Facts about Nurse Sharks
Nurse sharks are cosmopolitan carpet sharks belonging to the family Ginglymostomatidae. They typically attack humans only if directly threatened. Nurse sharks are benthic sharks, characterised as being sluggish and docile. The largest species of nurse shark, called simply the nurse shark Ginglymostoma cirratum, may reach a length of 4.3 m; the tawny nurse shark Nebrius ferrugineus is somewhat smaller at 3.2 m, and the short-tailed nurse shark Pseudoginglymostoma brevicaudatum is by far the smallest at just 75 cm in length. Nurse sharks have a tail exceeding one quarter the shark's body length. They have muscular pectoral fins, two spineless dorsal fins (the second of which is smaller) in line with the pelvic and anal fins. Their teeth are continually replaced throughout their life. Nurse sharks are yellowish to dark brown in colour. The mouths of nurse sharks are most distinctive; it is far ahead of the eyes. Behind each eye of nurse sharks is a very small circular opening called a spiracle, part of the shark's respiratory system. The serrated teeth of this shark are fan-shaped and independent; like other sharks. Nurse sharks are nocturnal animals, spending the day in large inactive groups of up to 40 individuals. The mating season runs from late June to the end of July. Most nurse sharks are ovoviviparous, meaning the eggs develop and hatch within the body of the female, where the hatchlings develop further until live birth occurs. Their diet consists primarily of crustaceans, molluscs, tunicates, and other fish, particularly stingrays. Nurse sharks are also known to graze algae and coral. The gestation period for nurse sharks is six months, with a typical litter of 30-40 pups. The young nurse sharks are born fully developed at about 30 cm long in Ginglymostoma cirratum. 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 possess a spotted coloration which fades with age. |
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