One of the largest leeches in the world, the Haementaria ghiliani from the Amazon. It can reach 1' in length and is a blood sucker
(but see below)
Leeches are segmented worms that belong to the phylum Annelida and comprise the subclass Hirudinea. Like other oligochaetes, such as earthworms, leeches share a clitellum and are hermaphrodites. Nevertheless, they differ from other oligochaetes in significant ways. For example, leeches do not have bristles and the external segmentation of their bodies does not correspond with the internal segmentation of their organs. Their bodies are much more solid as the spaces in their coelom are dense with connective tissues. They also have two suckers, one at each end.
The majority of leeches live in freshwater environments, while some species can be found in terrestrial and marine environments, as well. Most leeches are hematophagous, as they are predominantly blood suckers that feed on blood from vertebrate and invertebrate animals. Almost 700 species of leeches are currently recognized, of which some 100 are marine, 90 terrestrial and the remainder freshwater taxa.
Leeches, such as the Hirudo medicinalis, have been historically used in medicine to remove blood from patients. The practice of leeching can be traced to ancient India and Greece, and continued well into the 18th and 19th centuries in both Europe and North America. In modern times, the practice of leeching is much rarer and has been replaced by other contemporary uses of leeches, such as the reattachment of body parts and reconstructive and plastic surgeries and, in Germany, treating osteoarthritis.
Leeches are presumed to have evolved from certain Oligochaeta, most of which feed on detritus. However, some species in the Lumbriculidae are predatory and have similar adaptations as found in leeches. As a consequence, the systematics and taxonomy of leeches is in need of review. While leeches form a clade, the remaining oligochaetes are not their sister taxon, but in a diverse paraphyletic group containing some lineages that are closely related to leeches, and others that are far more distant.
There is some dispute as to whether Hirudinea should be a class itself, or a subclass of the Clitellata. The resolution mainly depends on the eventual fate of the oligochaetes, which as noted above, do not form a natural group as traditionally circumscribed. Another possibility would be to include the leeches in the taxon Oligochaeta, which would then be ranked as a class and contain most of the clitellates. The Branchiobdellida are leechlike clitellates that were formerly included in the Hirudinea, but are just really close relatives.
The more primitive Acanthobdellidea are often included with the leeches, but some authors treat them as a separate clitellate group. True leeches of the infraclass Euhirudinea have both anterior and posterior suckers. They are divided into two groups: Arhynchobdellida and Rhynchobdellida
Like other annelids, the leech is a segmented animal. But unlike other annelids, there is no correspondence between the external segmentation of a leech's body surface with the segmentation of its internal organs. The body surface of the animal can be divided into 102 annuli, whereas its internal structures are divided into 32 segments. Of the 32 segments within the body, the first four anterior segments are designated as head segments, which include an anterior brain and sucker. This is followed by 21 midbody segments, which include 21 neuronal ganglia, two reproductive organs, and 9 pairs of testes. Finally, the last seven segments are fused to form the animal's tail sucker, as well as its posterior brain. The leech also has 32 brains because a brain segment is located in each segmentation of the body.
Leeches are hermaphrodites, meaning each has both female and male reproductive organs (ovaries and testes, respectively). Leeches reproduce by reciprocal fertilization, and sperm transfer occurs during copulation. Similar to the earthworms, leeches also use a clitellum to hold their eggs and secrete the cocoon.
During reproduction, leeches use hyperdermic injection of their sperm. They use a spermatophore, which is a structure containing the sperm. Once next to each other, leeches will line up with one's anterior side opposite the other's posterior. The leech then shoots the spermatophore into the clitellur region of the opposing leech, where its sperm will make its way to the female reproductive parts.
The embryonic development of the la occurs as a series of stages. During stage 1, the first cleavage occurs, which gives rise to an AB and a CD blastomere, and is in the interphase of this cell division when a yolk-free cytoplasm called teloplasm is formed. The teloplasm is known to be a determinant for the specification of the D cell fate. In stage 3, during the second cleavage, an unequal division occurs in the CD blastomere. As a consequence, it creates a large D cell on the left and a smaller C cell to the right. This unequal division process is dependent on actinomycin, and by the end of stage 3 the AB cell divides. On stage 4 of development, the micromeres and teloblast stem cells are formed and subsequently, the D quadrant divides to form the DM and the DNOPQ teloblast precursor cells. By the end stage 6, the zygote contains a set of 25 micromeres, 3 macromeres (A, B and C) and 10 teloblasts derived from the D quadrant.
The teloblasts are pairs of five different types (M, N, O, P, and Q) of embryonic stem cells that form segmented columns of cells (germinal band) in the surface of the embryo. The M-derived cells make mesoderm and some small set of neurons, N results in neural tissues and some ventral ectoderm, Q contributes to the dorsal ectoderm and O and P in the leech are equipotent cells (same developmental potential) that produce lateral ectoderm; however the difference between the two of them is that P creates bigger batches of dorsolateral epidermis than O. The sludgeworm Tubifex, unlike the leech, specifies the O and P lineages early in development and therefore, these two cells are not equipotent. Each segment of the body of the leech is generated from one M, O, P cell types and two N and two Q cells types.
