Substances & Homeopatic Remedies

Limulus cyclops

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Limulus polyphemus, Xiphosura americana, Polyphemus occidentalis

Etymology

Polyphemus: in Greek mythology, a Cyclops. He was a shepherd and the son of Poseidon. In the Odyssey, Polyphemus imprisoned Odysseus and his men in his cave. They gave him wine and then, when he was drunk, they blinded him and escaped, hiding under Polyphemus' sheep as they left the cave. A later legend tells of the giant's futile love for the nymph Galatea.

Family

Traditional name

English: horseshoe crab, king crab
German: Atlantischer Schwertschwanz

Used parts

Triturations of the dried blood.

Classification

Animalia; Mollusca - Molluscs; Arthropoda - Arthropodes;  Chelicerata; Merostomata; Limulidae

Keywords

Original proving

Limulus was introduced by C. Hering and partially proved by him and Lippe.

Description of the substance

Populations.
There are four living species of horseshoe crabs. Three species are found in the Indo-pacific Ocean, the other species is found along the eastern cost of North America.  All four species are similar in terms of ecology, morphology, and serology.
Populations of the three Indo-pacific species ranges throughout Southeastern Asia from the southern coast of Japan to the northern tip of Australia and westward to the coast of Sumatra, just north east of India. The population of two Asian horseshoe crabs species are consider to be threaten and the third species is on the endanger list.
On the other hand the population of the American species is estimated to be 2 to 4 million crabs. The American horseshoe crab ranges from the Gulf of Maine to the Gulf of Mexico. About 98% of the population is found between Cape May, New Jersey to Cape Hatteras, North Carolina. The highest concentration of crabs are found in the Delaware bay.
Concerns for the horseshoe crab has brought about regulations to protect the animal.

Migration, spawning.
Every year in the spring the American horseshoe crab migrates from the mid-Atlantic portion of the continental shelf, from depth up to 750 feet, to their nesting beach in the Delaware and Chesapeake bays. Vertically blanking the beach for miles, number of 2 crabs per square feet have been recorded during the spring mass spawning.
There are approximately 83% more male than females during the spawning. Thus female crabs are surrounded by males when they come a shore to lay their eggs. The male crab paired, or clasped directly behind the female in known as the suitor male crab. All other male crabs around the female are called satellite males. Satellite and suitor males both fertilize the female's eggs externally.
The reproduction of horseshoe crabs is unique. They are the only arthropod that has external fertilization and it occurs at the ocean's edge during high tide.

Nesting, development, molting.
Eggs are laid in "nests" which are buried below the sand. Nests maybe up to one meter deep and range on the beach from three meters above the low water line to the spring high tide mark. Each female crab is capable of lay up to 3650 eggs per nest. Development of the egg is mainly temperature related and varies according to the location of the nest in the beach. Under control laboratory condition eggs begin to hatch 14 days after being fertilized. In the development of the young crab, it will under go four molts in the egg before it hatches.

The young horseshoe crab hatches in a form call a "trilobite larvae". This larvae is a very hardy animal that can tolerate a wide range of salinity and temperatures. The trilobite larva carries a yolk sac that supplies the young crab with food. For this reason the larvae doesn't need to feed before it undergoes its first molting process after hatching. After this first molt the young crab resembles a miniature of the adult crab. In its first year the horseshoe crab will undergo the molting process six times. Juvenile crabs are four times more active at night than during the day.

Horseshoe crabs have a hard shell, or exoskeleton made of chitin. To grow, the crab must shed it exoskeleton by molting. The molting process involves the opening of a seam at the forward base of the prosoma. Then the crab then slowly crawls out of its old outer shell. As the new crab emerges from the shell it begins to take on water and swell to its new size. Molting can be difficult and dangerous procedure. If a crab takes on water to fast and swells up to large before emerging from the old molt, it may become entrapped in the old exoskeleton and die. New exoskeletons are soft for a short period of time. During this time the horseshoe crab is more vulnerable to predation.

