Monday, February 28, 2011
The ghost knifefishes are a family, Apteronotidae, of ray-finned fishes in the order Gymnotiformes. These fish can be found in the freshwater of Panama and South America.
They are distinguished from other gymnotiform fishes by the presence of a caudal fin (all other families lack a caudal fin) as well as a fleshy dorsal organ represented by a longitudinal strip along the dorsal midline. The longest Apteronotid is Apteronotus magdalenensis, reaching 1.3 metres. These nocturnal fish have small eyes. Also, sexual dimorphism exists in some genera in snout shape and jaws.
Apteronotids use a high frequency tone-type (also called wave-type) electric organ discharge (EOD) to communicate.
Many Apteronotids are aggressive predators of small aquatic insect larvae and fishes, though there are also piscivorous and planktivorous species. Magosternarchus spp. are very unusual, preying on the tails of other electric fishes. Other species, such as Sternarchorhynchus and Sternarchorhamphus, have tubular snouts and forage on the beds of aquatic insect larvae and other small animals which burrow into the river bottom. At least one species (Sternarchogiton nattereri) eats freshwater sponges which grow on submerged trees, stumps, and other woody debris. The genus Apteronotus is artificial and many of the species do not actually belong in it.
The black ghost knifefish (Apteronotus albifrons) and brown ghost knifefish (Apteronotus leptorhynchus) are readily available as aquarium fish. Others, are known to appear in the trade, but are quite rare.
Sunday, February 27, 2011
Pseudoplatystoma is a genus of several South American catfish species of family Pimelodidae. The three species are known by a number of different common names. They inhabit the major rivers of north-eastern Argentina, Paraguay, Peru, Bolivia, Uruguay and Brazil. They prefer the main channels and tend to stay at maximum depth. They have robust bodies, and are important food fish.
In their native waters, these fish may be called Surubí in guaraní. This name is also used in some Spanish speaker countries. In Peruvian Spanish is called Doncella or Zúngaro. P. corruscans may be called molequepintado. They often are referred to in the vernacular as or Bagre rayado or Pintadillo (tiger catfish or tiger–shovelnose). P. corruscans, P. fasciatum, and P. tigrinum are also known as Spotted Sorubim, Barred Sorubim, and Tiger Sorubim, respectively. This genus contains the fish commonly known as the tiger shovelnose catfish in the aquarium hobby, though the species in this genus are relatively easy to confuse.
Pseudoplatystoma species live in a diverse range of habitats such as great rivers, lakes, side channels, floating meadows, and flooded forests. P. fasciatum is found in river beds and sometimes in flooded forests. Though it is biologically similar to P. tigrinum, this fish seems to favor shadier streams. P. tigrinum occurs in estuarine zones, mainly upstream of the first rapids up to the basin's headwaters. They live in the main bed of slow or fast zones, and the juveniles particularly live in flooded forests.
Pseudoplatystoma species are all large, boldly striped or spotted catfishes. They are familiar due to their distinctively marked color patterns. They are also recognized due to a depressed head, an occipital process extending backward to contact the pre dorsal plate, and a very long fontanel.
Saturday, February 26, 2011
The genus Glycera is a group of polychaetes (bristle worms) commonly known as blood worms. They are typically found on the bottom of shallow marine waters, and some species (e.g. the common blood worm, Glycera dibranchiata), are extensively harvested along the Northeastern coast of the United States for use as bait in fishing. Another common species is the tufted gilled bloodworm, G. americana.
Bloodworms have a creamy pink color, as their pale skin allows their red body fluids that contain hemoglobin to show through. This is the origin of the name "bloodworm". At the 'head', bloodworms have four small antennae and small fleshy projections called parapodia running down their bodies. Bloodworms can grow up to 35 centimetres (14 in) in length.
Bloodworms are poor swimmers but good burrowers, living on the sandy or silty bottoms of the intertidal or subtidal regions. Though usually marine, they can tolerate low salt levels in the water, and also poor oxygen levels. Bloodworms and all water worms have adapted to life in the sand and silt for the protection it offers.
Bloodworms are carnivorous. They feed by extending a large proboscis that bears four hollow jaws. The jaws are connected to glands that supply poison which they use to kill their prey, and their bite is painful even to a human. They are preyed on by other worms, by bottom-feeding fish and crustaceans, and by gulls.
Friday, February 25, 2011
The warty oreo, Allocyttus verrucosus, is an oreo of the genus Neocyttus, found in all southern oceans at depths of between 300 and 1,600 m. Its length is up to 42 cm.
The warty oreo resembles the spiky oreo. However, there are differences: the body, which has a shape much like a diamond, has a lower corner not as pointed, a dorsal which is not as tall as that of the spiky oreo, and there are spines along the warty oreo's anal fin. In addition, there are two rows of scales, which are relatively large and warty, bedecking the sides of the warty oreo between the fish's pelvic fin and its anal fin. The warty oreo has a dark gray colour and is black-finned.
Warty oreos live in the waters of continental slopes, and they form in large schools over rough terrain. Young warty oreos are pelagic and reside in shallow waters of the oceans - less than a kilometer in depth. They eat other fish, as well as cephalopods and shrimp. The eggs and larvae of warty oreos live on or near the surface of the sea.
They are very long living creatures, the oldest living to be 140 years old.
Thursday, February 24, 2011
This blind lobster, discovered in 2008 during a Census of Marine Life expedition, was given the scientific name Dinochelus ausubeli, which is derived from the Greek dinos, meaning terrible and fearful; chela, meaning claw; and ,ausubeli, in honor of Jesse Ausubel, a co-founder of the Census of Marine Life.
