Popular Science Monthly/Volume 11/September 1877/Odd Forms Among Fishes
|ODD FORMS AMONG FISHES.|
PROBABLY there is no group of animals—certainly no group of vertebrates—that exhibits more strange and even monstrous forms than fishes.
The typical fish, we may well believe, is some such form as the salmon, or the cod, or the bass, or an average of these and their numerous allies. In a word, the ordinary fishes of the ocean, lakes, and streams, give us essentially the true idea of the typical fish.
But what remarkable departures from these ordinary forms do we
find when we take a survey of the whole vast group of animals that are called fishes!
Let us take the salmon as a fair sample of an ordinary fish, and then briefly notice a few of the strange forms to which the name is applied.
If we look at the rays (Fig, 2), we see "fishes" whose width is so great in proportion to their length, that in giving their dimensions it would seem to be quite the natural thing to put down the width as the prominent measurement instead of the length, as is our custom in the case of ordinary fishes. And it may be remarked here that the great relative breadth of these animals is connected with the kind of movements which they exhibit in progression. Instead of ordinary swimming, these animals effect locomotion by a sort of flight through the waters; and hence are often called "sea-eagles," "sea-vampires," etc. They all belong to the sea. Some of the rays are of wonderful dimensions, although the ordinary kinds are only about two or three feet wide. One was taken near Messina which weighed half a ton. One taken near Barbadoes is said to have been so large that it required seven yoke of oxen to draw it! Levaillant tells us of one which was thirty feet wide and twenty-five feet long; and Dekay states that one of these monsters of the deep has been known to seize the cable of a small vessel at anchor, and draw it several miles with great velocity!
The rays have the mouth, nostrils, and gill-openings, on the under-side. Like the sharks, they are without gill-covers, and have the gills fixed by both margins. Their teeth differ from those of all ordinary
fishes, being of a definite form, bounded by planes symmetrically arranged, the whole forming a beautiful mosaic (Fig. 3).
Remarkable as are the form and general structure of the rays, as indicated above, a still more remarkable structure is exhibited in some
of them; for those known as torpedoes (Fig. 4) are so constructed that they are a powerful galvanic battery. These have the space between the pectoral fins, the head, and the gills, on each side, filled with membranous tubes which are divided by horizontal partitions into small cells filled with a sort of mucus and traversed by nerves; and by means of this apparatus they give violent shocks to animals with which they come in contact.
Hardly less strange than the rays are those animal structures
which remind us somewhat of the rays on the one hand, and the sharks on the other, but which differ from both in several important respects, but especially in having a very long depressed and bony
snout, armed on each side with spines implanted like teeth, the whole constituting a most formidable weapon. These are the sawfishes (Fig. 7), which attain a length of fifteen feet or more.
Every one sees at a glance that the sharks (Figs. 5, 6, 1) are widely different from all ordinary fishes. Their peculiar outline in general, their unequal-lobed tail, their transverse mouth on the underside of the head, their formidable array of lancet-shaped teeth,
their fixed gills without gill-covers, their rough skin, their pillow-shaped eggs with long, tendril-like appendages at the corners (Fig. 8), all combine to separate them about as far as possible from typical fishes. And if we compare them with one another, what wonderfully-
diversified forms do we see as we pass from the dog-sharks to the mackerel-sharks, and from the latter to the white sharks, and from these to the threshers, and to the hammer-heads, and so on through the whole list!
And who that has studied only the ordinary fishes would at length expect to find such a fish as the chimera (Fig. 9) an animal whose general appearance, it is true, is somewhat shark-like, but which, if possible, is more strange and monstrous than any of the sharks or
rays? This curious arctic fish, which attains the length of four feet, is not only exceedingly remarkable in its general appearance, but it is especially remarkable in its structure having no upper jaw, the four
upper teeth being supported on the front of the skull, and only two teeth in the lower jaw, and having no backbone, this important part being represented only by the most rudimentary structure, such as
exists in the ordinary embryonic vertebrate, and which is known under the name of chorda dorsalis. In the tropical regions of America and Africa there is found a strange "fish," about three feet long, and called the lepidosiren (Fig. 10)—scaly siren, as the name implies. In its general aspect it is decidedly reptilian, and some writers have described it under the reptiles. Nor is it strange that naturalists should have been in doubt in regard to its true affinities, for it is decidedly reptilian in appearance, and is so unlike the typical fishes in structure that it has both gills and lungs—thus leading a sort of double life. It is believed that in important respects this fish is like some of the fishes that lived in the old Devonian times.
The gar-pikes, too, depart considerably from ordinary fishes, especially in their teeth, hard, shining scales, and heterocercal tail (Fig. 11).
And the sturgeons (Fig. 12), ballasted and protected with rows of large bony plates, and with a nose fitted for "rooting," and a mouth
for sucking, and a tail more or less like that of a shark, are very unlike anything we should select as a typical fish.
