CRABS WITH FUR GLOVES.

Otago Daily Times, Issue 20291, 27 December 1927, Page 14

CRABS WITH FUR GLOVES.

ORIGIN OF A RARE LUNG DISEASE. The London Zoo has just received from a dealer in Germany a batch of exceedingly interesting fresh-water crabs. They are about the size of ordinary green shore crabs. The most striking thing about them is that their claws are covered with a brown silky down, which gives them the appearance of wearing a pair of , fur gloves. This adds greatly to their invisibility when at rest, for tne crab holds its claws in front of itself, and the fur, being set in motion by currents in the water, makes a screen indistinguishable from brown water-weed. The crab is thus safe from any passing enemy, while ever watchful for its unsuspecting prey (says the Zoological correspondent of the Morning Post). Hitherto this species of crab has only been known to live in the rivers of Japan and China, but the specimens which are now to bo seen in the insect house at the Zoo were collected from the Elbe, in Germany, where they made their appearance some little time ago. No one seems to know how they were introduced into Europe, but evidently the conditions in the Elbe so nearly approach those of their normal habitat that they are flourishing and multiplying. In the Far East they form a table delicacy, and are the chief ingredient of a special sauce which is eaten in an uncooked form. This gives rise to a rare and interesting lung disease known as _ Paragonimiasis. The symptoms are similar to those set up by tuberculosis of the lungs, and severe hcemorrh ages may occur. Various animals, as well as man, are subject to the disease, and it has been found in pigs, tigers, and other cats. The actual cause of Paragonimiasis is a small fluke which spends its adult life in the lungs, but which in the oourse of its development has to pass through a freshwater snail and one of these “ mittened crabs” before it can attain a state in which it is able to infect man or beast. Briefly the life cycle in which this crab is involved is as follows: The fluke in the lungs lay many eggs, which are coughed up and find their way into the waters of the nearest stream. Here they hatch and give rise to little mobile bodies, which are especially attracted towards a certain species of snail, in whose liver they develop and multiply. After a few days the infected snail begins to discharge still smaller bodies, which swim through the water with lashing tails. Each of these is armed with a spike in the head, by means of which it bores through the crab’s armour and, finding its way to the soft muscles, curls up and waits until its host is made into sauce and eaten, when it again wakes up, and, migrating to the lungs of the unfortunate gourmet, grows into an adult fluke onoe more. '

The fluke was first discovered in man by the late Sir Patrick Manaon in 1880, but its fascinating life cycle was not elucidated until qui e recently, and it required the brains of four of Japan’s cleverest scientists to do so.