The lobster likely uses its exaggerated claw, or cheliped, to defend against other crustaceans.
Wednesday, February 23, 2011
Tiny snails found on Australia’s eastern coast can flicker their spiral shells like dim, blue-green light bulbs.
Some snails excrete bioluminescent trails of snot or blink their muscly foot to attract mates. But the clusterwink snail is the first discovered to use the shell-flashing trick, which seems to have evolved as a form of self-defense.
“The snail produces light when tapped or around animals that might eat it, even while it’s hiding in its shell,” said Dimitiri Deheyn, a marine biologist at the Scripps Oceanographic Institute in San Diego. Deheyn and his colleague describe the bioluminescent trick of the snail, also known as Hinea brasiliana, in an upcoming study in the journal Proceedings of the Royal Society B.
The snail’s glow-in-the-dark-shell trick was noticed by scientists decades ago, but until now, nobody had any idea what chemicals are involved in generating the glow, or how the shell lights amplifies the light.
“Pinning down what particular biomechanism the snails use to glow is going to be important for the biotech industry,” said marine biologist Mark Moline of California Polytechnic State University, who wasn’t involved in the study.
When threatened, fingernail-sized H. brasiliana generates pulses of bioluminescent light from a single spot on its mushy body. The light pulses are variable, lasting as short as 1/50th of a second to as long as a few seconds. But the opaque shell diffuses only the blue-green color of light it generates — and no other color — like a highly selective frosted light bulb.
Tuesday, February 22, 2011
Mudskippers are members of the subfamily Oxudercinae (tribe Periophthalmini), within the family Gobiidae (Gobies). They are completely amphibious fish, fish that can use their pectoral fins to walk on land. Being amphibious, they are uniquely adapted to intertidal habitats, unlike most fish in such habitats which survive the retreat of the tide by hiding under wet seaweed or in tidal pools. Mudskippers are quite active when out of water, feeding and interacting with one another, for example to defend their territories.
They are found in tropical, subtropical and temperate regions, including the Indo-Pacific and the Atlantic coast of Africa.
The genus Periophthalmus is by far the most diverse and widespread genus of mudskipper. Eighteen species have been described. Periophthalmus argentilineatus is one of the most widespread and well known species. It can be found in mangrove ecosystems and mudflats of East Africa and Madagascar east through the Sundarbans of Bengal, South East Asia to Northern Australia, southeast China and southern Japan, up to Samoa and Tonga Islands. It grows to a length of about 9.5 cm and is a carnivorous opportunist feeder. It feeds on small prey such as small crabs and other arthropods. Another species, Periophthalmus barbarus, is the only oxudercine goby that inhabits the coastal areas of western Africa.
Monday, February 21, 2011
A piranha or piraña (pronounced /pɨˈrɑːnə/, /-njə/ or /pɨˈrænə/, /-njə/; Portuguese: [piˈɾɐ̃ɲɐ]) is a member of family Characidae in order Characiformes, an omnivorous freshwater fish that inhabits South American rivers. In Venezuela, they are called caribes. They are known for their sharp teeth and a voracious appetite for meat.
Piranhas are found in the Amazon basin, in the Orinoco, in rivers of the Guyanas, in the Paraguay-Paraná, and the São Francisco River systems. Some species of piranha have broad geographic ranges, occurring in more than one of the major basins mentioned above, whereas others appear to have more limited distributions.
Aquarium piranhas have been introduced into parts of the United States with specimens occasionally found in the Potomac River, Lake of the Ozarks in Missouri and even as far north as Lake Winnebago in Wisconsin, although they typically do not survive cold winters. Piranhas have also been discovered in the Kaptai Lake in south-east Bangladesh. Research is being carried out to establish how piranhas have moved to such distant corners of the world from their original habitat. It is anticipated that some rogue exotic fish traders have released them in the lake to avoid being caught by anti-poaching forces.
There are various myths about piranhas such as how they can dilacerate a human body or cattle in seconds. These myths refer specifically to Serrasalmus nattereri, the red-bellied piranha. A recurrent myth is that they can be attracted by blood and are exclusive carnivores. A Brazilian myth called "piranha cattle" states that they sweep the rivers at high speed and attack the first of the cattle entering the water allowing the rest of the group to traverse the river. These myths were dismissed through research by Helder Queiroz and Anne Magurran and published on Biology Letters. Nevertheless, a study in Suriname found that piranhas may occasionally attack humans, particularly when water levels are low.
Sunday, February 20, 2011
Leafy Sea Dragon
The leafy sea dragon or Glauerts Seadragon, Phycodurus eques, is a marine fish in the family Syngnathidae, which also includes the seahorses. It is the only member of the genus Phycodurus. It is found along the southern and western coasts of Australia. The name is derived from the appearance, with long leaf-like protrusions coming from all over the body. These protrusions are not used for propulsion; they serve only as camouflage. The leafy sea dragon propels itself by means of a pectoral fin on the ridge of its neck and a dorsal fin on its back closer to the tail end. These small fins are almost completely transparent and difficult to see as they undulate minutely to move the creature sedately through the water, completing the illusion of floating seaweed.
Much like the seahorse, the leafy sea dragon's name is derived from its resemblance to another creature (in this case, the mythical dragon). While not large, they are slightly larger than most sea horses, growing to about 20–24 cm (8–10 in). They feed on plankton and small crustaceans.
The lobes of skin that grow on the leafy sea dragon provide camouflage, giving it the appearance of seaweed. It is able to maintain the illusion when swimming, appearing to move through the water like a piece of floating seaweed. It can also change colour to blend in, but this ability depends on the sea dragon's diet, age, location, and stress level.
