Friday, December 31, 2010
Chinese Mitten Crab
The Chinese mitten crab, Eriocheir sinensis (also known as the big sluice crab (Chinese: 大閘蟹; pinyin: dà zhá xiè) and Shanghai hairy crab, Chinese: 上海毛蟹; pinyin: shànghǎi máo xiè) is a medium-sized burrowing crab that is native in the coastal estuaries of eastern Asia from Korea in the north to the Fujianprovince of China in the south. It has also been introduced to Europe and North America where it is considered an invasive species.
Formerly in the family Grapsidae, it is now placed in the Varunidae.
This species' distinguishing features are the dense patches of dark hair on its claws. The crab's body is the size of a human palm. The carapace width is 30–100 mm and the legs are about twice as long as the carapace is wide.
Mitten crabs spend most of their life in fresh water, but they must return to the sea to breed. During their fourth or fifth year in late summer, the crustaceans migrate downstream, and attain sexual maturity in the tidal estuaries. After mating, the females continue seaward, overwintering in deeper waters. They return to brackish water in the spring to hatch their eggs. After development as larvae, the juvenile crabs gradually move upstream into fresh water, thus completing the life cycle.
This species is very invasive and has been spread to North America and Europe, raising concerns that it competes with local species, and its burrowing nature damages embankments and clogs drainage systems. The crabs can make significant inland migrations. It was reported in the London Evening Standard in 1995 that the residents of Greenwich, UK, saw the Chinese mitten crabs coming out of the River Thames and moving towards the High Street, and other reports indicate that the crabs have been known to take up residence in swimming pools. In some places the crabs have been found hundreds of miles from the sea. There is especial concern in areas with a substantial native crab fishery, such as the Chesapeake Bay in Maryland and the Hudson River in New York (both locations where the crabs were first spotted in 2005), as the impact of the invasion by this species on the native population is unknown.
It is generally illegal to import, transport, or possess live Chinese mitten crabs in the United States, as accidental release or escape risks spreading these crabs to uninfested waters. In addition, some states may have their own restrictions on possession of mitten crabs. California allows fishing for mitten crabs with some restrictions.
The Chinese mitten crab has been introduced into the Great Lakes several times, but have not yet been able to establish a permanent population.
Thursday, December 30, 2010
The beluga or white whale, Delphinapterus leucas, is an Arctic and sub-Arctic species of cetacean. It is one of two members of the family Monodontidae, along with the narwhal. This marine mammal is commonly referred to simply as the beluga or sea canary due to its high-pitched twitter. It is up to 5 meters (16 ft) in length and an unmistakable all-white color with a distinctive protuberance on the head. From a conservation perspective, the beluga is considered "near threatened" by the International Union for Conservation of Nature; however the subpopulation from the Cook Inlet in Alaska is considered critically endangered and is under the protection of the United States' Endangered Species Act. Of seven Canadian beluga populations, two are listed as endangered, inhabiting eastern Hudson Bay, and Ungava Bay.
Belugas are highly sociable. Groups of males may number in the hundreds, while mothers with calves generally mix in slightly smaller groups. When pods aggregate in estuaries, they may number in the thousands. This can represent a significant proportion of the entire population and is when they are most vulnerable to hunting.
Pods tend to be unstable, meaning that they tend to move from pod to pod. Radio tracking has shown that belugas can start out in a pod and within a few days be hundreds of miles away from that pod. Mothers and calves form the beluga's closest social relationship. Nursing times of two years have been observed and lactational anestrus may not occur. Calves often return to the same estuary as their mother in the summer, meeting her sometimes even after becoming fully mature.
Belugas can be playful—they may spit at humans or other whales. It is not unusual for an aquarium handler to be drenched by one of his charges. Some researchers believe that spitting originated with blowing sand away from crustaceans at the sea bottom.
Unlike most whales, it is capable of swimming backwards.
Wednesday, December 29, 2010
The Caribbean Reef Squid (Sepioteuthis sepioidea), also known as just the Reef Squid, is a small (20 cm) torpedo-shaped squid with fins that extend nearly the entire length of the body and undulate rapidly as it swims. The squid has recently become notable when it was discovered that it could fly out of the water; a discovery which finally led to identification of six species of flying squid.
The Caribbean Reef Squid is found throughout the Caribbean Sea as well as off the coast of Florida, commonly in small schools of 4-30 in the shallows associated with reefs. The habitat of the Reef Squid changes according to the squid's stage of life and size. New hatchlings tend to reside close to the shore in areas from 0.2-1 meters below the surface on or under vegetation. Young small squid typically congregate in shallow turtle grass near islands and remain several centimeters to two meters from the surface to avoid bird predators. Adults venture out into open water and can be found in depths up to 100 m. When mating, adults are found near coral reefs in depths of 1.5-8 m. The Caribbean Reef Squid is the only squid species commonly sighted by divers over inshore reefs in the Florida, Bahamas and Caribbean region.
