Monday, January 31, 2011
Elephant seals are large, oceangoing seals in the genus Mirounga. There are two species: the Northern Elephant Seal (M. angustirostris) and the Southern Elephant Seal (M. leonina). Both were hunted to the brink of extinction by the end of the nineteenth century, but numbers have since recovered. The Northern Elephant Seal, somewhat smaller than its southern relative, ranges over the Pacific coast of the U.S., Canada and Mexico. The most northerly breeding location on the Pacific Coast is at Race Rocks, at the southern tip of Vancouver Island in the Strait of Juan de Fuca. The Southern Elephant Seal is found in the southern hemisphere on islands such as South Georgia, Macquarie Island, and on the coasts of New Zealand, South Africa, and Argentina in the Peninsula Valdés, which is the fourth largest elephant seal colony in the world.
Elephant seals take their name from the large proboscis of the adult males (bulls) which resembles an elephant's trunk. The bull's proboscis is used in producing extraordinarily loud roaring noises, especially during the mating season. More importantly, however, the nose acts as a sort of rebreather, filled with cavities designed to reabsorb moisture from the animals' exhalations. This is important during the mating season when the male seals rarely leave the beach to feed and therefore must conserve body moisture as they have no incoming source of water. Bulls of both the Northern Elephant Seal and the Southern Elephant Seal reach a length of 16 ft (5 m) and a weight of 6,000 lb (2,700 kg) and are much larger than the cows, which typically measure about 10 ft (3 m) and 1,900 lb (900 kg). The largest known bull elephant seal weighed 11,000 lb (5,000 kg) and measured 22.5 ft (6.9 m) in length. This makes the elephant seal the largest member of the order Carnivora.
Sunday, January 30, 2011
Snakeheads (Channidae) are a family of freshwater fish native to Africa and Asia. These predatory fish are distinguished by a long dorsal fin, large mouth and shiny teeth. They have a physiological need to breathe atmospheric air, which they do with a suprabranchial organ: a primitive form of a labyrinth organ. There are two extant genera, Channa in Asia, and Parachanna in Africa, consisting of 30-35 species.
They are considered valuable food fish. Called Ca Loc, ca Qua, or Ca Chuoi in Vietnamese, it is prized in clay pot dishes and pickled preparations. Larger species like Channa striata, Channa maculata, and Parachanna obscura are farmed in aquaculture. Snakeheads feed on plankton, aquatic insects, and molluskscarp, or frogs. In rare cases, small mammals such as rats are taken. The size of the snakehead species differs greatly. "Dwarf snakeheads" like when small. When adult, they mostly feed on other fish like Channa gachua grow to 10 inches (25 cm). Most snakeheads grow up to 2 or 3 feet (60–90 cm). Only two species (Channa marulius and Channa micropeltes) can reach a length of more than 1 meter and a weight of more than 6 kg.
It is illegal to keep snakeheads as pets in all states of the U.S. and other countries as they have become an invasive species due to individuals releasing them into the wild. In the U.S., National Geographic referred to snakeheads as "Fishzilla."
When the Snakehead eats it is a thrust predator. It will eat its prey all at once, striking and ingesting it whole.
The giant snakehead (Channa micropeltes) is native throughout Asia, and is the most aggressive Snakehead. They can grow to around 1 meter in length. Adult Snakeheads force their young to breathe air by pushing them to the surface.
From 2002 to 2003, one Los Angeles supermarket was found to have sold approximately 25,000 dollars worth of illegal live Snakeheads which caused breakouts in local ecosystems.
Saturday, January 29, 2011
Amphipoda is an order of malacostracan crustaceans with no carapace and generally with laterally compressed bodies. The name amphipoda means "different-footed", and refers to the different forms of appendages, unlike isopods, where all the legs are alike. Of the 7,000 species, 5,500 are classified into one suborder, Gammaridea. The remainder are divided into two or three further suborders. Amphipods range in size from 1 to 340 millimetres (0.039 to 13 in) and are mostly detritivores or scavengers. They live in almost all aquatic environments; 750 species live in caves and the order also includes terrestrial animals and sandhoppers such as Talitrus saltator.
Amphipods are typically less than 10 millimetres (0.39 in) long, but the largest recorded living amphipods were 28 centimetres (11 in) long, and were photographed at a depth of 5,300 metres (17,400 ft) in the Pacific Ocean. Samples from the Atlantic Ocean with a reconstructed length of 34 centimetres (13 in) have been assigned to the same species, Alicella gigantea. The smallest known amphipods are less than 1 millimetre (0.04 in) long. The size of amphipods is limited by the availability of dissolved oxygen, such that the amphipods in Lake Titicaca at an altitude of 3,800 metres (12,500 ft) can only grow up to 22 millimetres (0.87 in), compared to lengths of 90 millimetres (3.5 in) in Lake Baikal at 455 metres (1,500 ft).
Amphipods are found in almost all aquatic environments, from fresh water to water with twice the salinity of sea water. They are almost always an important component of aquatic ecosystems. Most species in the suborder Gammaridea are epibenthic, although they are often collected in plankton samples. Members of the Hyperiidea are all planktonic and marine. Many are symbionts of gelatinous animals, including salps medusae, siphonophores, colonial radiolarians and ctenophores, and most hyperiids are associated with gelatinous animals during some part of their life cycle.
Compared to other crustacean groups, such as the Isopoda, Rhizocephala or Copepoda, relatively few amphipods are parasitic on other animals. The most notable example of parasitic amphipods are the whale lice (family Cyamidae); unlike other amphipods, these are dorso-ventrally flattened, and have large, strong claws, with which they attach themselves to baleen whales. They are the only parasitic crustaceans which cannot swim during any part of their life cycle.
Related Articles : Pram Bug and Sandhopper
Friday, January 28, 2011
The wels catfish (pronounced /ˈwɛls/ or /ˈvɛls/; Silurus glanis), also called sheatfish, is a large catfish found in wide areas of central, southern, and eastern Europe, and near the Baltic and Caspian Seas. It is a scaleless fresh and brackish water fish recognizable by its broad, flat head and wide mouth. Wels catfish can live for at least thirty years and have very good hearing.
The wels catfish lives on annelid worms, gastropods, insects, crustaceans, and fish; the larger ones also eat frogs, mice, rats and aquatic birds such as ducks.
