Aquatic animal

“ LEVIATHAN, n. An enormous aquatic animal mentioned by Job. Some suppose it to have been the whale, but that distinguished ichthyologer, Dr. Jordan, of Stanford University, maintains with considerable heat that it was a species of gigantic Tadpole (Thaddeus Polandensis) or Polliwig—Maria pseudo-hirsuta. ”

“ The integuments of the aquatic animals are many in number. Some are covered with a hide and hair, as the sea-calf and hippopotamus, for instance; others again, with a hide only, as the dolphin; others again, with a shell, as the turtle; others, with a coat as hard as a stone, like the oyster and other shell-fish; others, with a crust, such as the cray-fish; others, with a crust and spines, like the sea-urchin; others, with scales, as fishes in general; others, with a rough skin, as the squatina, the skin of which is used for polishing wood and ivory; others, with a soft skin, like the muræna ”

“ Aquatic mammals which pass their lives entirely, or, for the greater part, in the water are, of course, subject to very different laws of distribution from those of the terrestrial forms. As regards aquatic mammals, land is of course an impassable barrier to their extension, and, subject to restrictions in certain cases, water offers them a free passage. ”

“ A favored feeding site is often the head of the pool, where a trout will have the first chance to seize insects or other organisms carried into the pool. It also has the option of hunting many of the forms of life that live in the stream with it: insect larvae and nymphs of many kinds, aquatic beetles and spiders, crayfish, leeches and worms, water-mites, snails, salamanders, tadpoles, and the smaller fish. ”

“ The stream of water also passes but once along the gills of fish, as it is sooner deprived of its virtue; whereas the air is both received and ejected by the action of the lungs of land-animals. The whale seems to be an exception to the above, as he receives water and spouts it out again from an organ, which I suppose to be a respiratory one. As spring-water is nearly of the same degree of heat in all climates, the aquatic plants, which grow in rills or fountains, are found equally in the torrid, temperate, and frigid zones, as water-cress, water-parsnip, ranunculus, and many others. ”

“ As would be expected, the greatest modifications of structure in the adaptation of air-breathers to water life are found in the limbs. No other parts of the body have such different functions in water and on land as the limbs and fins. The limbs of a dog, or a cat, or a man are feeble organs for swimming in comparison with the fins of a fish, and if the land animal must compete with fishes to prey upon them for food it must acquire like swimming powers. ”

“ At 614 sea it flies at a small height, but when flying over the land, or even when approaching it, should there be any suspicion of danger, it rises to a considerable height. Its food consists of shrimps, small fishes, roe, aquatic insects, and mollusca, which it procures by diving. The flesh is dark, and generally tastes of fish, but that of the female is good during the period of her sojourn on the fresh-water ponds.
The male takes three years to acquire his full plumage, although many individuals breed in the second year. The female is perfect in the second spring. ”

“ And now, having got the aquarium in order, comes the point how to keep it in order,—how to keep the creatures alive, and how to prevent the water from growing cloudy and thick. The main rule is to secure sunlight,--hot enough to raise the water to a temperature above that of the outer air,-- to remove all dirt and floating scum, and to furnish the tank on every cloudy day with a supply of air and with motion by means of a syringe. The creatures should never be fed in warm weather with any animal substance, its decay being certain to corrupt the water. ”

“ As a rule they prefer shallow water, in which, when not feeding, they lie near the bottom. In deeper water they often float, with the body much arched, the rounded 542 back close to the surface, and the head, limbs and tail hanging downwards. The air in the lungs assists them to maintain this position. Their food consists exclusively of aquatic plants, on which they feed beneath the water. ”

“ The principles on which aquaria should be kept are now pretty generally understood. There should always be a small quantity of growing aquatic vegetation, and a supply of minute life to furnish food for the larger forms. Excess of light should be avoided, and the temperature should not be allowed to rise much above 50° F. Carnivorous beetles and their larvae may be fed with small pieces of meat, small garden worms, or tadpoles. ”

