Popular Science Monthly/Volume 5/June 1874/About Crabs
WITH one's eyes kept open, how very much there is to excite interest in a summer stroll beside the sea! Marine life—the creatures that represent the life-zone that belts or fringes the great murmuring world of waters—is so peculiar, some exquisitely beautiful, as the sea anemones, others droll and grotesque, as the great class known as the Crustacea. The tide is out. See that bird with bill curving upward. A beautiful functional adaptation it is—for with it small stones are turned over so deftly, and thus its food, the sheltered worms, are exposed. It is the avocet. So we turn avocet, using a stick in the operation. Ah! we have disturbed a poor polydactyled refugee in his retreat. See how threateningly he snaps at us his two pairs of pincers like formidable blacksmith-tongs. What a crusty-looking fellow he is! Now he is off, running sidewise; for they can go "forward, backward, and oblique." There is speed enough, but the gait is so comical. But crabs are given to flank-movements. We determine to try one on him; so with the stick just touching him laterally, and a fillip, and he is on his back. At this point, Frank, who is always facetious, and who had just been saying that he had come from the Bowling Green (he meant Alley), says, we have knocked the poor fellow off his pins—and that it was a ten-strike, adding for our enlightenment, "Don't you see that crab stands on ten pins?" Now, it so happens in this connection that it is just on this "ten-pin" arrangement that the naturalist founds his division Decapoda as one of the three orders of the great class Crustacea. The decapods, or ten-footed, include the crabs and lobsters, and rank the highest in their class.
Those who cater to high-living are now announcing the arrival of "Soft-shell Crabs." We propose to give a succinct account of four of our commonest crabs, and shall in passing take note of these "soft shells."
An artist once made a picture of a child; a gay, graceful, romping, and petulant little one it was. It was years afterward, in another place, that he limned a youth, lovable and full of life. And it was long after this, and in some other place, that he painted the portrait of a full-grown man, with a countenance staid, stern, and uncompanionable. Although the artist did not then know it, the three paintings were of the same individual—it was simply the childhood, youth, and manhood, of one person. Many years ago the naturalist described a little crustacean which was noticed swimming gayly and briskly in the sea. It was a pert little thing, rather pretty, and very quaint. It had large, full eyes. In fact, they were enormously so for such a diminutive being. Between these great optics, projecting downward like the coulter of a plough, was a long, sharp spine. On each side of the body was a much shorter spine, and over this short spine on each side, and high up near the back, were two fan-like structures, almost suggestive of wings, as with these four it really sped its way through the water. Between these, and from its back, rose by far the longest spine, almost equal to its entire self in length. It was immensely long, yet delicate and sharp. This outré little thing received the name Zoëa pelagica. In rank it was considered an entomostracan, the lowest, the very pariah of the race. The naturalists also found another little crustacean, something larger, and not so testy-looking either. It had not the formidable spines, but it had feet on the abdomen, which Zoe had not. There were also other great differences. It had, however, like Zoe, large eyes; and so the systematists named it Megalops. Well, just here the joke comes in, if indeed we may suppose a joke possible in so serious a science as zoology, especially in the department of the crabs. But the fact was that Zoe, and Megalops, and Cancer, were but the childhood, youth, and adult stages of the same individual, namely, the crab. Now, as Cancer by common consent belongs rightly to the highest crustacean rank—that is, the decapods—so do Zoëa and Megalops.
The common edible crab of Europe has for its scientific name
Cancer pagurus. It is a much more massive crab than our edible crabs; individuals have been known to weigh twelve pounds each! Let the reader compare the cut of the European crab. Fig. 1, with that of the American edible crab (Lupa dicantha), Fig. 2. It will be noticed that our species has a sharp, spiny extension each side of the carapace, and a pair of oar-like, swimming legs behind. It is a much more active animal.
All crustaceans exuviate, or cast their hard, shelly covering at least once a year. It has been said quite graphically that "the new integument is so soft and yielding, and the muscles in such a flaccid condition, that the limbs are drawn through the small openings at the
joints, much as a sack nearly filled with some fluid may be drawn through an opening much smaller than the sack itself." It should not be forgotten, however, that the neck in the great claws, or nippers, is crossed by thin, knife-like blades, or plates of shell; and it is certain that in drawing out the thumbs they are cut into long shreds, which doubtless, when drawn out, come together immediately and heal.
As giving a peep at the private life of the European crabs, let us skim off the cream of a paragraph from Gosse. The naturalist has been exploring the rocks on the English coast, and says:
"Peering into a hole I saw a fine large crab. I pulled him out, and carried him home. There came out with him the claw of a crab of similar size, but quite soft, which I supposed might have been carried in there by my gentleman to eat. After I had got him out—it was a male—I looked in, and saw another at the bottom of the hole. Arrived at home, I found that I had left my pocket-knife at the mouth of the crab-hole. I returned; the crab had not moved. I drew it out. But lo! it was a soft crab, the shell being of the consistence of wet parchment. It was a female, too, and had lost one claw. What, then, are we to infer from this association? Do the common crabs live in pairs? And does one keep guard at the mouth of the cavern, while its consort is undergoing its change of skin? I have no doubt that the claw of its mate was unintentionally torn off in its efforts to effect some hold, when resisting my tugs in dragging him out."