The ectoderm and mesoderm of the body trunk are exclusively derived from the teloblast cells in a region called the posterior progress zone. The head of the leech that comes from an unsegmented region, is formed by the first set of micromeres derived from A, B, C and D cells, keeping the bilateral symmetry between the AD and BC cells.
In most blood-sucking leeches the digestive system starts with the so-called jaws, three blades set at an angle to each other. In feeding they slice their way through the skin of the host, leaving a Y-shaped incision. Behind the blades is the mouth, located ventrally at the anterior end of the body. It leads successively into the pharynx, then the esophagus, the crop, the gizzard, and the intestinum, which ends at the posterior sucker. The crop is a distension of the alimentary canal that functions as an expandable storage compartment. In the crop, some blood-sucking species of leech can store up to five times the body mass of blood. The leech produces an anticoagulant that prevents the stored blood from clotting, plus other agents that inhibit microbial decay of the blood. These measures are so effective that a mature medicinal leech does not need to feed more than twice a year. Possibly as an adaptation, its digestive process is extremely slow.
The bodies of predatory leeches are similar, though instead of jaws many have a protrusible proboscis, which for most of the time they keep retracted into the mouth. Such leeches often are ambush predators that lie in wait till they can strike prey with the proboscises in a spear-like fashion. Some kinds that live on small invertebrates or detritus have neither proboscis nor jaws, but simply engulf their food with the mouth.
Bacteria in the gut were long thought to carry on digestion for the leech, instead of endogenous enzymes that are very low or absent in the intestine. As discovered relatively recently, all leech species studied do produce endogenous intestinal exopeptidases, which can unlink free terminal-end amino acids, one monomer at a time from a gradually unwinding and degrading protein polymer. However, unzipping of the protein can start from either the amino (tail) or carboxyl (head) terminal-end of the protein molecule. The leech exopeptidases (arylamidases), possibly aided by proteases from endosymbiotic bacteria in the intestine, starting from the tail or amino end, slowly but progressively removing many hundreds of individual terminal amino acids for resynthesis into proteins that constitute the leech. Since leeches lack endopeptidases, the mechanism of protein digestion cannot follow the same sequence as it would in all other animals in which exopeptidases act sequentially on peptides produced by the action of endopeptidases. Exopeptidases are especially prominent in the common North American worm-leech Erpobdella punctata. This evolutionary choice of exopeptic digestion in Hirudinea distinguishes these carnivorous clitellates from Oligochaeta.
Deficiency of digestive enzymes (except exopeptidases), but, more importantly, deficiency of vitamins, B complex for example, in leeches is compensated for by enzymes and vitamins produced by endosymbiotic microflora. In Hirudo medicinalis, these supplementary factors are produced by an obligatory symbiotic relationship with two bacterial species, Aeromonas veronii and a still-uncharacterized Rikenella species. Nonbloodsucking leeches, such as Erpobdella punctata, are host to three bacterial symbionts, Pseudomonas, Aeromonas, and Klebsiella spp. (a slime producer). The bacteria are passed from parent to offspring in the cocoon as it is formed.
Leeches are able to display a variety of behaviors that allow them to explore their environments and feed on their hosts. Exploratory behavior includes head movements and body waving.
Most leech species do not feed on human blood, but instead prey on small invertebrates, which they eat whole. To feed on their hosts, leeches use their anterior suckers to connect to hosts for feeding, and also release an anesthetic to prevent the hosts from feeling them. Once attached, leeches use a combination of mucus and suction to stay attached and secrete an anticoagulant enzyme, hirudin, into the hosts' blood streams. Though certain species of leeches feed on blood, not all species can bite; 90% of them feed solely on decomposing bodies and open wounds of amphibians, reptiles, waterfowl, fish, and mammals (including humans). A leech attaches itself when it bites, and it will stay attached until it becomes full, at which point it falls off to digest. Due to the hirudin that leeches secrete, bites may bleed more than a normal wound after the leech is removed. The effect of the anticoagulant will wear off several hours after the leech is removed and the wound is cleaned. The bite of a leech is painless because they inject anesthetic so they go unnoticed when they attach.
Leeches normally carry parasites in their digestive tracts, which cannot survive in humans and do not pose a threat. However, bacteria, viruses, and parasites from previous blood sources can survive within a leech for months, but only a few cases of leeches transmitting pathogens to humans have been reported. A study found both HIV and hepatitis B in African leeches from Cameroon.
One recommended method of removal is using a fingernail or other flat, blunt object to break the seal of the oral sucker at the anterior end of the leech, repeating with the posterior end, then flicking the leech away. As the fingernail is pushed along the person's skin against the leech, the suction of the sucker's seal is broken, at which point the leech will detach its jaws.
Common, but medically inadvisable, techniques to remove a leech are to apply a flame, a lit cigarette, salt, soap, or a chemical such as alcohol, vinegar, lemon juice, insect repellent, heat rub, or certain carbonated drinks. These will cause the leech to quickly detach; however, it will also regurgitate its stomach contents into the wound. The vomit may carry disease, and thus increase the risk of infection.
An externally attached leech will detach and fall off on its own when it is satiated on blood, which may be anywhere from 20 minutes to two hours or more. After feeding, the leech will detach and depart. Internal attachments, such as inside the nasal passage or vaginal attachments, are more likely to require medical intervention.