Tuesday, December 28, 2010
The presence of ocean blooms is usually seasonal, responding to prey availability and increasing with temperature and sunshine. Ocean currents tend to congregate jellyfish into large swarms or "blooms", consisting of hundreds or thousands of individuals. In addition to sometimes being concentrated by ocean currents, blooms can result from unusually high populations in some years. Bloom formation is a complex process that depends on ocean currents, nutrients, temperature, predation, and oxygen concentrations. Jellyfish are better able to survive in oxygen-poor water than competitors, and thus can thrive on plankton without competition. Jellyfish may also benefit from saltier waters, as saltier waters contain more iodine, which is necessary for polyps to turn into jellyfish. Rising sea temperatures caused by climate change may also contribute to jellyfish blooms, because many species of jellyfish are better able to survive in warmer waters. Jellyfish are likely to stay in blooms that are quite large and can reach up to 100,000 in each.
The global increase in jellyfish bloom frequency may stem from human impact. In some locations jellyfish may be filling ecological niches formerly occupied by now overfished creatures, but this hypothesis lacks supporting data. Jellyfish researcher Marsh Youngbluth further clarifies that "jellyfish feed on the same kinds of prey as adult and young fish, so if fish are removed from the equation, jellyfish are likely to move in."
Jellyfish blooms cause problems for mankind. The most obvious are human stings (sometimes deadly) and tourism declines on coasts.
Other severe implications are destroying fish nets, poisoning or crushing captured fish, consuming fish eggs and young fish.
Clogging also causes many problems including stoppage of nuclear power plants and desalination plants, as well as clogging engines of ships and even overturning of boats by one of the largest species, the Nomura's jellyfish.
Monday, December 27, 2010
Ring of Fire
The Pacific Ring of Fire (or sometimes just the Ring of Fire) is an area where large numbers of earthquakes and volcanic eruptions occur in the basin of the Pacific Ocean. In a 40,000 km (25,000 mi) horseshoe shape, it is associated with a nearly continuous series of oceanic trenches, volcanic arcs, and volcanic belts and/or plate movements. The Ring of Fire has 452 volcanoes and is home to over 75% of the world's active and dormant volcanoes. It is sometimes called the circum-Pacific belt or the circum-Pacific seismic belt.
About 90% of the world's earthquakes and 80% of the world's largest earthquakes occur along the Ring of Fire. The next most seismic region (5–6% of earthquakes and 17% of the world's largest earthquakes) is the Alpide belt, which extends from Java to Sumatra through the Himalayas, the Mediterranean, and out into the Atlantic. The Mid-Atlantic Ridge is the third most prominent earthquake belt.
Sunday, December 26, 2010
The taimen (Hucho taimen), also known as Siberian taimen and Siberian salmon, is a species of fish in the salmon family (family Salmonidae) of order Salmoniformes.
The taimen is distributed from the Volga and Pechora River basins east to the Yana River in the north and that of the Amur River in the south. On a larger scale, this includes parts of the Caspian and Arctic drainages in Eurasia and portions of the Pacific drainage in Mongolia and Russia (the Amur River). In Mongolia the taimen is found in both the Arctic and Pacific drainages, specifically the Yenisei/Selenga, the Lena, and the Amur River Basins. The taimen lives in flowing water and is only occasionally found in lakes, usually near the mouth of a tributary. The taimen is not anadromous, but does show increased movement rates during the spawning season. The average home range size of taimen in the Eg-Uur River of Mongolia is 23km, but some tagged individuals show home ranges up to 93km. Some authors consider the taimen to be a subspecies of the Huchen, i.e. Hucho hucho taimen.
Coloration varies geographically, but is generally olive green on the head blending to reddish brown in the tail. Adipose, anal, and caudal fins are often dark red. The belly ranges from nearly white to dark gray. The taimen is the largest salmonid in the world. The maximum size is not well known, but a fish caught in the Kotui River in Russia with a length of 210 cm (83 in) and a weight of 105 kg (231 lb) is the largest reliable record (Holcik et al. 1988). The IGFA world record is a little under 100 lb or 45 kg. It can reach at least 55 years of age.
Saturday, December 25, 2010
The killer whale (Orcinus orca), commonly referred to as the orca, and less commonly as the blackfish, is a toothed whale belonging to the oceanic dolphin family. Killer whales are found in all oceans, from the frigid Arctic and Antarctic regions to tropical seas. Killer whales as a species have a diverse diet, although individual populations often specialize in particular types of prey. Some feed exclusively on fish, while others hunt marine mammals such as sea lions, seals, walruses and even large whales. Killer whales are regarded as apex predators, lacking natural predators and preying on even large sharks.
Killer whales are highly social; some populations are composed of matrilineal family groups which are the most stable of any animal species. Their sophisticated hunting techniques and vocal behaviors, which are often specific to a particular group and passed across generations, have been described as manifestations of culture.
The IUCN currently assesses the orca's conservation status as data deficient because of the likelihood that one or more killer whale types are separate species. Some local populations are considered threatened or endangered due to prey depletion, habitat loss, pollution (by PCBs), capture for marine mammal parks, and conflicts with fisheries. In late 2005, the killer whales known as the "southern resident killer whales" were placed on the U.S. Endangered Species list.
Wild killer whales are not considered a threat to humans, although there have been cases of captives killing or injuring their handlers at marine theme parks. Killer whales feature strongly in the mythologies of indigenous cultures.
