Monday, June 29, 2009

Bathynomus

A giant isopod may be one of approximately nine species of large isopods (crustaceans related to the shrimp and crabs) in the genus Bathynomus. They are thought to be abundant in cold, deep waters of the Atlantic. Bathynomus giganteus, the species upon which the generitype is based, is the largest known isopod and is the one most often referred to by the common name "giant isopod".



Giant isopods are important scavengers in the deep-sea benthic environment; they are found from the gloomy sublittoral zone at a depth of 170 metres (560 ft) to the pitch darkness of the bathypelagic zone at 2,140 metres (7,000 ft), where pressures are high and temperatures are very low – down to about 4 °C (39 °F).[4] Over 80 percent are found at a depth between 365 and 730 metres (1,200 and 2,400 ft). They are thought to prefer a muddy or clay substrate and lead solitary lives.
The first of these segments is fused to the head; the most posterior segments are often fused as well, forming a "caudal shield" over the shortened abdomen (pleon). The large eyes are compound with nearly 4,000 facets, sessile and spaced far apart on the head . There are two pairs of antennae.

The uniramous thoracic legs or pereiopods are arranged in seven pairs, the first of which are modified into maxillipeds to manipulate and bring food to the four sets of jaws. The abdomen has five segments called pleonites each with a pair of biramous pleopods; these are modified into natatory legs and rami, flat respiratory structures acting as gills. The isopods are a pale lilac in colour.



Although generalist scavengers, these isopods are mostly carnivorous and feed on dead whales, fish, and squid; they may also be active predators of slow-moving prey such as sea cucumbers, sponges, radiolarians, nematodes, and other zoobenthos, and perhaps even live fish. They are known to attack trawl catches.

Thursday, June 25, 2009

Cymothoa exigua.

Cymothoa exigua is a parasitic crustacean of the family Cymothoidae. It tends to be 3 to 4 cm long. This parasite attaches itself at the base of the spotted rose snapper's (Lutjanus guttatus) tongue, entering the fish's mouth through its gills. It then proceeds to extract blood through the claws on its front three pairs of legs. As the parasite grows, less and less blood reaches the tongue, and eventually the organ atrophies from lack of blood. The parasite then replaces the fish's tongue by attaching its own body to the muscles of the tongue stub. The fish is able to use the parasite just like a normal tongue. It appears that the parasite does not cause any other damage to the host fish. Once C. exigua replaces the tongue, some feed on the host's blood and many others feed on fish mucus. They do not eat scraps of the fish's food. This is the only known case of a parasite functionally replacing a host organ.



In 2005, a fish parasitised by what could be Cymothoa exigua was discovered in the United Kingdom. As the parasite is normally found off the coast of California, this led to speculation that the parasite's range may be expanding.

Tuesday, June 2, 2009

The White-faced Saki (Pithecia pithecia)



The White-faced Saki (Pithecia pithecia), also known as the Guianan Saki and the Golden-faced Saki, is a species of saki monkey, a type of New World monkey, found in Brazil, French Guiana, Guyana, Suriname, and Venezuela. This species lives in the understory and lower canopy of the forest, feeding mostly on fruits, but also eating nuts, seeds, and insects. Sakis are omnivores. They eat fruits, leaves, flowers, insects, and small vertebrates, such as rodents and bats.
Sakis are small-sized monkeys with long, bushy tails. Their furry, rough skin is black, grey or reddish-brown in color depending upon the species. The faces of some species are naked, but their head is hooded with fur. Their bodies are adapted to life in the trees, with strong hind legs allowing them to make far jumps. Sakis reach a length of 30 to 50 cm, with a tail just as long, and weigh up to 2 kg.
Sakis live in family federations, which consist of parents and their offspring, with mated pairs usually forming lifelong pair bonds. They are territorial animals, defending their territory in relation to other families. Sakis know a set of communication possibilities: while shrill cries or bird-like twitter serves as a connection among family members, a loud roar serves to warn other animals off their territory.
Whilst not an endangered species, Sakis and other South American primates are vulnerable due to the destruction of their habitat by humans. They are also hunted for food and for the pet trade.