After removal or detachment, the wound should be cleaned with soap and water, and bandaged. Bleeding may continue for some time, due to the leech's hirudin. Bleeding time will vary, with location, from a few hours to three days. This is a function of the hirudin and other compounds that reduce the surface tension of the blood. Anticlotting medications also affect the bleeding time. Applying pressure can reduce bleeding, although blood loss from a single bite is not dangerous. The wound normally itches as it heals, but should not be scratched, as this may complicate healing and introduce other infections. An antihistamine can reduce itching, and applying a cold pack can reduce pain or swelling.
Some people suffer severe allergic or anaphylactic reactions from leech bites and require urgent medical care. Symptoms include red blotches or an itchy rash over the body, swelling around the lips or eyes, feeling faint or dizzy, and difficulty breathing.
The European medical leech Hirudo medicinalis and some congeners, as well as some other species, have been used for clinical bloodletting for thousands of years. The use of leeches in medicine dates as far back as 2,500 years ago, when they were used for bloodletting in ancient India. Leech therapy is explained in ancient Ayurvedic texts. Many ancient civilizations practiced bloodletting, including Indian and Greek civilizations. In ancient Greek history, bloodletting was practiced according to the humoral theory, which proposed that, when the four humors, blood, phlegm, black and yellow bile in the human body were in balance, good health was guaranteed. An imbalance in the proportions of these humors was believed to be the cause of ill health. Records of this theory were found in the Greek philosopher Hippocrates' collection in the fifth century BC. Bloodletting using leeches was one method used by physicians to balance the humors and to rid the body of the plethora.
The use of leeches in modern medicine made its comeback in the 1980s after years of decline, with the advent of microsurgeries, such as plastic and reconstructive surgeries. In operations such as these, problematic venous congestion can arise due to inefficient venous drainage. Sometimes, because of the technical difficulties in forming an anastomosis of a vein, no attempt is made to reattach a venous supply to a flap at all. This condition is known as venous insufficiency. If this congestion is not cleared up quickly, the blood will clot, arteries that bring the tissues their necessary nourishment will become plugged, and the tissues will die. To prevent this, leeches are applied to a congested flap, and a certain amount of excess blood is consumed before the leech falls away. The wound will also continue to bleed for a while due to the anticoagulant hirudin in the leeches' saliva. The combined effect is to reduce the swelling in the tissues and to promote healing by allowing fresh, oxygenated blood to reach the area.
The active anticoagulant component of leech saliva is a small protein, hirudin. Discovery and isolation of this protein led to a method of producing it by recombinant technology. Recombinant hirudin is available to physicians as an intravenous anticoagulant preparation for injection, particularly useful for patients who are allergic to or cannot tolerate heparin.
Hementin is an anticoagulant protease from the salivary glands of the giant Amazon leech (Haementeria ghilianii). Hementin dissolves a type of platelet rich blood clot which cannot be dissolved by other well used drugs like streptokinase and urokinase.
Hematophagy (sometimes spelled haematophagy or hematophagia) is the practice of certain animals of feeding on blood (from the Greek words, haima "blood" and phagein "to eat"). Since blood is a fluid tissue rich in nutritious proteins and lipids that can be taken without enormous effort, hematophagy has evolved as a preferred form of feeding in many small animals such as worms and arthropods. Some intestinal nematodes, such as Ancylostomids, feed on blood extracted from the capillaries of the gut and about 75% of all species of leeches (e.g. Hirudo medicinalis),][ a free-living worm, are hematophagous. Some fish, such as lampreys and Candirus and mammals, especially the vampire bats, and birds, such as the vampire finches, Hood Mockingbirds, and oxpeckers, also practice hematophagy.
These hematophagous animals have mouth parts and chemical agents for penetrating vascular structures in the skin of hosts, mostly of mammals, birds, and fish. This type of feeding is known as phlebotomy (from the Greek words, phleps "vein" and tomos "cutting").
Once phlebotomy is performed (in most insects by a specialized fine hollow "needle" called proboscis which perforates skin and capillaries; in bats by sharp incisor teeth that act as a razor to cut the skin), blood is acquired either by sucking action directly from the vases, from a pool of escaped blood, or by lapping (again, in bats). In order to overcome natural hemostasis (blood coagulation), vasoconstriction, inflammation, and pain sensation in the host, biochemical solutions in the saliva for instance, for pre-injection, anesthesia and capillary dilation have evolved in different hematophagous species. Anticoagulant medicines have been developed on the basis of substances found in the saliva of several hematophagous species such as leeches (hirudin).
Hematophagy can be classified into obligatory and optional practice. Obligatory hematophagous animals do not have any other type of food besides blood; one such species is Rhodnius prolixus (an assassin bug from South America). This contrasts with optional hematophages, like the many mosquitoes species, such as Aedes aegypti, which may also feed on pollen, fruit juice, and other biological fluids. Sometimes only the female of the species is a hematophage (this is essential for egg production and reproduction). Coyotes, wolves, and other canids may lick blood.
Hematophagy has apparently evolved independently in many disparate arthropod, annelid, nematode and mammalian taxa. For example Diptera (insects with two wings, such as flies) have eleven families with hematophagous habits (more than half of the 19 hematophagous arthropod taxa). About 14,000 species of arthropods are hematophagous, even including some genera that were not previously thought to be, such as moths of the genus Calyptra. Several complementary biological adaptations for locating the hosts (usually in the dark, as most hematophagous species are nocturnal and silent, in order to avoid detection and destruction by the host) have also evolved, such as special physical or chemical detectors (for sweat components, 2CO, heat, light, movement, etc.).