The wels catfish lives in large, warm lakes and deep, slow-flowing rivers. It prefers to remain in sheltered locations such as holes in the riverbed, sunken trees, etc. It consumes its food in the open water or on the bottom, where it can be recognized by its large mouth. Wels catfish are kept in fish ponds as food fish.
Wels catfish's mouth contains lines of numerous small teeth, two long barbels on the upper jaw and four shorter barbels on the lower jaw. It has a long anal fin that extends to the caudal fin, and a small sharp dorsal fin positioned relatively far forward. It uses its sharp pectoral fins to capture prey. With these fins, it creates an eddy to disorient its victim, which it then simply engulfs in its enormous throat. It has very slippery green-brown skin. Its belly is pale yellow or white. Colour varies with environment. Clear water will give the fish a black coloration while muddy water will often tend to produce brownish specimens. Weight and length are not correlated linearly, and also depend on the season.
Thursday, January 27, 2011
An algal bloom is a rapid increase or accumulation in the population of algae in an aquatic system. Algal blooms may occur in freshwater as well as marine environments. Typically, only one or a small number of phytoplankton species are involved, and some blooms may be recognized by discoloration of the water resulting from the high density of pigmented cells. Although there is no officially recognized threshold level, algae can be considered to be blooming at concentrations of hundreds to thousands of cells per milliliter, depending on the severity. Algal bloom concentrations may reach millions of cells per milliliter. Algal blooms are often green, but they can also be other colors such as yellow-brown or red, depending on the species of algae.
Bright green blooms are a result of blue-green algae, which are actually bacteria (cyanobacteria). Blooms may also consist of macroalgal, not phytoplankton, species. These blooms are recognizable by large blades of algae that may wash up onto the shoreline.
Of particular note are harmful algal blooms (HABs), which are algal bloom events involving toxic or otherwise harmful phytoplankton such as dinoflagellates of the genus Alexandrium and Karenia. Such blooms often take on a red or brown hue and are known colloquially as red tides.
In the marine environment, single-celled, microscopic, plant-like organisms naturally occur in the well-lit surface layer of any body of water. These organisms, referred to as phytoplankton or microalgae, form the base of the food web upon which nearly all other marine organisms depend. Of the 5000+ species of marine phytoplankton that exist worldwide, about 2% are known to be harmful or toxic. Blooms of harmful algae can have large and varied impacts on marine ecosystems, depending on the species involved, the environment where they are found, and the mechanism by which they exert negative effects.
Harmful algal blooms have been observed to cause adverse effects to varying species of marine mammals and sea turtles, with each presenting specific toxicity-induced reductions in developmental, immunological, neurological, and reproductive capacities. A mass mortality event of 107 bottlenose dolphins occurred along the Florida panhandle in the spring of 2004 due to ingestion of contaminated menhaden with high levels of brevetoxin. Manatee mortalities have also been attributed to brevetoxin but unlike dolphins, the main toxin vector was endemic seagrass species (Thalassia testudinum) in which high concentrations of brevetoxins were detected and subsequently found as a main component of the stomach contents of manatees.
Related Articles : Dead Zones
Wednesday, January 26, 2011
Stellar's Sea Cow
Steller's sea cow (Hydrodamalis gigas) was a large herbivorous marine mammal. In historical times, it was the largest member of the order Sirenia, which includes its closest living relative, the dugong (Dugong dugon), and the manatees (Trichechus spp.). Formerly abundant throughout the North Pacific, its range was limited to a single, isolated population on the uninhabited Commander Islands by 1741 when it was first described by Georg Wilhelm Steller, chief naturalist on an expedition led by explorer Vitus Bering. Within 27 years of discovery by Europeans, the slow moving and easily captured Steller's sea cow was hunted to extinction.
The sea cow grew at least 8 metres (26 ft) to 9 meters or 30 feet long, much larger than the manatee or dugong. Steller's work contains two contradictory weights: 4 and 24.3 tons. The true value probably lies between these figures, around 8-10 tons. It looked somewhat like a large seal, but had two stout forelimbs and a whale-like tail and the fluke. According to Steller, "The animal never comes out on shore, but always lives in the water. Its skin is black and thick, like the bark of an old oak…, its head in proportion to the body is small…, it has no teeth, but only two flat white bones—one above, the other below". It was completely tame, according to Steller. They fed on a variety of kelp. Wherever sea cows had been feeding, heaps of stalks and roots of kelp were washed ashore. The sea cow was also a slow swimmer and apparently was unable to submerge.
The population of sea cows was small and limited in range when Steller first described them. Steller said they were numerous and found in herds, but zoologist Leonhard Hess Stejneger later estimated that at discovery there had been fewer than 1,500 remaining, and thus had been in immediate danger of extinction from overhunting by humans. They were quickly wiped out by the sailors, seal hunters, and fur traders that followed Bering's route past the islands to Alaska, who hunted them both for food and for their skins, which were used to make boats. They were also hunted for their valuable subcutaneous fat, which was not only used for food (usually as a butter substitute), but also for oil lamps because it did not give off any smoke or odor and could be kept for a long time in warm weather without spoiling. By 1768, 27 years after it had been discovered by Europeans, Steller's sea cow was extinct.
Fossils indicate that Steller's sea cow was formerly widespread along the North Pacific coast, reaching south to Japan and California. Given the rapidity with which its last population was eliminated, it is likely that aboriginal hunting caused its extinction over the rest of its original range (aboriginal peoples apparently never inhabited the Commander Islands).
Tuesday, January 25, 2011
The archerfish (Spinner Fish or Archer Fish) are a family (Toxotidae) of fish known for their habit of preying on land based insects and other small animals by literally shooting them down with water droplets from their specialized mouths. The family is small, consisting of seven species in the genus Toxotes; which typically inhabit brackish waters of estuaries and mangroves, but can also be found in the open ocean as well as far upstream in fresh water in India to the Philippines, Australia, and Polynesia.
Archerfish or Spinnerfish bodies are deep and laterally compressed, with the dorsal fin set far back, and the profile a straight line from dorsal fin to mouth. The mouth is protractile, and the lower jaw juts out. Sizes are generally small,about 5–10 cm but T. chatareus can reach 40 centimetres (16 in).