And what shall we say of the "sea-horses," or hippocamps (Fig. 13), whose head reminds us far more of the head of a horse than it
Fig. 13.—Sea-Horse (Hippocampus Hudsonius, Dekay).
Fig. 14.—Pipe-fish (Sygnathus Peckianus, Storer).
does of that of a typical fish? And of the pipe-fishes (Fig. 14), or sygnathi, whose body is all length, nearly, and whose mouth is just at the extremity of a long snout; and which have this strange habit. namely, that the males receive the eggs into a pouch, in which they carry them till they are hatched?
Who that has studied and heard of only ordinary fishes would ever expect to see such an animal as the sunfish (Orthagoriscus); and who, when he sees one for the first time, would regard it as anything short of a monstrosity? This huge fish (Fig. 15), weighing, in some
cases, five hundred pounds, is so abbreviated behind, that it is scarcely represented behind the dorsal fin, making it one of the most remarkable forms, and one of the most difficult to explain, to be found in the whole class.
The trunk-fishes (Fig. 16) are very remarkable forms. They have an inflexible shield of bony plates, so that the mouth, tail, and fins, are the only movable parts. These small fishes—from three inches to
|Fig. 16.—Trunk-fish (Lactophrys Camelinus, Dekay).||Fig. 17.—Puffer (Tetraodon turgidus, Mitchell).|
a foot, in length are thus in strong contrast with the ordinary fishes, whose whole bodies are so flexible that there is the greatest freedom of motion throughout nearly the entire structure.
Again, the puffers (Fig. 17) are remarkable forms. Being more or less covered with spines, and having the habit of inflating themselves by swallowing air, thus giving them more or less of a rounded appearance, they may perhaps not improperly be called the "sea-urchins" among fishes.
Another strange form is the fishing-frog, or angler (Fig. 18), whose enormous mouth enables it to swallow animals nearly as large as
itself, and whose anterior dorsal rays bear fleshy filaments, which it is said to use as a bait to decoy other fishes, that it may secure them as food.
In the cavities under stones in the sea are found the little toad-fishes (Fig. 19), whose head is so like that of a toad that we are ready to concede that both the popular and scientific names of these animals (batrachus) are well bestowed.
There are many other fishes that depart so much from the ordinary forms that the common fisherman instinctively names them after some land-animals. The sea-wolf or wolf-fish is one of these, although its head is more like that of a wild-cat or a lynx than it is like that of a wolf. It is sometimes called the sea-cat. Its body is long, with a dorsal fin nearly the whole length, and the head is round; its mouth is armed with a most formidable array of teeth, making this animal, which is five or six feet long, a most dangerous antagonist when the fisherman comes in direct conflict with it.
The hand-fishes of the tropics are very small, but their grotesque appearance and hand-shaped fins, suited for creeping, make them very
proper subjects of notice in this connection. One very small species is found on our Atlantic coast.
Nor ought the lump-fish (Fig. 21) to be omitted in this enumeration; for, although it is not specially remarkable in its general aspect, it is very remarkable in at least one portion of its structure. It has
its ventral fins united so as to form a cup-shaped disk, and by means of this disk this fish is able to attach itself to any surface with great firmness. Pennant states that, upon putting one into a pailful of water, it adhered to the bottom so firmly that he lifted it by the fish's tail.
Nor ought we to omit to mention the sword-fish, although it exhibits nothing specially remarkable in its general form, excepting its sword-like prolongation of the jaw (Fig. 22). And on account of its movable spine at the base of the tail we may merely mention the herbivorous lancet-fish, although in its general outline it is scarcely more remarkable than a perch or a bream.
"Sea-ravens" (Hemipterus Fig. 23), "sea-robins" (Prionotus), "sea-swallows" (Dactylopterus), and sculpins (Cottus) may well be called strange fishes, for their forms are so marked and so strange that they at once arrest the attention of the commonest observer at the
|Fig. 23—Sea-Raven (Hemipterus Acadianus, Storer).||Fig. 24.—Star-Gazer (Uranoscopus anoplos, Cuvier).|
sea-side. While all these have a certain general resemblance to one another, all agreeing in being remarkably ugly, each has its own marked peculiarities in the development of the head and fins, and in the curious fleshy filaments which are found upon some of them.
We may also justly include the little star-gazers (Uranoscopus, Fig. 24) of the Atlantic, whose eyes are so placed that they appear as if looking constantly toward the heavens, and whose mouth is cleft vertically, and has in it a long filament which can be protruded at will, and which is said to be used in attracting small fishes while the owner lies concealed in the mud.
Next we may mention the remora (Fig. 25), on whose head there is a sort of disk composed of laminæ which are serrated and movable, by means of which the fish can firmly attach itself to other animals.
It is said that it can be made useful by putting a ring attached to a line around its tail, and then allowing it to swim away in search of a victim; when it has firmly attached itself to a fish, both the remora and its captive are hauled in together.
