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A Giant Isopod may be one of approximately nine species of large isopods (crustaceans related to the shrimp and crabs) in the genus Bathynomus. They are thought to be abundant in cold, deep waters of the Atlantic. Bathynomus giganteus, the species upon which the generitype is based, is the largest known isopod and is the one most often referred to by the common name "giant isopod".
French zoologist Alphonse Milne-Edwards was the first to describe the genus in 1879 after fishing a juvenile male B. giganteus from the Gulf of Mexico; this was an exciting discovery for both scientists and the public, as at the time the idea of a lifeless or "azoic" deep ocean had only recently been refuted by the work of Sir Charles Wyville Thomson and others. Females were not recovered until 1891.
Giant isopods are of little interest to most commercial fisheries owing to the typical paucity of catches and because ensnared isopods are usually scavenged beyond marketability before they are recovered. However, in Northern Taiwan and other areas, they are not uncommon at seaside restaurants, served boiled and bisected with a clean lateral slice. The white meat, similar to crab or lobster in texture, is then easily removed.
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The Basking Shark, Cetorhinus maximus, is the second largest living shark, after the whale shark. It is a cosmopolitan species — it is found in all the world's temperate oceans. It is a slow moving and generally harmless filter feeder.
Like other large sharks, basking sharks could some day be at risk of extinction due to a combination of low resilience and overfishing if good conservation practices are not followed.
This shark is called the basking shark because it is most often observed when feeding at the surface and appears to be basking. It is the only member of the family Cetorhinidae. It was first described and named Cetorhinus maximus by Gunnerus in 1765 from a specimen found in Norway. The genus name Cetorhinus comes from the Greek, ketos which means marine monster or whale and rhinos meaning nose, the species name maximus is from Latin and means "greatest". It was later described as Squalus isodus by Macri in 1819, Squalus elephas by Lesueur in 1822, Squalus rashleighanus by Couch in 1838, Squalus cetaceus by Gronow in 1854, Cetorhinus blainvillei by Capello in 1869, Selachus pennantii by Cornish in 1885, Cetorhinus maximus infanuncula by Deinse & Adriani 1953, and finally as Cetorhinus maximus normani by Siccardi 1961.
The basking shark is a coastal-pelagic shark found worldwide in boreal to warm-temperate waters around the continental shelves. It has traditionally been observed in waters between 8 and 14° C (46 and 57° F) but recently they have been confirmed to cross the equator. It is often seen close to land and will enter enclosed bays. The shark will follow concentrations of plankton in the water column and is therefore often visible on the surface. They are a highly migratory species leading to seasonal appearances in certain areas of the range.The basking shark is found from the surface down to at least 910 metres (3,000 ft).
The basking shark is one of the largest known sharks, second only to the whale shark. The largest specimen accurately measured was trapped in a herring net in the Bay of Fundy, Canada in 1851.
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The few specimens caught in the Americas with baited traps are sometimes seen in public aquaria.
Maturing to a length between 19 and 37 centimetres (7.5 and 15 in), and maximally reaching a weight of approximately 1.7 kilograms (3.7 lb) in B. giganteus, giant isopods are a good example of deep-sea gigantism (cf. giant squid); most other isopods range in size from 1 to 5 centimetres (0.39 to 2.0 in). Their morphology is nonetheless familiar to most people as giant isopods closely resemble their terrestrial cousin, the woodlouse: their bodies are dorso-ventrally compressed, protected by a rigid, calcareous exoskeleton composed of imbricate segments. The first of these segments is fused to the head; the most posterior segments are often fused as well, forming a "caudal shield" over the shortened abdomen (pleon) . The large eyes are compound with nearly 4,000 facets, sessile and spaced far apart on the head . There are two pairs of antennae.
The uniramous thoracic legs or pereiopods are arranged in seven pairs, the first of which are modified into maxillipeds to manipulate and bring food to the four sets of jaws. The abdomen has five segments called pleonites each with a pair of biramous pleopods; these are modified into natatory legs and rami, flat respiratory structures acting as gills. The isopods are a pale lilac in colour.Giant isopods are important scavengers in the deep-sea benthic environment; they are found from the gloomy sublittoral zone at a depth of 170 metres (560 ft) to the pitch darkness of the bathypelagic zone at 2,140 metres (7,000 ft), where pressures are high and temperatures are very low – down to about 4 °C (39 °F). Over 80 percent are found at a depth between 365 and 730 metres (1,200 and 2,400 ft). They are thought to prefer a muddy or clay substrate and lead solitary lives.
