Crustacean

“ Given a bright sun, a light sandy bottom and clear water, a small crustacean swimming between the eye of the observer and the surface often will not appear to be like the creature when it is seen out of the water. ”

“ If we go still further back in time, we discover, in the oldest rocks of all, the remains of animals, constructed on the same general plan as the lobster, and belonging to the same great group of Crustacea; but for the most part totally different from the lobster, and indeed from any other living form of crustacean; and thus we gain a notion of that successive change of the animal population of the globe, in past ages, which is the most striking fact revealed by geology. ”

“ The crustacean class of animals, of which the lobster, crab, and shrimp are familiar examples, have this peculiarity of structure—that their soft bodies are inclosed within a coat-of-mail formed of carbonate and phosphate of lime. In fact, they carry their skeleton outside their [Pg 114] bodies, both for defense of the vital parts within, and for the attachment of the muscles which move their limbs, and every part of their frame. ”

“ Perhaps, as we are now on the subject of crustacea, we may just remind the reader of the wonderful conditions of growth which are common to the greater number of our shell fish. Lobsters, crabs, shrimps, prawns, crayfish,—in fact, the crustaceans generally, have to change their shelly covering in order that they may increase in size. During the first year of their age the crab and lobster must change their suit of clothes more than once, they grow with such rapidity ”

“ In monstrous plants we often get direct evidence of the possibility of one organ being transformed into another; and we can actually see in embryonic crustaceans and in many other animals, and in flowers, that organs, which when mature become extremely different, are at an early stage of growth exactly alike." ... "Why should one crustacean, which has an extremely complex mouth formed of many parts consequently always have fewer legs; or conversely, those with many legs have simpler mouths? ”

“ Most of the crustaceans live in water, a few being found in damp soil or in other moist places. Some are fresh-water animals and some marine. They vary in size from the tiny water-fleas, a millimeter long, to crabs two feet across the shell or sixteen feet from tip to tip of legs. They present great differences in form and general appearance of body, being adapted for various conditions of life. Some crustaceans live as parasites on other animals, in some cases on other crustaceans. Such parasitic species have the body much modified and are hardly to be recognized as members of the class. ”

“ As the crustaceans, excepting a few of the arrows indicating the direction the lowest, are covered with a hard shell of dead matter, they can not respire through the skin, and hence of necessity require special organs. ”

“ We have the further fact that the crustaceans, the highest marine animals of the annulose type, are predominant in the waters; and that in the mollusks the highest and lowest groups are most plentiful, the middle less so. The whole number of species is small, and this may arise either from our having here reached an early period in the history of life, or from our information being defective. ”

“ If we pass over the long series of the most ancient strata in which doubtful forms of obscure elementary plant and animal life appear almost together, we shall come to shell-fish, and crustaceans fully established in the water, and scorpions, and some insects even on land, before plants made any great show. For the Carboniferous—the age of acrogen plants, par excellence—does not occur till after swarms of Trilobite Crustaceans had filled the sea and passed away, and after the Devonian fish-age had nearly passed away ”

“ The fact of the Lobster or Crab throwing off its entire shell at certain seasons, to admit of the increased growth of the animal is a truly marvellous phenomenon, still, it would more excite our wonder were we to find that, instead of being cast away at all, the hard, inelastic envelope which surrounds the bodies of crustaceans was made to swell or expand proportionately with the soft parts of the animal! ”

“ In the Primordial or oldest fossiliferous rocks next in succession to those great Eozoic formations in which protozoa alone have been discovered, we find the remains of crustaceans, mollusks, and radiates—such as shrimps, shell-fish, and starfishes—which appear to have inhabited the bottom of a shallow ocean. ”

“ There are other crustaceans, next-door neighbors of the squilla, whose gills are still more simplified. Here the legs themselves are turned into extremely thin plates, which play the part of gills, and are thus organs for two purposes, serving at the same time to swim and breathe with.
We have in our house one little crustacean, the only one I know of who associates with men, and that is the wood-louse. You must know the little grizzly beast, which rolls itself up into a ball whenever it thinks itself in danger, and who would be taken for an insect by anyone who was not taught otherwise. ”

“ Often we went around tall, pointed rocks rising like pyramids. In their dark crevices huge crustaceans, aiming their long legs like heavy artillery, watched us with unblinking eyes, while underfoot there crept millipedes, bloodworms, aricia worms, and annelid worms, whose antennas and tubular tentacles were incredibly long. ”

“ The Crustaceans, so far as they are aquatic, respire by means of branchiæ, or gills. In the larger species these branchiæ are lamellous, or with filaments, whose supports are traversed by two canals, one of which leads the blood into the general economy, the other directs it towards the heart. These organs are enclosed in the body. ”

“ Excepting the eyes and phosphorescent spots beneath, which are bright red, the bodies of the crustaceans are almost transparent, yet such is the density of the schools in which they congregate that a distinctly reddish tinge is often imparted to the water. They are very active, and frequently avoid the rush of the fish by vigorous strokes of their powerful caudal paddles, which throw them several inches above the surface. ”

“ In many parts of the Primordial ocean the muddy bottom swarmed with crustaceans, relatives of our shrimps and lobsters, but of a form which differs so much from these modern shell-fishes that the question [44] of their affinities has long been an unsettled onfi with zoologists. Hundreds of species are known, some almost microscopic in size, others a foot in length. ”

“ These creatures, together with the mollusks, are often called shell-fish, although the "shell" of a crab is not in the least like the shell of an oyster, for example, or like that of a whelk, or a snail. It is only a sort of crust upon the skin, made chiefly of carbonate of lime. That is why these animals are called crustaceans; and instead of growing, like true shells, this coat never increases in size at all.
But crabs and lobsters grow? Yes: but not as other animals do, a little every day. They only grow, as a rule, once a year ”

