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The living FOSSIL

limulus polyphemus

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Kingdom: Animalia

Phylum: Arthropoda

Subphylum: Chelicerata

Class: Merostomata

Order: Xiphosura

Family: Limulidae

Genus: Limulus

Species: L. polyphemus

Scientific classification

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Nomenclature

#Limulus: (odd) it was thought

to have only one eye.

Horseshoe

King crab: protect crabs

Big brown

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Evolution

• The Limulus is a "living fossil“

• NOchange in the last 445 million yearsold.

• origin dates back to Triassic times, over 200 million years ago, a time when the first dinosaurs and primitive mammals appeared .

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Limulus can reach maturity in nine to 11 years

Maturity

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Habitat

• Limulus is found along the Atlantic coast .

• spending summers in the shallow coastal waters.

• winters offshore in the mud.

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migration

• main area of annual

migration is Delaware Bay

(The male is smaller than the female.) when female goes ashore to lay her 200-300 dark greenish eggs in a depression in the sand. The males then release sperm which fertilize the eggs.

Red Knot eats the eggs

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Mouth

• Mouth shifted to be between legs (Merostomata).

• He uses his specialized strong front legs (gnathobase) to accomplish this grasping .

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feeding

feeding on sea worms and young clams

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Breathing • By gill books do much the same things as lungs. • Five in number, each gill book

contains 100 "leaves"

• The total surface area is large enough to permit the exchange of oxygen and carbon dioxide.

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• the gill books can sometimes be used by the animal as paddles while swimming upside down in the water .

• it also allow them to breathe underwater .

• also allow them to breathe on land for short periods of time

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Carapace & molting• Because Limulus has a

hard outer shell (called an exoskeleton) .

• it has to shed (molt) its shell periodically in order to grow.

• Many of the "dead" Limuli you find on

The beach is not dead, but the castoff shells of molted Limuli

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• Once a Limulus sheds its old shell, it has a new, soft one that hardens

In about 12 hours.**it leaves exuvium back in

contract to other animals.

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Tail

• Tail is not a weapon.• If horseshoe crabs get turned

on their back in the surf and get stranded on the beach, they use their long tail to turn over. If they cannot get turned back over they die.

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Eye• Limulus has four eyes - two small, simple eyes up forward and two larger, compound eyes (much like a fly's

eyes) on either side of the shell.

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Eye Research• Much of what we know about the

function of our eyes is the result of studies that began over 50 years ago on the large, compound eyes of the horseshoe crab.

• Its eyes have a relatively simple construction, and the optic nerve is readily accessible.

• it is easy to keep Limulus alive in the laboratory, making it an ideal animal for eye research.

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• In 1967, Dr. H. Keffer Hartline received the Nobel Prize for his research on horseshoe crab vision.

He discovered how sensory cells in the retina help the brain process visual cues, enabling horseshoe crabs to see

lines, shapes, and borders.

This mechanism, called lateral inhibition, allows horseshoe crabs to distinguish mates in murky water.

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Research of this type is helpful to :

• understanding human eye diseases like retinitis pigmentosa, which causes tunnel vision and can lead to total blindness

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Chitin Research• horseshoe crabs have a hard outer shell,

or exoskeleton, that provides protection from predators.

• Millions of tightly interwoven strands of a cellulose-like material called chitin serve as a tough and flexible glue that holds together the shell .

• The chitin in horseshoe crabs is favored for research over that found in other arthropods because it is very pure. Chitin is natural, non-toxic, non-allergenic, anti-microbial.

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Check Out the Many Uses of Chitin!

• chitin had wound-healing which enhanced healing time by 35 to 50%.

• make dressings for burns which accelerate healing and reduce pain

• anti-bacterial sponges.• contact lenses , tumor inhibition,

blood cholesterol control, and tampons.

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when chitin is heated with a chemical solution called Chitosan that has some advantages over chitin because

* it is more water-soluble.• good for cleaning up toxic organic

compounds. • can bind with fat, acting like a

sponge in the digestive tract. without ever entering the bloodstream.

• Seeds treated with chitosan are larger and stronger and more resistant to fungal diseases .

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limulus Blood• Human blood is red because it has a

red pigment called hemoglobin which contains iron. The Limulus blood pigment hemocyanin contains copper so it has blue color .

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LAL Research • Limulus amoebocyte lysate.• It's a very sensible system.• Seawater comes into contact with the tissue and

bacteria come into contact with the blood and• begin to enter (i.e. infect) the body of limulus. • small bits of the cell wall slough off as the

bacteria propels itself through the blood.• 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.

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coagulogen

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One liter of LAL is worth $15,000!

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LAL applications• in the initial management of peritoneal

dialysis patients with peritonitis .• Sterile medical equipments.• Can detect and kill bacteria, virus .• LAL early diagnosis for• leukemia.• Anemia.• Mental disorders in babies.• Meningitis.• Vitamin deficiency.

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