Friday, December 24, 2010
A globster, or blob, is an unidentified organic mass that washes up on the shoreline of an ocean or other body of water. The term was coined by Ivan T. Sanderson in 1962 to describe the Tasmanian carcass of 1960, which was said to have "no visible eyes, no defined head, and no apparent bone structure". A globster is distinguished from a normal beached carcass by being hard to identify, at least by initial untrained observers, and by creating controversy as to its identity.
Globsters may present such a puzzling appearance that their nature remains controversial even after being officially identified by scientists. Some globsters lack bones or other recognisable structures, while others may have bones, tentacles, flippers, eyes or other features that can help narrow down the possible species. In the past these were often described as sea monsters, and myths and legends about such monsters may often have started with the appearance of a globster. Globsters are most frequently studied in the field of cryptozoology.
Many globsters have initially been described as gigantic octopuses, although they later turned out to be the decayed carcasses of whales or large sharks. As with the "Chilean Blob" of 2003, many are masses of whale blubber released from decaying whale corpses. Others initially thought to be dead plesiosaurs later turned out to be the decayed carcases of basking sharks. Others remain unexplained. Giant and colossal squid may also explain some globsters, particularly those tentatively identified as monster octopuses.
Some globsters have been examined only after they had decomposed too much to be used as evidence for a new species, or have been destroyed, as happened with the famous "Cadborosaurus willsi" carcass, found in 1937. However, Canadian scientists did in fact perform a DNA analysis of the Newfoundland Blob that indicated the tissue was from a sperm whale. In their resulting paper, the authors point out a number of superficial similarities between the Newfoundland Blob and other famous globsters, concluding a similar origin for those globsters is likely. Analyses of other globsters have yielded similar results.
Thursday, December 23, 2010
Pipefishes or pipe-fishes (Syngnathinae) are a subfamily of small fishes, which, together with the seahorses, form the family Syngnathidae.
Pipefish look like straight-bodied seahorses with tiny mouths. The name is derived from the peculiar form of their snout, which is like a long tube, ending in a narrow and small mouth which opens upwards and is toothless. The body and tail are long, thin, and snake-like. They have a highly modified skeleton formed into armored plating. This dermal skeleton has several longitudinal ridges, so that a vertical section through the body looks angular, not round or oval as in the majority of other fishes.
A dorsal fin is always present, and is the principal (in some species, the only) organ of locomotion. The ventral fins are constantly absent, and the other fins may or may not be developed. The gill openings are extremely small and placed near the upper posterior angle of the gill cover.
Many are very weak swimmers in open water, moving slowly by means of rapid movements of the dorsal fin. Some species of pipefish have tails that are prehensile, as in seahorses. The majority of pipefishes have some form of a caudal fin (unlike seahorses), which can be used for locomotion. See fish anatomy for fin descriptions. There are species of pipefish with more developed caudal fins, such as the group collectively known as flagtail pipefish, which are quite strong swimmers.
Pipefishes, like their seahorse relatives, leave most of the parenting duties to the male. Courtship tends to be elaborately choreographed displays between the males and females. Pair bonding varies wildly between different species of pipefish. While some are monogamous or seasonally monogamous, others are not.
Wednesday, December 22, 2010
Hypostomus plecostomus is the scientific name for a type of freshwater tropical Central and South American fish belonging to the family Loricariidae. They are large algae eaters, and to differentiate them from small algae eaters, they are often referred to as plecostomus, often abbreviated as plecos or plecs. They are extremely popular in aquaria for their ability to clean tanks by eating algae growth. In Malaysia, these fish are called 'ikan bandaraya' or 'municipal fish' in English because of their ability to clean fish tanks. These friendly-natured fish can typically be purchased when about 8 cm (3 inches) and may grow up to 60 cm (2 ft) if there is adequate room, making them mostly impracticable for any but the largest aquariums.
Plecos are omnivorous but, in the wild, feed mostly on plant material at night. During the day, their unusual omega irides block a lot of the light out of their eyes, but they are usually open at night. They can roll their eye within their sockets.
As they age, their foreheads enlarge in a peculiar manner. Plecos may become more peaceful with age and are best kept individually in tanks. Because of their potentially large size and peaceful behaviour, it may be advisable to procure a less aggressive catfish. In a suitably large tank, a solitary plecostomus will live amicably enough in a community alongside other tropical fish. These catfish may survive in tanks with "cold-water" species like goldfish, but it is generally not advised due to the different temperature preferences and the fact that some plecos will suck the protective slime coat off the goldfish. This however would indicate your pleco is starving and seeking the algae stuck to the slime coat.
Plecostomus catfish are some of the most commonly kept algae-eating catfish, and are also some of the largest. Individuals measuring over 60 cm (2 ft) long have been reported in ponds and large tanks; most people think they only grow large enough for their aquarium, but a small tank may only slow their rate of growth. Their growth may also become stunted in a smaller tank, leading to bad health and possibly an early death.
Tuesday, December 21, 2010
The Kaluga (Huso dauricus) is a large predatory sturgeon found in the Amur River basin. Also known as the River Beluga, they are claimed to be the largest freshwater fish in the world, with a maximum size of at least 1,000 kg (2,205 lb) and 5.6 m (18.6 ft). Like the slightly larger Beluga, it spends part of its life in saltwater.The Kaluga is one of the biggest of the sturgeon family.