But it is in America, after all, that the habits of crabs at their time of exuviation should be the best known. The soft-shell crab is condemned as food in Europe, it being considered as in a sickly state at that time, just as birds are when moulting. And may not this be so? However, in this country the procuring of the soft-shell crab is a great and profitable industry. Hence any intelligent "crabber" knows a good deal of their habits. For many years we knew an old fisherman. He was quite illiterate, but of more than the average intelligence of his class. He was an old "crabber" too. As he long supplied my family with fish, I often got him into conversation. But here I must be allowed to quote myself, as in the American Naturalist, vol. iii., giving the old man's own words: "I hev ketched soft crabs for market many a year. The crab sheds every year, chiefly in early summer. At that time the he one is mighty kind to his mate. When she shows signs of shedding, the he one comes along, and gets on the she one's back, quite tenderly-like, and entirely protects her from all enemies, whether of fishes, or of their own kind. She is now getting ready to shed, and is called a shedder. Soon the back begins to burst nigh to the tail. She is then called a buster. The he one is then very anxious to find a good place for her, either by digging a hole in the sand, or mud, or else looking up a good cover under some sea-weed. Here he brings her, all the time hovering nigh, and doing battle for her, if any thing comes along. She now—and it only takes a few minutes—withdraws from the old shell. And she comes out perfect, in every part, even to the inside of the hairs, the eyes, and long feelers, almost like the whiskers of a cat. At the first tide she is fat, and the shell is soft, just like a thin skin. She is then called a soft-shell, and it's the first-tiders that bring the high price. At the second tide she is perfectly watery, and transparent, and is then called a buckler; but she is not worth much then. At the third tide she is again a hard-shell, as she always was, only bigger."
"Have you seen all this with your own eyes?" we asked.
"Lor', sir, yes; hundreds and hundreds of times."
To the epicure, the soft-shell crab, when fried, is a great dainty. It is eaten entirely, like boned turkey; and, as a luxury, might be compared to a boneless fish. That it is an entirely unobjectionable food, is far from certain. It does not agree with every one, that is sure. It is a great business in New Jersey. Almost any morning, in summer, the sight may be seen at the Port Monmouth dock of unloading them from the cars on to the steamboat. They are shipped to market in boxes, each containing about six dozen of these soft-shell crabs, and covered on the top with wet sea-weed. Some idea of the importance of this business, while it lasts, may be formed from the fact that the neighborhood of Shark River will ship daily about five hundred dozen. These will bring, on an average, about $1.50 a dozen. When scarce, they bring almost fabulous prices. The business is, however, somewhat precarious. In some places, noted for being good, a seeming desertion sometimes occurs, which may continue for several seasons. Shark River is a good crabbing-ground, and yet it is subject to a closing up at the mouth by the washing up of the sea. When this occurs, the water is too fresh, and the crabs may perish.
The crabbers are now working more systematically. They build pens, or cars, out in the water, the top being opened to the light, and the sides being latticed, or made of laths, which admit the water freely. The bottom is covered with clean stones or coarse gravel. Into these the crabs are put as fast as caught, whether shedding or not; and, as fast as they shed, they are taken out.
As mentioned, our edible crab literally backs out of the shell; that is, it comes out at an opening behind. The Limulus, or horseshoe-crab, acts directly contrariwise. The shell cracks open at the front, and the animal emerges forward, instead of from behind, or backward. In fact, the structure of the shell makes this the only possible mode. A few years ago, the officers superintending the building of the fort at Sandy Hook became greatly interested at witnessing this exuviation of the shell of Limulus Polyphemus, and they declared that the fellow was spewing himself out of his mouth!
But we have two others to introduce—a brace of queer creatures they are, truly; and one of them is a positively "crusty customer." Some call him the soldier-crab; and certainly, if agility and seeming-courage make up the martial element, then a valorous little fellow he is. The males have one hand enormously large. This, when closed upon the front of the body, is suggestive of the attitude of a violinist—hence we boys used to call it the fiddler-crab, Fig. 3. The naturalist
names it Gelasimus vocans, a name highly expressive of its attributes. Some have rendered the words "calling crab." This is too far short of their significance. The words are intended to indicate both the action of the crab and its effect upon the beholder. When alarmed, they go scuttling over the mud to their burrows, the males each holding his great claw aloft, and waving it in a manner that looks ludicrously like beckoning, or challenging, and at the same time threatening, and this, too, while in full and masterly retreat. Each seems, as it might be, a Liliputian Falstaff; and, if rendered in Homeric strain, Gelasimus vocans would signify the "laughter-provoking challenger." Indeed, Gelasimus never sees anybody, whether great or small, but forth he hurls his challenge in pantomime, for up goes that threatening huge member, so that its owner appears to be habitually bent on something high-handed. As this swaying of the great fiddle-like claw seems to start and direct or animate the retreat, it is ludicrously suggestive of a musical conductor beating time by swaying a bass-viol instead of his bâton, the effect of his eccentricity being to cause a stampede of all the fiddlers. This crab excavates holes in the earth, a male and a female occupying one hole. Into this retreat it retires with astonishing celerity when alarmed, and, having gained its hole, it literally barricades the entrance, by turning round and closing it up with its big hand, leaving just room enough for the little keen eyes to keep a sharp lookout at whatever may be passing. In these burrows they spend the winter, probably in hibernation. More than once, when pursuing the fiddler who, with fiddle aloft, ran swiftly, has the writer had the luxury of a slip and fall on the slimy clay of Fiddler Town, as we called a certain place in the salt-meadows, where these fiddlers lived. Those mishaps were really enjoyable—that is, to those who looked on.
