Nurse sharks
Overview
 
Ginglymostomatidae is a cosmopolitan
Cosmopolitan distribution
In biogeography, a taxon is said to have a cosmopolitan distribution if its range extends across all or most of the world in appropriate habitats. For instance, the killer whale has a cosmopolitan distribution, extending over most of the world's oceans. Other examples include humans, the lichen...

 family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...

 of carpet shark
Carpet shark
The carpet sharks are an order, Orectolobiformes, of sharks, so called because many members have ornate patterns reminiscent of carpets....

s, containing the three monotypic
Monotypic
In biology, a monotypic taxon is a taxonomic group with only one biological type. The term's usage differs slightly between botany and zoology. The term monotypic has a separate use in conservation biology, monotypic habitat, regarding species habitat conversion eliminating biodiversity and...

 genera
Genera
Genera is a commercial operating system and development environment for Lisp machines developed by Symbolics. It is essentially a fork of an earlier operating system originating on the MIT AI Lab's Lisp machines which Symbolics had used in common with LMI and Texas Instruments...

 of nurse sharks. Common in shallow, tropical and subtropical waters, these sharks are sluggish and docile bottom-dwellers. Nurse sharks typically attack humans only if directly threatened.

The name nurse shark is thought to be a corruption of nusse, a name which once referred to the catshark
Catshark
Catsharks are ground sharks of the family Scyliorhinidae, with over 150 known species. While they are generally known as catsharks, many species are commonly called dogfish....

s of the family Scyliorhinidae.
Discussions
Encyclopedia
Ginglymostomatidae is a cosmopolitan
Cosmopolitan distribution
In biogeography, a taxon is said to have a cosmopolitan distribution if its range extends across all or most of the world in appropriate habitats. For instance, the killer whale has a cosmopolitan distribution, extending over most of the world's oceans. Other examples include humans, the lichen...

 family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...

 of carpet shark
Carpet shark
The carpet sharks are an order, Orectolobiformes, of sharks, so called because many members have ornate patterns reminiscent of carpets....

s, containing the three monotypic
Monotypic
In biology, a monotypic taxon is a taxonomic group with only one biological type. The term's usage differs slightly between botany and zoology. The term monotypic has a separate use in conservation biology, monotypic habitat, regarding species habitat conversion eliminating biodiversity and...

 genera
Genera
Genera is a commercial operating system and development environment for Lisp machines developed by Symbolics. It is essentially a fork of an earlier operating system originating on the MIT AI Lab's Lisp machines which Symbolics had used in common with LMI and Texas Instruments...

 of nurse sharks. Common in shallow, tropical and subtropical waters, these sharks are sluggish and docile bottom-dwellers. Nurse sharks typically attack humans only if directly threatened.

The name nurse shark is thought to be a corruption of nusse, a name which once referred to the catshark
Catshark
Catsharks are ground sharks of the family Scyliorhinidae, with over 150 known species. While they are generally known as catsharks, many species are commonly called dogfish....

s of the family Scyliorhinidae. The nurse shark family name, Ginglymostomatidae, derives from the Greek
Greek language
Greek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...

: from gynglimos meaning "hinge" and stoma meaning "mouth".

Description

The largest species, called simply the nurse shark
Nurse shark
The nurse shark, Ginglymostoma cirratum, sometimes referred to as the Nur Shark is a shark in the nurse sharks family, the only member of its genus Ginglymostoma...

 Ginglymostoma cirratum, may reach a length of 4.3 metres (14.1 ft); the tawny nurse shark
Tawny nurse shark
The tawny nurse shark is a species of carpet shark in the family Ginglymostomatidae, and the only extant member of the genus Nebrius. It is found widely along coastlines in the Indian and Pacific Oceans, preferring reefs, sandy flats, and seagrass beds from very shallow water to a depth of 70 m...

 Nebrius ferrugineus is somewhat smaller at 3.2 metres (10.5 ft), and the short-tailed nurse shark Pseudoginglymostoma brevicaudatum is by far the smallest at just 75 centimetres (2.5 ft) in length. The first of the three species may reach a weight of 110 kg. Yellowish to dark brown in colour, nurse sharks have muscular pectoral fins, two spineless dorsal fin
Dorsal fin
A dorsal fin is a fin located on the backs of various unrelated marine and freshwater vertebrates, including most fishes, marine mammals , and the ichthyosaurs...

s (the second of which is smaller) in line with the pelvic and anal fins, and a tail exceeding one quarter the shark's body length.

The mouths of nurse sharks are most distinctive; it is far ahead of the eyes and before the snout (sub-terminal), an indication of the bottom-dwelling (benthic) nature of these sharks. Also present on the lower jaw are two fleshy barbels
Barbel (anatomy)
A barbel on a fish is a slender, whiskerlike tactile organ near the mouth. Fish that have barbels include the catfish, the carp, the goatfish, sturgeon, the zebrafish and some species of shark...

, chemosensory organs which help the nurse sharks find prey hidden in the sediments. Behind each eye is a very small circular opening called a spiracle
Spiracle
Spiracles are openings on the surface of some animals that usually lead to respiratory systems.-Vertebrates:The spiracle is a small hole behind each eye that opens to the mouth in some fishes. In the primitive jawless fish the first gill opening immediately behind the mouth is essentially similar...