Kaluga caviar comes from the Kaluga "River Beluga" sturgeon.
Monday, December 20, 2010
The giant barb or Siamese giant carp, Catlocarpio siamensis (Thai: กระโห้ or กะมัน), is the largest species of carp in the world. These migratory fish are found only in the Mae Klong, Mekong and Chao Phraya river basins. This fish is a desirable food fish, which may have caused a serious decline in its numbers.
They are usually seen in the big pools along the edges of large rivers, but will seasonally enter smaller canals, floodplains and flooded forests. Young barbs are usually found in smaller tributaries and swamps, but can acclimatize to living in ponds, canals and swamps. The fish generally live in pairs.
These are migratory fish, swimming to favorable areas for feeding and breeding in different parts of the year.
These slow-moving fish subsist on algae, phytoplankton and fruits of inundated terrestrial plants, rarely (if ever) feeding on active animals. In the lower Mekong basin, young giant barbs have been reported as occurring primarily in October.
Sunday, December 19, 2010
Sawfishes are a family of rays, characterized by a long, toothy snout. Several species can attain sizes up to approximately 7 metres or 23 ft, but the family as a whole is largely unknown and little studied. They are members of the sole living family Pristidae within the order Pristiformes, from the Ancient Greek pristēs (πρίστης) meaning "a sawyer" or "a saw".
They are not to be confused with sawsharks (order Pristiophoriformes), which have a similar appearance.
All species of sawfishes are considered Critically Endangered by the IUCN, and the only legal international trade involves live Pristis microdon to appropriate aquaria for primarily conservation purposes.
The most distinctive feature of a sawfish is the saw-like rostrum. The rostrum is covered with motion- and electro-sensitive pores that allow sawfish to detect movement and even heartbeats of buried prey in the ocean floor as the sawfish hovers over the bottom. It is also used as a digging tool to unearth buried crustaceans. When a suitable prey swims by, the normally lethargic sawfish will spring from the bottom and slash at it with its saw. This generally stuns or injures the prey sufficiently for the sawfish to devour it without much resistance. Sawfish have also been known to defend themselves with their rostrum, against predators such as sharks, and against intruding divers. The "teeth" protruding from the rostrum are not real teeth, but modified tooth-like structures called denticles.
Saturday, December 18, 2010
River dolphins are four living species of dolphin which reside in freshwater rivers and estuaries. River dolphins inhabit areas of Asia and South America. They are classed in the Platanistoidea superfamily of cetaceans. Three species live in fresh water rivers. The fourth species, the La Plata Dolphin, lives in salt-water estuaries and near-shore marine environments. However, it is scientifically classed in the river dolphin group rather than the oceanic dolphin family.
River dolphins are in danger of extinction due to habitat loss, hunting by humans, and naturally low numbers.
The largest river dolphins usually grow up to 2.4 meters (8 feet) long, but most of the animals are smaller. River dolphins may be white, pink, yellow, brown, gray, or black.
The four families of river dolphins are classified by Rice, 1998 as belonging to Platanistoidea. Formerly Platanistidae was listed as the only extant family of the Platanistoidea superfamily. The previously accepted classification treated all four families as belonging to this family and treated the Ganges and Indus River Dolphins as separate species. Five lineages of dolphin have evolved to live in big, muddy rivers. River dolphins are thought to have relictual distributions. Their ancestors originally occupied marine habitats, but were then displaced from these habitats by modern dolphin lineages. Many of the morphological similarities and adaptations to freshwater habitats arose due to convergent evolution. A December 2006 survey found no members of Lipotidae (commonly known as the Yangtze River dolphin) and declared the species functionally extinct.
Friday, December 17, 2010
Oceana is the largest international ocean conservation and advocacy organization. Oceana works to protect and restore the world’s oceans through targeted policy campaigns.
Oceana bases its policy campaign goals on science to achieve concrete and measurable results through targeted campaigns that combine policy advocacy, science, law, media, and public pressure to prevent collapse of fish populations, marine mammals, and other sea life caused by industrial fishing and pollution. Campaigns are designed to produce clear, identifiable policy changes within a 3-5 year timeframe.
Oceana is headquartered in Washington, D.C. and has North American offices in New York, NY, Juneau, AK, Anchorage, AK, Portland, OR, Monterey, CA, Boston, MA and Los Angeles, CA. In Europe, Oceana has offices in Brussels, Belgium and Madrid, Spain. The South American office is in Santiago, Chile and the Central American office is in Belize City, Belize.
Oceana was established in 2001 by a group of leading foundations—The Pew Charitable Trusts, Oak Foundation, Marisla Foundation (formerly Homeland Foundation), and the Turner Foundation. Those foundations had discovered through a study commissioned in 1999 that less than one-half of one percent of all resources spent by environmental non-profit groups in the United States went to ocean advocacy. Thus Oceana was created to identify practical solutions to the problems facing the oceans and to make those solutions happen.