Although generalist scavengers, these isopods are mostly carnivorous and feed on dead whales, fish, and squid; they may also be active predators of slow-moving prey such as sea cucumbers, sponges, radiolarians, nematodes, and other zoobenthos, and perhaps even live fish. They are known to attack trawl catches. As food is scarce in the deep ocean biome, giant isopods must make do with what fortune brings; they are adapted to long periods of famine and have been known to survive over eight weeks without food in the aquariums of irresponsible owners. When a significant source of food is encountered, giant isopods gorge themselves to the point of compromising their locomotive ability. One study examining the contents of 1651 giganteus' guts found that fish were most common there, followed by cephalopods and decapods, particularly carideans and galatheids.[citation needed]
In 1990, the Scavengers of East Australian Seas expedition (SEAS) started to document the scavenging crustaceans along the east coast of Australia by setting traps. The deeper the water, the fewer number of species they found and the larger the species tended to be. The giant isopods found in very deep waters off Australia were compared to those found off Mexico and India. From the fossil record it is known that Bathynomus existed more than 160 million years ago, before the break-up of the supercontinent Pangaea, so it did not evolve independently in all three locations, but since then it would be expected that Bathynomus would show divergent evolution in the various locations. However, the SEAS study found that the giant isopods in all three locations were almost identical. Andrew Parker in his book In the Blink of an Eye (from where this description of the SEAS expedition is taken) links this lack of evolution to the extremely low light levels of their habitat.
Study of the seasonal abundance of B. giganteus juveniles and adults suggests a peak in reproductive capacity in the spring and winter months. This is apparently due to a shortage of food during the summer. Mature females develop a brood pouch or marsupium when sexually active, the pouch being formed by overlapping oostegites or brood plates grown from the medial border of the pereopods. The fertilized eggs — thought to be the largest of all marine invertebrates — are retained safely within the marsupium for an unknown period. A brooding female is at risk of losing her eggs if she overindulges in food to the point of bloating.
The young isopods emerge from the marsupium as miniatures of the adults, known as mancae. This is not a larval stage: the mancae are fully developed, lacking only the last pair of pereopods.
Source : Wikipedia
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Its total length was 12.27 metres (40.3 ft), and it weighed an estimated 19 tons. There are reports from Norway of three basking sharks over 12 m (the largest being 13.7 m), but those are considered dubious since few if any sharks anywhere near such size have been caught in the area since. Normally the basking shark reaches a length of between 6 metres (20 ft) and a little over 8 metres (26 ft). Some specimens surpass 9 or even 10 metres (33 ft), but after years of hard fishing, specimens of this size have become exceedingly rare.
These sharks possess the typical lamniform body plan and have been mistaken for great white sharks. The two species can be easily distinguished, however, by the basking shark's cavernous jaw (up to 1 m in width, held wide open whilst feeding), longer and more obvious gill slits (which nearly encircle the head and are accompanied by well-developed gill rakers), smaller eyes, and smaller average girth. Great white sharks possess large, dagger-like teeth, whilst those of the basking shark are much smaller (5–6 mm) and hooked; only the first 3 or 4 rows of the upper jaw and 6 or 7 rows of the lower jaw are functional. There are also several behavioural differences between the two (see Behaviour).
Other distinctive characteristics of the basking shark include a strongly keeled caudal peduncle, highly textured skin covered in placoid scales and a layer of mucus, a pointed snout (which is distinctly hooked in younger specimens), and a lunate caudal fin. In large individuals the dorsal fin may flop over when above the surface. Colouration is highly variable (and likely dependent on observation conditions and the condition of the animal itself): commonly, the colouring is dark brown to black or blue dorsally fading to a dull white ventrally. The sharks are often noticeably scarred, possibly through encounters with lampreys or cookiecutter sharks. The basking shark's liver, which may account for 25% of its body weight, runs the entire length of the abdominal cavity and is thought to play a role in buoyancy regulation and long-term energy storage.
In females, only the right ovary appears to be functional: if so, this is a unique characteristic among sharks.
The basking shark is an extremely passive filter feeder, filtering zooplankton, small fish and invertebrates from up to 2,000 tons of water per hour. Unlike the megamouth shark and whale shark, the basking shark does not appear to actively seek its quarry, but it does possess large olfactory bulbs that may guide it in the right direction. Unlike the other large filter feeders, it relies only on the water that is pushed through the gills by swimming; the megamouth shark and whale shark can suck or pump water through their gills.