Archerfish are remarkably accurate in their shooting; adult fish almost always hit the target on the first shot. They can bring down an insect that includes grasshoppers, spiders and butterflies on a branch overhanging the water, 3 m above the water's surface. This is partially due to their good eyesight, but also their ability to compensate for the refraction of light as it passes through the air water interface when aiming for their prey. They typically spit at prey at a mean angle of about 74 degrees from the horizontal, but can still aim accurately when spitting at angles between 45 and 110 degrees.
When an archerfish selects its prey, it rotates its eye so that the image of the prey falls on a particular portion of the eye in the ventral temporal periphery of the retina and its lips just break the surface, squirting a jet of water at its victim. It does this using the narrow groove in the roof of its mouth. It presses its tongue against this groove to form a narrow channel, then contracts its gill covers to force a powerful jet of water through the channel. The resulting jet of water can be up to 2–5 m long, but their accuracy only allows them to shoot insects 1–2 m away depending on body size. The fish can alter the power of the shot for prey of different sizes. If the first shot does not knock the victim into the water, the archerfish will keep trying.
Archerfish will often leap out of the water and grab an insect in their mouth if it happens to be within reach. Individuals typically prefer to remain close to the surface of the water.
Monday, January 24, 2011
Dead zones are hypoxic (low-oxygen) areas in the world's oceans, the observed incidences of which have been increasing since oceanographers began noting them in the 1970s. These occur near inhabited coastlines, where aquatic life is most concentrated. (The vast middle portions of the oceans which naturally have little life are not considered "dead zones".) The term can also be applied to the identical phenomenon in large lakes.
In March 2004, when the recently established UN Environment Programme published its first Global Environment Outlook Year Book (GEO Year Book 2003) it reported 146 dead zones in the world's oceans where marine life could not be supported due to depleted oxygen levels. Some of these were as small as a square kilometre (0.4 mi²), but the largest dead zone covered 70,000 square kilometres (27,000 mi²). A 2008 study counted 405 dead zones worldwide.
Aquatic and marine dead zones can be caused by an increase in chemical nutrients (particularly nitrogen and phosphorus) in the water, known as eutrophication. These chemicals are the fundamental building blocks of single-celled, plant-like organisms that live in the water column, and whose growth is limited in part by the availability of these materials. Eutrophication can lead to rapid increases in the density of certain types of these phytoplankton, a phenomenon known as an algal bloom. Although these algae produce oxygen in the daytime via photosynthesis, during the night hours they continue to undergo cellular respiration and can therefore deplete the water column of available oxygen. In addition, when algal blooms die off, oxygen is used up further during bacterial decomposition of the dead algal cells. Both of these processes can result in a significant depletion of dissolved oxygen in the water, creating hypoxic conditions. Dead zones can be caused by natural and by anthropogenic factors. Use of chemical fertilizers is considered the major human-related cause of dead zones around the world. Natural causes include coastal upwelling and changes in wind and water circulation patterns. Runoff from sewage, urban land use, and fertilizers can also contribute to eutrophication.
Notable dead zones in the United States include the northern Gulf of Mexico region, surrounding the outfall of the Mississippi River, and the coastal regions of the Pacific Northwest, and the Elizabeth River in Virginia Beach, all of which have been shown to be recurring events over the last several years.
Related Articles : Fish Kill and Algae Blooms
Sunday, January 23, 2011
A seamount is a mountain rising from the ocean seafloor that does not reach to the water's surface (sea level), and thus is not an island. These are typically formed from extinct volcanoes, that rise abruptly and are usually found rising from a seafloor of 1,000–4,000 metres (3,281–13,123 ft) depth. They are defined by oceanographers as independent features that rise to at least 1,000 metres (3,281 ft) above the seafloor. The peaks are often found hundreds to thousands of metres below the surface, and are therefore considered to be within the deep sea. There are an estimated 100,000 seamounts across the globe, with only a few having been studied. Seamounts come in all shapes and sizes, and follow a distinctive pattern of growth, activity, and death. In recent years, several active seamounts have been observed, for example Loihi in the Hawaiian Islands.
Because of their abundance, seamounts are one of the most common oceanic ecosystems in the world. Interactions between seamounts and underwater currents, as well as their elevated position in the water, attract plankton, corals, fish, and marine mammals alike. Their aggregational effect has been noted by the commercial fishing industry, and many seamounts support extensive fisheries. There are ongoing concerns on the negative impact of fishing on seamount ecosystems, and well-documented cases of stock decline, for example with the orange roughy (Hoplostethus atlanticus). 95% of ecological damage is done by bottom trawling, which literally scrapes whole ecosystems off seamounts.
Because of their large numbers, many seamounts remain to be properly studied, and even mapped. Bathymetry and satellite altimetry are two technologies working to close the gap. There have been instances where naval vessels have collided with uncharted seamounts; for example, Muirfield Seamount is named after the ship that struck it in 1973. However, the greatest danger from seamounts are flank collapses; as they get older, extrusions seeping in the seamounts put pressure on their sides, causing landslides that have the potential to generate massive tsunamis.
Saturday, January 22, 2011
The Nile perch (Lates niloticus) is a species of freshwater fish in family Latidae of order Perciformes. It is widespread throughout much of the Afrotropic ecozone, being native to the Congo, Nile, Senegal, Niger, and Lake Chad, Volta, Lake Turkana and other river basins. It also occurs in the brackish waters of Lake MaryutEgypt. Originally described as in Labrus niloticus, among the marine wrasses, the species has also been referred to as Centropomus niloticus. Common names include African snook, Capitaine, Victoria perch (a misleading trade name, as the species is not native to Lake Victoria), and a large number of local names in various African languages, such as the Luo name Mbuta.
Lates niloticus is silver in colour with a blue tinge. It has a distinctive dark black eye, with a bright yellow outer ring. One of the largest freshwater fish, it reaches a maximum length of nearly two metres (more than six feet), weighing up to 200 kg (440 lb). Mature fish average 121–137 cm (48–54 in), although many fish are caught before they can grow this large.
Adult Nile perch occupy all habitats of a lake with sufficient oxygen concentrations, while juveniles are restricted to shallow or nearshore environments. A fierce predator that dominates its surroundings, the Nile perch feeds on fish (including its own species), crustaceans, and insects; the juveniles also feed on zooplankton.