The organization was not started from scratch, as the Ocean Law Project—also initiated by The Pew Charitable Trusts—was absorbed into Oceana in 2001 as the Oceana’s legal arm. In 2002, Oceana merged with American Oceans Campaign, founded by actor/environmentalist Ted Danson, to more effectively address our common mission of protecting and restoring the world’s oceans. Danson remains a committed and active member of Oceana’s Board of Directors.
Related Articles : Census of Marine Life
Thursday, December 16, 2010
The Blue whale (Balaenoptera musculus) is a marine mammal belonging to the suborder of baleen whales (called Mysticeti). At over 33 metres (108 ft) in length and 180 metric tons (200 short tons) or more in weight, it is the largest animal ever known to have existed.
Long and slender, the blue whale's body can be various shades of bluish-grey dorsally and somewhat lighter underneath. There are at least three distinct subspecies: B. m. musculus of the North Atlantic and North Pacific, B. m. intermedia of the Southern Ocean and B. m. brevicauda (also known as the pygmy blue whale) found in the Indian Ocean and South Pacific Ocean. B. m. indica, found in the Indian Ocean, may be another subspecies. As with other baleen whales, its diet consists almost exclusively of small crustaceans known as krill.
Blue whales were abundant in nearly all the oceans on Earth until the beginning of the twentieth century. For over 40 years, they were hunted almost to extinction by whalers until protected by the international community in 1966. A 2002 report estimated there were 5,000 to 12,000 blue whales worldwide, located in at least five groups. More recent research into the Pygmy subspecies suggests this may be an underestimate. Before whaling, the largest population was in the Antarctic, numbering approximately 239,000 (range 202,000 to 311,000). There remain only much smaller (around 2,000) concentrations in each of the North-East Pacific, Antarctic, and Indian Ocean groups. There are two more groups in the North Atlantic, and at least two in the Southern Hemisphere.
The blue whale is the largest animal ever known to have lived. The largest known dinosaur of the Mesozoic Era was the Argentinosaurus, which is estimated to have weighed up to 90 metric tons (99 short tons), though a controversial vertebra of Amphicoelias fragillimus Furthermore, there are weight estimates for the very poorly known may indicate an animal of up to 122 metric tons (134 short tons) and 40–60 metres (130–200 ft).Bruhathkayosaurus ranging from 140–220 metric tons (150–240 short tons), besides length estimates up to about 45 metres (148 ft). The extinct fish Leedsichthys may have approached its size. However, complete fossils are difficult to come by, making size comparisons difficult. All these animals are considered to be smaller than the blue whale.
Wednesday, December 15, 2010
Paddlefish (family Polyodontidae) are primitive Chondrostean ray-finned fishes. The paddlefish can be distinguished by its large mouth and its elongated snout called a rostrum (gill). These spatula-like snouts comprise half the length of their entire body. There are only two extant species of these fish: the Chinese and the American paddlefish. In some areas, paddlefish are referred to as "Spoonbill", "Spoonies" or "Spoonbill Catfish". The American species is Missouri's State Aquatic Animal.
These fish are not closely related to sharks, which are in a different class, but they do have some body parts that resemble those of sharks such as their skeletons, primarily composed of cartilage, and deeply forked heterocercal tail fins.
The Chinese paddlefish (Psephurus gladius) lives in the Yangtze River. 9' (3-meter) specimens weighing 300 kilograms (660 lb) have been recorded; reports of 7 metres (23 ft) fish exist, although the existence of such large specimens is doubtful. They are said to now be extinct, with a recently completed three-year survey of the Yangtze finding no specimens.
The American paddlefish (Polyodon spathula) lives in the slow-flowing waters of the Mississippi River, Missouri River, Des Moines River, Yellowstone River, Ohio River, Wisconsin River, and Arkansas River systems (and was historically found in the Great Lakes). In May 2000, the Canadian Species at Risk Act listed the Paddlefish as being extirpated in Canada. The American paddlefish is one of the largest freshwater fish in North America. They commonly reach 5 feet (1.5 m) or more in length and can weigh more than 60 pounds (27 kg). The largest American paddlefish on record was caught in Kansas and weighed 144 pounds (65 kg), by Clinton Boldridge out of Atchison Watershed. The largest unofficial record was 206 pounds from Lake Cumberland in Kentucky. Postcards from the 1960s show a photo of this huge fish. This type of fish's age is hard to determine but many scientists think that they live 50 years or more.
Fossils of other paddlefish have been found. One such species is Crossopholis magnicaudatus. C. magnicaudatus has been found in the Green River Shale deposit of Wyoming and dates to the Eocene.
Tuesday, December 14, 2010
Electric catfish is the common name for the catfish (order Siluriformes) family Malapteruridae. This family includes two genera, Malapterurus and Paradoxoglanis with 19 species. Several species of this family have the ability to produce an electric shock of up to 350 volts using electroplaques of an electric organ. Electric catfish are found in tropical Africa and the Nile River. Electric catfish are usually nocturnal and feed primarily on other fish, incapacitating their prey with electric discharges.
Malapteruridae is the only group of catfish with a well-developed electrogenic organ; however, electroreceptive systems are widespread in catfishes. The electrogenic organ is derived from anterior body musculature and lines the body cavity. Electric catfish do not have dorsal fins or fin spines. They have three pairs of barbels (the nasal pair is absent). The swim bladder with elongate posterior chambers, two chambers in Malapterrus and three in Paradoxoglanis.