The phlebotomic action opens a channel for contamination of the host species with bacteria, viruses and blood-borne parasites contained in the hematophagous organism. Thus, many animal and human infectious diseases are transmitted by hematophagous species, such as the bubonic plague, Chagas disease, dengue fever, filariasis, leishmaniasis, Lyme disease, malaria, rabies, sleeping sickness, St. Louis encephalitis, tularemia, typhus, Rocky Mountain spotted fever, West Nile fever, and many others.
Insects and arachnids of medical importance for being hematophagous, at least in some species, include the sandfly, blackfly][, tsetse fly, bedbug, assassin bug, mosquito, tick, louse, mite, midge, and flea.
Hematophagous organisms have been used by physicians for beneficial purposes (hirudotherapy). Some doctors now use leeches to prevent the clotting of blood on some wounds following surgery or trauma.][ The anticoagulants in the laboratory-raised leeches' saliva keeps fresh blood flowing to the site of an injury, actually preventing infection and increasing chances of full recovery. In a recent study a genetically engineered drug called desmoteplase based on the saliva of Desmodus rotundus (the vampire bat) was shown to improve stroke patients.
Drinking blood and manufacturing foodstuffs and delicacies with animal blood is also a feeding behavior in many societies. Cow blood mixed with milk, for example, is a mainstay food of the African Maasai. Some sources say][ that Mongols would drink blood from one of their horses if it became a necessity. Black pudding is eaten in many places around the world. Some societies, such as the Moche, had ritual hematophagy, as well as the Scythians, a nomadic people of Russia, who had the habit of drinking the blood of the first enemy they would kill in battle. Some religious rituals and symbols seemingly mirror hematophagy, such as in the transubstantiation of wine as the blood of Jesus Christ during Christian eucharist. Psychiatric cases of patients performing hematophagy also exist. Sucking or licking one's own blood from a wound is also a behavior commonly seen in humans, and in small enough quantities is not considered taboo. Finally, human vampirism has been a persistent object of literary and cultural attention.
The giant squid (genus: Architeuthis) is a deep-ocean dwelling squid in the family Architeuthidae, represented by as many as eight species. Giant squid can grow to a tremendous size (see Deep-sea gigantism): recent estimates put the maximum size at 13 m (43 ft) for females and 10 m (33 ft) for males from the posterior fins to the tip of the two long tentacles (second only to the colossal squid at an estimated 14 m (46 ft), one of the largest living organisms). The mantle is about 2 m (6.6 ft) long (more for females, less for males), and the length of the squid excluding its tentacles is about 5 m (16 ft). Claims of specimens measuring 20 m (66 ft) or more have not been scientifically documented.
On 30 September 2004, researchers from the National Science Museum of Japan and the Ogasawara Whale Watching Association took the first images of a live giant squid in its natural habitat. Several of the 556 photographs were released a year later. The same team successfully filmed a live adult giant squid for the first time as it was brought aboard on 4 December 2006. A live adult was first filmed in its natural habitat off Chichi-jima in July 2012 by a joint NHK/Discovery Channel team.
Like all squid, a giant squid has a mantle (torso), eight arms, and two longer tentacles (the longest known tentacles of any cephalopod). The arms and tentacles account for much of the squid's great length, making it much lighter than its chief predator, the sperm whale. Scientifically documented specimens have masses of hundreds, rather than thousands, of kilograms.
The inside surfaces of the arms and tentacles are lined with hundreds of subspherical suction cups, 2 to 5 cm (0.79 to 2.0 in) in diameter, each mounted on a stalk. The circumference of these suckers is lined with sharp, finely serrated rings of chitin. The perforation of these teeth and the suction of the cups serve to attach the squid to its prey. It is common to find circular scars from the suckers on or close to the head of sperm whales that have attacked giant squid. Each arm and tentacle is divided into three regions – carpus ("wrist"), manus ("hand") and dactylus ("finger"). The carpus has a dense cluster of cups, in six or seven irregular, transverse rows. The manus is broader, close to the end of the arm, and has enlarged suckers in two medial rows. The dactylus is the tip. The bases of all the arms and tentacles are arranged in a circle surrounding the animal's single, parrot-like beak, as in other cephalopods.
Giant squid have small fins at the rear of their mantles used for locomotion. Like other cephalopods, they are propelled by jet – by pulling water into the mantle cavity, and pushing it through the siphon, in gentle, rhythmic pulses. They can also move quickly by expanding the cavity to fill it with water, then contracting muscles to jet water through the siphon. Giant squid breathe using two large gills inside the mantle cavity. The circulatory system is closed, which is a distinct characteristic of cephalopods. Like other squid, they contain dark ink used to deter predators.
The giant squid has a sophisticated nervous system and complex brain, attracting great interest from scientists. It also has the largest eyes of any living creature except perhaps the colossal squid – up to at least 27 cm (11 in) in diameter, with a 9 cm (3.5 in) pupil (only the extinct ichthyosaurs are known to have had larger eyes). Large eyes can better detect light (including bioluminescent light), which is scarce in deep water. The giant squid probably cannot see colour, but it can probably discern small differences in tone, which is important in the low-light conditions of the deep ocean.