There is a group of crabs which has a curious habit, made necessary on account of the unprotected condition of the hinder part of
their bodies. This is entirely naked; hence these crabs occupy the empty shells of sea-snails, winkles, and such univalves. It is called the hermit-crab, or Pagurus, by the systematists,Fig. 4. The most common species on the Atlantic coast is the little hermit—Pagurus longicarpus. A pair of nippers at the extremity of the tail, or naked abdomen, enables it to grip the columella, or upper part of the inside of the shell that it occupies, thus keeping itself snugly in place. As the crab increases in size by growth, it has to change its home for one more roomy; and this leads to some remarkable exhibitions of its instincts. The sight, which we have often beheld, is one of exciting interest. Watch, now, if you please. Here is a fat little hermit-crab, whose domicile, like a strait-jacket, has become decidedly uncomfortable, and he is somewhat distracted about it. He is out a house-hunting—that is a literal fact. See, he has found an empty shell. It is not so handsome as the one he now occupies, but it is a little larger. Look, how he almost lifts it up among his ten feet, every one of which is an interested inspector, as each must bear its part in sustaining the establishment. Now he rolls it round and round, all over and over, delicately manipulating its sculpture occasionally; he is not only testing its specific gravity like a philosopher, but also seems to have an eye to appearances. Now comes the most essential, the inspection of the interior. Will it fit? That is the chief consideration. He inserts his longest finger, and thoroughly probes the whole matter. One more trial— and now it seems that the antennæ, or feelers, enter into the consultation. And what an amount of feeling deliberation does this step involve! Well, the thing appears to be satisfactory. It is evidently decided that the new house will answer. And now comes the most trying time of all—for "moving" is a trying time. But Pagurus is actuated by considerations that fall not to the lot of migratory mortals of the bipedal sort. His accountability is of the ten-talent order. With his eyes he surveys the entire situation. What! Yes, it is so! He has moved, and settled, and has got the house "all to-rights." The whole thing was done in the twinkling of an eye. It vacates the old house, whisks its tail round, and enters the new one backward, as if shot into it from a gun. In fact, unless watching intently, the whole movement will elude the eye, like a trick of legerdemain. And the cause is not far to seek. If that soft, nude, defenceless body were exposed but for an instant, it might become the prey of some darting fish.
These hermit-crabs are highly pugnacious. We once took a pair of them that we suspected of being anxious to change their houses. They were put in a vessel of sea-water, and, full in sight of them, was placed an empty winkle-shell, which we supposed was of the right size. How they did fight for it! It was a battle for life. One succumbed, at last, and died. The survivor coolly surveyed his victim, and then surveyed the new premises. After this, he promptly entered into possession; and then, pitiful to relate, he fell-to eating his defunct comrade. Oh, the cannibal!
The cut (Fig. 4) given of a hermit-crab shows actinea, or zoöphite, upon the shell. These are sometimes called sea-anemones, and animal flowers, on account of their being real animals, with a flower-like form.
The class Crustacea, which embraces the creatures of whom we have given this brief sketch, is immense in the number of species which compose it; and these have a wide range of size, some being so small as to be only discernible by the microscope, while some are many feet in length. The hugest of them all is a spider-like creature, the Macrocheira or long-armed crab of Japan. The cabinet of Rutgers College, New Jersey, contains one of them. It is the Macrocheira Camperi. We made an actual measure of it, and found that, with its long limbs extended, it had a length of eleven feet six inches. This specimen is probably the largest known.
After a while, a crab ceases to grow. Of course, then all enlargement stops, and. it is no longer necessary for it to get new clothes, as the old ones are large enough. It is liable now to become the victim of the strangest sort of parasitism. In the British Museum is an old crab of the edible species, with some half-dozen oysters of large size growing on its back, which load, ever increasing, the old crab was doomed to carry to the end of its days. A singular piece of imposition—and enough to make crabbed the disposition of the most amiable. Another specimen preserved is that of a hairy crab, whose habit seems to have been to encourage the presence of sponges. And it got "sponged on" with a vengeance, seeing that it is not larger than a walnut, and yet is saddled with a sponge as big as a man's fist.