The leafy sea dragon is found only in the waters of Australia from Kangaroo Island on the Southern shoreline to Jurien Bay on the Western shoreline. It was once thought to be very limited in its range; however, further research has discovered that the sea dragon will actually travel several hundred metres from its habitat, returning to the same spot using a strong sense of direction. They are mostly found around clumps of sand in waters up to 50 metres (164 feet) deep, hiding among rocks and sea grass. They are commonly sighted by scuba divers near Adelaide.
Saturday, February 19, 2011
The Electric eel (Electrophorus electricus), is an electric fish, and the only species of the genus Electrophorus. It is capable of generating powerful electric shocks, which it uses for both hunting and self-defense. It is an apex predator in its South American range. Despite its name it is not an eel but rather a knifefish.
The electric eel has three abdominal pairs of organs that produce electricity: the Main organ, the Hunter's organ, and the Sachs organ. These organs make up four-fifths of its body, and are what give the electric eel the ability to generate two types of electric organ discharges (EODs), low voltage and high voltage. These organs are made of electrocytes, lined up so that the current flows through them and produces an electrical charge. When the eel locates its prey, the brain sends a signal through the nervous system to the electric cells. This opens the ion channel, allowing positively-charged sodium to flow through, reversing the charges momentarily. By causing a sudden difference in voltage, it generates a current.
The electric eel generates its characteristic electrical pulse in a manner similar to a battery, in which stacked plates produce an electrical charge. In the electric eel, some 5,000 to 6,000 stacked electroplaques are capable of producing a shock at up to 500 volts and 1 ampere of current (500 watts). Such a shock could be deadly for an adult human. (Electrocution death is due to current flow; the level of current that is fatal in humans is roughly 0.75A.)
The Sachs organ is associated with electrolocation. Inside the organ are many muscle-like cells, called electrocytes. Each cell can only produce 0.15 V, though working together the organ transmits a signal of about 10 V in amplitude at around 25 Hz. These signals are what is emitted by the main organ and Hunter's organ that can be emitted at rates of several hundred Hz.
The electric eel is unique among the gymnotiforms in having large electric organs capable of producing lethal discharges that allows them to stun prey. There are reports of this fish producing larger voltages, but the typical output is sufficient to stun or deter virtually any other animal. Juveniles produce smaller voltages (about 100 volts). Electric eels are capable of varying the intensity of the electrical discharge, using lower discharges for "hunting" and higher intensities for stunning prey, or defending themselves. When agitated, it is capable of producing these intermittent electrical shocks over a period of at least an hour without signs of tiring.
Friday, February 18, 2011
The Goodwin Sands are a 10-mile-long sand bank in the English Channel, lying six miles east of Deal in Kent, England. The Brake Bank lying shorewards is part of the same geological unit. As the shoals lie close to major shipping channels, more than 2,000 ships are believed to have been wrecked upon them, and as a result they are marked by lightvessels and buoys. Notable shipwrecks include the VOC ship Rooswijk, HMS Stirling Castle, the SS Montrose and the South Goodwin Lightship'. Several naval battles have been fought nearby, including the Battle of Goodwin Sands in 1652 and the Battle of Dover Strait in 1917.
There is currently a lightship on the end of the sands, on the farthest part out, to warn ships. The sands were once covered by two lighthouses on the Kent mainland, one each at the north and south ends of the sands. The southern lighthouse is now owned by the National Trust, and the northern one is still in operation.
Thursday, February 17, 2011
Chinese Giant Salamander
The Chinese giant salamander (Andrias davidianus) is the largest salamander in the world, reaching a length of 180 cm (6 ft), although it rarely - if ever - reaches that size today. Endemic to rocky mountain streams and lakes in China, it is considered critically endangered due to habitat loss, pollution, and over-collecting, as it is considered a delicacy and used in traditional Chinese medicine. Records from Taiwan may be the results of introductions. It has been listed as one of the top-10 "focal species" in 2008 by the Evolutionarily Distinct and Globally Endangered (EDGE) project.
It has a large head, small eyes and dark and wrinkly skin. It is one of only two extant species in the genus Andrias, the other being the slightly smaller, but otherwise very similar Japanese giant salamander (Andrias japonicus). The Chinese giant salamander feeds on insects, frogs, and fish. It has very poor eyesight, and therefore depends on special sensory nodes that run in a line on the creature's body, from head to tail. They are capable of sensing the slightest vibrations around them with the help of these nodes. The female lays 500 eggs in an underwater breeding cavity, which is guarded by the male until the eggs hatch after 50–60 days. The average adult salamander is 25–30 kg (55-66 lb) and 1.15 m (3.8 ft).
A medium-sized specimen, approximately 3 ft (0.91 m) long, was kept for several years at the Steinhardt Aquarium in San Francisco, California, and now is on display again in the "Water Planet" section of the new California Academy of Sciences building. Per early 2008, ISIS records only show five individuals held in US zoos (Zoo Atlanta, Cincinnati Zoo, and Saint Louis Zoological Park), and an additional four in European zoos (Zoo Dresden and Rotterdam Zoo). It is likely additional individuals are kept in non-ISIS zoos and animals parks in its native China. There are several of them in the aquarium of Shanghai. It has been bred in captivity, but it is doubtful if this can be achieved to an extent where the pressure on the wild populations is reduced.
It has been argued that the correct scientific name of this species is Andrias scheuchzeri (in which case Andrias davidianus would be a junior synonym) – a name otherwise restricted to an extinct species described from Swiss fossils.