Giant squid and some other large squid species maintain neutral buoyancy in seawater through an ammonium chloride solution which is found throughout their bodies and is lighter than seawater. This differs from the method of flotation used by most fish, which involves a gas-filled swim bladder. The solution tastes somewhat like salmiakki and makes giant squid unattractive for general human consumption.
Like all cephalopods, giant squid use organs called statocysts to sense their orientation and motion in water. The age of a giant squid can be determined by "growth rings" in the statocyst's statolith, similar to determining the age of a tree by counting its rings. Much of what is known about giant squid age is based on estimates of the growth rings and from undigested beaks found in the stomachs of sperm whales.
The giant squid is the second-largest mollusc and the second largest of all extant invertebrates. It is only exceeded by the colossal squid, Mesonychoteuthis hamiltoni, which may have a mantle nearly twice as long. Several extinct cephalopods, such as the Cretaceous vampyromorphid Tusoteuthis, the Cretaceous coleoid Yezoteuthis, and the Ordovician nautiloid Cameroceras may have grown even larger.
Giant squid size, particularly total length, has often been exaggerated. Reports of specimens reaching and even exceeding 20 m (66 ft) are widespread, but no animals approaching this size have been scientifically documented. According to giant squid expert Steve O'Shea, such lengths were likely achieved by greatly stretching the two tentacles like elastic bands.
Based on the examination of 130 specimens and of beaks found inside sperm whales, giant squids' mantles are not known to exceed 2.25 m (7.4 ft). Including the head and arms, but excluding the tentacles, the length very rarely exceeds 5 m (16 ft). Maximum total length, when measured relaxed post mortem, is estimated at 13 m (43 ft) for females and 10 m (33 ft) for males from the posterior fins to the tip of the two long tentacles.
Giant squid exhibit sexual dimorphism. Maximum weight is estimated at 275 kg (610 lb) for females and 150 kg (330 lb) for males.
Little is known about the reproductive cycle of giant squid. They are thought to reach sexual maturity at about three years old; males reach sexual maturity at a smaller size than females. Females produce large quantities of eggs, sometimes more than 5 kg (11 lb), that average 0.5 to 1.4 mm (0.020 to 0.055 in) long and 0.3 to 0.7 mm (0.012 to 0.028 in) wide. Females have a single median ovary in the rear end of the mantle cavity and paired, convoluted oviducts, where mature eggs pass exiting through the oviducal glands, then through the nidamental glands. As in other squid, these glands produce a gelatinous material used to keep the eggs together once they are laid.
In males, as with most other cephalopods, the single, posterior testis produces sperm that move into a complex system of glands that manufacture the spermatophores. These are stored in the elongate sac, or Needham's sac, that terminates in the penis from which they are expelled during mating. The penis is prehensile, over 90 cm (35 in) long, and extends from inside the mantle.
How the sperm is transferred to the egg mass is much debated, as giant squid lack the hectocotylus used for reproduction in many other cephalopods. It may be transferred in sacs of spermatophores, called spermatangia, which the male injects into the female's arms. This is suggested by a female specimen recently found in Tasmania, having a small subsidiary tendril attached to the base of each arm.
Post-larval juveniles have been discovered in surface waters off New Zealand, with plans to capture more and maintain them in an aquarium to learn more about the creature.
Analysis of the mitochondrial DNA of giant squid individuals from all over the world has found that there is little variation between individuals across the globe (just 181 differing genetic base pairs out of 20,331). This suggests that there is but a single species of giant squid in the world. Squid larvae may be dispersed by ocean currents across vast distances.
Recent studies have shown giant squid feed on deep-sea fish and other squid species. They catch prey using the two tentacles, gripping it with serrated sucker rings on the ends. Then they bring it toward the powerful beak, and shred it with the radula (tongue with small, file-like teeth) before it reaches the esophagus. They are believed to be solitary hunters, as only individual giant squid have been caught in fishing nets. Although the majority of giant squid caught by trawl in New Zealand waters have been associated with the local hoki (Macruronus novaezelandiae) fishery, hoki do not feature in the squid's diet. This suggests giant squid and hoki prey on the same animals.
The only known predators of adult giant squid are sperm whales, but pilot whales may also feed on them. Juveniles are preyed on by deep-sea sharks and other fish. Because sperm whales are skilled at locating giant squid, scientists have tried to observe them to study the squid.
Giant squid are widespread, occurring in all of the world's oceans. They are usually found near continental and island slopes from the North Atlantic Ocean, especially Newfoundland, Norway, the northern British Isles, Spain and the oceanic islands of the Azores and Madeira, to the South Atlantic around southern Africa, the North Pacific around Japan, and the southwestern Pacific around New Zealand and Australia. Specimens are rare in tropical and polar latitudes.
The vertical distribution of giant squid is incompletely known, but data from trawled specimens and sperm whale diving behaviour suggest it spans a large range of depths, possibly 300–1000 m.