Growth of horseshoe crabs is a stair step process. In each step of its growth, the crab will remain a certain size for a long period of time. Then the crab will shed its exoskeleton, and suddenly the crab
has become much larger in a very short time. Young crabs shed their shells in a few minutes a here as adults may require several hours to complete the process. Since horseshoe crabs do not retain any hard structure throughout its lifetime, it is very difficult to determine the age of an individual. The estimate life span for the American horseshoe crabs is any where between 16 and 40 years.

Colonization by sessile fouling organisms (epibionts) is the usual fate for solid surfaces in the marine environment. Limulus polyphemus, ceases molting upon reaching maturity and lives several years as an adult in an epibiont-rich milieu, yet it typically maintains a cuticle that is largely free of macroscopic flora and fauna. Indeed, it is in the interest of the animal to maintain its carapace free from such organisms, as colonization of the cuticle by green and blue-green algae can be fatal.

Predator and prey.
Horseshoe crab feed on nematodes, polychaete worms, soft shell clams and mussels. Because horseshoe crabs feed on juvenile mussels and clams, fishermen have long regarded these crabs as pest that should be destroyed whenever possible to protect their fisheries from predation.

There are a large number of marine and terrestrial animals feed on the eggs and young of the horseshoe crab. Sand shrimp, fiddler and blue crabs, American eel, killifish, weakfish, and summer and winter flounders are a few of these marine predators.

Horseshoe crab eggs provide a high energy resource that is a crucial food source for millions of migratory shorebirds. Many of these birds are on the endangered species list. These shorebirds gorge themselves on the eggs of the crab before continuing their migratory trip north to there nesting grounds. Some of these birds can eat up to 9,000 eggs per day.

Adult crabs do not as many predators. The sharp and strong jaw of the loggerhead turtle has no problem cutting through the hard shell of adult horseshoe crab. Pufferfish have been see feeding on the softer gills and legs of the crab, and adult horseshoe crabs have been found in the stomach con tents of leopard sharks. Sea gulls will attack and feed on the soft undersides of overturned adult horseshoe crab

The horseshoe crab is a docile animal and can easily be handled for a closer examination. It is not recommended to pick up the crab by the tail. The tail does not contain any poison and will not sting, but carrying the crab by the tail may cause injury to the horseshoe crab. The only way of getting injured is by mishandling the crab. While holding the crab, always be aware of where the tail is and where other people are standing. One place the crab should not be held is between the prosoma and opisthosoma. The back edge of the prosoma is sharp and can cause an injury. Claws of the horseshoe crab are not very sharp and the crab does not pinch very hard.  Biblio (3), (4), (8)


The horseshoe crab belongs in the large group of animals called Arthropoda, which includes lobsters, crabs, insects, spiders and scorpions. Even though it looks crab-like, the horseshoe crab is more closely related to scorpions and spiders.
Horseshoe crabs are not true crabs, but are actually closer in form to spiders and scorpions as they lack antennae and mandibles. Further separating the horseshoe crab from true crabs are its book gills, chelicera and the fact that it has seven pairs of legs rather than five. The horseshoe crab is a creature whose external appearance has remained relatively unchanged over the last 360 million years.

Over 300 million years ago, long before the dinosaurs appeared on earth, there were hundreds of kinds, or species, of horseshoe crabs and their relatives, the sea scorpions. Today sea scorpions are extinct, and only four species of horseshoe crabs remain. Three of these are in the Far East, from Japan through Vietnam; the fourth is found along the Atlantic Coast, from Nova Scotia south to Mexico's Yucatan peninsula. The scientific name for the Atlantic Coast horseshoe crab is Limulus polyphemus.

Because its basic body design has remained almost unchanged for millions of years, the horseshoe crab is often called a "living fossil". The horseshoe crab gets its common name from the "U" or horseshoe shaped of its shell, which is called a carapace. The carapace is the color of sand or mud. This helps the animal blend in with the muddy and sandy bottoms on which it lives.