The Nile fish was well known to the ancient Egyptians. The Egyptians have depicted the fish in their mural paintings and elsewhere; the first extant depiction of an electric catfish is that on the slate palette of the pre-dynastic Egyptian ruler Narmer, about 3100 BC. An account of its electric properties was given by an Arab physician of the 12th century; then as now the fish was known by the suggestive name of Raad or Raash, which means thunder (literally trembler, shaker).
Though the shock an electric catfish can generate is not known to be fatal to humans, the catfish does use its electricity as a weapon to ward off predators.
Monday, December 13, 2010
The angel sharks are an unusual genus of sharks with flattened bodies and broad pectoral fins that give them a strong resemblance to rays. The 16+ known species are in the genus Squatina, the only genus in its family, Squatinidae, and order Squatiniformes. They occur worldwide in temperate and tropical seas. Most species inhabit shallow temperate or tropical seas, but one species inhabits deeper water, down to 1,300 metres (4,300 ft).
While the forward part of the angel shark's body is broad and flattened, the rear part retains a muscular appearance more typical of other sharks. The eyes and spiracles are on top, and the five gill slits are underneath. Both the pectorals and the pelvic fins are large and held horizontally. There are two dorsal fins, no anal fin, and unusually for sharks, the lower lobe of the caudal fin is longer than the upper lobe. Most types grow to a length of 1.5 m (5 ft), with the Japanese angel shark, Squatina japonica, known to reach 2 m. Angel sharks possess extensible jaws that can rapidly snap upwards to capture prey, and have long, needle-like teeth. They bury themselves in sand or mud lying in wait for prey, which includes fish, crustaceans, and various types of mollusks. They are ovoviviparous, producing litters of up to 13 pups.
Although this shark is a bottom dweller and appears harmless, it should be respected due to its powerful jaws and sharp teeth which can inflict painful lacerations if provoked. It may bite if a diver approaches the head or grabs the tail. If they are left alone, they will not attack.
Sunday, December 12, 2010
The stoplight loosejaws are small, deep-sea dragonfishes of the genus Malacosteus, classified either within the subfamily Malacosteinae of the family Stomiidae, or in the separate family Malacosteidae. They are found worldwide, outside of the Arctic and Subantarctic, in the mesopelagic zone below a depth of 500 meters (1,640 ft). This genus once contained three nominal species: M. niger (the type), M. choristodactylus, and M. danae, with the validity of the latter two species being challenged by different authors at various times. In 2007, Kenaley examined over 450 stoplight loosejaw specimens and revised the genus to contain two species, M. niger and the new M. australis.
Malacosteus and the related genera Aristostomias and Pachystomias are the only fishes that produce red bioluminescence. As most of their prey organisms are not capable of perceiving light at those wavelengths, this allows Malacosteus to hunt with an essentially invisible beam of light. Furthermore, Malacosteus is unique amongst animals in using a chlorophyll derivative to perceive red light. The name Malacosteus is derived from the Greek malakos meaning "soft" and osteon meaning "bone". Another common name for these fishes is "rat-trap fish", from the unusual open structure of their jaws.
As long wavelengths of light (i.e. red) do not reach the deep sea, many deep-sea organisms are red-colored (effectively appearing black) and are insensitive to red wavelengths. The red photophore of Malacosteus thus allows it to illuminate prey without being detected. These fishes exhibit a number of adaptations for feeding on large prey. The "open" structure of its jaws reduces water resistance, allowing them to be snapped shut more quickly, while large recurved teeth and powerful jaw closing muscles assure a secure hold on prey items. The connection between the head and the body is reduced, with unossified vertebrae, allowing the cranium to be tilted back and the jaws thrust forward for a wider gape. Finally, the gills are exposed to the outside, allowing the fish to continue respiring while slowly swallowing large prey.
Saturday, December 11, 2010
A rare pink bottlenose dolphin has been spotted in a Louisiana lake. The albino dolphin has been making a splash with locals and visitors to the area since it was first spotted last year.
The animal has been photographed by local charter boat Captain Erik Rue, 42, who has been studying the dolphin since it first surfaced in Lake Calcasieu, an inland saltwater estuary, north of the Gulf of Mexico in south-west Louisiana. Rue originally saw the rare albino dolphin, which also has reddish eyes, swimming with a pod of four other dolphins.
"I just happened to see a little pod of dolphins, and I noticed one that was a little lighter ... I had never seen anything like it. It's the same colour throughout the whole body," said Rue.
"The dolphin appears to be healthy and normal other than its coloration, which is quite beautiful and stunningly pink," Rue said he had seen the dolphin 40 to 50 times.
"As time has passed the young mammal has grown and sometimes ventures away from its mother to feed and play but always remains in the vicinity of the pod," he said.
Regina Asmutis-Silvia, a senior biologist with the Whale and Dolphin Conservation Society, said: "I have never seen a dolphin coloured in this way in all my career."
"It is a truly beautiful dolphin but people should be careful, as with any dolphins, to respect it - observe from a distance, limit their time watching, don't chase or harass it."