The taxonomy of the giant squid, as with many cephalopod genera, has not been resolved. Lumpers and splitters may propose as many as eight species or as few as one. The broadest list is:
These are probably not distinct species. No genetic or physical basis for distinguishing between them has been proposed, as evidenced by the place names – of location of specimen capture – used to describe several of them. The rarity of observations of specimens and the extreme difficulty of observing them alive, tracking their movements, or studying their mating habits militates against a complete understanding.
In the 1984 FAO Species Catalogue of the Cephalopods of the World, Roper, et al. wrote:
"Many species have been named in the sole genus of the family Architeuthidae, but they are so inadequately described and poorly understood that the systematics of the group is thoroughly confused."
Nesis (1982) considered only three species were likely to be valid.
In 1991, Frederick Aldrich of Memorial University of Newfoundland wrote:
"I reject the concept of 20 separate species, and until that issue is resolved, I choose to place them all in synonymy with Architeuthis dux Steenstrup."
In a letter to Richard Ellis dated 18 June 18 1996, Martina Roeleveld of the South African Museum wrote:
"So far, I have seen nothing to suggest that there might be more than one species of Architeuthis."
In Cephalopods: A World Guide (2000), Norman writes:
"The number of species of giant squid is not known, although the general consensus amongst researchers is that there are at least three species, one in the Atlantic Ocean (Architeuthis dux), one in the Southern Ocean (A. sanctipauli) and at least one in the northern Pacific Ocean (A. martensi)."
In March 2013, researchers at the University of Copenhagen suggested that, based on DNA research, there is probably only one species:
"...researchers at the University of Copenhagen leading an international team, have discovered that no matter where in the world they are found, the fabled animals are so closely related at the genetic level that they represent a single, global population, and thus despite previous statements to the contrary, a single species worldwide."
Aristotle, who lived in the fourth century BC, already described a large squid, which he called teuthus, distinguishing it from the smaller squid, the teuthis. He mentions, "of the calamaries, the so-called teuthus is much bigger than the teuthis; for teuthi [plural of teuthus] have been found as much as five ells long."
Pliny the Elder, living in the first century AD, also described a gigantic squid in his Natural History, with the head "as big as a cask", arms 30 ft (9.1 m) long, and carcass weighing 700 lb (320 kg).
Tales of giant squid have been common among mariners since ancient times, and may have led to the Norse legend of the kraken, a tentacled sea monster as large as an island capable of engulfing and sinking any ship. Japetus Steenstrup, the describer of Architeuthis, suggested a giant squid was the species described as a sea monk to the Danish king Christian III circa} 1550. The Lusca of the Caribbean and Scylla in Greek mythology may also derive from giant squid sightings. Eyewitness accounts of other sea monsters like the sea serpent are also thought to be mistaken interpretations of giant squid.
Steenstrup wrote a number of papers on giant squid in the 1850s. He first used the term "Architeuthus" (this was the spelling he chose) in a paper in 1857. A portion of a giant squid was secured by the French gunboat Alecton in 1861, leading to wider recognition of the genus in the scientific community. From 1870 to 1880, many squid were stranded on the shores of Newfoundland. For example, a specimen washed ashore in Thimble Tickle Bay, Newfoundland on 2 November 1878; its mantle was reported to be 6.1 m (20 ft) long, with one tentacle 10.7 m (35 ft) long, and it was estimated as weighing 2.2 tonnes.][ In 1873, a squid "attacked" a minister and a young boy in a dory in Bell Island, Newfoundland. Many strandings also occurred in New Zealand during the late 19th century.
Although strandings continue to occur sporadically throughout the world, none have been as frequent as those at Newfoundland and New Zealand in the 19th century. It is not known why giant squid become stranded on shore, but it may be because the distribution of deep, cold water where squid live is temporarily altered. Many scientists who have studied squid mass strandings believe they are cyclical and predictable. The length of time between strandings is not known, but was proposed to be 90 years by Architeuthis specialist Frederick Aldrich. Aldrich used this value to correctly predict a relatively small stranding that occurred between 1964 and 1966.
In 2004, another giant squid, later named "Archie", was caught off the coast of the Falkland Islands by a fishing trawler. It was 8.62 m (28.3 ft) long and was sent to the Natural History Museum in London to be studied and preserved. It was put on display on 1 March 2006 at the Darwin Centre. The find of such a large, complete specimen is very rare, as most specimens are in a poor condition, having washed up dead on beaches or been retrieved from the stomachs of dead sperm whales.
Researchers undertook a painstaking process to preserve the body. It was transported to England on ice aboard the trawler; then it was defrosted, which took about four days. The major difficulty was that thawing the thick mantle took much longer than the tentacles. To prevent the tentacles from rotting, scientists covered them in ice packs, and bathed the mantle in water. Then they injected the squid with a formol-saline solution to prevent rotting. The creature is now on show in a 9-m (20-ft) glass tank at the Darwin Centre of the Natural History Museum.
In December 2005, the Melbourne Aquarium in Australia paid A$100,000 for the intact body of a 7 metre long giant squid, preserved in a giant block of ice, which had been caught by fishermen off the coast of New Zealand's South Island that year.
The number of known giant squid specimens was close to 600 in 2004, and new ones are reported each year. The search for a live Architeuthis specimen includes attempts to find live young, including larvae. The larvae closely resemble those of Nototodarus and Onykia, but are distinguished by the shape of the mantle attachment to the head, the tentacle suckers, and the beaks.
