Lisa Rivea, Age 8, of Gary, Ind., for her question:
CAN YOU TELL ME SOMETHING ABOUT THE NURSE SHARK?
About 250 different kinds of sharks are known. They are divided into 19 families and seven suborders. One of the more interesting is the nurse shark which can readily be distinguished from all others by the presence of a conspicuous pair of external grooves, one on each side, running from the mouth to the nostril. Each of these oronasal grooves, as they are called, has at its anterior end a thick, fleshy barbell a whisker like sensory organ.
The nurse shark is from the family Orectolobidae. Most of them are small, inshore forms, but there are a few, such as the Atlantic nurse shark, which has a maximum length of 14 feet.
Usually the nurse shark is between eight and 11 feet, with an 8 foot specimen weighing in at about 350 pounds. It is common in the shallow waters from the Florida Keys southward into the West Indies and down to Brazil. It has been seen as far north as Cape Lookout, North Carolina, and also has been spotted along the tropical West African coasts.
Of particular interest is the fact that the Atlantic nurse shark has also moved to the Pacific Ocean. They did not reach their new environment in the Hawaiian Islands by natural means but by being transported in a sealed plastic bag filled with sea water and oxygen.
The story started when a litter of young nurse sharks, each about one foot in length, had just been born in one of the large tanks at the Seaquarium in Miami. The young sharks were shipped to the Steinhart Aquarium in San Francisco, and shortly thereafter to the Waikiki Aquarium in Honolulu. Despite these relocations, all of the litter survived. Nurse sharks proved they do well in captivity.
Nurse sharks are born alive. This creature, along with others of the family, that are born alive, are actually hatched from eggs within the uterus of the mother. This type of reproduction is called ovoviviparity. Three of the seven sharks in the orectolobid family are born this way.
Our friend the nurse shark is not considered dangerous under normal circumstances. Because of their brilliant markings, often white on a rich brown background, their hides are sometimes used in the shark leather industry.
The orectolobits, including the nurse shark, have two dorsal fins and spiracles, but lack nictitating eye membranes found on most other sharks. The tail is not turned upward but is in line with the rest of the body.