Nile perch have been introduced to many other lakes in Africa, including Lake Victoria (see below) and the artificial Lake Nasser. The IUCN's (World Conservation Union) Invasive Species Specialist Group considers Lates niloticus one of the world's 100 worst invasive species. The state of Queensland in Australia levies heavy fines on anyone found in possession of a living Nile perch, since it competes directly with the native Barramundi, which is similar but does not reach the same size as the Nile perch.
Friday, January 21, 2011
The leopard shark (Triakis semifasciata) is a species of houndshark, family Triakidae, found along the Pacific coast of North America from the U.S. state of Oregon to Mazatlán in Mexico. Typically measuring 1.2–1.5 m (3.9–4.9 ft) long, this slender-bodied shark is immediately identifiable by the striking pattern of black saddle-like markings and large spots over its back, from which it derives its common name. Large schools of leopard sharks are a common sight in bays and estuaries, swimming over sandy or muddy flats or rock-strewn areas near kelp beds and reefs. They are most common near the coast, in water less than 4 m (13 ft) deep.
Active-swimming predators, groups of leopard sharks often follow the tide onto intertidal mudflats to forage for food, mainly clams, spoon worms, crabs, shrimp, bony fish, and fish eggs. Most leopard sharks tend to remain within a particular area rather than undertaking long movements elsewhere, which has led to genetic divergence between populations of sharks living in different regions. This species is aplacental viviparous, meaning that the young hatch inside the uterus and are nourished by yolk. From March to June, the female gives birth to as many as 37 young after a gestation period of 10–12 months. It is relatively slow-growing and takes many years to mature.
Harmless to humans, the leopard shark is caught by commercial and recreational fisheries for food and the aquarium trade. This species is mostly fished in the waters off California where, after a period of population decline in the 1980s, new fishing regulations in the early 1990s reduced harvesting to sustainable levels. The International Union for Conservation of Nature has assessed this species as of Least Concern, while noting that local stocks may easily become overfished because of the shark's slow growth and limited migratory habits.
The leopard shark occurs in the cool to warm-temperate continental waters of the northeastern Pacific Ocean, from Coos Bay, Oregon to Mazatlán, Mexico, including the Gulf of California. It favors muddy or sandy flats within enclosed bays and estuaries, and may also be encountered near kelp beds and rocky reefs, or along the open coast. Numbers have been known to gather near discharges of warm effluent from power plants. Leopard sharks generally swim close to the bottom and are most abundant from the intertidal zone to a depth of 4 m (13 ft), though they may be found as deep as 91 m (299 ft). Many leopard sharks, particularly in the north, leave their coastal habitats in winter and return in early spring. A study in Tomales Bay in northern California determined that they depart when the water temperature drops below 10–12° C (50–54° F); one tagged shark was found to have swum some 140 km (87 mi) south.
Thursday, January 20, 2011
Manatees (family Trichechidae, genus Trichechus) are large, fully aquatic, mostly herbivorous marine mammals sometimes known as sea cows. There are three accepted living species of Trichechidae, representing three of the four living species in the order Sirenia: the Amazonian manatee (Trichechus inunguis), the West Indian manatee (Trichechus manatus), and the West African manatee (Trichechus senegalensis). They measure up to 3.6 metres (12 ft)), and have paddle-like flippers. The name manatí comes from the Taíno, a pre-Columbian people of the Caribbean, meaning "breast".
Half a manatee's day is spent sleeping in the water, surfacing for air regularly at intervals no greater than 20 minutes. Manatees spend most of the rest of the time grazing in shallow waters at depths of 1–2 metres (3.3–6.6 ft). The Florida subspecies (T. m. latirostris) has been known to live up to 60 years.
Manatees inhabit the shallow, marshy coastal areas and rivers of the Caribbean Sea and the Gulf of Mexico (T. manatus, West Indian Manatee), the Amazon Basin (T. inunguis, Amazonian Manatee), and West Africa (T. senegalensis, West African Manatee). A fourth species, the Dwarf Manatee (T. "pygmaeus"), was recently proposed for a population found in the Brazilian Amazon, although some believe it to be an immature Amazon Manatee.
They enjoy warmer waters and are known to congregate in shallow waters, and frequently migrate through brackish water estuaries to freshwater springs. Manatees cannot survive below 15°C (288 K; 60°F). Their natural source for warmth during winter is warm-spring fed rivers.
Wednesday, January 19, 2011
Triggerfishes are about 40 species of often brightly colored fishes of the family Balistidae. Often marked by lines and spots, they inhabit tropical and subtropical oceans throughout the world, with the greatest species richness in the Indo-Pacific. Most are found in relatively shallow, coastal habitats, especially at coral reefs, but a few, such as the aptly named oceanic triggerfish (Canthidermis maculata), are pelagic. While several species from this family are popular in the marine aquarium trade, they are often notoriously ill-tempered.
The largest member of the family, the stone triggerfish (Pseudobalistes naufragium) reaches 1 metre (3.3 ft), but most species have a maximum length between 20 and 50 centimetres (7.9 and 20 in).
The rather bizarre anatomy of the triggerfishes reflects their typical diet of slow-moving, bottom dwelling crustaceans, mollusks, sea urchins and other echinoderms, generally creatures with protective shells and spines. Many will also take small fishes and some, notably the members of the genus Melichthys, feed on algae. A few, for example the redtoothed triggerfish (Odonus niger), mainly feed on plankton. They are known to exhibit a level of intelligence that is unusual among fishes, and have the ability to learn from previous experiences.
Some triggerfish species can be quite aggressive when guarding their eggs. Both the picasso (Rhinecanthus aculeatus) and titan triggerfish (Balistoides viridescens) viciously defend their nests against intruders, including scuba divers and snorkelers. Their territory extends in a cone from the nest toward the surface, so swimming upwards can put a diver further into the fishes' territory; a horizontal swim away from the nest site is best when confronted by an angry triggerfish. Unlike the relatively small picasso triggerfish, the titan triggerfish poses a serious threat to inattentive divers due to its large size and powerful teeth.
Triggerfish are notorious bait stealers; rather than swallowing a bait whole, they nibble off small bites of it, making a small, stout hook essential to success in hooking them. Accordingly, the best baits are tough strips of fish skin, squid mantle etc.