“ It can never acquire new material, never get new fingers and toes, new organs or parts of organs; all its possibilities lie in the improved and new uses it can make of the material which it received from its ancestors.
The beginning of aquatic adaptation of the limbs lies in the membranous webs between the toes of frogs, salamanders, ducks, seal, otters, etc., where the feet are used largely or entirely for propulsion through the water, in the absence of a propelling tail. And this membrane, in the majority of cases, is the extent of aquatic adaptation in air-breathing animals. ”

“ As some sea-gentlemen are much more rapacious than others, and as some prey upon others, the arranging of them must have been very like the old puzzle of the fox, the goose, and the bag of seed. Then when new creatures arrive it necessitates fresh arrangements.
There is not much vegetation as yet in the tanks, which may puzzle some people who have been accustomed to balance the animal and vegetable life in their aquaria by introducing full-grown sea-weeds. ”

“ In most fish, and in all the rudest types, the swim-bladder is merely a float or balloon, which can be filled with air, and compressed or expanded, so as to make the animal rise or sink at pleasure. But many fish exist in tropical ponds and shallow swamps to whom what has happened artificially to the carp in my friend’s ornamental water happens naturally every dry season; the marshy sheets in which they live evaporate altogether, and they are therefore compelled to lie dormant in the mud without food or drink for many weeks at a time. ”

“ Fishes are readily kept in captivity in properly constructed aquaria. Unless injured in capture or transportation, there are few species outside the deep seas which cannot adapt themselves to life in a well-constructed aquarium.
Reproduction of Lost Parts.—Fishes have little power to reproduce lost parts. Only the tips of fleshy structures are thus restored after injury. Sometimes a fish in which the tail has been bitten off will survive the injury. The wound will heal, leaving the animal with a truncate body, fin-rays sometimes arising from the scars.
[Pg 151] ”

“ They swim about in companies of some hundreds, and frequent the still water of deep pools, will not take a bait, and are only seen when the water is clear. Then it is a delightful sight for any one to lie upon the bank of some ti-tree-fringed creek or pool, when the sun illumines the water and reveals the bottom, and watch a school of these fish swimming closely and very slowly together, passing over submerged logs, roots of trees or rocks, their scales of pure silver gleaming in the sunlight as they make a simultaneous side movement. ”

“ The miserable fish, flying for their lives, speed towards the shallow water, and often, unable to stop themselves, are carried by their impetus out on the mud and lie there on the land for a few seconds till they leap back again. Even the jack will sometimes run himself aground in the eagerness of his pursuit. Looking over the pool, the splash of the falling fish as they descend after the leap into the air may be heard in several directions at once, and the glint of their silvery sides in the sunshine is at the same time visible. ”

“ Here will be found hydroids, sea-anemones, starfishes, sea-urchins, barnacles, mussels. In the shallow water, crabs and shrimps are crawling along the sandy bottom or are lying concealed in the mud, while schools of little fishes scoot across the pool. If a fine silk net is drawn through the water and then emptied into a glass dish a whole new world of creatures will be revealed—jellyfishes, ctenophores, hydroids, eggs of fish, tiny copepods, the larvae or young of sea-urchins, starfishes, or oysters. ”

“ Thus generalized fishes should be considered those of medium size, medium defenses, medium powers of progression, omnivorous feeding habits, and wide distribution, and these might be regarded as having provided the staples of survival in every branch of descent.
"Aquatic living has not demanded wide divergence from the ancestral stem, and the divergent forms which may culminate in a profusion of families, genera, and species do not appear to be again productive of more generalized groups. ”

“ Why, as a general rule, are aquatic, and especially sea birds, very numerous in individuals? Not because they are more prolific than others, generally the contrary; but because their food never fails, the sea-shores and river-banks daily swarming with a fresh supply of small mollusca and crustacea. ”