Studies in 2003 have disproved the idea that basking sharks hibernate and have shown that they are active throughout the year.In winter, basking sharks move to deeper water (depths of up to 900 m) feeding on deep water plankton. Satellite tagging confirmed that basking sharks move thousands of kilometres during the winter months locating plankton blooms. It was also found that basking sharks shed and renew their gillrakers in an ongoing process, rather than over one short period.
A study published in 2009, in which 25 basking sharks were tagged off the coast of Cape Cod, Massachusetts, indicated that at least some individuals in the North Atlantic migrate south in the winter. Remaining at depths between 200 metres (660 ft) and 1,000 metres (3,300 ft) for many weeks, the tagged sharks traveled as far south as Brazil, crossing the equator. One individual spent a month in the waters near the mouth of the Amazon River. It is unknown why the sharks undertake this journey. The lead author of the study, Gregory Skomal of the Massachusetts Division of Marine Fisheries, suspects it may be related to the shark's reproduction. It was also found that basking sharks shed and renew their gill rakers in an ongoing process, rather than over one short period.
They feed at or close to the surface with their mouths wide open and gill rakers erect. They are slow-moving sharks (feeding at about 2 knots) and do not attempt to evade approaching boats (unlike great white sharks). They are harmless to humans if left alone and will not be attracted to chum.
Basking sharks are social animals and form schools segregated by sex, usually in small numbers (3 or 4) but reportedly up to 100 individuals.Their social behaviour is thought to follow visual cues, as although the basking shark's eyes are small, they are fully developed and have been known to visually inspect boats, possibly mistaking them for conspecifics. Females are thought to seek out shallow water to give birth.
These sharks have few predators, but orcas and tiger sharks are known to feed on them, and the aforementioned lampreys are often seen attached to them, although it is unlikely that they are able to cut through the shark's thick skin.
Even though the basking shark is large and slow it can breach and has been reported jumping fully out of the water. This behaviour could be an attempt to dislodge parasites or commensals.
Basking sharks are ovoviviparous: the developing embryos first rely on a yolk sac, and as there is no placental connection, they later feed on unfertilized ova produced by the mother (a behaviour known as oophagy). Gestation is thought to span over a year (but perhaps 2 or 3 years), with a small though unknown number of young born fully developed at 1.5–2 m (5–6.5 ft). Only one pregnant female is known to have been caught; she was carrying 6 unborn young. Mating is thought to occur in early summer and birthing in late summer, following the female's movement into shallow coastal waters.
The onset of maturity in basking sharks is not known but is thought to be between the age of 6 and 13 and at a length of between 4.6 and 6 m. Breeding frequency is also unknown, but is thought to be 2 to 4 years.
The seemingly useless teeth of basking sharks may play a role before birth since the basking shark seems to feed on unfertilized eggs in utero.
Historically, the basking shark has been a staple of fisheries because of its slow swimming speed, unaggressive nature and previously abundant numbers. Commercially it was put to many uses: the flesh for food and fishmeal, the hide for leather, and its large liver (which has a high squalene content) for oil. It is currently fished mainly for its fins (for shark fin soup). Parts (such as cartilage) are also used in traditional Chinese medicine and as an aphrodisiac in Japan, further adding to demand.
As a result of rapidly declining numbers, the basking shark has been protected and trade in its products restricted in many countries. It is fully protected in the UK, Malta, Florida and US Gulf and Atlantic waters. Targeted fishing for basking sharks is illegal in New Zealand. Once considered a nuisance along the Canadian Pacific coast, basking sharks were the target of a government eradication program there from 1945 to 1970. As of 2008[update], efforts are underway to determine if any sharks still live in the area and monitor their potential recovery.
It is tolerant of boats and divers approaching it and may even circle divers, making it an important draw for dive tourism in areas where it is common.
Source : Wikipedia
Paddlefish (family Polyodontidae) are primitive Chondrostean ray-finned fishes. The paddlefish can be distinguished by its large mouth and its elongated snout called a rostrum (bill). These spatula-like snouts comprise half the length of their entire body. There are only two extant species of these fish: the Chinese and the American paddlefish. The American species is Missouri's State Aquatic Animal.
These fish are not closely related to sharks, but they do have some body parts that resemble those of sharks such as their skeletons, primarily composed of cartilage, and deeply forked heterocercal tail fins.