Wednesday, February 16, 2011
Aurelia aurita (moon jelly, moon jellyfish, common jellyfish, saucer jelly) is one of a group of more than ten morphologically nearly identical jellyfish species in the genus Aurelia. In general, it is nearly impossible to identify Aurelia medusae without genetic sampling, so most of what follows about Aurelia aurita, could equally be applied to any species of the genus. The medusa is translucent, usually about 25–40 cm in diameter, and can be recognized by its four horseshoe-shaped gonads that are easily seen through the top of the bell. It feeds by collecting medusae, plankton and mollusks with its mucusy bell nematocyst-laden tentacles and bringing the prey into its body for digestion, but is capable of only limited motion; like other jellies it primarily drifts with the current, even when it is swimming.
The cosmopolitan genus Aurelia is found throughout most of the world's oceans, from the tropics to as far north as 70° latitude and as far south as 40°. The species Aurelia aurita, whose distribution has been confirmed by Michael Dawson using genetic analysis, is found along the eastern Atlantic coast of Northern Europe and the western Atlantic coast of North America in New England and Eastern Canada. In general, Aurelia is an inshore genus that can be found in estuaries and harbors. It lives in ocean water temperatures ranging from 6 °C to 31 °C; with optimum temperatures of 9 °C to 19 °C. A. aurita prefers temperate seas with consistent currents. It has been found in waters with salinity as low as 6 parts per thousand.
Aurelia aurita is known to be eaten by a wide variety of predators including the Ocean Sunfish (Mola mola), the Leatherback Sea Turtle (Dermochelys coriacea), the scyphomedusa Phacellophora camtschatica, and a very large hydromedusa (Aequorea victoria). Moon jellies are also fed upon by sea birds, which may be more interested in the amphipods and other small arthropods that frequent the bells of Aurelia, but in any case, birds do some substantial amount of damage to these jellyfish that often are found just at the surface of bays.
Aurelia jellyfish naturally die after living and reproducing for several months. It is probably rare for these moon jellies to live more than about six months in the wild, although specimens cared for in public aquarium exhibits typically live several to many years. In the wild, the warm water at the end of summer combines with exhaustive daily reproduction and lower natural levels of food for tissue repair, leaving these jellyfish more susceptible to bacterial and other disease problems that likely lead to the demise of most individuals. Such problems are responsible for the demise of many smaller species of jellyfish. In 1997, Arai summarized that seasonal reproduction leaves the gonads open to infection and degradation.
Some metazoan parasites attack Aurelia aurita, as well as most other species of jellyfish.
Tuesday, February 15, 2011
Bluntnose Sixgill Shark
The bluntnose sixgill shark, Hexanchus griseus, often simply called the cow shark, is the largest hexanchoidshark, growing to more than 5.4 m (18 ft) in length.
The bluntnose sixgill shark is a member of the Hexanchidae family. Many of its relatives are extinct. The living species that are closest genetically include the dogfish, the Greenland shark, as well as other six- and sevengilled sharks. There are more closely related relatives in the fossil record than living species. Some of the shark's relatives date back to 200 million years ago. This shark is a notable species due to both its primitive and current physical characteristics.
This species typically inhabits depths greater than 90 m (300 ft), and has been recorded as deep as 1,875 m (6,150 ft). Like many deep-sea creatures, the bluntnose sixgill shark is known to undertake nightly vertical migrations (travelling surfaceward at night, returning to the depths before dawn).
The bluntnose sixgill shark can be seen at depths of 30 m (100 ft) and shallower during parts of the year in some specific places e.g. Flora Islet, near Hornby Island, Sightings during shallow evening dives in Whytecliff Park West Vancouver in British Columbia, in Puget Sound, Monterey Canyon off Monterey, California and in fjords in Norway. The sharks are deepsea sharks, but like most fish that prefer the deep, they come to the shallower depths to feed.
Monday, February 14, 2011
An unidentified purple octopus (pictured) is one of 11 potentially new species found this month during a deep-sea expedition off Canada's Atlantic coast, scientists say.
Still at sea, a team of Canadian and Spanish researchers is using a remotely operated vehicle called ROPOS for dives off Newfoundland with a maximum depth of about 9,800 feet (3,000 meters).
The 20-day expedition aims to uncover relationships between cold-water coral and other bottom-dwelling creatures in a pristine yet "alien" environment, according to the researchers' blog.
"It's been really spectacular," Ellen Kenchington, research scientist with the Fisheries Department of Canada—one of the organizations involved in the project—told Canada's CTV News website.
"It's really changing our perception of the diversity that's out there. ... We're seeing new species in deeper waters."
Sunday, February 13, 2011
Exxon Valdez Oil Spill
The Exxon Valdez oil spill occurred in Prince William Sound, Alaska, on March 24, 1989, when the Exxon Valdez, an oil tanker bound for Long Beach, California, struck Prince William Sound's Bligh Reef and spilled 260,000 to 750,000 barrels (41,000 to 119,000 m3) of crude oil. It is considered to be one of the most devastating human-caused environmental disasters. As significant as the Valdez spill was—the largest ever in U.S. waters until the 2010 Deepwater Horizon oil spill—it ranks well down on the list of the world's largest oil spills in terms of volume released. However, Prince William Sound's remote location, accessible only by helicopter, plane and boat, made government and industry response efforts difficult and severely taxed existing plans for response. The region is a habitat for salmon, sea otters, seals and seabirds. The oil, originally extracted at the Prudhoe Bay oil field, eventually covered 1,300 miles (2,100 km) of coastline, and 11,000 square miles (28,000 km2) of ocean. Then Exxon CEO, Lawrence G. Rawl, shaped the company's response.