"While this animal looks pink, it is an albino which you can notice in the pink eyes. Albinism is a genetic trait and it unclear as to the type of albinism this animal inherited."
A different dolphin species, the endangered Amazon river boto (Inia geoffrenis), which lives in South America , is sometimes called the pink river dolphin because of its appearance.
Friday, December 10, 2010
The kitefin shark or seal shark (Dalatias licha) is a species of dogfish shark in the family Dalatiidae, and the only species in its genus. It is found sporadically around the world, usually close to the sea floor at depths of 200–600 m (660–2,000 ft). With a sizable oil-filled liver to maintain neutral buoyancy, this shark is able to cruise slowly through the water while expending little energy. The kitefin shark has a slender body with a very short, blunt snout, large eyes, and thick lips. Its teeth are highly differentiated between the upper and lower jaws, with the upper teeth small and narrow and the lower teeth large, triangular, and serrated. Its typical length is 1.0–1.4 m (3.3–4.6 ft).
Armed with large teeth and a strong bite, the kitefin shark is a powerful, solitary predator that takes many different types of prey, ranging from bony fishes, sharks and rays, to cephalopods, crustaceans, polychaete worms, siphonophores, and possibly carrion. It also takes bites out of animals larger than itself, similar to its smaller relative, the cookiecutter shark (Isistius brasiliensis). This shark is aplacental viviparous and gives birth to 10–14 young. The kitefin shark is fished commercially for its meat, skin, and liver oil, primarily by Portugal and Japan. A fishery targeting this species existed off the Azores from the 1970s to the 1990s, but collapsed due to overfishing and falling liver oil prices; the rapid depletion of the Azores stock is often cited as an example of the susceptibility of deep-sea sharks to human exploitation. The low reproductive rate of this species renders it susceptible to overfishing and, coupled with known population declines, has led it to be assessed as Near Threatened by the International Union for Conservation of Nature (IUCN).
Thursday, December 9, 2010
The legend of the Flying Dutchman concerns a ghost ship that can never make port, doomed to sail the oceans forever. It probably originates from 17th century nautical folklore. The oldest extant version dates to the late 18th century.
Sightings in the 19th and 20th centuries report the ship to be glowing with ghostly light. It is said that if hailed by another ship, its crew will try to send messages to land or to people long dead. In ocean lore, the sight of this phantom ship is a portent of doom.
Versions of the story are numerous in nautical folklore and related to medieval legends such as Captain Falkenburg, who was cursed to ply the North Sea until Judgment Day, playing dice with the Devil for his own soul.
According to some sources, the 17th-century Dutch captain Bernard Fokke is the model for the captain of the ghost ship. Fokke was renowned for the speed of his trips from Holland to Java and was suspected of being in league with the Devil. The first version of the legend as a story was printed, in Blackwood's Edinburgh Magazine for May 1821, which puts the scene as the Cape of Good Hope. This story introduces the name Vanderdecken for the captain and the motifs (elaborated by later writers) of letters addressed to people long dead being offered to other ships for delivery, but if accepted will bring misfortune; and the captain having sworn to round the Cape of Good Hope though it should take until the day of judgment.
Wednesday, December 8, 2010
The Alcyonacea, or the soft corals are an order of corals which do not produce calcium carbonate skeletons and so are neither reef-building corals nor do they lay new foundations for future corals. Instead they contain minute, spiney skeletal elements called sclerites. Aside from their scientific utility in species identification, sclerites give these corals some degree of support and give their flesh a spiky, grainy texture that deters predators.
Unlike stony corals, most soft corals thrive in nutrient-rich waters with less light intensity. Almost all utilize zooxanthella as a major energy source. However, most will readily eat any free floating food, such as brine shrimp, out of the water column.
Many soft corals are easily collected in the wild for the reef aquarium hobby, as small cuttings are less prone to infection or damage during shipping than stony corals. Nevertheless, home-grown specimens are more practical. Soft corals grow quickly in captivity and are easily divided into new individuals, and so those grown via aquaculture are often hardier and less expensive than imported corals from the wild. The most common example of this is various species of Actinodiscus, especially common red mushroom coral.
Tuesday, December 7, 2010
Pygmy Sperm Whale
The Pygmy Sperm Whale (Kogia breviceps) is one of three species of toothed whale in the sperm whale family. They are not often sighted at sea, and most of what is known about the creatures comes from the study of washed-up specimens.
There has been debate and differing opinion as to the correct classification of the Pygmy and Dwarf Sperm Whales (see sperm whale family for details). The two were widely considered to be the same species, until 1966, when a scientist at the Smithsonian Institution definitively diagnosed them as separate species. The pygmy sperm whale was first named by de Blainville in 1838.
Pygmy sperm whales are found in the temperate waters of the Atlantic, Pacific and Indian Oceans. However, they are rarely sighted at sea, so most data comes from stranded animals - making a precise range and migration map difficult. They are believed to prefer off-shore waters. Their status is usually described as rare, but occasional patches of higher density of strandings suggest it may be rather more common than previously supposed. The total population is unknown.
Monday, December 6, 2010
The Sparkling Enope Squid (Watasenia scintillans), also known as the Firefly Squid, is a species of squid in the family Enoploteuthidae. It is the sole species in the genus Watasenia.
