Animalia Life

The white shark (Carcharodon carcharias), also known as the great white shark, white pointer, or white death, is one of the best-known sharks principally due to interest surrounding the occasionally fatal interactions between humans and this species. Nevertheless, surprisingly little is knownabout their biology. White sharks are large, active fish that are only infrequently encountered by humans and which have not survived long in the few attempts that have been made to keep them in captivity. Attempts to study the biology of white sharks are therefore limited to brief observations of their biology and what can be inferred from the anatomy of captured dead sharks.

White Shark Anatomy and Physiology
Like all sharks, the white shark possesses a skeleton composed of cartilage, a tough elastic connective tissue found in all vertebrates. The cartilage in the skeleton of white sharks is strengthened by deposits of calcium carbonate, but there is no true bone as in most other fishes. Like most sharks, the white shark has five pairs of gill slits located just in front of the broad pectoral fin and a heterocercal tail, in which the spinal column extends into the upper lobe. The tail, or caudal fin, of the white shark, as in all members of the family Lamnidae, is almost symmetrical and possesses a pronounced lateral keel at the point where the tail is attached to the body trunk. Such a lateral keel may improve the efficiency of the tail in swimming and turning and is a common element of many large, fastswimming fishes. The upper jaw of white sharks is suspended from the skull by ligaments rather than fused directly to the skull, as in most terrestrial vertebrates. This amphistylic suspension of the jaws allows them to be pushed forward and out, increasing the efficiency of the biting mechanism in a mouth that is located below and behind the broadly conical snout. White sharks, like all sharks, lack a gas-filled swim bladder to provide buoyancy in the water and rely on the lifting action of their fins and body shape to prevent them from sinking. The streamlined, spindle-shaped body, broad fins, and powerful, symmetrical tail of the white shark suit it well to a fast and powerful swimming style, and white sharks, like others in the family Lamnidae, are among the most active sharks. White sharks possess special modifications of the circulatory system in the body wall and central nervous system that are known as rete mirabile. These modifications permit the shark to return the heat generated by metabolism to the body core, rather than losing it to the surrounding water as in most fish. The rete mirabile allows white sharks to maintain a core body temperature that is higher than the surrounding water; this may provide an advantage to the shark by raising its metabolic rate and permitting greater activity in the cooler waters which they typically inhabit.

White Shark Reproduction and Feeding Habits
Little is known about the reproductive biology of white sharks. Like all sharks and rays, fertilization is internal, and the males possess special modifications of the pelvic fins called claspers, which are inserted into the female oviduct. White sharks are believed to be viviparous (“born alive”), with juvenile sharks developing within the uterus of the mother until they are ready to be born. During early embryonic development the developing white sharks are nourished by the yolk sac of the egg. When this is consumed, the developing shark consumes unfertilized eggs produced by the mother, a reproductive strategy known as intrauterine oöphagy. There have been relatively few captures of pregnant females or free-swimming juveniles, and the duration of gestation and the size of the juveniles at birth are unknown. The best estimate of white shark size at birth is between 1.2 and 1.4 meters. White sharks are known to reach a length of six meters (twenty-one feet) and may possibly grow larger. Their life span is unknown. As the white shark grows, the nature of its diet changes; juvenile white sharks appear to feed principally upon fish, whereas marine mammals play an important role in the diet of mature sharks. The high energy yield of the blubber in seals and sea lions may make them attractive prey for these very large predators. White sharks hunt seals and sea lions by swimming deep below them and searching for their silhouettes against the bright surface. Once prey is spotted, the shark attacks with a very swift lunge from below and inflicts an incapacitating or mortal wound with its bite. White sharks have been responsible for fatal attacks on humans, but humans are not a normal part of their diet. It is more likely that the shark mistakes a human for a marine mammal or may merely be curious. White sharks themselves are in considerably more danger fromhumans, and several nations and states have passed laws protecting these sharks from the effects of human depredations.

White Shark Facts

Classification:
Kingdom: Animalia
Subkingdom: Bilateria
Phylum: Chordata
Subphylum: Vertebrata
Superclass: Gnathostomata
Class: Chondrichthyes
Subclass: Elasmobranchii (sharks, skates, and rays)
Order: Lamniformes
Family: Lamnidae (mackerel sharks, also porbeagle salmon and mako sharks)
Genus and species: Carcharodon carcharias
Geographical location: Worldwide, generally in temperate and subtropical seas, occasionally in tropical seas
Habitat: Continental shelf and occasionally inshore
Gestational period: Unknown
Life span: Unknown
Special anatomy: Large (up to six meters long) and moderately stout-bodied, with a blunt, conical snout and an almost symmetrical caudal fin; pronounced lateral ridge or keel where the tail is attached to the body; large teeth, broadly triangular and serrated; gray-blue or gray-brown (often bronze) on the upper body surfaces, with a white belly; a black spot often present at the axil (armpit) on the bottom surface of the pectoral fin

Other popular Animals