Two pairs of eyes are on the rounded, front part of the carapace. The largest pair is located near the top, one on each side. These eyes are compound, like those of insects. They allow the animal to see in all directions and are good at detecting movement.  Two very small eyes are located on each side of a small spine found on the front of the shell.

Beneath the shell are seven pairs of appendages, four of which bear claws. The first pair, called chelicera, are small, and are used to push food into the mouth. The mouth is located at the base of the legs. Then come five pairs of long walking legs. The last set of appendages, the chelaria, are also small, and are used to help the first pair move food towards the mouth.

Though the eggs and flesh of Limulus polyphemus are not toxic to people (that of the other three species are), they are not eaten by people today. Years ago, however, Indians did eat the lump of meat in the abdomen that moves the tail. They also used the shells to bail water out of their canoes, and the tails as spear tips.

Today horseshoe crabs are important to people for their use in medicine. For over 50 years they have been used in eye research. They are easy to study because they have large eyes and a large optic nerve (the nerve that sends signals from the eye to the brain). Scientists have learned a great deal about how human eyes function from research on horseshoe crab eyes.

Chitin is a substance found in the shells, or exoskeletons, of horseshoe crabs, as well as other arthropods, such as lobsters, crabs, shrimps, spiders, beetles, and mosquitoes. It has received the attention of scientists because is non-toxic, biodegradabl e, and when processed to produce another substance called chitosan, can be used to produce a variety of important products.
Contact lenses, skin creams, and hair sprays can be made from chitin. It can be used to remove lead and other harmful metals that may be dissolved in drinking water, and clean certain harmful chemicals from wastewater. Chitin joins the fight against fat when it is added to foods. It has the ability to bind with fats and then passes them through and out of the body without being digested. Chitin can also be made into string used to sew up wounds and used in wound dressings. People do not have an allergic reaction to the stitches, which dissolve slowly, and the dressings actually promote healing.

To find a meal of its favorite foods - worms, mollusks and dead fish, the horseshoe crab crawls along the bay bottom, using its small first pair of legs as feelers to detect the presence of prey. When it comes upon a worm or clam the small claws pick it up and move it to the bristly area near the base of the walking legs. The horseshoe crab has no jaws and uses these bristles to crush the food as it moves its legs. This means that a horseshoe crab can only eat while it walks along the bottom.
Adult horseshoe crabs feed primarily on marine worms and shellfish, including razor clams and soft-shelled clams. Because they lack jaws, horseshoe crabs use the spiny bases of their legs to crush and grind their food items which they then push into their mouths. In turn, horseshoe crabs play an important ecological role in the food web. Adults are a major item in the diet of juvenile loggerhead turtles, a threatened species that utilizes Chesapeake Bay as a summer nursery area. Horseshoe crab eggs are also a seasonally preferred food item to several fin fish species.

Like many animals with shells, eventually a horseshoe crab outgrows its own, and must molt. This means it grows a new shell and leaves its old one. To do this, the old shell splits around the front edge, and the crab crawls out. At first the new shell is very soft, but it soon hardens, and the horseshoe crab is about one-quarter larger than it was before. Females are larger than males, and can grow to a length of 60 cm (24 inches).

Females lay eggs--approximately 88,000 each-- in clusters or nest sites along the beach, usually between the tide marks. Dependent on temperature, moisture, and oxygen, egg development usually takes a month or more. Upon hatching, the larvae are mobile and spend about a week swimming until they settle to the bottom where they molt. Juvenile horseshoe crabs generally spend their first and second summer on the intertidal flats.

Horseshoe crabs can tolerate a wide range of temperatures and have special physiological processes that enable them to survive low oxygen environments. Adult horseshoe crabs have been found burrowed into anoxic muds and intertidal flats at low tide but spawning adults will avoid anaerobic sediments in beach areas. They can move out of the water during their spawning and survive extended periods of time out of the water if their book gills are kept moist.


Biol Bull. 2001 Apr;200(2):169-76. Related Articles, Links  

 
Limulus vision in the marine environment.

