of differences in age, with N. concolor representing younger individuals.[2]

The genus name Nebrius is derived from the Greek word nebris or nebridos, meaning the skin of a fawn. The

common names for this species include giant sleepy shark, Madame X (a name coined by the shark fisherman Norman Caldwell in the 1930s for the then-unidentified Australian specimens),[4] nurse shark, rusty catshark, rusty shark, sleepy shark, spitting shark, and tawny shark.[5] Based on morphological similarities, Nebrius is believed to be the sister genus of Ginglymostoma, with both being placed in a clade that also contains the short-tail nurse shark (Pseudoginglymostoma brevicaudatum), the whale shark (Rhincodon typus), and the zebra shark (Stegostoma tigrinum).[6]

Distribution and habitat

The tawny nurse shark is widely distributed in the Indo-Pacific region. In the Indian Ocean, it is found from

Ma). The presence of these fossils indicates that the range of the tawny nurse shark once extended to the tropical Atlantic Ocean, prior to the formation of the Isthmus of Panama.[7]

An inshore species, the tawny nurse shark inhabits continental and insular shelves over sandy flats or beds of seagrass, as well as along the outer edges of coral or rocky reefs. This shark may be found from the surf zone, often in water barely deep enough to cover its body, to a maximum depth of 70 m (230 ft) on coral reefs; it is most common at a depth of 5–30 m (16–98 ft). Young sharks are generally found in the shallow areas of lagoons, while adults may be encountered across a variety of habitats.[2]

Description

The sickle-shaped pectoral fins of the tawny nurse shark are one of its characteristic traits.

The tawny nurse shark grows to a maximum length of 3.2 m (10 ft).

fan, with a broad base rising to a small, sharp central point flanked by 3 or more smaller cusps on both sides. As the shark ages, the teeth become relatively taller and thicker. The fourth and fifth pairs of gill slits are placed much closer together than the others.[2][3]

The dorsal and

dermal denticles are diamond-shaped, bearing 4–5 faint ridges radiating from a blunt point. Tawny nurse sharks are yellowish, reddish, or grayish brown above and off-white below, and are capable of slowly changing their color to better blend with the environment. Young sharks have starkly white lower eyelids.[2]

Many tawny nurse sharks found off the coasts of Japan, Taiwan, and the Ryukyu Islands lack a second dorsal fin. This physical abnormality has been speculated to result from pregnant females being exposed to water of unusually high salinity and/or temperature, possibly from human activity. In 1986, a 2.9 m (9 ft 6 in) long adult male with both a missing dorsal fin and partial albinism (in the form of white body color with gray-brown eyes) was captured off Wakayama Prefecture, Japan. This anomalous individual is the largest albino shark known to date, having survived for a long time in the wild despite its lack of camouflage.[8][9]

Biology and ecology

Tawny nurse sharks often rest piled together during the day.

With a more streamlined form than other nurse sharks, the tawny nurse shark is believed to be a less benthic, more active swimmer. The characteristics of its body, head, fins, and teeth are comparable to other active reef sharks sharing its range, such as the sicklefin lemon shark (Negaprion acutidens). Tawny nurse sharks are primarily nocturnal, though they are said to be active at all hours off Madagascar, and in captivity they will become diurnally active if presented with food. During the day, groups of two dozen or more sharks can be found resting inside caves and under ledges, often stacked atop one another. Individual sharks have small home ranges that they consistently return to each day.[2]

The tawny nurse shark has few natural predators; attacks on this species have been reported from

tapeworms in the genus Pedibothrium, which infest the shark's spiral intestine.[10]

Feeding

The tawny nurse shark may be one of the few fishes specializing in preying on octopus.

surgeonfish, queenfish, and rabbitfish), and the occasional sea snake. Hunting tawny nurse sharks swim slowly just above the sea floor, poking their heads into depressions and holes. When a prey item is found, the shark forcefully expands its large, muscular pharynx, creating a powerful negative pressure that sucks the prey into its mouth.[2]

Life history

Mating in the tawny nurse shark is known to occur from July to August off Madagascar.