In some areas, paddlefish are referred to as "Spoonbill", "Spoonies" or "Spoonbill Catfish". Paddlefish are also extremely oily. Mounted specimens occasionally leak an oily substance.
The American paddlefish, Polyodon spathula, also called the Mississippi paddlefish or spoonbill, lives in slow-flowing waters of the Mississippi River drainage system. It appears to have been extirpated from Lake Erie and its tributaries. They are closely related to the sturgeons. This large Chondrostian freshwater fish may grow to 220 cm (7 feet) and weigh up to 100 kg (220 pounds). The paddlefish takes its common and scientific names from its distinctive snout, which is greatly elongated and flattened into a paddle shape. The American paddlefish is believed to use sensitive electroreceptors on its paddle to detect prey, as well as to navigate while migrating to spawning sites. The paddlefish feeds primarily on zooplankton but also feeds on crustaceans and bivalves.
Early investigators once thought that paddlefishes used their snouts to dig vegetation from the bottom of lakes and rivers. In fact, they feed by filtering out zooplankton from the water, using filaments on their gill arches called "gill rakers".
The rostrum contains receptors in its rostrum that can detect weak electrical fields, suggesting that they use their rostrum as an antenna to detect zooplankton.
Even though the rostrum seems to help the fish feed, it has been observed that fish with severely damaged or missing rostrums are able to feed and are just as healthy as other fish with them intact.
The rostrum also helps the fish to feed by acting as a stabilizer. As the fish moves through the water with its mouth open, the rostrum creates lift, much like a wing of an airplane. This helps the fish by keeping its head in a steady position and helps it keep from diving to the bottom.
Paddlefish lay their eggs in midstream over bare rocks or gravel. The eggs are adhesive, and stick to the rocky substrate. After hatching, the young are swept downstream and grow to adulthood in deep freshwater pools.
Once common throughout the Midwest, overfishing and habitat changes have caused major population declines; both the meat and roe of the paddlefish are desirable as food. Dams and other barriers can prevent the fish from recolonizing places where they once occurred and can deny them access to important critical habitats such as spawning areas. Until about 1900, the paddlefish was also found in the Lake Erie and in river systems tributary thereto in the US and Canada. Invasive species such as zebra mussels have reduced the number of zooplankton in the Great Lakes to such low levels that any hypothetical reintroduction program would seem likely to fail. Recently, paddlefish were spotted in the Danube river. It has not been determined whether these fished escaped from Romanian or Bulgarian fish farms during the 2006 European floods, or whether they were let into the Danube earlier and matured in the river.
The American paddlefish remains a popular sport fish in those parts of its range where populations are sufficient to allow harvesting. Since they are filter-feeders, paddlefish will not accept bait or lures and must be caught by snagging. Several states, including Missouri, have enacted stocking programs for these fish in reservoirs where the resident populations were low or nonexistent, or in areas where historical populations are no longer naturally sustainable. Paddle fish are killed for their eggs which are used as caviar.
Polyodon spathula is one of two living species of Paddlefish.
During the last century, paddlefish and sturgeon have stimulated the world stock trades with their eggs (roe), called caviar. Paddlefish and sturgeon are two of the most important fish for freshwater caviar. Paddlefish take many years before they are able to spawn. A female may take 9 to 10 years, when they are about 42 inches long, and males 7 years old and 40 inches long are able to spawn. When able to spawn, the female releases adhesive eggs randomly over the water bottom and abandons them. They are capable of producing over one-half million eggs a year, but they may not spawn every year.
Due to the value of their eggs, paddlefish are a constant target for poachers, and they are subsequently a protected resource over a large part of their range. Additionally, in many of the 22 states that paddlefish reside, habitat destruction is causing their numbers to decrease more rapidly. Paddlefish need free flowing rivers that have shallow pools with sandy, rocky bottoms. These types of areas are perfect for their spawning. Water must also be at the right temperature for the fish to be capable of spawning. Since today's rivers are constantly being modified by the construction of dams, dredging, and excessive water removal for farming purposes, these types of areas are hard for the paddlefish to locate.
In some areas, free flowing lakes with reservoirs are able to provide paddlefish with the right breeding habitat. One such area is the Missouri River-Lake Sakakawea system in North Dakota. This area is capable of producing good paddlefish numbers because it is a free flowing system with many good areas for paddlefish to spawn. Fishing for paddlefish in violation of local fishing regulations in some states is a felony.
Source : Wikipedia
Hagfish are marine craniates of the class Myxini, also known as Hyperotreti. Myxini is the only class in the clade Craniata that does not also belong to the subphylum Vertebrata. That is, they are the only animals which have a skull but not a vertebral column.