“ Fishes which deposit their eggs in water that contains only a limited portion of air, make combinations which would seem almost the result of scientific knowledge or reason, though depending upon a more unerring principle, their instinct for preserving their offspring. Those fishes that spawn in spring or p. 144the beginning of summer and winch inhabit deep and still waters, as the carp, bream, pike, tench, &c., deposit their eggs upon aquatic vegetables, which by the influence of the solar light constantly preserve the water in a state of aëration. ”

“ In this small space may be found animal and vegetable life of all kinds, anemonæ, lovely weeds, zoophytes, curious fish, sponges, shells, coral, and a hundred other things, all in such perfection and orderly wildness that no artificial aquarium [Pg 153] can ever hope to present, for they are made by hands, and can never vie with Nature in the formation of the wild and picturesque aspect of these rocky pools. ”

“ Aquatic in different ways, the differences depending on bodily relation to external temperature and on habit of life, are such animals on the one hand as take in air but live in water, and such on the other hand as take in water and are furnished with gills but go upon dry land and get their living there. ”

“ Many species of fish, as the Salmon, Smelt, and others, in forsaking the deep water, and approaching a suitable spawning station, leave the sea altogether for a time, ascend the rivers and their tributary streams, and, having deposited their eggs, return again to their usual haunts. Even a certain species of fish, inhabiting lakes, as the Roach, betake themselves to the tributary streams, as the most suitable places for spawning. ”

“ When the extremities are made to move in a horizontal or slightly downward direction, they at once propel and support the body. When, however, they are made to act in an upward direction, as in diving, they submerge the body. This shows that the movements of the swimming surfaces may, according to their direction, either augment or destroy buoyancy. The swimming surfaces enable the seal, sea-bear, otter, ornithorhynchus, bird, etc., to disappear from and regain the surface of the water. Similar remarks may be made of the whale, dugong, manatee, and fish. ”

“ Being mostly small and defenceless creatures, lurking among the marine vegetation of the shoals and reefs, they are usually accustomed to cling for support by their snake-like tails to the stalks or leaves of those submerged forests. The omniscient schoolboy must often have watched in aquariums the habits and manners of the common sea-horses, twisted together by their long thin bodies into one inextricable mass of living matwork, or anchored firmly with a treble serpentine coil to some projecting branch of coralline or of quivering sea-wrack. ”

“ If you have ever strolled about in the country, you must have often come across those great pools of water which collect at rainy seasons in the ruts of deep lanes. Amuse yourself by looking into them in early summer, and unless the land is too parched and dry, the chances are that you will see quantities of little black fishes, almost entirely composed of a long tail joined to a large head, playing jovially in the muddy waters, and looking as if they had dropped there from the skies. ”

“ Some of the marine animals obtained from our shores feed entirely on the minute and invisible organisms that are always present in the sea water, and others subsist principally on certain of the weeds. Many, however, of a more predaceous disposition, capture and devour living prey, while some, and more especially the crustaceans, are partial to carrion. If, therefore, the observer desires to study the ways in which the various creatures secure and devour their food, he should introduce into his aquaria live marine worms and other small animals, and also small pieces of fish or flesh. ”

“ Whether it be fishing in deep water amid rolling billows, or engaged in eluding its foes, it disappears beneath the surface so suddenly, remains so long in the water, and rises at so extraordinary a distance, often in a direction quite the reverse of that supposed to be followed by it, that your eyes become wearied in searching for it, and you renounce the wish of procuring it out of sheer vexation. ”

“ There will be shoals of fish, too, playing in and out, as strange and gaudy as the rest,—parrot-fish who browse on the live coral with their beak-like teeth, as cattle browse on grass; and at the bottom, it may be, larger and uglier fish, who eat the crabs and shell-fish, shells and all, grinding them up as a dog grinds a bone, and so turning shells and corals into fine soft mud, such as this stone is partly made of. ”