Tuesday, January 18, 2011
Tetrodotoxin (also known as "tetrodox" and frequently abbreviated as TTX, sometimes colloquially referred to as "zombie powder" by those who practice Vodou or are of Haitian descent) is a potent neurotoxin with no known antidote. There have been successful tests of a possible antidote in mice, but further tests must be carried out to determine efficacy in humans. Tetrodotoxin blocks action potentials in nerves by binding to the voltage-gated, fast sodium channels in nerve cell membranes, essentially preventing any affected nerve cells from firing by blocking the channels used in the process. The binding site of this toxin is located at the pore opening of the voltage-gated Na+ channel. Its name derives from Tetraodontiformes, the name of the order that includes the pufferfish, porcupinefish, ocean sunfish or mola, and triggerfish, several species of which carry the toxin. Although tetrodotoxin was discovered in these fish and found in several other animals (e.g., blue-ringed octopus, rough-skinned newt, and Naticidae) it is actually produced by certain symbiotic bacteria, such as Pseudoalteromonas tetraodonis, certain species of Pseudomonas and Vibrio, as well as some others that reside within these animals.
Tetrodotoxin has been isolated from widely differing animal species, including western newts of the genus Taricha (where it was termed "tarichatoxin"), pufferfish, toads of the genus Atelopus, several species of blue-ringed octopodes of the genus Hapalochlaena (where it was called "maculotoxin"), several sea stars, certain angelfish, a polyclad flatworm, several species of Chaetognatha (arrow worms), several nemerteans (ribbonworms) and several species of xanthid crabs. The toxin is variously used as a defensive biotoxin to ward off predation, or as both a defensive and predatory venom (the octopodes, chaetognaths and ribbonworms). Tarichatoxin and maculotoxin were shown to be identical to tetrodotoxin in 1964 and 1978, respectively. Recent evidence has shown the toxin to be produced by bacteria within blue-ringed octopuses. The most common source of bacteria associated with TTX production is Vibrio bacteria, with Vibrio alginolyticus being the most common species. Pufferfish, chaetognaths, and nemerteans have been shown to contain Vibrio alginolyticus and TTX.
Tetrodotoxin is roughly 100 times more poisonous than potassium cyanide. Fish poisoning by consumption of members of the order Tetraodontiformes is extremely serious. The organs (e.g. liver) of the pufferfish can contain levels of tetrodotoxin sufficient to produce paralysis of the diaphragm and death due to respiratory failure. Toxicity varies between species and at different seasons and geographic localities, and the flesh of many pufferfish may not usually be dangerously toxic. It is not always entirely fatal; however, at near-lethal doses, it can leave a person in a state of near-death for several days, while the person continues to be conscious.
Monday, January 17, 2011
The Baychimo was a steel 1,322 ton cargo steamer built in 1914 in Sweden and owned by the Hudson's Bay Company, used to trade pelts for provisions in Inuit settlements along the Victoria Island coast of the Northwest Territories of Canada. It became a notable ghost ship along the Alaska coast.
On October 1, 1931, at the end of a trading run and loaded with a cargo of fur, Baychimo became trapped in pack ice. The crew briefly abandoned the ship, travelling over a half-mile of ice to the town of Barrow to take shelter for two days, but then the ship broke free of the ice and the crew returned. The ship became mired again on October 8, more thoroughly this time, and on October 15 the Hudson's Bay Company sent aircraft to retrieve 22 of the crew. 15 crew remained behind, intending to wait out the winter if necessary, and they constructed a wooden shelter some distance away. On November 24 a powerful blizzard struck, and after it abated there was no sign of the Baychimo; the skipper concluded that it must have broken up and sunk in the storm. A few days later, however, an Inuit seal hunter informed them that he had seen the Baychimo about 45 mi (72 km) away from their position. The 15 men proceeded to track the ship down and, deciding that the ship was unlikely to survive the winter, retrieved the most valuable furs from the hold to transport by air. The Baychimo was abandoned.
The Baychimo did not sink, however, and over the next several decades there were numerous sightings of the ship. People managed to board her several times, but each time they were either unequipped to salvage the ship or driven away again by bad weather. The last recorded sighting of the Baychimo was by a group of Inuit in 1969, 38 years after she was abandoned. She was stuck fast in the pack ice of the Beaufort Sea between Point Barrow and Icy Cape in the Chukchi Sea off the northwestern Alaskan coast.
Baychimo's ultimate fate is unknown and is presumed sunk.
Sunday, January 16, 2011
The wonderpus octopus (Wunderpus photogenicus) is a species of octopus in the monotypic genusWunderpus. It is found in shallow waters from Bali and Sulawesi north to the Philippines and east to Vanuatu. W. photogenicus is a long-armed species characterised by "small eyes on elongate stalks, a long, conical papilla over each eye and a dramatic and fixed colour pattern of white bars and spots over a brown-red background."
W. photogenicus is often confused with the similarly coloured Mimic Octopus, Thaumoctopus mimicus. Both T. mimicus and W. photogenicus can have variable activity patterns, however T. mimicus is most often diurnal, while Wunderpus tends to emerge very slowly from dens in the sand at dusk and dawn and is a crepuscular hunter.
Wunderpus photogenicus has well-defined white spots on the mantle, and bars on the arms. They lack a white border at the base of the suckers. These are some of the traits that distinguish it from T. mimicus, which has poorly-defined dark and white markings on the mantle, and a bright white line along the base of the suckers.
The white spots of Wunderpus are unique among individuals, allowing for the use of photo identification to monitor individuals in the wild.
Wunderpus hatchlings can be identified by their unique 'founder chromatophore' patterns.
Saturday, January 15, 2011
Pygmy Killer Whale
The pygmy killer whale (Feresa attenuata) is a small, rarely-seen cetacean of the oceanic dolphin family (Delphinidae). It derives its common name from sharing some physical characteristics with the orca ("killer whale".) It is the smallest species that has "whale" in its common name. In fact, "killer" may be more apt in the case of the pygmy killer whale than its larger cousin. When a number of Pygmy Killers were brought into captivity in Hawaii and South Africa they were extremely aggressive—even killing one another. A pod captured in Japan did not display such aggression.
The pygmy killer is an average-sized dolphin (a little larger and heavier than a grown man) and may easily be confused at sea with other species, in particular the melon-headed whale. The body is robust and dark-colored. The cape is particularly dark. The head is rounded without a beak. The sides are lighter and the belly is often white. Several individuals have been seen with a white lining around the mouth and chin. The dorsal fin is tall and slightly falcate.
The pygmy avoids human contact. Some spy-hopping, breaching and other active behavior has been recorded but it is not an acrobatic animal.