By the turn of the 21st century, the giant squid remained one of the few extant megafauna to have never been photographed alive, either in the wild or in captivity. Marine biologist and author Richard Ellis described it as "the most elusive image in natural history". In 1993, an image purporting to show a diver with a live giant squid (identified as Architeuthis dux) was published in the book European Seashells. However, the animal in this photograph was a sick or dying Onykia robusta, not a giant squid. The first footage of live larval giant squid ever captured on film was in 2001. The footage was shown on Chasing Giants: On the Trail of the Giant Squid on the Discovery Channel and on Giant Squid: Filming the Impossible - Natural World Special on BBC Two.
The first image of a live mature giant squid was taken on 15 January 2002, on Goshiki beach, Amino Cho, Kyoto Prefecture, Japan. The animal, which measured about 2 m (6.6 ft) in mantle length and 4 m (13 ft) in total length, was found near the water's surface. It was captured and tied to a quay, where it died overnight. The specimen was identified by Koutarou Tsuchiya of the Tokyo University of Fisheries. It is on display at the National Science Museum of Japan.
The first photographs of a live giant squid in its natural habitat were taken on 30 September 2004, by Tsunemi Kubodera (National Science Museum of Japan) and Kyoichi Mori (Ogasawara Whale Watching Association). Their teams had worked together for nearly two years to accomplish this. They used a five-ton fishing boat and only two crew members. The images were created on their third trip to a known sperm whale hunting ground 970 km (600 mi) south of Tokyo, where they had dropped a 900-m (3000-ft) line baited with squid and shrimp. The line also held a camera and a flash. After over 20 tries that day, an 8 m (26 ft) giant squid attacked the lure and snagged its tentacle. The camera took over 500 photos before the squid managed to break free after four hours. The squid's 5.5 m (18 ft) tentacle remained attached to the lure. Later DNA tests confirmed the animal as a giant squid.
On 27 September 2005, Kubodera and Mori released the photographs to the world. The photo sequence, taken at a depth of 900 metres (3,000 ft) off Japan's Ogasawara Islands, shows the squid homing in on the baited line and enveloping it in "a ball of tentacles". The researchers were able to locate the likely general location of giant squid by closely tailing the movements of sperm whales. According to Kubodera, "we knew that they fed on the squid, and we knew when and how deep they dived, so we used them to lead us to the squid." Kubodera and Mori reported their observations in the journal Proceedings of the Royal Society.
Among other things, the observations demonstrate actual hunting behaviors of adult Architeuthis, a subject on which there had been much speculation. The photographs showed an aggressive hunting pattern by the baited squid, leading to it impaling a tentacle on the bait ball's hooks. This may disprove the theory that the giant squid is a drifter which eats whatever floats by, rarely moving so as to conserve energy. It seems the species has a much more aggressive feeding technique.
In November 2006, American explorer and diver Scott Cassell led an expedition to the Sea of Cortez with the aim of filming a giant squid in its natural habitat. The team employed a novel filming method: using a Humboldt squid carrying a specially designed camera clipped to its fin. The camera-bearing squid caught on film what was claimed to be a giant squid, with an estimated length of 40 feet (12 m), engaging in predatory behavior. The footage aired a year later on a History Channel program, MonsterQuest: Giant Squid Found. Cassell subsequently distanced himself from this documentary, claiming that it contained multiple factual and scientific errors.
On 4 December 2006, an adult giant squid was caught on video near the Ogasawara Islands, 1,000 km (620 mi) south of Tokyo, by researchers from the National Science Museum of Japan led by Tsunemi Kubodera. It was a small female about 3.5 m (11 ft) long and weighing 50 kg (110 lb). The bait used by the scientists initially attracted a medium-sized squid measuring around 55 cm (22 in), which in turn attracted the giant squid. It was pulled aboard the research vessel, but died in the process.
In July 2012, a crew from television networks NHK and Discovery Channel captured what they describe as "the first-ever footage of a live giant squid in its natural habitat". The footage was revealed on a NHK Special on January 13, 2013, and was shown on Discovery Channel's show Monster Squid: The Giant Is Real on January 27, 2013. The squid was about 3 m (9.8 ft) long and was missing its feeding tentacles, likely from a failed attack by a sperm whale. It was drawn into viewing range by both artificial bioluminescence created to mimic panicking jellyfish and by using a Thysanoteuthis rhombus as bait. The squid was filmed feeding for about 23 minutes by Tsunemi Kubodera until it departed.
The elusive nature of the giant squid and its foreign appearance, often perceived as terrifying, have firmly established its place in the human imagination. Representations of the giant squid have been known from early legends of the kraken through books such as Moby-Dick and Twenty Thousand Leagues Under the Sea on to novels such as Ian Fleming's Dr. No and Peter Benchley's Beast (adapted as a film called The Beast) and modern animated television programs.
In particular, the image of a giant squid locked in battle with a sperm whale is a common one, although the squid is, in fact, the whale's prey, and not an equal combatant.
The Bluehead sucker (Catostomus discobolus) is one of six catostomidae endemic to Arizona. There are a total of 23 members of the Catostomus discobolus, all of which can be found in North America. C. discobolus and C. yarrowi are two sister subspecies that have very similar Arizona habitats.