Despite their name, there is some debate about whether they are strictly fish (as there is for lampreys), since they belong to a much more primitive lineage than any other group that is placed in the category of fish (Chondrichthyes and Osteichthyes). Their unusual feeding habits and slime-producing capabilities have led members of the scientific and popular media to dub the hagfish as the most "disgusting" of all sea creatures. Although hagfish are sometimes called "slime eels," they are not eels at all.
Hagfish average about half a meter (18 in) long; The largest known species is Eptatretus goliath with a specimen recorded at 127 cm, while Myxine kuoi and Myxine pequenoi seem to reach no more than 18 cm.
Hagfish have elongated, eel-like bodies, they have 4 hearts and two brains, and paddle-like tails. They have cartilaginous skulls and tooth-like structures composed of keratin.
Colours depend on the species, ranging from pink to blue-grey, and black or white spots may be present. Eyes are simple eyespots, not compound eyes that can resolve images. Hagfish have no true fins and have six or eight barbels around the mouth and a single nostril. Instead of vertically articulating jaws like Gnathostomata (vertebrates with jaws), they have a pair of horizontally moving structures with tooth-like projections for pulling off food.
The circulatory systems of the hagfish have both closed and open blood vessels, with a heart system that is more primitive than that of vertebrates, bearing some resemblance to that of some worms. This system is comprised of a "brachial heart", which functions as the main pump, and three types of accessory hearts: the four hearts which carry blood from intestines to liver, the "cardinal" heart(s) which move blood from the head to the body, and the "caudal" heart(s) which pump blood from the trunk and kidneys to the body. None of these hearts are innervated, so their function is probably modulated, if at all, by hormones.
Hagfish are long and vermiform, and can exude copious quantities of a slime or mucus (from which the typical species Myxine glutinosa was named) of unusual composition. When captured and held e.g. by the tail, they secrete the microfibrous slime, which expands into a gelatinous and sticky goo when combined with water; if they remain captured, they can tie themselves in an overhand knot which works its way from the head to the tail of the animal, scraping off the slime as it goes and freeing them from their captor, as well as the slime. It has been conjectured that this singular behavior assists them in extricating themselves from the jaws of predatory fish or from the interior of their own "prey", and that the "sliming" might act as a distraction to predators.
Recently, though, it has been reported that the slime entrains water in its microfilaments, creating a slow-to-dissipate viscoelastic substance, rather than a simple gel, and it has been proposed that the primary protective effect of the slime is related to impairment of the function of a predator fish's gills. Reportedly, most of the known predators of hagfish are birds or mammals, which could lend weight to the "gill-clogging hypothesis" as a highly successful evolutionary strategy tuned specifically to predatory fish.
Free-swimming hagfish also "slime" when agitated and will later clear the mucus off by way of the same traveling-knot behavior.The reported gill-clogging effect suggests that the traveling-knot behavior is useful or even necessary to restore the hagfish's own gill function after "sliming".
An adult hagfish can secrete enough slime to turn a 20 litre bucket of water into slime in a matter of minutes.
Research is ongoing regarding the properties and possible applications of the components of hagfish slime filament protein.
In December 2003, an article was published by the University of Queensland claiming the hagfish's eye, which lacks both lens and extrinsic musculature, as being significant to the evolution of more complex eyes. Hagfish eyespots when present can detect light, but as far as is known none can resolve detailed images. In Myxine and Neomyxine, the eyes are partly covered by the trunk musculature.
Very little is known about hagfish reproduction. In some species, sex ratio has been reported to be as high as 100:1 in favor of females. Some hagfish species are thought to be hermaphroditic, with both ovaries and testes, but with female gonads which remain non-functional until the individual has reached a particular age, or possibly until it encounters particular environmental stresses. These two factors in combination suggest that the survival rate of hagfish is quite high.
Depending on species, females lay from one or two, to 20 to 30 tough, yolky eggs. These tend to aggregate due to having Velcro-like tufts at either end. Hagfish are sometimes seen curled around small clutches of eggs. It is not certain if this constitutes actual brooding behavior.
Hagfish do not have a larval stage, in contrast to lampreys, which have a long larval phase.
While polychaete marine worms on or near the sea floor are a major source of nutrition, hagfish can feed upon and often even enter and eviscerate the bodies of dead and dying/injured sea creatures much larger than them.