oviparous. The egg capsules of this species are onion-shaped, with thin, brown, translucent shells.[9] The tawny nurse shark is the only carpet shark in which there is oophagy: once the developing embryos exhaust their supply of yolk, they gorge on eggs produced by the mother and acquire the distended abdomen characteristic of such oophagous embryos. Unlike in mackerel sharks, the eggs consumed by the embryos are large and shelled rather than small and undeveloped. There is no evidence of sibling cannibalism as in the sand tiger shark (Carcharias taurus).[2]

Various authors have reported the length at birth anywhere from 40 to 80 cm (16 to 31 in), with the discrepancy possibly reflecting geographic variation. Although females release up to four

fertilized eggs into each uterus, the very large size of the newborns suggest that the litter size may be as few as one or two. In one examined female that had two embryos sharing a single uterus, one embryo was much smaller and thinner than the other, implying that competition may eliminate the additional siblings. Males attain sexual maturity at a length of 2.5 m (8 ft 2 in), and females at a length of 2.3–2.9 m (7 ft 7 in – 9 ft 6 in).[1][2]

Human interactions

The tawny nurse shark is prized by recreational anglers off Queensland.

Encounters with tawny nurse sharks underwater indicate a more docile demeanor than the similar nurse shark; usually divers are able to approach the sharks closely and even touch and play with them without incident. However, this species has been infrequently provoked into biting, and merits respect due to its strength, small but sharp teeth, and extremely powerful jaws. Tawny nurse sharks are favored attractions for

Okinawa, and Singapore, where they may become tame enough to be hand-fed.[2] An Australian woman was bitten while hand feeding them in 2018.[12]

The tawny nurse shark is taken by commercial fisheries operating throughout its range, including off Pakistan, India, Thailand, and the Philippines; an exception is in Australian waters, where it is only taken in small numbers as

gill nets, and on hook-and-line.[1] The meat is sold fresh or dried and salted, the fins are used for shark fin soup, and the offal processed into fishmeal. In addition, the liver is a source of oil and vitamins, and the thick, tough skin is made into leather products. Off Queensland, Australia, the tawny nurse shark is valued by big-game anglers. When hooked, large individuals are tenacious opponents and are difficult to subdue due to their habit of spinning. They are also capable of spitting a powerful jet of water into the faces of their captors, making grunting noises in between jets (making the tawny shark one of the few species of sharks to produce a noise);whether this is a deliberate defensive behavior is uncertain.[2]

The

Least Concern, as there it is not targeted by fisheries.[1]

References

  1. ^
    doi:10.2305/IUCN.UK.2021-2.RLTS.T41835A173437098.en. Retrieved 19 November 2021.{{cite journal}}: CS1 maint: multiple names: authors list (link
    )
  2. ^
    ISBN 92-5-104543-7
    .
  3. ^ a b c Bester, C. Biological Profiles: Tawny Nurse Shark Archived 2012-05-24 at the Wayback Machine. Florida Museum of Natural History Ichthyology Department. Retrieved on June 7, 2009.
  4. ISBN 0-7316-0234-X
    .
  5. ^ a b Froese, Rainer; Pauly, Daniel (eds.) (2009). "Nebrius ferrugineus" in FishBase. June 2009 version.
  6. ^ Goto, T. (2001). "Comparative Anatomy, Phylogeny and Cladistic Classification of the Order Orectolobiformes (Chondrichthyes, Elasmobranchii)". Memoirs of the Graduate School of Fisheries Science, Hokkaido University. 48 (1): 1–101.
  7. doi:10.11137/2005_2_31-58
    .
  8. ^ Taniuchi, T. & Yanagisawa, F. (1987). "Albinism and lack of second dorsal fin in an adult tawny nurse shark, Nebrius concolor, from Japan". Japanese Journal of Ichthyology. 34 (3): 393–395.
  9. ^ a b Teshima, K.; Kamei, Y.; Toda, M. & Uchida, S. (December 1995). "Reproductive Mode of the Tawny Nurse Shark Taken from the Yaeyama Islands, Okinawa, Japan with Comments on Individuals Lacking the Second Dorsal Fin". Bulletin of the Seikai National Fisheries Research Institute. 73: 1–12.
  10. S2CID 24554892
    .
  11. doi:10.1098/rstb.1996.0094
    .
  12. ^ Campbell, Kate. "Shark feeding in Kimberley ends with painful lesson after Perth woman bitten". The West.

External links

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