Barlow RB, Hitt JM, Dodge FA.

Center for Vision Research, Department of Ophthalmology, Upstate Medical University, Syracuse, New York 13210, USA. barlowr@upstate.edu

Horseshoe crabs use vision to find mates. They can reliably detect objects resembling potential mates under a variety of lighting conditions. To understand how they achieve this remarkable performance, we constructed a cell based realistic model of the lateral eye to compute the ensembles of optic nerve activity ("neural images") it transmits to the brain. The neural images reveal a robust encocding of mate-like objects that move underwater during the day. The neural images are much less clear at night, even though the eyes undergo large circadian increases of sensitivity that nearly compensate for the millionfold decreasein underwater lighting after sundown. At night the neurral images are noisy, dominated by bursts of nerve impulses from random photon events that occur at low nighttime levels of illumination. Deciphering the eye's input to the brain begins at the first synaptic level with lowpass temporal and spatial filtering. Both neural filtering mechanisms improve the signal-to-noise properties of the eye's input, yielding clearer neural images of potential mates, especiallyat night. Insights about visual processing by the relatively simple visual system of Limulus may aid in the designof robotic sensors for the marine environment.

Cell Mol Life Sci. 2004 Jun;61(11):1257-65. Related Articles, Links  


Structure and function of coagulogen, a clottable protein in horseshoe crabs.

Osaki T, Kawabata S.

Department of Biology, Faculty of Sciences, Kyushu University, Fukuoka 812-8581, Japan.

Mammalian blood coagulation is based on the proteolytically induced polymerization of fibrinogens. Initially, fibrin monomers noncovalently interact with each other. The resulting homopolymers are further stabilized when the plasma transglutaminase (TGase) intermolecularly cross-links epsilon-(gamma-glutamyl)lysine bonds. In crustaceans, hemolymph coagulation depends on the TGase-mediated cross-linking of specific plasma-clotting proteins, but without the proteolytic cascade. In horseshoe crabs, the proteolytic coagulation cascade triggered by lipopolysaccharides and beta-1,3-glucans leads to the conversion of coagulogen into coagulin, resulting in noncovalent coagulin homopolymers through head-to-tail interaction. Horseshoe crab TGase, however, does not cross-link coagulins intermolecularly. Recently, we found that coagulins are cross-linked on hemocyte cell surface proteins called proxins. This indicates that a cross-linking reaction at the final stage of hemolymph coagulation is an important innate immune system of horseshoe crabs.

Bang was studying the circulation of blood using horseshoe crabs when he found that one of his crabs died as a result of a Vibrio bacterial infection. The infection caused a strange disease in which almost the entire blood volume of the crab clotted into a semi-solid mass. Other bacteria had not produced this sort of reaction at all. Bang began to investigate further and found that only gram-negative bacteria produced this reaction. Furthermore, heat-treated bacteria (dead bacteria) continued to produce the reaction so it wasn't a pathological disease but something different. His original 1956 paper describing his first observations is available here.
Bang noted that the reaction he was observing was very similar to a well-known endotoxin reaction in mammals, the Schwartzman reaction. Back at Johns Hopkins University, he pushed to have this new phenomenon researched more intensively. Jack Levin, a hematologist, joined Dr. Bangs laboratory. What they eventually found was the "fire alarm" system that could be used to detect, with exquisite sensitivity, the fever-producing endotoxins that are so dangerous to people.

Limulus lives in an aquatic world; the sea. The sea is almost literally awash in gram-negative bacteria. Millions can be found in a single gram of sediment. Bacteria that are both harmless as well as pathogenic (disease-causing).

Why is horseshoe crab blood blue?


The oxygen-carrying pigment in horseshoe brab blood is a protein called hemocyanin. It is very similar to the hemoglobinmolecule we have in our blood. Hemoglobin gets it's red color (which makes our blood red) from the iron molecule in the center of the protein. Hemocyanin contains a copper molecule which results in a blue color.
 