Like leeches, they have a sluggish metabolism and can survive months between feedings. But their feeding behavior appears, by contrast, quite vigorous.
In captivity, hagfish are observed to use the overhand-knot behavior "in reverse" (tail-to-head) to assist them in gaining mechanical advantage to pull out hunks of flesh from carrion fish or cetaceans, eventually making an opening to permit entry to the interior of the body cavity of larger carcasses. It is to be expected that a healthy larger sea creature would be able to outfight or outswim this sort of assault.
However, this energetic opportunism on the part of the hagfish can be a great nuisance to fishermen, as they can devour or spoil entire deep-drag netted catches before they can be pulled to the surface. Since hagfish are typically found in large clusters on and near the bottom, a single trawler's catch could contain several dozens or even hundreds of hagfish as bycatch, and all the other struggling, captive sealife makes easy prey for them.
The digestive tract of the hagfish is unique among the vertebrates because the food in the gut is enclosed in a permeable membrane, analogous to the peritrophic matrix of insects.
Source : Wikipedia
The Short-beaked Echidna (Tachyglossus aculeatus), also known as the Spiny Anteater because of its diet of ants and termites, is one of four living species of echidna and the only member of the genus Tachyglossus. The Short-beaked Echidna is covered in fur and spines and has a distinctive snout and a specialized tongue, which it uses to catch its prey at a great speed. Like the other extant monotremes, the Short-beaked Echidna lays eggs; the monotremes are the only group of mammals to do so.
The species is found throughout Australia, where it is the most widespread native mammal, and in coastal and highland regions of southwestern New Guinea, where it is known as the Mungwe in the Daribi and Chimbu languages. It is not threatened with extinction, but human activities, such as hunting, habitat destruction, and the introduction of foreign predatory species and parasites, have reduced the distribution of the Short-beaked Echidna in Australia.
The Short-beaked Echidna was first described by George Shaw in 1792. He named the species Myrmecophaga aculeata, thinking it might be related to the South American anteater. Since Shaw first described the species, its name has undergone four revisions: from M. aculeata to Ornithorhynchus hystrix, Echidna hystrix, Echidna aculeata and, finally, Tachyglossus aculeatus. The name Tachyglossus means "quick tongue", in reference to the speed with which the Echidna uses its tongue to catch ants and termites, and aculeatus means "spiny" or "equipped with spines".
The Short-beaked Echidna is the only member of its genus, sharing the family Tachyglossidae with the extant species of the genus Zaglossus that occurs in New Guinea.
Zaglossus species, which includes the Western Long-beaked, Sir David's Long-beaked and Eastern Long-beaked Echidna, are all significantly larger than T. aculeatus, and their diet consists mostly of worms and grubs rather than ants and termites. Species of the Tachyglossidae are egg-laying mammals; together with the related family Ornithorhynchidae, they are the only extant monotremes in the world.
Short-beaked Echidnas are typically 30 to 45 centimetres (12-18 in) in length, have a 75-millimetre (3 in) snout, and weigh between two and five kilograms (4.5-11 lb). However, the Tasmanian subspecies, T. a. setosus, is larger than its Australian mainland counterparts. Because the neck is not externally visible, the head and body appear to merge together. The earholes are on either side of the head, with no external pinnae. The eyes are small and at the base of the wedge-shaped snout. The nostrils and the mouth are at the distal end of the snout; the mouth of the Short-beaked Echidna cannot open wider than 5 mm.[8] The body of the Short-beaked Echidna is, with the exception of the underside, face and legs, covered with cream-coloured spines. The spines, which may be up to 50 mm (2 in) long, are modified hairs, mostly made of keratin. Insulation is provided by fur between the spines, which ranges in colour from honey to a dark reddish-brown and even black; the underside and short tail are also covered in fur. Colouration of the fur and spines varies with geographic location. The Echidna's fur may be infested with what is said to be the world's largest flea, Bradiopsylla echidnae, which is about 4 mm long.
The limbs of the Short-beaked Echidna are adapted for rapid digging, their limbs are short and have strong claws. The claws on the hind feet are elongated and curve backwards to enable cleaning and grooming between the spines. Like the Platypus it has a low body temperature — between 30 and 32 °C, but unlike the Platypus, which shows no evidence of torpor or hibernation, the body temperature of the echidna may fall as low as 5 °C.The Echidna does not pant or sweat and normally seeks shelter in hot conditions. In autumn and winter the Echidna shows periods of torpor or deep hibernation. Because of the low body temperature of the Short-beaked Echidna, it becomes sluggish in very hot and very cold weather. Like all monotremes, it has one orifice for the passage of faeces, urine and reproductive products, which is known as the cloaca. The male has internal testes, no external scrotum and a highly unusual penis with four knobs on the tip. The gestating female develops a pouch on its underside, where it raises its young.