The Sparkling Enope Squid is found in the Western Pacific ocean at depths of 183 to 366 metres (600 - 1200 feet) and exhibits bioluminescence. Each tentacle has an organ called a photophore, which produces light. By flashing these lights, the Sparkling Enope Squid can attract little fish to feed upon. The Sparkling Enope Squid is the only species of cephalopod in which evidence of color vision has been found. While most cephalopods have only one visual pigment, firefly squid have three, along with a double-layered retina. These adaptations for color vision may have evolved to enable firefly squid to distinguish between ambient light and bioluminescence. The Sparkling Enope Squid measures about 3 inches long at maturity and dies after one year of life.
Sunday, December 5, 2010
In ecology, a feeding frenzy is a situation where oversaturation of a supply of food leads to rapid feeding by predatory animals. For example, a large school of fish can cause nearby sharks to enter a feeding frenzy. This can cause the sharks to go wild, biting anything that moves, including each other or anything else within biting range. This term is most often used when referring to sharks or piranhas, due to these being some of the most feared predators.
Saturday, December 4, 2010
Copepods (pronounced /ˈkoʊpɪpɒd/) are a group of small crustaceans found in the sea and nearly every freshwater habitat. Many species are planktonic (drifting in sea waters), but more are benthic (living on the ocean floor), and some continental species may live in limno-terrestrial habitats and other wet terrestrial places, such as swamps, under leaf fall in wet forests, bogs, springs, ephemeral ponds and puddles, damp moss, or water-filled recesses (phytotelmata) of plants such as bromeliads and pitcher plants. Many live underground in marine and freshwater caves, sinkholes, or stream beds. Copepods are sometimes used as bioindicators.
Planktonic copepods are important to global ecology and the carbon cycle. They are usually the dominant members of the zooplankton, and are major food organisms for small fish, whales, seabirds and other crustaceans such as krill in the ocean and in fresh water. Some scientists say they form the largest animal biomass on earth. They compete for this title with Antarctic krill (Euphausia superba). Because of their smaller size and relatively faster growth rates, however, and because they are more evenly distributed throughout more of the world's oceans, copepods almost certainly contribute far more to the secondary productivity of the world's oceans, and to the global ocean carbon sink than krill, and perhaps more than all other groups of organisms together. The surface layers of the oceans are currently believed to be the world's largest carbon sink, absorbing about 2 billion tons of carbon a year, the equivalent to perhaps a third of human carbon emissions, thus reducing their impact. Many planktonic copepods feed near the surface at night, then sink into deeper water during the day to avoid visual predators. Their moulted exoskeletons, faecal pellets and respiration at depth all bring carbon to the deep sea.
About half of the estimated 13,000 described species of copepods are parasitic and have strongly modified bodies. They attach themselves to fish, sharks, marine mammals, and many kinds of invertebrates such as molluscs, tunicates, or corals. They live as endo- or ectoparasites on fish or invertebrates in fresh water as well as in marine environments.
Friday, December 3, 2010
The axolotl (pronounced /ˈæksəlɒtəl/), Ambystoma mexicanum, is the best known of the Mexican neotenicmole salamanders belonging to the Tiger Salamander complex. Larvae of this species fail to undergo metamorphosis, so the adults remain aquatic and gilled. The species originates from the lake underlying Mexico City and is also called ajolote (which is also the common name for the Mexican Mole Lizard). Axolotls are used extensively in scientific research due to their ability to regenerate most body parts, ease of breeding, and large embryos. They are commonly kept as pets in the United States, Great Britain, Australia, Japan (sold under the name wooper looper (ウーパールーパー, Ūpā Rūpā)) and other countries.
Axolotls should not be confused with waterdogs, the larval stage of the closely related Tiger Salamanders (Ambystoma tigrinum and Ambystoma mavortium), which are widespread in much of North America and also occasionally become neotenic, nor with mudpuppies (Necturus spp.), fully-aquatic salamanders which are not closely related to the axolotl but bear a superficial resemblance.
As of 2010, wild axolotls are near extinction due to urbanization in Mexico City and polluted waters. Nonnative fish such as African tilapia and Asian carp have also recently been introduced to the waters. These new fish have been eating the axolotls' young, as well as its primary source of food. The axolotl is currently on the International Union for Conservation of Nature's annual Red List of threatened species.[update]
Thursday, December 2, 2010
The Antarctic Ocean is unique amongst the worlds oceans in that it has no Decapod Crustaceans - crabs and lobsters that are found in abundance in the rest of the world have never crossed the Antarctic Convergence, so their role is taken by other organisms of which this is one. Antarcturus signiensis has only been so far found in and around Signy Island and the South Orkneys where it is regularly encountered on dives down to 25m.
There are a whole host of organisms that take the place of Decapod crustaceans in Antarctica, many of which display signs of gigantism compared to their relatives elsewhere in the world. Underwater Antarctica is a place where entirely new species to science may be encountered.
Wednesday, December 1, 2010
Ceratoserolis is a genus of serolid isopods that live mainly in Antarctic coasts. They are known to resemble trilobites. They were once consider to be part of the genus Serolis.