Limulus is an arthropod, a close relative to spiders. In fact more closely related to spiders than to true crabs. Arthropods possess a semi-closed circulatory system. We mammals have literally thousands of miles of blood vessels that carry blood to our tissues through vast networks of capillaries. Bacteria entering our bodies through these capillaries are initially limited in the area they can infect, having to fight their way into the body through these narrow channels, all the while in contact with the white blood cells that are our first line of defense.

The circulatory system of Limulus is far more open. Large sinuses exist that allow blood direct contact with tissues. There are many wide open spaces and bacteria entering a crack in the shell of a horseshoe crab have easy access to large internal areas of the crab, a potentially deadly scenario. Over the course of it's hundreds of millions of years of interacting with the bacterial swarms it coexists with, Limulus, like us, has developed exquisitely sensitive means for detecting the presence of bacteria through the LPS they shed into their environment.


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See the illustrations of Milne Edwards for a look at the eerily beautiful illustrations of the circulatory system of Limulus
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Limulus is cold-blooded. It can't raise it's body temperature to kill off an infection. Nor does it have the vast confusing network of blood vessels to contain an infection. It needs to act quickly, and sometimes even rashly. The soldiers of the immune system in Limulus are it's single type of blood cell, the amoebocyte. As it's name implies it is an ameoboid cell (it has motility). The cell itself is often obloid in the blood stream and perform most of the normal functions associated with blood cells, engulfing foreign or dead cells, transport and storage of digested materials, repair of wound sites, etc. The cells appear oval when seen inside a living crab and they are packed with small granules. These granules contain clotting factors that are released outside the cell when it detects the bacterial endotoxin. When the hemocyte is in the presence of endotoxin it changes dramatically, so much so that it was originally believed Limulus had several types of blood cells. The compact shape changes to an irregular amoeboid shape with numerous cytoplasmic processes streaming in all directions. The cell discharges the granules of coagulogen which empty the cell.

It's a very sensible system. Imagine a horseshoe crab has sustained a small injury. Seawater comes into contact with the tissue and bacteria come into contact with the blood and begin to enter (ie infect) the body of the crab. small bits of the cell wall slough off as the bacteria propels itself through the blood. A Limulus blood cells detects this tiny fragment and responds by releasing the contents of the granules into the surround medium. These granules contain a clotting factor, called coagulogen. The thought is that by clotting the immediate surroundings very quickly, the invading bacteria can become enmeshed and therefore stopped! Larger clots may not only stop enmeshed bacteria but serve as a barrier to the outside environment in the case of a severed limb or large incision. Bang found these clots to be very stable and prevented even Brownian motion in trapped bacteria.

The bottom line to all this is that Limulus contains an exceeding sensitive means to detect the presence of bacterial endotoxins that can be detected by the formation of a gel-like clot. This may not strike one as significant until one understands the impact of endotoxins on our health and healthcare systems.

Anything that goes into your body during surgery, by injection, or for therapy, has to be free of bacteria. If not, the recipient will get an infection. Not only must this material be sterile (meaning no living bacteria are present) but it must be pyrogen-free.! As was demonstrated long ago, our bodies, like the bodies of horseshoe crabs , respond to the presence or endotoxin, not just the bacteria. The industry of ensuring that injectable drugs, irrigation fluids, surgical tubing, etc are free of bacterial endotoxins is a big business. In the past, companies maintained large rabbit colonies. Rabbits, like use, are sensitive to endotoxin and if a suspect sample of saline injected into a rabbit caused a fever then it was contaminated. No fever, no contamination. This method was not only expensive (it isn't cheap to keep thousands of rabbits) it is also slow. A rabbit test might require 48 hours to obtain a result. A Limulus amoebocyte lysate (LAL) assay can take as little as 45 minutes. A suspect sample is mixed with reconstituted LAL and allowed to sit in a small tube. After 45 minutes the tube is inverted and if a clot has formed it will stick to the top of the inverted tube.