The musculature of the Short-beaked Echidna has a number of unusual aspects. The panniculus carnosus is an enormous muscle that is just beneath the skin and covers the entire body. By contraction of various parts of the panniculus carnosus, the Short-beaked Echidna can change shape—the most characteristic shape change is achieved by rolling itself into a ball when threatened, protecting its belly and presenting a defensive array of sharp spines. It has one of the shortest spinal cords of any mammal, extending only as far as the thorax.
The musculature of the face, jaw and tongue is specialised to allow the Echidna to feed. The tongue of the Short-beaked Echidna is the animal's sole means of catching prey, and can protrude up to 180 mm (8 in) outside the snout. The tongue is sticky because of the presence of glycoprotein-rich mucous, which both lubricates movement in and out of the snout and helps to catch ants and termites, which adhere to it. Protrusion of the tongue is achieved by contracting the circular muscles that change the shape of the tongue and force it forward, and contraction of two genioglossal muscles attached to the caudal end of the tongue and to the mandible. The protruded tongue is stiffened by the rapid flow of blood, allowing it to penetrate wood and soil. Retraction requires the contraction of two internal longitudinal muscles, known as the sternoglossi. When the tongue is retracted, the prey is caught on backward-facing keratinous "teeth", located along the roof of the buccal cavity, allowing the animal both to capture and grind food.The tongue moves with great speed, and has been measured to move in and out of the snout 100 times a minute.
Numerous physiological adaptations aid the lifestyle of the Short-beaked Echidna. Because the animal burrows, it can tolerate very high levels of carbon dioxide in inspired air, and will voluntarily remain in situations where carbon dioxide concentrations are high. Its ear is sensitive to low-frequency sound, which may be ideal for detecting sounds emitted by termites and ants underground. The leathery snout is covered in mechano- and thermoreceptors, which provide information about the surrounding environment. The Short-beaked Echidna has a well-developed olfactory system, which may be used to detect mates and prey. It has a highly sensitive optic nerve, and has been shown to have visual discrimination and spatial memory comparable to those of a rat. The brain and central nervous system of the Short-beaked Echidna have been extensively studied for evolutionary comparison with placental mammals. The Short-beaked Echidna has the largest prefrontal cortex with respect to body size of any mammal, it shows rapid eye movement during sleep, and its brain has been shown to contain a claustrum that is similar to placental mammals, linking this structure to their common ancestor.
The solitary Short-beaked Echidna looks for a mate between May and September; the precise timing of the mating season varies with geographic location. Both males and females give off a strong odour during the mating season. During courtship — observed for the first time in 1989 — males locate and pursue females. Trains of up to ten males may follow a single female in a courtship ritual that may last for up to four weeks; the duration of the courtship period varies with location. In cooler parts of their range, such as Tasmania, females may mate within a few hours of arousal from hibernation.
Before mating, the male smells the female, paying particular attention to the cloaca. The male is often observed to roll the female onto her side and then assumes a similar position so that the two animals are abdomen to abdomen. Each side of the bilaterally symmetrical, rosettelike 4 headed penis (similar to reptiles) is used alternately, with the other half being shut down between ejaculations. Sperm bundles of ~100 each, appears to confer increased sperm motility, which may provide the potential for sperm competition between males. Each mating results in the production of a single egg, and females are known to mate only once during the breeding season; each mating is successful.
Fertilisation occurs in the oviduct. Gestation takes between 21 and 28 days, during which time the female constructs a nursery burrow. Following the gestation period, a single rubbery-skinned egg between 13 and 17 millimetres in diameter is laid directly into a small, backward-facing pouch that has developed on her abdomen. Ten days after it is laid, the egg hatches within the pouch. The embryo develops an "egg tooth" during incubation, which it uses to tear open the egg; the tooth disappears soon after hatching.
