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Animals

What are nurse sharks and whale sharks?

The Nurse Shark, Ginglymostoma cirratum, is a sluggish species that spends much of its time lying quietly on the bottom in the shallow waters of the tropical Atlantic. It is well known in Florida, where it is extensively fished for its hide, considered the best from any American shark for the production of leather.

Nurse sharks have large broods, as many as twenty-six young being born at a time. Newly born nurse sharks are less than a foot in length and generally show numerous spots that are usually lost as they grow up. Their ground color ranges from gold to light brown. Although nurse sharks mature at about five feet, individuals as long as fourteen feet have been caught. They feed mostly on creatures like crabs, shrimp, spiny lobsters, squid, and sea urchins, and on small fish.

The Whale Shark, Rhincodon typus, is the largest of living fishes. Accurately measured specimens forty-five feet long are on record and some of sixty feet have been reliably reported. No one knows just how much such monsters weigh, but the estimated weight of a thirtyeight-foot example was nearly 26,600 pounds.

Found in all tropical seas, the whale shark occasionally ventures into temperate waters. It sometimes gathers in schools. Often it basks or feeds at the surface, and is so fearless or lazy, that it is sometimes rammed by ships.

The whale shark eats only smaller invertebrates and fishes. It has a large mouth with very small teeth and a strainer-like apparatus at the gills. Swimming open-mouthed through schools of little fish or aggregations of other small sea animals, the whale shark engulfs them. The water is then forced out through its gills, and the animals are caught on the specially contrived gill arches which act like sieves. There are also reports that this shark feeds in a vertical position, head up, and that it sucks in its prey.

The whale shark’s back and sides are distinctively marked with round white or yellowish spots that show up plainly against the dark gray or brown of the skin.