These dolphins always move in groups, usually of 10 to 30, but occasionally much larger.
Data from strandings, which seem to be common in the species, indicates a diet of cephalopods and small fish. They have been observed attacking, killing and eating other cetacean species such as the Common Dolphin.
Friday, January 14, 2011
Swimming Sea Cucumber
Sea cucumbers resemble large, leathery slugs that typically amble across the seabed. Unusually, Enypniastes has developed webbed swimming structures at the front and back of the body, and can swim long distances of up to 1,000m (3,280 ft) up into the water column.
They are brilliant red in colour, with a soft, delicate, transparent body, through which their intestine and other internal organs are visible.
Their mouths are surrounded by tentacles which are used to gather sediment from the sea floor.
Sea cucumbers are capable of swimming up from the bottom by undulating the cape-like structure around the top of the animal. They are graceful, slow swimmers.
When attacked by predators, they produce bioluminescence across their entire body surface, before shedding the sticky glowing skin as a distraction ploy.
Thursday, January 13, 2011
The green humphead parrotfish, Bolbometopon muricatum, is the largest species of parrotfish growing to lengths of 1.3 metres (4.3 ft) and weighing up to 46 kilograms (100 lb). It is found on reefs in the Indian and Pacific Oceans, from the Red Sea in the west to Samoa in the east, and from the Yaeyama Islands in the north to the Great Barrier Reef, Australia in the south.
Other common names include bumphead parrotfish, humphead parrotfish, double-headed parrotfish, buffalo parrotfish and giant parrotfish.
Unlike wrasses, it has a vertical head profile, and unlike other parrotfishes, it is uniformly covered with scales except for the leading edge of the head which is often light green to pink. Primary phase colouration is a dull gray with scattered white spots, gradually becoming uniformly dark green. This species does not display sex-associated patterns of color change. Adults develop a bulbous forehead and their teeth plates are exposed (only partly covered by lips). The species is slow growing and long-lived (up to 40 years), with delayed reproduction and low replenishment rates. This species is gregarious and usually occurs in small aggregations, but group size can be quite large (> 75) on seaward and clear outer lagoon reefs.
Wednesday, January 12, 2011
The ranchu is a hooded variety of fancy goldfish developed in Japan. It is referred to as the "king of goldfish" by the Japanese.
The modern-day ranchu is a Japanese development of the lionhead. They are the direct outcome of crossbreeding experiments of different Chinese lionhead specimens.
A ranchu has an egg-shaped body with a deep belly that is between 5/8 to 3/4 the length of the fish. This goldfish does not have a dorsal fin and breeding standards require that the back should not have any vestiges of the dorsal fin on it. The back should be rounded and not flat, as in the case of lionheads. The area of the caudal peduncle should curve sharply downwards to meet the tail. The caudal peduncle itself should be broad and neither lengthy or too short (a properly formed caudal peduncle avoids swimming motion impairments to this type of goldfish). The ranchu's tail meets the caudal peduncle at a forty-five degree angle, giving the fish a unique swimming motion. Furthermore, the tail lobes are rounded, and all other finnage are paired.
The most prominent feature of the ranchu is its head. There must be sufficient space between the eyes, and also from the eyes to the front of the head. The gill cover should figuratively extend quite far towards the tail. The headgrowth should seem to begin from the bottom of the gill cover and move upward. The headgrowths of young ranchu fry may take at least a year to develop. Young ranchus possessing broad foreheads and square noses generally produce better headgrowths. Mature ranchus can reach between 6 to 8 inches (15 to 20 centimeters) in length.
Tuesday, January 11, 2011
Great Blue Hole
The Great Blue Hole is a large underwater sinkhole off the coast of Belize. It lies near the center of Lighthouse Reef, a small atoll 70 kilometres (43 mi) from the mainland and Belize City. The hole is circular in shape, over 300 metres (984 ft) across and 124 metres (407 ft) deep. It was formed during several episodes of Quaternary glaciation when sea levels were much lower - the analysis of stalactites found in Great Blue Hole shows that formation has taken place 153,000; 66,000; 60,000; and 15,000 years ago. As the ocean began to rise again, the caves were flooded. The Great Blue Hole is a part of the larger Belize Barrier Reef Reserve System, a World Heritage Site of the United Nations Educational, Scientific and Cultural Organization (UNESCO).
This site was made famous by Jacques-Yves Cousteau, who declared it one of the top ten scuba diving sites in the world. In 1971, he brought his ship, the Calypso, to the hole to chart its depths. Investigations by this expedition confirmed the hole's origin as typical karst limestone formations, formed before rises in sea level in at least four stages, leaving ledges at depths of 21, 49 and 91 meters (69, 161 and 299 ft). Stalactites were retrieved from submerged caves, confirming their previous formation above sea level. Some of these stalactites were also off-vertical by 5° in a consistent orientation, thus indicating that there had also been some past geological shift and tilting of the underlying plateau, followed by a long period in the current plane.
Initial measured depth of Great Blue Hole was 125m which is the most often cited depth up to this day. An expedition by the Cambrian Foundation in 1997 measured the hole's depth as 124m at its deepest point. This difference in measurement can be explained by ongoing sedimentation or by imprecision in earlier measurements. The purpose of this expedition was the collection of core samples from the floor of the Blue Hole and documentation of the cave system. To accomplish these tasks, all of the divers had to be certified in cave diving and mixed gases.
Monday, January 10, 2011
Christmas Island Migration
At the beginning of the wet season (usually October / November), most adult red crabs suddenly begin a spectacular migration from the forest to the coast to breed. Breeding is usually synchronized island-wide. The rains provide moist overcast conditions for crabs to make their long and difficult journey to the sea.
During peak migration times, sections of roads where crabs cross in high numbers may be closed to vehicles for short periods of time. You can park your vehicle and carefully walk amongst the moving sea of crabs as they relentlessly make their way to and from the shore.
While the rains provide the moist preconditions for the march to begin, the timing of the migration breeding sequence is also linked to the phases of the moon. Eggs are released by the female red crabs into the sea precisely at the turn of the high tide during the last lunar quarter.
The sea level at the base of the cliffs and on the beaches, where the females release their eggs, at this time varies the least for a longer period, and it is therefore safer for the females approaching the water's edge to release their eggs. Sometimes there are earlier and later migrations of smaller numbers of crabs but all migrations retain this same lunar rhythm.