Hatchlings are about 1.5 cm long and weigh between 0.3 and 0.4 grams. After hatching, young Echidnas are known as puggles. Hatchlings attach themselves to their mothers' milk areolae, a specialised patch on the skin that secretes milk (monotremes lack nipples). The way in which puggles imbibe the milk is not yet known, but they have been observed ingesting large amounts during each feeding period, since mothers may leave them unattended in the burrow for between five and ten days. The principal components of the milk are fucosyllactose and saialyllactose; it is high in iron content, giving it a pink colour. Juveniles are eventually ejected from the pouch at around two to three months of age, because of the continuing growth in the length of their spines. Suckling gradually decreases until juveniles are weaned at about six months of age. The duration of lactation is about 200 days, and the young leave the burrow between 180 and 240 days.
The age of sexual maturity is uncertain, but may be four to five years. A twelve-year field study, published in 2003, found that the Short-beaked Echidna reached sexual maturity between five and 12 years of age, and that the frequency of reproduction varies from once every two years to once every six years.The Short-beaked Echidna can live as long as 45 years in the wild.
Similar to its fellow monotreme the Platypus, the Short-beaked Echidna has an unusual system of sex chromosomes, resulting in males having one fewer chromosomes than females. Male individuals appear to be XYXYXYXYX, with the final X unpaired, while females are XXXXXXXXXX. Weak identity between chromosomes results in meiotic pairing that yields only two possible genotypes of sperm, XXXXX or YYYY, thus preserving this complex system.
Source : Wikipedia
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The 12-foot-tall leaf- eater was the Santa Barbara Zoo's most famous inhabitant. Her bones were a mystery.
January 12, 2008|Steve Chawkins, Times Staff Writer
Gemina, a much-visited Baringo giraffe who held her head high on a mysteriously crooked neck, has died at the Santa Barbara Zoo. She was 21.
"She was the most famous individual we had," said Alan Varsik, the zoo's director of animal programs and conservation. "She's been a part of Santa Barbara for a long time."
Gemina's most recent brush with fame was a 2006 appearance on "The Miracle Workers," an ABC reality show that devoted an episode to obtaining medical help for a 3-year-old with severe scoliosis. Watching Gemina at the zoo, the toddler remarked that the giraffe "has a bump like me."
Born without any apparent deformity at San Diego Wild Animal Park, Gemina moved to Santa Barbara when she was a year old.
When she was 3, her neck bones started to jut out in a way that had been last documented in a giraffe in 1902.
Zoo visitors asked about her neck all the time, but providing answers was a tall order. X-rays showed vertebrae that appeared fused, but the zoo's scientific staff could find no reason for it. When Gemina was 2, a worker saw her tumble end over end, but no injury was detected at the time.
The 12-foot-tall leaf-eater lived a normal life, Varsik said. In 1991, she gave birth, but her calf died of pneumonia.
Last July, she was serenaded by children on her 21st birthday, and a video of the occasion was posted on the zoo's website. She had outlived most giraffes by six years.
Over the last two weeks, Gemina stopped eating and her health deteriorated. Old age -- not her zigzag neck -- was taking its toll, Varsik said. Results of a necropsy are pending.
She was euthanized Wednesday.
"We did everything we could, but the time came when we had to make the humane decision," Varsik said. "She was off-exhibit in the giraffe barn when she died."
Source: latimes.com
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There were three identical mechanical sharks used in filming, and they malfunctioned constantly. Because the sharks were not tested in water before filming, the first one sunk as soon as it was put in the water. The crew that worked on the film took to calling it "Flaws" because of all of the on-set trouble.
•After Robert Shaw finished filming his scenes as Quint, he had to flee to country to escape the IRS. Ironically, Shaw was the second choice for the role and was given the spot after the first actor selected had to leave the country to escape his IRS problems.
•Roy Scheider didn't believe that the crew would save him if something went wrong when he filmed his scene on the sinking Orca. He hid axes at various spots around the boat in case he needed to use them to save himself.
•Spielberg's own dog played the role of Brody's dog.
•One of the mechanical sharks used in the movie was lost at sea during filming.
•The movie was supposed to feature many more shots of the mechanical sharks, but they broke down so much that Spielberg was forced to change his plans and use shots from the shark's perspective instead of actually showing the shark. In retrospect, the director believes that this change made the movie much scarier.
•The scene featuring the death of character Alex Kintner had to be re-shot because the film rating's board said if it stayed in the film as it was, they would be forced to rate the movie R instead of PG.
•Robert Shaw and Richard Dreyfuss did not get along and fought often on set.
•When Shaw showed up to film the scene in which he tells the story of the Indianapolis, he was too drunk to deliver his lines and instead kept going off track and talking about his family. The scene had to be redone the next day, and he got it in one take.
Source: movies.lovetoknow.com
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