is centrifuged to separate the 

 amoebocyte, or blood cell, from 

 the plasma. The freeze-dried 

 product of the cells is used in the 

 iysate test. 



"This is an in vitro test for fever- 

 producing subtances that are 

 found in drugs or devices," Finn 

 says. 



At more than $15,000 a quart, 

 Iysate is still more cost-efficient 

 than its predecessor. It replaces 

 the more cumbersome, expensive 

 and less sensitive rabbit test, in 

 which test solution was injected 

 into the bloodstream of a live 

 rabbit. 



The animal was subsequently 

 monitored for fever, shock or 

 death. Drugs causing even a 

 fever in rabbits were rejected. 



The Iysate test is a simple one, 

 in which a small amount of the 

 Iysate reagent is mixed with an 

 equal part of the solution to be 

 tested. After about an hour of in- 

 cubation at body temperature, the 

 mixture is examined. A clot indi- 

 cates the presence of bacteria. 



The case of the tainted swine 

 flu vaccine in 1976 apparently 

 resolved the rabbit-versus-crab 

 debate. The Iysate test, the sole 

 detector of the deadly endotoxins 

 in some of the vaccine, emerged 

 the victor. 



Following that incident, the FDA 

 provided guidelines for use of 

 Iysate in testing drugs, blood prod- 

 ucts, intravenous fluids and medi- 

 cal devices such as syringes. 



In addition to these uses, re- 

 search continues into lysate's 

 clinical applications. 



Lysate's use as a diagnostic tool 

 for bacterial diseases has been 

 limited by its inability to differen- 

 tiate between species of bacterial 

 toxins. This distinction is neces- 

 sary for prescribing antibiotic 

 therapy. 



Still Iysate has contributed to 

 diagnoses of many diseases, in- 

 cluding spinal meningitis, urinary 

 tract infections and gonorrhea. 



Carl Shuster, adjunct professor 

 at the Virginia Institute of Marine 

 Science and a pioneer of horse- 

 shoe crab research, is building a 

 library about the animal at the 

 school. 



In evidence of the rapid research 

 strides made since its introduc- 

 tion, Shuster says information on 

 Iysate work alone nearly equals 

 that on the animal's history. 



And when you talk horseshoe 

 crabs, you're talking history. Hun- 

 dreds of millions of years of it. 



The earliest ancestor of the 

 horseshoe crab, the aglaspids, 

 swam the waters 500 million years 

 ago. 



The horseshoe crab is really not 

 a crab at all. It's a member of the 

 same phylum as crabs- 

 arthropod— but is most closely 

 related to spiders and scorpions. 



The animal has three segments: 

 the head and chest region, cov- 

 ered by a hard shell or exoskel- 

 eton; the abdomen, carrying its 

 six pairs of appendages; and its 

 spiny tail or telson, used for 

 leverage. 



The horseshoe crab's eyes are 

 also medically important. Much of 

 what we know about human vision 

 has stemmed from research on 

 the animal's large compound eyes 

 and long optic nerve. 



One must wonder about the 

 animal's chance of survival amid 



the demand and virtual require- 

 ment for its blood. 



"There's no doubt we've got to 

 start getting a serious handle on 

 population dynamics," says 

 Shuster, but he noted that labora- 

 tory bleeding is not to blame for 

 high mortality. "The biggest im- 

 pact is when they take them for 

 fisheries, cutting them up for eel 

 bait and conch bait." 



Experts believe that laboratory 

 bleeding does not significantly in- 

 crease horseshoe crab mortality. 

 And crabs can regain their blood 

 volume in three to seven days, 

 though it takes months to regen- 

 erate amoebocytes. 



A study by Anne Rudloe in the 

 early 1980s, in which 10,000 

 crabs were tagged and half were 

 bled, revealed a 10 to 11 percent 

 increase in mortality among bled 

 crabs. 



"Crabs have been found two 

 years after being bled breeding 

 on beaches," says Finn, who is in- 

 volved in a tagging program with 

 Shuster to learn more about the 

 animal. 



The horseshoe crab has co- 

 existed all these years in a "soup" 

 of aquatic bacteria and toxins. 

 The reaction of its blood to invad- 

 ing bacteria suggests a sort of 

 primitive immune system that has 

 helped the animal— and mankind— 

 to survive. 