Exxon Valdez left the Valdez oil terminal in Alaska at 9:12 pm on March 23, 1989, bound for Long Beach, California. The ship was under the control of Shipmaster Joseph Jeffrey Hazelwood. The outbound shipping lane was obstructed with small icebergs (possibly from the nearby Columbia Glacier), so Hazelwood got permission from the Coast Guard to go out through the inbound lane. Following the maneuver and sometime after 11 p.m., Hazelwood left Third Mate Gregory Cousins in charge of the wheel house and Able Seaman Robert Kagan at the helm. Neither man had been given his mandatory six hours off duty before beginning his 12-hour watch. The ship was on autopilot, using the navigation system installed by the company that constructed the ship. The ship struck Bligh Reef at around 12:04 a.m. March 24, 1989.
According to official reports, the ship was carrying approximately 55 million US gallons (210,000 m3) of oil, of which about 11 to 32 million US gallons (42,000 to 120,000 m3) were spilled into the Prince William Sound. A figure of 11 million US gallons (42,000 m3) was a commonly accepted estimate of the spill's volume and has been used by the State of Alaska's Exxon Valdez Oil Spill Trustee Council, the National Oceanic and Atmospheric Administration and environmental groups such as Greenpeace and the Sierra Club. Some groups, such as Defenders of Wildlife, dispute the official estimates, maintaining that the volume of the spill has been underreported. Alternative calculations, based on an assumption that the sea water rather than oil was drained from the damaged tanks, estimate the total to have been 25 to 32 million US gallons (95,000 to 120,000 m3).
Saturday, February 12, 2011
Cuvier's Beaked Whale
Cuvier's beaked whale (Ziphius cavirostris) is the most widely distributed of all the beaked whales. It is the only member of the genus Ziphius. Another common name for the species is goose-beaked whale on account of the fact that its head is said to be shaped like the beak of a goose. Georges Cuvier first described it in 1823 from part of a skull found in France in 1804.
Cuvier's beaked whale has a short beak in comparison with other species in its family, with a slightly bulbous melon. The melon is white or creamy in color and a white strip runs back to the dorsal fin about two-thirds of the way along the back. The rest of the body color varies by individual: some are dark grey; others a reddish-brown. Individuals commonly have white scars and patches caused by cookiecutter sharks. The dorsal fin varies in shape from triangular to highly falcate. The fluke of the whale is about one-quarter the body length. The whale grows up to about 7 meters (23 ft) in length and weighs 2–3 tonnes (2.0–3.0 LT; 2.2–3.3 ST). They live for forty years.
The Cuvier's beaked whale is difficult to distinguish from many of the mesoplodont whales at sea.
Their range is known mainly from strandings. It is widespread across the Atlantic, Pacific and Indian Oceans. Individuals have been found as far north as the Shetland Islands and as far south as Tierra del Fuego. Deep waters are preferred in anything from cool to tropical habitats.
Because of identification difficulties, the global population is unknown.
Beaked whales may also be sensitive to noise. A higher incidence of strandings has been recorded in noisy seas such as the Mediterranean. Multiple mass strandings (beachings) have occurred following operations by the Spanish Navy.
Friday, February 11, 2011
Human Face Fish
The Human Face Fish is a cyprinid fish found in 2003 purported to have markings on its head reminiscent of the facial features of a human. It has been reported by Reuters as being a cross between two varieties of the carp Cyprinus carpio, specifically the common carp and the leather carp, but by other news outlets as a true hybrid between the common carp and the ayu sweetfish Plecoglossus altivelis. The latter is almost certainly incorrect though, as carps and ayu belong to quite different superorders of Teleostei.
The fish resides in a pond in Chongju near Seoul, South Korea. They are also found in Slovenia, in the caves under and around Lake Bohinj.
Thursday, February 10, 2011
Clownfish or anemonefish are fishes from the subfamily Amphiprioninae in the family Pomacentridae. About twenty-nine species are recognized, one in the genus Premnas, while the remaining are in the genus Amphiprion. In the wild they all form symbiotic mutualisms with sea anemones. Depending on species, clownfish are overall yellow, orange, reddish or blackish, and many show white bars or patches. The largest can reach a length of 18 centimetres (7.1 in), while some barely can reach 10 centimetres (3.9 in). In popular culture, "Finding Nemo" by Pixar / Disney prominently features clownfish as the main characters.
Clownfish are native to warmer waters of the Indian and Pacific oceans, including the Great Barrier Reef and the Red Sea. While most species have restricted distributions, others are widespread. They are generally highly host specific, and especially the genera Heteractis and Stichodactyla, and the species Entacmaea quadricolor are frequent partners.
Clownfish live at the bottom of the sea in sheltered reefs or in shallow lagoons, usually in pairs. They are also found in northwest Australia, southeast Asia, Japan and the Indo-Malaysian region. There are no clownfish in the Caribbean.
Clownfish live in pairs inhabiting a single anemone. When the female dies, the dominant male changes sex and becomes the female. This life history strategy is known as sequential hermaphroditism. Because clownfish are all born as males, they are protandrous hermaphrodites (pro=first; androus=male). On the top of the hierarchy is the reproducing female followed by the mating male. Below them are a bunch of non-mating males. But, if the female dies, the whole hierarchy gets disrupted. The predominant male then morphs into a female and chooses a partner from the various non-mating males. The largest fish in the group is a female and the second biggest is a male. All the other clownfish are neuter, which means they have not fully developed functioning sex organs for either gender. If the female should die, the male will change sex, while the biggest neuter clownfish will develop functioning male sex organs to replace the male.
