Nurse Shark

Nurse sharks can be identified by the two barbs on the upper lip

The nurse shark can be identified by two barbs protruding from the upper lip, two dorsal fins of nearly equal size positioned far back on the organism, and a small mouth.  Nurse sharks can range in color from gray to yellow brown and are typically between five and nine feet.  They can reach as large as 14 feet.

The nurse shark, or Ginglymostoma cirratum, belongs to the class Chondrichthyes, or cartilaginous fishes.  This class contains all sharks and rays.  The nurse shark belongs to the Ginglymostomatidae family, or carpet sharks.  Carpet sharks are closely related to the whale shark family Rhincodontidae, the largest fishes in the world.  The name, nurse shark, is thought to derive from "nusse," the common name applied to cat-sharks, in which nurse sharks were thought to belong.  In many parts of the caribbean the nurse shark is still called "tiburon gato," or cat-shark.

Nurse sharks are nocturnal and often can be seen sitting on the sea floor during the day, hence their family "carpet" sharks.  They are common to shallow water reefs up to 100 feet.  The nurse shark's main diet consists of fish, sting rays, molluscs, and crustaceans.  To capture their prey, nurse sharks use a high speed sucking force.  This method is thought to allow the nurse shark to feed on small fish that are hiding at night and remove molluscs and crustaceans from their shells.

A nurse shark resting in the sand

When it comes to reproduction, marine biologists have a fairly good understanding of these sharks.  nurse sharks reproduce for five weeks during the summer by gathering in their regional shallow water breeding grounds.  Females are quite stubborn and fight off males as they attempt to mate.  Eventually, males will bite and wrestle female nurse sharks until they concede to mate.  Once the the female has agreed to mate, the male must cling to the female's fin with his mouth, roll her over, and then begin copulation.  The eggs hatch inside the mother and gives birth to roughly 20 to 30 pups.

References: DeLoach, Ned, and Paul Humann. Reef Fish Behavior: Florida, Caribbean, Bahamas. Jacksonville, FL: New World Publications, 2007. 306-08. Print.; Humann, Paul, and Ned DeLoach. Reef Fish Identification: Florida, Caribbean, Bahamas. Jacksonville, FL: New World Publications, 2002. 440-43. Print.