Related Articles : Christmas Island Red Crab
Sunday, January 9, 2011
Christmas Island Red Crab
The Christmas Island red crab, Gecarcoidea natalis, is a species of terrestrial crab endemic to Christmas Island in the Indian Ocean. Although restricted to a relatively small area, it is estimated that up to 120 million red crabs may live there, making it the most abundant of the 14 terrestrial crab species on Christmas Island. Christmas Island red crabs eat mostly fallen leaves and flowers, but will occasionally eat other animals, including other red crabs (see cannibalism) if the opportunity arises.
Christmas red crabs live in burrows for shelter from the sun. Since they breathe through gills, the possibility of drying out is dangerous. They are famous for their annual migration to the sea to lay their eggs in the ocean. During the migration, the crabs cover highways so densely that they are visible from the air. Volunteers shovel the crabs off the roads and, although no harm is intended, some of the countless millions inevitably get injured.
Early inhabitants of Christmas Island rarely mentioned these crabs. It is possible that their large population size was caused by the extinction of the endemic Maclear's Rat, Rattus macleari in 1903, which may have controlled the crab's population.
An exploding population of the yellow crazy ant, an invasive species accidentally introduced to Christmas Island and Australia from Africa, is believed to have killed 15–20 million red crabs in recent years.
Related Articles : Christmas Island Migration
Saturday, January 8, 2011
The Barramundi (Lates calcarifer), also known as Asian Seabass, is a species of catadromous fish in familyLatidae of order Perciformes. The native species is widely distributed in the Indo-West Pacific region from the Persian Gulf, through Southeast Asia to Papua New Guinea and Northern Australia. Known in Thai language as Pla Krapong (Thai: ปลากระพง), it is very popular in Thai cuisine. It is known as pandugappa in the Telugu language in India.
Barramundi is a loanword from an Australian Aboriginal language of the Rockhampton area in Queensland Originally, the name barramundi referred to saratoga and Gulf saratoga. meaning "large-scaled river fish". However, the name was appropriated for marketing reasons during the 1980s, a decision which has aided in raising the profile of this fish significantly.L. calcarifer is broadly referred to as Asian seabass by the international scientific community, but is also known as giant perch, giant seaperch, Australian seabass, and by a variety of names in other local languages, such as Ikan Siakap or Ikan Kakap Putih in Indonesian and also known as selunsung in local sabahan. 'Barra Mundi' when pronounced as two words, is clearly of Indian origin meaning 'big head'.
Friday, January 7, 2011
The bowhead whale (Balaena mysticetus) is a baleen whale of the right whale family Balaenidae in suborderMysticeti. A stocky dark-colored whale without a dorsal fin, it can grow to 20 meters (66 ft) in length. Estimated maximum weight of this thick-bodied species is 136 tonnes (134 LT; 150 ST), second only to the blue whale, although the bowhead's maximum length is less than several other whales. It lives entirely in fertile Arctic and sub-Arctic waters, unlike other whales that migrate to feed or reproduce. It is also known as Greenland right whale or Arctic whale. The bowhead is perhaps the longest-living mammal, and has the largest mouth of any animal.
The bowhead was an early whaling target. Its population was severely reduced before a 1966 moratorium. The population is estimated to be over 24,900 worldwide, down from an estimated 50,000 before whaling.
The bowhead whale has a robust, dark-colored body, no dorsal fin and a strongly bowed lower jaw and narrow upper jaw. Its baleen, the longest of any whale at 3 meters (10 ft), strains tiny prey from the water. The whale has a massive bony skull which it uses to break through the Arctic ice to breathe. Inuit hunters have reported them surfacing through 60 cm (24 in) of ice. The bowhead may reach up to 20 m (66 ft). The largest yet reported was 21.2 m (70 ft) m for an unweighed giant caught off Spitsbergen, Norway. Females are larger than males. Its blubber is the thickest of any animal, averaging 43–50 cm (17–20 in).
Thursday, January 6, 2011
The signal crayfish, Pacifastacus leniusculus, is a North American species of crayfish. It was introduced to Europe in the 1960s to supplement the Scandinavian Astacus astacus fisheries, which were being damaged by crayfish plague, but the imports turned out to be a carrier of that disease. The signal crayfish is now an invasive species, ousting native species across Europe and Japan.
From 1907, crayfish plague, an infectious disease caused by the water mould Aphanomyces astaci, damaged stocks of the native European crayfish Astacus astacus. Since the signal crayfish occupied a similar ecological niche in its native range, it was imported in the 1960s to Sweden and Finland to allow recreational and commercial crayfish capture. It was not realised at the time that the signal crayfish was a carrier of the crayfish plague. All American species carry the infection, but it is only lethal to individuals that are already stressed; to European species, the infection is rapidly fatal.
The signal crayfish is now the most widespread alien crayfish in Europe, occurring in 25 countries, from Finland to Great Britain and from Spain to Greece. It was first introduced to Great Britain in 1976, and is now widespread across the island as far north as the Moray Firth. It has also been observed on the Isle of Man, but has not yet been introduced to Ireland.
Wednesday, January 5, 2011
The velvet crab (alternatively velvet swimming crab or devil crab), Necora puber, is a species of crab. It is the largest swimming crab (family Portunidae) found in British coastal waters, with a carapace width of up to 100 millimetres (3.9 in), and the only species in the genus Necora. The body is coated with short hairs, giving the animal a velvety texture, hence the common name. It is one of the major crab species for United Kingdom fisheries.
The velvet crab lives from southern Norway to Western Sahara in the North Sea and north Atlantic as well as western parts of the Mediterranean Sea, on rocky bottoms from the shoreline to a depth of about 65 metres (213 ft). The last pair of pereiopods are flattened to facilitate swimming.
Tuesday, January 4, 2011
The Mary Celeste (often incorrectly referred to as Marie Celeste following an intervention by Conan Doyle - see below) was a brigantine merchant ship famous for having been discovered on 4 December 1872 in the Atlantic Ocean unmanned and apparently abandoned, despite the fact that the weather was fine and her crew had been experienced and able seamen. The Mary Celeste was in seaworthy condition and still under sail heading towards the Strait of Gibraltar. She had been at sea for a month and had over six months' worth of food and water on board. Her cargo was virtually untouched and the personal belongings of passengers and crew were still in place, including valuables. The crew was never seen or heard from again. Their disappearance is often cited as the greatest maritime mystery of all time.