In a group of clownfish, there is a strict hierarchy of dominance. The largest and most aggressive female is found at the top. Only two clownfish, a male and a female, in a group reproduce through external fertilization. The clownfish are hermaphrodites, meaning that they develop into males first, and when they mature, they become females. Also, as mentioned earlier, more than one clownfish is able to live in a sea anemone. If the female clownfish is removed from the group, such as by death, one of the largest and most dominant males would become a female. The rest of the remaining males will move up a rank on the hierarchy.
Wednesday, February 9, 2011
A fiddler crab, sometimes known as a calling crab, may be any of approximately 94 species of semi-terrestrial marine crabs which make up the genus Uca. As members of the family Ocypodidae, fiddler crabs are most closely related to the ghost crabs of the genus Ocypode. This entire group is composed of small crabs – the largest being slightly over two inches across. Fiddler crabs are found along sea beaches and brackish inter-tidal mud flats, lagoons and swamps.
Like all crabs, fiddler crabs shed their shells as they grow. If they have lost legs or claws during their present growth cycle a new one will be present when they molt. If the large fiddle claw is lost, males will develop one on the opposite side after their next molt. Newly molted crabs are very vulnerable because of their soft shells. They are reclusive and hide until the new shell hardens.
Fiddler crabs communicate by a sequence of waves and gestures; males have an oversized claw or cheliped; used in clashes of ritualised combat of courtship over a female and signal their intentions between conspecifics. The movement of the smaller claw from ground to mouth during feeding underlines the crabs' common name; it seems that animal plays the larger claw somewhat like a fiddle.
Fiddler crabs live rather brief lives of no more than two years (up to three years in captivity). During courtship, the males wave their oversized claws high in the air and tap them on the ground in an effort to attract females. Fights between males will also occur, which are presumably meant to impress the females; if a male loses his larger claw, the smaller one will begin to grow larger and the lost claw will regenerate into a new (small) claw. For at least some species of fiddler crabs, however, the small claw remains small, while the larger claw regenerates over a period of several molts, being about half its former size after the first molt. The female fiddler carries her eggs in a mass on the underside of her body. She remains in her burrow during a two week gestation period, after which she ventures out to release her eggs into the receding tide. The larvae remain planktonic for a further two weeks.
Tuesday, February 8, 2011
Sacculina is a genus of barnacles that parasitize crabs. The adults bear no resemblance to the barnacles that cover ships and piers; they are recognised as barnacles because their larval forms are like other members of the barnacle class Cirripedia. Depending on the location, the prevalence of this unusual crustacean parasite in its crab host can be as high as 50%.
The female Sacculina larva finds a crab and walks on it until it finds a joint. It then molts, injecting its soft body into the crab while its shell falls off. The Sacculina grows in the crab, emerging as a sac, known as an externa, on the underside of the crab's rear thorax, where the crab's eggs would be incubated.
When a female Sacculina is implanted in a male crab it will interfere with the crab's hormonal balance. This sterilizes it and changes the bodily layout of the crab to resemble that of a female crab by widening and flattening its abdomen, among other things. The female Sacculina has even been known to cause the male crabs to perform mating gestures typical of female crabs.
After this invasion of the Sacculina, the crab is now unable to perform the normal function of molting. This would result in a loss of nutrition of the Sacculina and impair its overall growth. The natural ability of regrowing a severed claw that is commonly used for defense purposes is lost after the infestation of Sacculina. Although all energy otherwise expended on reproduction is directed to the Sacculina, the crab develops a nurturing behavior typical of a female crab. The natural hatching process of a crab consists of the female finding a high rock and grooming its brood pouch on its abdomen and releasing the fertilized eggs in the water through a bobbing motion. The female crab stirs the water with her claw to aid the flow of the water. When the hatching parasite eggs of the Sacculina are ready to emerge from the brood pouch of Sacculina, the crab performs a similar process. The crab shoots them out through pulses creating a large cloud of parasites. The crab then uses the familiar technique of stirring the water to aid in flow.
The male Sacculina looks for a female Sacculina adult on the underside of a crab. He then enters and fertilizes her eggs. The crab (male or female) then cares for the eggs as if they were its own, having been rendered infertile by the parasite.
Monday, February 7, 2011
Whale song is the sounds made by whales and which is used for different kinds of communication.
Whale song is the sounds made by whales and which is used for different kinds of communication.
The word "song" is used to describe the pattern of regular and predictable sounds made by some species of whales, notably the Humpback Whale. This is included with or in comparison with music, and male humpback whales have been described as "inveterate composers" of songs that are "'strikingly similar' to human musical traditions". Male Humpback whales sing only on calving grounds and only in the mating period and humpback songs are similar, almost identical, within a single population. It has been suggested that humpback songs communicate male fitness to female whales. The click sounds made by Sperm whales and dolphins are not strictly song, but the clicking sequences have been suggested to be individualized rhythmic sequences that communicate the identity of a single whale to other whales in its group and allows the groups to coordinate foraging activities.
The mechanisms used to produce sound vary from one family of cetaceans to another. Marine mammals, such as whales, dolphins, and porpoises, are much more dependent on sound for communication and sensation than are land mammals, because other senses are of limited effectiveness in water. Sight is less effective for marine mammals because of the way water absorbs light. Smell also is limited, as molecules diffuse more slowly in water than in air, which makes smelling less effective. In addition, the speed of sound is roughly four times greater in water than in the atmosphere at sea level. Because sea mammals are so dependent on hearing to communicate and feed, environmentalists and cetologists are concerned that they are being harmed by the increased ambient noise in the world's oceans caused by ships, sonar and marine seismic surveys.
