Showing posts with label Sea Creatures. Show all posts
Showing posts with label Sea Creatures. Show all posts

Monday, January 27, 2014

Great White Shark

The great white shark (Carcharodon carcharias), also known as the great white, white pointer, white shark, or white death, is a species of large lamniform shark which can be found in the coastal surface waters of all the major oceans. The great white shark is mainly known for its size, with mature individuals growing up to 6.4 m (21 ft) in length (although reports have been published of great white sharks measuring over 8 m (26 ft), and 3,324 kg (7,330 lb) in weight). This shark reaches its maturity around 15 years of age and was previously believed to have a life span of over 30 years. The true lifespan of Great white sharks is far longer; now estimated to be as long as 70 years or more, making it one of the longest lived cartilaginous fish currently known.  Great white sharks can accelerate to speeds that exceed 56 km/h (35 mph).
The great white shark is an apex predator of the seas and has no natural predators. The great white shark is arguably the world's largest known extant macropredatory fish, and is one of the primary predators of marine mammals. It is also known to prey upon a variety of other marine animals, including fish and seabirds. It is the only known surviving species of its genus Carcharodon, and is ranked first in having the most attacks on humans. The IUCN list the great white shark as a vulnerable species, while it is included in Appendix II of CITES.

The bestselling novel Jaws by Peter Benchley and the subsequent blockbuster film by Steven Spielberg depicted the great white shark as a "ferocious man eater". In reality, humans are not the preferred prey of the great white shark, however of all shark species, the great white shark is responsible for by far the largest number of fatal unprovoked attacks on humans.

Box Jellyfish

Box jellyfish (class Cubozoa) are cnidarian invertebrates distinguished by their cube-shaped medusae. Some species of box jellyfish produce extremely potent venom: Chironex fleckeri, Carukia barnesi and Malo kingi are among the most venomous creatures in the world. Stings from these and a few other species in the class are extremely painful and sometimes fatal to humans.
Box jellyfish most visibly differ from the Scyphozoan jellyfish in that they are umbrella shaped, rather than domed or crown-shaped. The underside of the umbrella includes a flap, or velarium, concentrating and increasing the flow of water expelled from the umbrella. As a result, box jellyfish can move more rapidly than other jellyfish. In fact, speeds of up to six meters per minute have been recorded.
The box jellyfish's nervous system is also more developed than that of many other jellyfish. Notably, they possess a nerve ring around the base of the umbrella that coordinates their pulsing movements; a feature found elsewhere only in the crown jellyfish. Whereas some other jellyfish do have simple pigment-cup ocelli, box jellyfish are unique in the possession of true eyes, complete with retinas, corneas and lenses. Their eyes are located on each of the four sides of their bell in clusters called rhopalia. This enables them to see specific points of light, as opposed to simply distinguishing between light and the dark. Box jellyfish also have 20 ocelli (simple eyes), that do not form images but detect light and dark; they therefore have a total of 24 eyes. A box jellyfish has the closest thing a known jellyfish has to a brain. Box jellyfish also display complex, probably visually guided behaviors such as obstacle avoidance and fast directional swimming. Tests have