, part of the shark's respiratory system. The serrated teeth are fan-shaped and independent; like other sharks, the teeth are continually replaced throughout the animal's life.

Habits

Nurse sharks are nocturnal animals, spending the day in large inactive groups of up to 40 individuals. Hidden under submerged ledges or in crevices within the reef
Reef
In nautical terminology, a reef is a rock, sandbar, or other feature lying beneath the surface of the water ....

, the nurse sharks seem to prefer specific haunts and will return to them every day. By night, the sharks are largely solitary; they spend most of their time rifling through the bottom sediments in search of food. Their diet consists primarily of crustacean
Crustacean
Crustaceans form a very large group of arthropods, usually treated as a subphylum, which includes such familiar animals as crabs, lobsters, crayfish, shrimp, krill and barnacles. The 50,000 described species range in size from Stygotantulus stocki at , to the Japanese spider crab with a leg span...

s, molluscs, tunicate
Tunicate
Tunicates, also known as urochordates, are members of the subphylum Tunicata, previously known as Urochordata, a group of underwater saclike filter feeders with incurrent and excurrent siphons that is classified within the phylum Chordata. While most tunicates live on the ocean floor, others such...

s, and other fish
Fish
Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...

, particularly stingray
Stingray
The stingrays are a group of rays, which are cartilaginous fishes related to sharks. They are classified in the suborder Myliobatoidei of the order Myliobatiformes, and consist of eight families: Hexatrygonidae , Plesiobatidae , Urolophidae , Urotrygonidae , Dasyatidae , Potamotrygonidae The...

s.

Nurse sharks are thought to take advantage of dormant fish which would otherwise be too fast for the sharks to catch; although their small mouths limit the size of prey items, the sharks have large throat cavities which are used as a sort of bellows valve. In this way nurse sharks are able to suck in their prey. Nurse sharks are also known to graze algae
Algae
Algae are a large and diverse group of simple, typically autotrophic organisms, ranging from unicellular to multicellular forms, such as the giant kelps that grow to 65 meters in length. They are photosynthetic like plants, and "simple" because their tissues are not organized into the many...

 and coral
Coral
Corals are marine animals in class Anthozoa of phylum Cnidaria typically living in compact colonies of many identical individual "polyps". The group includes the important reef builders that inhabit tropical oceans and secrete calcium carbonate to form a hard skeleton.A coral "head" is a colony of...

.

Reproduction

The mating season runs from late June to the end of July. Most nurse sharks are ovoviviparous
Ovoviviparity
Ovoviviparity, ovovivipary, or ovivipary, is a mode of reproduction in animals in which embryos develop inside eggs that are retained within the mother's body until they are ready to hatch...

, meaning the eggs develop and hatch within the body of the female, where the hatchlings develop further until live birth occurs. The gestation
Gestation
Gestation is the carrying of an embryo or fetus inside a female viviparous animal. Mammals during pregnancy can have one or more gestations at the same time ....

 period is six months, with a typical litter of 30-40 pups. The mating cycle is biennial, as it takes 18 months for the female's ovaries to produce another batch of eggs. The young nurse sharks are born fully developed at about 30 cm long in Ginglymostoma cirratum. They possess a spotted coloration which fades with age.

Genera and species

  • Genus Ginglymostoma J. P. Müller
    Johannes Peter Müller
    Johannes Peter Müller , was a German physiologist, comparative anatomist, and ichthyologist not only known for his discoveries but also for his ability to synthesize knowledge.-Early years and education:...

     & Henle
    Friedrich Gustav Jakob Henle
    Friedrich Gustav Jakob Henle was a German physician, pathologist and anatomist. He is credited with the discovery of the loop of Henle in the kidney. His essay "On Miasma and Contagia" was an early argument for the germ theory of disease...

    , 1837
    • Ginglymostoma cirratum Bonnaterre
      Pierre Joseph Bonnaterre
      Abbé Pierre Joseph Bonnaterre was a French naturalist who contributed sections on cetaceans, mammals, birds, reptiles, amphibians, and insects to the Tableau encyclopédique et méthodique...

      , 1788
      (Nurse shark)
    • Ginglymostoma sp. (Pacific Nurse Shark)
  • Genus Nebrius Rüppell
    Eduard Rüppell
    Wilhelm Peter Eduard Simon Rüppell was a German naturalist and explorer. Rüppell is occasionally transliterated to "Rueppell" for the English alphabet....

    , 1837
    • Nebrius ferrugineus Lesson, 1831 (Tawny nurse shark)
  • Genus Pseudoginglymostoma Dingerkus, 1986 (proposed family Pseudoginglymostomatidae)
    • Pseudoginglymostoma brevicaudatum Günther
      Albert C. L. G. Günther
      Albert Karl Ludwig Gotthilf Günther FRS, also Albert Charles Lewis Gotthilf Günther , was a German-born British zoologist, ichthyologist, and herpetologist....

      , 1867
      (Short-tail nurse shark)

External links

The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
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