Sunday, February 6, 2011
The sardine run of southern Africa occurs between May and July when millions of sardines - or more specifically the Southern African pilchard Sardinops sagax - spawn in the cool waters of the Agulhas Bank and move northward along the east coast of South Africa. Their sheer numbers create a feeding frenzy along the coastline. The run, containing millions of individual sardines, occurs when a current of cold water heads north from the Agulhas Bank up to Mozambique where it then leaves the coastline and goes further east into the Indian Ocean.
In terms of biomass, researchers estimate the sardine run could rival East Africa's great wildebeest migration. However, little is known of the phenomenon. It is believed that the water temperature has to drop below 21°C in order for the migration to take place. In 2003, the sardines failed to 'run' for the third time in 23 years. While 2005 saw a good run, 2006 marked another non-run.
The shoals are often more than 7 km long, 1.5 km wide and 30 meters deep and are clearly visible from spotter planes or from the surface.
Sardines group together when they are threatened. This instinctual behaviour is a defense mechanism, as lone individuals are more likely to be eaten than large groups.
Dolphins (estimated as being up to 18,000 in number, mostly the common dolphin but also the bottlenose dolphin) are largely responsible for rounding up the sardines into bait balls. These bait balls can be 10–20 metres in diameter and extend to a depth of 10 metres. The bait balls are short lived and seldom last longer than 10 minutes. Once the sardines are rounded up, sharks (primarily the bronze whaler, but also dusky shark, grey nurse shark, blacktip shark, spinner shark and zambezi shark), game fish (like shad/elf a.k.a. bluefish, king mackerel, various kingfish species, garrick, geelbek and eastern little tuna) and birds (like the Cape gannet, cormorants, terns and gulls) take advantage of the opportunity.
The Cape Fur Seal follows the shoals up the Eastern Cape coastline as far as Port St Johns.
Related Articles : Shoals and Schools
Saturday, February 5, 2011
Sockeye salmon (Oncorhynchus nerka), also called red salmon or blueback salmon in the USA, is an anadromous species of salmon found in the Northern Pacific Ocean and rivers discharging into it. There are also completely landlocked populations of the same species, which are known as the kokanee. Sockeye salmon is the third most common Pacific salmon species, after pink and chum salmon. The name "sockeye" is believed to be a folk adaptation of the anglicization of sθə́qəy̓, its name in Halkomelem, the language of the indigenous people along the lower reaches of the Fraser River.
Some sockeye live and reproduce in lakes and are called "kokanee", a word in the Okanagan language for this kind of fish. They are much smaller than the ones that go to the ocean and are rarely over 350 millimetres (14 in) long. In Okanagan Lake and many others there are two kinds of kokanee populations - one spawns in streams and one spawns in the lake near the shore. As an aside, the Kokanee Glacier gets its name from Kokanee Creek, which enters Kootenay Lake near Nelson, British Columbia (see Kokanee).
Sockeye salmon ranges as far south as the Columbia River in the eastern Pacific (though individuals have been spotted as far south as the 10 Mile River on the Mendocino Coast of California) and northern Hokkaidō Island in Japan in the western Pacific, and as far north as Bathurst Inlet in the Canadian Arctic in the east and the Anadyr River in Siberia in the west. Landlocked populations occur in the Yukon Territory and British Columbia in Canada, and in Alaska, Washington, Oregon, California, New York, Utah, Idaho, Montana, Colorado, New Mexico, and Wyoming in the United States. Nantahala Lake is the only spot in North Carolina where kokanee salmon are found. The fish, which is native to the western United States, was stocked in Nantahala Lake in the mid-1960s by the N.C. Wildlife Resources Commission in an attempt to establish the species as a forage fish for other predator fishes in the lake. This stock has remained and become a favorite target for anglers.
Friday, February 4, 2011
Lungfish (also known as salamanderfish) are freshwater fish belonging to the Subclass Dipnoi. Lungfish are best-known for retaining characteristics primitive within the Osteichthyes, including the ability to breathe air, and structures primitive within Sarcopterygii, including the presence of lobed fins with a well-developed internal skeleton. Today, they live only in Africa, South America, and Australia. While vicariance would suggest this represents an ancient distribution limited to the Mesozoic supercontinent Gondwana, the fossil record suggests that advanced lungfish had a widespread freshwater distribution and that the current distribution of modern lungfish species reflects extinction of many lineages following the breakup of Pangaea, Gondwana, and Laurasia.
All lungfish demonstrate an uninterrupted cartilaginous notochord and an extensively developed palatal dentition. The lungfish is a true carnivore. Basal lungfish groups may retain marginal teeth and an ossified braincase, but derived lungfish groups, including all modern species, show a significant reduction in the marginal bones and a cartilaginous braincase. The bones of the skull roof in primitive lungfish are covered in a mineralized tissue called cosmine, but in post-Devonian lungfishes, the skull roof lies beneath the skin and the cosmine covering is lost. All modern lungfish show significant reductions and fusions of the bones of the skull roof, and the specific bones of the skull roof show no homology to the skull roof bones of ray-finned fishes or tetrapods. During the breeding season, the South American lungfish develops a pair of feathery appendages that are actually highly modified pelvic fins. It is thought these fins improve gas exchange around the fish's eggs in its nest.
The dentition of lungfish is different from that of any other vertebrate group. "Odontodes" on the palate and lower jaws develop in a series of rows to form a fan-shaped occlusion surface. These odontodes then wear to form a uniform crushing surface. In several groups, including the modern lepidosireniformes, these ridges have been modified to form occluding blades.