“ We have gasteropods which, when the tide is down, habitually creep snail-like over sand and sea-weed, even up as far as high-water mark. We have several kinds of crustaceans, of which the crab is the most conspicuous, running about on the wet beach, and sometimes rambling beyond the reach of the water. And then note the striking fact that each of the forms thus habituated to changes of media, is allied to forms which are mainly or wholly terrestrial. ”

“ Most crustaceans are hatched from eggs, usually in a form very different from their parents; and they reach the adult state only after passing through a series of transformations quite as remarkable as those that a caterpillar undergoes in becoming a butterfly. All crustaceans, except a few much modified land forms, breathe by means of feathery or platelike gills which are always an appendage of the legs, where they appear as one or more lobes. ”

“ The body could be rolled into a ball when danger threatened, by bringing head and tail together.
These remarkable, extinct trilobites were the first crustaceans. Their nearest living relative to-day is the horseshoe crab. The fresh-water crayfish and the lobster are more distant relatives: so are the shrimps and the prawns. ”

“ We have just seen that the higher crustaceans, with their well-mounted eyes, their enormous antennæ, and their formidable pincers, are not all of them the great lords they pretend to be; more than one of them has to hold out its hand and to accept humbly the assistance of its neighbours. ”

“ Great numbers of crustaceans of more advanced types live in the open sea, and at all depths; and many of them assume extraordinary shapes. The space between tide marks, and the mud of salt marshes and tidal creeks abound in a wide variety of species, some of which are familiar to everyone who lives at or visits the seashore. Thus the sand and rows of drifted seaweed on all our eastern beaches are likely to harbor flocks of amphipods, well called "sea fleas" or "sand hoppers," which sometimes jump away before you in hundreds as you walk along. ”

“ Fish eat crawfish, which feed upon smaller crustaceans pulled with their pincers from beneath the flat rocks, while the crustaceans prey upon defenseless mollusks, and these forage upon microscopic fungi. ”

“ And now what will be the character of these new strata? They will necessarily contain scarcely any traces of life. 369 The deposits that had previously been slowly formed at the bottom of this wide ocean, would be sprinkled with fossils of but few species. The oceanic Fauna is not a rich one; its hydrozoa do not admit of preservation; and the hard parts of its few kinds of molluscs and crustaceans and insects are mostly fragile. ”

“ The liquid masses support the largest known species of mammals and perhaps conceal mollusks of incomparable size or crustaceans too frightful to contemplate, such as 100-meter lobsters or crabs weighing 200 metric tons! ”

“ My son, when examining these fishes, in his passage from Cape Verd to Rio de Janeiro, found in the cavity of their mouth an enormous female, firmly wedged in the branchial arches, with its head inclined outwards, and the male, which was rather smaller, installed at her side. Their dwelling thus by pairs, as well as the entire conformation of the animal, plainly shows that these crustaceans make themselves at home, and live as true messmates. ”

“ First, passing by that long series of geological formations in which no remains of life have been found, or only those of boneless or invertebrate animals, we find ourselves in a sea abounding in stone-lilies and huge crustaceans,190 having among them the small forms of the earliest fish known to us, those having gristly skeletons. ”

“ The crustaceans live within their shells or take advantage of ready-made refuges of limestone, expelling their former owners; the animal-plants exhale toxins; the planctonic beings, transparent and gelatinous, burn like a crystal exposed to fire; some organisms apparently weak and flabby, have in their tails the force of a carpenter's bit, perforating the rock sufficiently to create a cavern of refuge in its hard interior.... ”

“ Besides the above analogies between the. Trilobites and certain forms of living Crustaceans, there remains a still more important point of resemblance in the structure of their eyes. This point deserves peculiar consideration, as it affords the most ancient, and almost the only example yet found in the fossil world, of the preservation of parts so delicate as the visual organs of animals that ceased to live many thousands, and perhaps millions of years ago. ”

“ In the complex struggle for life it is quite credible that crustaceans, not very high in their own class, might beat cephalopods, the highest molluscs; and such crustaceans, though not highly developed, would stand very high in the scale of invertebrate animals, if judged by the most decisive of all trials — the law of battle. ”

“ Those who have made but a slight acquaintance with the common crustaceans of our shores must have noted the frequency with which imperfect specimens occur—specimens with missing appendages, or with a well-formed limb on one side of the body opposed to a puny and almost useless fellow on the opposite side. ”

“ In various crustaceans, belonging to distinct families, the anterior antennæ are furnished with peculiar thread-like bodies, which are believed to act as smelling-organs, and these are much more numerous in the males than in the females. ”

“ By means of millions of stinging cells on its four frilled lips and on its marginal tentacles it is able to paralyse and lasso minute crustaceans and the like, which it then wafts into its mouth. It has a very eventful life-history, for it has in its early youth to pass through a fixed stage, fastened to rock or seaweed, but it is a successful animal, well suited for its habitat, and practically cosmopolitan in its distribution. It is certainly an old-established creature. Yet it is very variable in colour and in size, and even in internal structure. ”

“ We now come to the Stalk-eyed Crustaceans (Podophthalmata) , which contain those members of the class most generally known, such as crabs, lobsters, shrimps, and prawns. In these the eyes are mounted on movable pedicels, the head and thorax are generally covered by a large shield called the carapace, and the appendages are adapted partly for seizing and masticating, and partly for locomotion. ”

“ In other crustaceans the transparent cones which are coated by pigment, and which properly act only by excluding lateral pencils of light, are convex at their upper ends and must act by convergence; and at their lower ends there seems to be an imperfect vitreous substance. ”