The Bluehead Sucker is the largest of all Arizona endemic suckers, reaching lengths of over 11.8 inches. Their colors are very similar to the Desert Sucker, with dark green or dark silvery top portions and light yellow bottoms. The Bluehead has the largest lips of any sucker and has tiny papillae on the lower lip. This is also the only species with the absence of an inguinal process, just behind the pectoral fins, distinguishing it from the other eight suckers. The lower lip is slightly notched at the midline, with lateral line scales in large numbers that range from 70 to 100. They have 7 to 9 dorsal fin rays and a smaller amount of caudal fin rays. During breeding, the males obtain a blue patch on the top of their large heads, and the lower fins become yellow/orange with red/rosy lateral lines. These drastic coloration changes are probably due to sexual selection and female mate choice. An easy way to distinguish the Bluehead from the other Arizona suckers is to notice the distinct cartilaginous lower jaw.
Primary records are concentrated at the Colorado River main stem and the Grand Canyon tributaries, as well as the Colorado River drainages at Lake Mead. Blueheads are also found at Snake River above Shoshone Falls and Bear/Weber River drainages. There are scattered reports around the Bonneville Basin. Arizona Bluehead sucker distributions are more specifically the Clear, Bright Angel, Shinumo, Kanab, and Havasu Creeks rarely below Diamond Head. Some can be found near the Navajo Reservation and the San Juan drainage. Their biotic communities are restricted to aquatic wetland and riparian zones within Arizona, with a more restricted elevation distribution of 609 to 2060 meters.
Bluehead suckers prefer larger streams and rivers due to their larger size, however they can be found in a variety of habitats (Sublette et. Al. 1990). This species has a wide temperature preference as well, ranging from cold mountain brooks at 12 degrees Celsius, to warmer desert rivers at 27 degrees Celsius. If times are good and water is clear, the suckers will stay in shallow steams and eddies during the day, finding their way to hard-bottomed streams to forage at night. Primary spawning areas include a high concentration of juvenile minnows in the Grand Canyon Tributaries and Colorado River drainages. Populations will remain stable unless humans destroy habitats.
The Bluehead sucker has unique spawning techniques, which make it different from most of the other Arizona native fish. Arizona fish usually mate and breed during the winter months, due to specific physiological parameters and water temperature preferences. The Bluehead sucker is the opposite, preferring the spring/summer months and much warmer water temperatures, exceeding 15.72 degrees Celsius. Males will join females in gravel/sandy-bottomed streams and copulation begins, taking only a few seconds. In the Grand Canyon Tributaries, mating can extend even later into the year through April, May, and July. This species will not mate unless the water depth is strictly fewer than 1 meter, probably because the shallow water is easily heated to their desired temperature by the sun. Juveniles grow exponentially fast, reaching lengths of 60 mm and sexual maturity within the first year.
Suckers use their cartilaginous jaws to scrap the algae and detritus off the stones at the bottom, and despite any shortages of these foods, suckers show little seasonal movement. Diatoms, detritus, algae, and other organic debris have been found in the gut. Bluehead suckers are unique in that they are the only members of the genus to hybridize with other members of the same genus, increasing gene flow among species. They can also live to be more than twenty years old.
Haementeria ghilianii, the giant Amazon leech, is one the world's largest species of leeches. It can grow to 450 mm (17.7 in) in length and 100 mm (3.9 in) in width. As adults, these leeches are a greyish-brown colour, as opposed to juveniles, which do not have a uniform colour, but rather, a noncontinuous stripe of colour, and patched colouring. They live from the Guianas to the Amazon. The leech produces the anticoagulant protease hementin from its salivary glands.
Catostomidae is the sucker family of the order Cypriniformes. There are 80 species in this family of freshwater fishes. Catostomidae are found in North America, east central China, and eastern Siberia. They are not usually fished recreationally; they are not highly prized in North America for their flesh although they are a fairly popular target with spear fisherman, and in some areas, such as the Ozarks, they are a common food fish.
Their mouth is located on the underside of the head (subterminal), with thick, fleshy lips. Most species are less than 60 centimetres (2.0 ft) in length but the largest species can reach 100 centimetres (3.3 ft). They are distinguished from related fish by having a long pharyngeal bone in the throat, containing a single row of teeth.
Catostomids are most often found in rivers but can be found in any freshwater environment. Their food ranges from detritus and bottom dwelling organisms (such as crustaceans and worms), to surface insects and small fishes.
Catostomidae have been uncovered and dated to the Middle Eocene in Colorado and Utah. An enormous gap (36.2 million years) in the fossil record occurs from the Late Eocene to Early Pleistocene
They can be taken by many fishing methods including angling and gigging. Often species such as Catostomus commersonii and Hypentelium nigricans are preferred for eating. They can be canned, smoked or fried, however often small incisions must be made in the flesh (termed "scoring") before frying to allow small internal bones to be palatable.
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In journalism, a human interest story is a feature story that discusses a person or people in an emotional way. It presents people and their problems, concerns, or achievements in a way that brings about interest, sympathy or motivation in the reader or viewer.
Human interest stories may be "the story behind the story" about an event, organization, or otherwise faceless historical happening, such as about the life of an individual soldier during wartime, an interview with a survivor of a natural disaster, a random act of kindness or profile of someone known for a career achievement.