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Showing posts with label Crab. Show all posts
Showing posts with label Crab. Show all posts

Tuesday, June 5, 2012

Yeti Crab

Beauty Of Animal | Yeti Crab  | Yeti Crab  (Kiwa hirsuta) is a crustacean discovered in 2005 in the South Pacific Ocean. This decapod, which is approximately 15 cm (6 inches) long, is notable for the quantity of silky blond setae (resembling fur) covering its pereiopods (thoracic legs, including claws). Its discoverers dubbed it the "yeti lobster" or "yeti crab"

K. hirsuta was discovered in March 2005 by a group organised by Robert Vrijenhoek of the Monterey Bay Aquarium Research Institute in Monterey, California, using the submarine DSV Alvin, operating from RV Atlantis. The discovery was announced on the 7th of March, 2006. It was found 1,500 km (900 miles) south of Easter Island in the South Pacific, at a depth of 2,200 m (7,200 feet), living on hydrothermal vents along the Pacific-Antarctic Ridge Based on both morphology and molecular data, the species was deemed to form a new genus and family (Kiwaidae). The animal has strongly reduced eyes that lack pigment, and is thought to be blind.
The 'hairy' pincers contain filamentous bacteria, which the creature may use to detoxify poisonous minerals from the water emitted by the hydrothermal vents where it lives. Alternatively, it may feed on the bacteria, although it is thought to be a general carnivore. Its diet also consists of green algae and small shrimp.

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Friday, June 24, 2011

The Beauty Horseshoe Crab

Beauty Of Animals | The Beauty  Horseshoe Crab | Horseshoe crabs are arthropods that live primarily in shallow ocean waters on soft sandy or muddy bottoms. They will, however, occasionally come on shore, e.g. for mating. They are commonly used as bait and in fertilizer, and in recent years there has been a decline in number of individuals, as a consequence of coastal habitat destruction in Japan and overharvesting along the east coast of North America. Tetrodotoxin may be present in the roe of species inhabiting the waters of Thailand. Horseshoe crabs are considered living fossils.

The entire body of the horseshoe crab is protected by a hard shell. They have two large compound eyes and multiple smaller simple ones atop the carapace. Beneath the carapace they look quite similar to a large spider. They have five pairs of legs for walking, swimming and moving food into the mouth. The long, straight, rigid tails can be used to flip themselves over if they are turned upside down, so a horseshoe crab with a broken tail is more susceptible to desiccation or predation.

Behind their legs, they have book gills, which exchange respiratory gases and are also occasionally used for swimming. While they can swim upside down, they usually are found on the ocean floor searching for worms and mollusks, which are their main food. They may also feed on crustaceans and even small fish. Females are larger than males; C. rotundicauda is the size of a human hand, while L. polyphemus can be up to 60 centimetres (24 in) long (including tail). The juveniles grow about 33% larger with every molt until reaching adult size.

One synapomorphy for the order Xiphosura is the fusion of opisthosomal tergites behind opercular tergite (free abdominal segments) to form a thoracetron. Fusion of opisthosomal tergites to form a thoracetron has previously been considered a characteristic of the xiphosuran superfamilies Euproopoidea and Limuloidea, but evidence was presented by Anderson & Selden that fusion also occurs in Bellinuroidea. Giribet et al. used the character in their matrix and found it to be in a synapomorphy for Limulus and Carcinoscorpius

During the breeding season, horseshoe crabs migrate to shallow coastal waters. Males select a female and cling onto her back. The female digs a hole in the sand and lays her eggs while the male fertilizes them. The female can lay between 60,000–120,000 eggs in batches of a few thousand at a time. Many shore birds eat the eggs before they hatch. The eggs take about 2 weeks to hatch. The larvae molt six times during the first year.

It has proven to be difficult to raise horseshoe crabs in captivity. There is reason to believe that mating only takes place in the presence of the sand or mud in which the horseshoe crab eggs were hatched. It is not known with certainty what in the sand is being sensed by the crabs nor how they sense it

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Green Crab-Carcinus Maenas

Beauty Of Animals | Green Crab-Carcinus Maenas  | Carcinus maenas is a common littoral crab, and an important invasive species, listed among the 100 "world's worst alien invasive species". It is native to the north-east Atlantic Ocean and Baltic Sea, but has colonised similar habitats in Australia, South Africa, South America and both Atlantic and Pacific coasts of North America. It grows to a carapace width of 90 millimetres (3.5 in), and feeds on a variety of molluscs, worms and small crustaceans, potentially impacting a number of fisheries. Its successful dispersion has occurred via a variety of mechanisms, such as on ships' hulls, packing materials, bivalves moved for aquaculture, and rafting.
C. maenas is known by different names around the world. In the British Isles, it is generally referred to simply as the shore crab. In North America and South Africa, it bears the name green crab or European green crab. In Australia and New Zealand, it is referred to as either the European green crab or European shore crab.
C. maenas has a carapace up to 60 millimetres (2.4 in) long and 90 mm (3.5 in) wide,[3] with five short teeth along the rim behind each eye, and three undulations between the eyes. The undulations, which protrude beyond the eyes, are the simplest means of distinguishing C. maenas from the closely-related C. aestuarii, which can also be an invasive species. In C. aestuarii, the carapace lacks any bumps and extends forward beyond the eyes. Another characteristic for distinguishing the two species is the form of the first and second pleopods (collectively the gonopods), which are straight and parallel in C. aestuarii, but curve outwards in C. maenas.
The colour of C. maenas varies greatly, from green to brown, grey or red. This variation has a genetic component, but is largely due to local environmental factors. In particular, individuals which delay moulting become red–coloured rather than green. Red individuals are stronger and more aggressive, but are less tolerant of environmental stresses, such as low salinity or hypoxia.

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The Beauty Blue Crab

 Beauty Of Animals | The Beauty  Blue Crab  | T he blue crab is so named because of its sapphire-tinted claws. Its shell, or carapace, is actually a mottled brownish color, and mature females have red highlights on the tips of their pincers. Prized by humans for their sweet, tender meat, these wide-ranging, ten-legged crustaceans are among the most heavily harvested creatures on the planet. Their scientific name, Callinectes sapidus, means "savory beautiful swimmer."

Blue crabs are found in brackish coastal lagoons and estuaries from Nova Scotia, through the Gulf of Mexico, and as far south as Uruguay. Close relatives of the shrimp and lobster, these bottom-dwelling omnivores have a prickly disposition and are quick to use their sharp front pincers. Large males can reach 9 inches (23 centimeters) in shell width. They feed on almost anything they can get hold of, including mussels, snails, fish, plants, and even carrion and smaller blue crabs. They are also excellent swimmers, with specially adapted hind appendages shaped like paddles.

 
Blue crabs are extremely sensitive to environmental and habitat changes, and many populations, particularly in the Chesapeake Bay in the eastern United States, have experienced severe declines. Blue crabs also play a key role in managing the populations of the animals they prey on, and constant overharvesting has had wide-ranging negative effects on the ecosystems they inhabit. For this reason, comprehensive management schemes are in place in several parts of the blue crab's range.

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