The fate of her crew has been the subject of much speculation. Theories range from alcoholic fumes, to underwater earthquakes, to waterspouts, to paranormal explanations involving extraterrestrial life, unidentified flying objects (UFOs), sea monsters, and the phenomena of the Bermuda Triangle, although the Mary Celeste is not known to have sailed through the Bermuda Triangle area. The Mary Celeste is often described as the archetypal ghost ship, since she was discovered derelict without any apparent explanation, and her name has become a synonym for similar occurrences.
Oliver Deveau, chief mate of the Dei Gratia, boarded the Mary Celeste. He reported he did not find anyone on board, and said that "the whole ship was a thoroughly wet mess". There was only one operational pump, two apparently having been disassembled, with a lot of water between decks and three and a half feet (1.1 m) of water in the hold. However, the ship was not sinking and was still seaworthy.
All of the ship's papers were missing, except for the captain's logbook. The forehatch and the lazarette were both open, although the main hatch was sealed. The ship's clock was not functioning, and the compass was destroyed; the sextant and marine chronometer were missing. The only lifeboat on the Mary Celeste, a yawl located above the main hatch, was also missing. The peak halyard, used to hoist the main sail, had disappeared. A rope, perhaps the peak halyard, was found tied to the ship very strongly and the other end, very frayed, was trailing in the water behind the ship.
Popular stories of untouched breakfasts with still-warm cups of tea on the cabin table are untrue and most likely originated with fictionalized accounts of the incident, especially one by Sir Arthur Conan Doyle. At the inquiry, Oliver Deveau stated that he saw no preparations for eating and there was nothing to eat or drink in the cabin.
Deveau returned to his ship and reported to the captain. Two men, Charles Augustus Anderson and Charles Lund, then boarded the Mary Celeste.
The cargo of 1,701 barrels of alcohol Devreau reported was in good order. However, when it was eventually unloaded in Genoa, nine barrels were found to be empty.
A six-month supply of uncontaminated food and fresh water was still aboard, and the crew's personal possessions and artifacts were left untouched, making a piracy raid seem extremely unlikely. It appeared the vessel had been abandoned in a hurry. There was no sign of a struggle, or any sort of violence.
Monday, January 3, 2011
Upside-down catfish, Synodontis nigriventris, is a species of catfish. It is particularly noteworthy because of its habit of swimming upside down most of the time. Upside-down catfish originate from the Central Congo basin of Africa.
Upside-down catfish are small, reaching a maximum of 9.6 centimetres (4 in). Like other members of the mochikidae family, they have large eyes, a large dorsal fin and three pair of barbels. Upside-down catfish are adapted to spend most of their time upside-down. This is reflected in the fish's pigmentation—their bellies are darker than their backs, a form of countershading.
These fish are mostly nocturnal, and feed on insects, crustaceans, and plant matter. These fish lay eggs. The young fish do not swim upside-down until they are about two months old.
Sunday, January 2, 2011
The term fish kill is applied to a localized die-off of fish populations which may also be associated with more generalized mortality of aquatic life. It may result from a variety of causes, most frequently ecological hypoxia (oxygen depletion). The hypoxic event may be brought on by factors including high and temperatures, weather, drought, thermal pollution and algae blooms. Fish kills may also occur due to the presence of disease, agricultural sewage runoff, oil or chemical spill, hazardous waste spills, sea-quakes, inappropriate re-stocking of fish, underwater explosions, and other catastrophic events that upset a normally stable aquatic population.
Fish kills are often the first visible signs of ecological hypoxia and are usually investigated as a matter of urgency by environmental agencies to determine the cause of the hypoxic event and whether or not the cause was man made, due to pollution, or naturally occurring.
Related Articles : Dead Zones
Saturday, January 1, 2011
Tetraodontidae is a family of primarily marine and estuarine fish of the Tetraodontiformes order. The family includes many familiar species which are variously called pufferfish, balloonfish, blowfish, bubblefish, globefish, swellfish, toadfish, toadies, honey toads, and sea squab. They are morphologically similar to the closely related porcupinefish, which have large external spines (unlike the thinner, hidden spines of Tetraodontidae, which are only visible when the fish has puffed up). The scientific name refers to the four large teeth, fused into an upper and lower plate, which are used for crushing the shells of crustaceans and mollusks, their natural prey.
Puffer fish are generally believed to be the second–most poisonous vertebrate in the world, after the Golden Poison Frog. Certain internal organs, such as liver, and sometimes their skin are highly toxic to most animals when eaten, but nevertheless the meat of some species is considered a delicacy in Japan (as 河豚, pronounced as fugu), Korea (as bok), and China (as 河豚 he2 tun2) when prepared by chefs who know which part is safe to eat and in what quantity.
The tetraodontidae contains at least 121 species of puffers in 20 genera. They are most diverse in the tropics and relatively uncommon in the temperate zone and completely absent from cold waters. They are typically small to medium in size, although a few species can reach lengths of greater than 100 centimetres (39 in).
The puffer's unique and distinctive natural defenses help compensate for their slow locomotion. Puffers move by combining pectoral, dorsal, anal, and caudal fins. This makes them highly maneuverable but very slow, and therefore comparatively easy predation targets. Their tail fin is mainly used as a rudder, but it can be used for a sudden evasive burst of speed that shows none of the care and precision of their usual movements. The puffers excellent eyesight combined with this speed burst is the first and most important defense against predators. Their back up defense mechanism, used if they are successfully pursued, is to fill their extremely elastic stomachs with water (or air when outside the water) until they are much larger and almost spherical in shape. Even if they are not visible when the puffer is not inflated, all puffers have pointed spines, so a hungry predator may suddenly find itself facing an unpalatable pointy ball rather than a slow, tasty fish. Predators which don't heed this warning (or who are "lucky" enough to catch the puffer suddenly, before or during inflation) may die from choking, and predators that do manage to swallow the puffer may find their stomaches full of tetrodotoxin, making puffers an unpleasant, possibly lethal, choice of prey. This neurotoxin is found primarily in the ovaries and liver, although smaller amounts exist in the intestines and skin, as well as trace amounts in muscle. It does not always have a lethal effect on large predators, such as sharks, but it can kill humans.