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One leech in southern Chile (Macrobdellci valdi- 

 vicma) reaches a length of 30 inches as a burrower 

 in soil, probably depending for food on earthworms 

 and insects; otherwise the 12-inch horse leeches 

 (Haemopis) acting as predators in ponds and lakes 

 over much of the world hold the record for size. 



One leech (Haeinodipsa) in the moist jungles of 

 southern Asia is terrestrial, and stays on foliage or 

 tree trunks beside animal trails as much as 1 1.000 

 feet above sea level in the Himalayas. Holding firmly 

 by its posterior sucker, it reaches out its slender 1 -inch 

 body, ready to catch a victim and be carried while 

 collecting a blood meal. The bite is painless but is 

 often followed by an ulcer due to infection of the 

 wound. And a few dozen of these leeches can with- 

 draw substantial amounts of blood, since each is un- 

 willing to drop off before its dimensions resemble 

 those of a small cigar. Other leeches live in ponds and 

 streams, the sea, and wet soil. 



Marine leeches are encountered on sharks and 

 rays, although smaller kinds attack a variety of bony 

 fishes. Branchellion is a very active leech which is as 

 much as 9 inches long, highly distinctive because the 

 sides of its dark-colored body bear lobed, fleshy, 

 overlapping gills. Pontobdella has only little tuber- 

 cles over the surface of its 3-inch cylindrical body. 

 Both of these attack skates, but Pontobdella appears 

 to favor sharks, especially the hammerhead shark. 

 Smaller leeches, 1 inch or less in length, are some- 

 times found among the gills of bony fishes. Smooth- 

 bodied Piscicola is commonest on flounders, attach- 

 ing itself to the upper side. Tnichelobdella, with con- 

 spicuous transverse wrinkles, seems less selective. 



Even the method by which a leech's sperm cells 

 reach the eggs seems bizarre. Each leech is a her- 

 maphrodite, with both ovaries and testes. At mating 

 season, one leech deposits on the back of another a 

 small mass of mucus loaded with sperm cells. The 

 mass remains cemented in place until the body wall 

 becomes irritated and develops an open sore. Through 

 this gap in the body defenses the sperms penetrate 

 and work their way through the blood spaces to the 

 ovaries, fertilizing the eggs there. Meanwhile the mu- 

 cus mass drops off and the skin heals over. 



In fresh waters the turtle leech Placobdella is often 

 found clinging to the skin at the base of the hind legs 

 of pond turtles, including snapping turtles. While un- 

 molested, its body remains broad, flat, and hand- 

 somely patterned in yellow on a green background. 

 But if disturbed, Placobdella drops off and curls into 

 a ball that sinks quickly to the bottom. 



Glossiphonia. the common flattened leech of run- 

 ning water, has a similar shape and color pattern. 

 Both of these leeches are interesting because they 

 lay their eggs in large gelatinous capsules, and each 

 parent carries a capsule attached to the undersurface 



of the body until the young hatch out. Sometimes the 

 young leeches cling for a week or more to the par- 

 ent's back, and drop off one at a time. This may help 

 get them distributed more widely as the parent swims 

 about. 



Other leeches ordinarily deposit their eggs in a flat 

 cocoon, attaching this to a stone or other firm sup- 

 port in the water. In a few kinds the parent remains 

 close to the eggs and protects them from disturbance 

 for as much as three consecutive months. 



The common bloodsucker Macrobdella is dark 

 olive-green, with a thin body as much as 6 inches 

 long and Vi of an inch in width. It frequents ditches 

 and pond margins hunting for food of many kinds: 

 frog's eggs, tadpoles, worms, and insect larvae. It is 

 particularly sensitive to any vibrations in the water, 

 however, and comes swimming to get a blood meal 

 from fish, frog, turtle, cow, or man. 



Picnickers should know that it is far easier to get 

 an attached leech to drop off by sprinkling a little 

 salt on its body than by pulling at the slippery, elastic 

 animal itself. The same recipe is effective with the 

 jet-black or chocolate-brown Herpohdella, which 

 manages to get a blood meal occasionally despite the 

 fact that its mouth has neither jaws (as have Haemo- 

 pis and Macrobdella) or a stabbing muscular pro- 

 boscis (as is found in Placobdella and Glossiphonia). 



The medicinal leech Hinido medicinalis has gone 

 somewhat out of fashion, although it may still be 

 purchased over the counter of pharmacies in big cities 

 of America, and more readily on the European con- 

 tinent and throughout Asia. It is cultured deliberately 

 in fish ponds, especially carp ponds, in Europe and 

 the Orient, and has become a relatively docile ani- 

 mal. Medicinal leeches released in New World lakes 

 and streams have often succeeded in colonizing 

 American waters. 



Hinido medicinalis is so easy to handle that it will 

 attach itself where guided. With its clot-liquefying en- 

 zyme hirudin it can remove the color-producing evi- 

 dence of a bruise or a black eye. Or, in the hands of 

 primitive medicine men, it will draw off load after 

 load of "bad blood" in the practice of blood-letting. 

 Application of a little salt to the engorged leech in- 

 duces it to disgorge; the freshly washed leech is then 

 ready for another meal. 



So common was this use of leeches in the Middle 

 Ages that physicians became known as "leeches." In 

 1846 the French physician Moquin-Tandon calcu- 

 lated that between twenty and thirty million leeches 

 were used annually in his country. By 1863 the hos- 

 pitals in Paris were requisitioning close to six million 

 leeches a year, those in London another seven mil- 

 lion. The requisitions usually specified full-grown 5- 

 to 6-inch adult leeches because these have the largest 

 capacity for blood. 



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