Remarkable and strange as are all the forms of fishes which we have so far noticed, not one of them exhibits any want of bilateral symmetry. But we now come to a whole group of fishes, including halibuts, turbots, soles, flounders (Fig. 26), etc., whose two sides are totally unlike—a peculiarity which is not only not found in any other
group of fishes, but not in any other group of vertebrate animals. These strange fishes have the body flat, both eyes on the same side
of the head, and the sides of the mouth unequal. They are without a swimming-bladder, live at the bottom of the sea, and are of all sizes,
from those not more than six or eight inches in length to those that attain a weight of six hundred pounds.
As for the gars, I should not mention them in this article, although they are quite peculiar in several respects, were it not for one fact connected with the nature of their skeleton. Their bones are of a green color, a peculiarity which, so far as I am informed, is unique among vertebrates.
Nor is there anything very peculiar about the flying-fishes, except the excessive development of their pectoral fins, and the habit of "flight" connected with this development (Fig. 28).
But perhaps we ought not to omit to mention the siluroids (Fig, 29), or catfish, for, although they are more like ordinary fishes than some of those already mentioned, their large, broad, and flat head, and large mouth with its fleshy filaments, give them a decidedly outre appearance, making them quite marked forms in the class of fishes.
As to the little blind-fishes (Fig. 30), or Amblyopsidæ, of the Mammoth Cave, they are very similar in general outline to ordinary fishes, but are peculiar in having the eyes rudimentary and concealed
|Fig. 30.—Blind-fish (Amblyopsis spelœus, Dekay).||Fig. 31.—Lamprey (Petromyzon Americanus, LeSueur).|
under the skin, and in having the vent before the base of the pectoral fins at the point indicated by the dotted line in Fig. 30.
The eels are only or mainly remarkable on account of their elongated form. But the lampreys (Fig. 31), though eel-like in form, are not only different from ordinary eels in their structure, but very different from all the fishes we have hitherto noticed. Their respiratory apparatus is very peculiar, being composed of seven pouches on each side, which receive water from the lateral openings of a canal distinct from the œsophagus, and discharge the same through seven branchial openings on each side of the neck; and their mouth and tongue are more strange than their breathing apparatus." The mouth is round, and the tongue moves forward and backward in it like a piston, thus enabling the animal to produce a vacuum to fix itself firmly to a stone or any other body in the water.
As we get near the bottom of the scale in the examination of fishes, we find forms which, so far as their general outline is concerned, give no intimation of their true affinities. The myxines, or hags (Fig. 32), are of this sort: small fishes which have the general aspect of
|Fig. 32.—Hag, or Myxine (Myxine limosa, Girard).||Fig. 33.-Lancelet, or Amphioxus (Branchionstoma).|
worms, but whose plan of structure shows them to be vertebrates, and whose circular mouth and piston-like tongue ally them to the lampreys.
And at the very bottom of the group of fishes we find the little amphioxus, or lancelet (Fig. 33); and how wide is the gap between this soft, nearly transparent vertebrate, without teeth or jaws, with out skeleton or real head, and with only a mere slit for a mouth, and the typical fish as we see it in the shad, the cod, and the salmon! So little does the amphioxus appear like even a vertebrate, that Pallas, the naturalist who first described it, thought that it was some sort of slug or snail.
These strange forms of fishes are facts; and the important question is, What do they mean? What has caused them? What are they for? Will they continue? These and other questions quickly suggest themselves, and are easily asked; but are not so easily answered.
The whole subject of the origin and meaning of organic forms is a very important one. It is not so narrow as indicated by the questions asked above about the queer forms of certain fishes; but it is a subject which embraces inquiry into the origin and full significance of all organic forms upon the earth and within its crust.
Are these fishes and all other organic forms just as they were created? The creationist says "Yes;" the evolutionist says "No." Suppose we admit the doctrine that they were all created as they now appear what does it mean that there are 15,000 specific forms of fishes, and that a thousand, or two thousand, more or less, are of these outré forms described above? Can any one give a satisfactory answer? Or suppose we accept the doctrine of evolution and natural selection—does that, when we come right down to the facts as revealed in these 15,000 forms of fishes and all other organic forms, solve all the difficulties for us, or enable us to solve them? Does evolution alone enable us to account for the wonderful diversity of form, to say nothing of the scarcely less wonderful diversity of size, among these numerous vertebrates—especially when we remember that thousands of the most diverse forms have always been under essentially the same physical conditions?
Is there any rational explanation that we can yet give of such a form and structure as those exhibited in the torpedo (Fig. 4), in the sawfish and the hammer-head shark (Fig. 7), the chimæra (Fig. 9), the remora (Fig. 25), or the lamprey (Fig. 31)?
Is it not true that we have much yet to learn before we can give a satisfactory explanation of the wonderfully diverse forms in the animal kingdom, or even in a single group like that of fishes?