The modern lungfishes have a number of larval features, which suggest paedomorphosis. They also demonstrate the largest genome among the vertebrates.
Modern lungfish all have an elongate body with fleshy paired pectoral and pelvic fins and a single unpaired caudal fin replacing the dorsal, caudal, and anal fin of most fishes.
Thursday, February 3, 2011
The Olm, or Proteus (Proteus anguinus), is a blind amphibian endemic to the subterranean waters of caves of the Dinaric karst of southern Europe. It lives in the waters that flow underground through this extensive limestone region including waters of the Soča river basin near Trieste in Italy, through to southern Slovenia, southwestern Croatia, and Herzegovina. The olm is the only species in its genus Proteus, the only European species of the family Proteidae, and the only European exclusively cave-dwelling chordate. It is also occasionally called the "human fish" by locals because of its skin color, similar to that of white people (translated literally from Slovene: človeška ribica and Croatian: čovječja ribica), as well as "cave salamander" or "white salamander." In Slovenia it is also known by the name močeril, which translates as "the one that burrows into wetness."
This animal is most notable for its adaptations to a life of complete darkness in its underground habitat. The olm's eyes are undeveloped, leaving it blind, while its other senses, particularly those of smell and hearing, are acutely developed. It also lacks any pigmentation in its skin. In contrast to most amphibians, the olm is entirely aquatic, and it eats, sleeps, and breeds underwater. It has 3 toes on its forelimbs, but 2 toes on its hind feet. It also exhibits neoteny, retaining larval characteristics like external gills into adulthood, like the American amphibians, the axolotl and the mud puppy.
The olm's body is snakelike, 20–30 cm (8–12 in) long, with some specimens reaching up to 40 centimetres (16 in). The trunk is cylindrical, uniformly thick, and segmented with regularly spaced furrows at the myomeretail is relatively short, laterally flattened, and surrounded by a thin fin. The limbs are small and thin, with a reduced number of digits compared to other amphibians: the front legs have three digits instead of the normal four, and the rear have two digits instead of five. Its body is covered by a thin layer of skin, which contains very little of the pigment riboflavin, making it yellowish-white or pink in color. The internal organs can be seen shining through on the abdominal part of the body. The resemblance in color to that of white humans is the reason why the borders. The Proteus is called human fish in some languages. However, the olm's skin retains the ability to produce melanin. When exposed to light, it will gradually turn dark, and in some cases the larvae are also colored. Its pear-shaped head ends with a short, dorsoventrally flattened snout. The mouth opening is small, with tiny teeth forming a sieve to keep larger particles inside the mouth. The nostrils are so small as to be imperceptible, but are placed somewhat laterally near the end of the snout. The regressed eyes are covered by a layer of skin. The olm breathes with external gills that form two branched tufts at the back of the head. They are red in color because the oxygen-rich blood shows through the non-pigmented skin. The olm also has rudimentary lungs, but their role in respiration is only accessory. The sexes are very similar in appearance, with males having a somewhat thicker cloaca than females.
Wednesday, February 2, 2011
The halloween crab, Gecarcinus quadratus, also known as the moon crab, mouthless crab or harlequin land crab, is a colorful land crab from the family Gecarcinidae. It is found in mangrove, sand dunes and rainforest along the Pacific coast from Mexico south to Peru. The taxonomy in relations to the Atlantic Gecarcinus lateralis is disputed, with many considering it and G. quadratus to be conspecific.
In the pet-trade it is sometimes confused with the African Cardisoma armatum (sometimes also referred to as the Moon crab) or the primarily Caribbean Gecarcinus ruricola. Unlike these, G. quadratus combines a pair of largely purple claws, reddish-orange legs, and an almost entirely blackish carapace with a pair of yellow, orange or maroon spots behind the eyes, and an additional pair of whitish spots on the central-lower carapace. Additionally, the name Halloween crab sometimes leads to confusion with the entirely different halloween hermit crab. The carapace of G. quadratus may reach a length of 5 centimetres (2.0 in).
This nocturnal crab digs burrows — sometimes as long as 1.5 metres (4.9 ft) — in the coastal rainforests of Central America, and is common along the coasts of Costa Rica, Panama, and Nicaragua. There it lives in the forest at least some of its adult life, but needs to return to the ocean to breed. The halloween crab is very territorial and will defend itself if threatened. It is largely herbivorous, and consumes leaf litter and seedlings. They will, however, also take animal matter if available.
Tuesday, February 1, 2011
The nurse shark, Ginglymostoma cirratum, is a shark in the nurse sharks (Ginglymostomatidae) family, the only member of its genus Ginglymostoma. Nurse sharks can reach a length of 4.3 m (14 ft) and a weight of 330 lbs (150 kg).
The nurse shark is a common inshore bottom-dwelling shark, found in tropical and subtropical waters on the continental and insular shelves. It is frequently found at depths of one metre or less but may occur down to 75 m. Its common habitats are reefs, channels between mangrove islands and sand flats. It occurs in the Western Atlantic from Rhode Island down to southern Brazil; in the Eastern Atlantic from Cameroon to Gabon (and possibly ranges further north and south); in the Eastern Pacific from the southern Baja California to Peru; and around the islands of the Caribbean.
Nurse sharks are nocturnal animals, spending the day in large inactive groups of up to 40 individuals. Hidden under submerged ledges or in crevices within the reef, the nurse sharks seem to prefer specific resting sites and will return to them each day after the night's hunting. By night, the sharks are largely solitary; they spend most of their time rifling through the bottom sediments in search of food. Their diet consists primarily of crustaceans, molluscs, tunicates, sea snakes, and other fish, particularly stingrays.