Devil Fishes and their Kin
Animal Life (Column)
A. Hyatt Verrill, with photos from nature by the author
Of all the various groups of mollusca none are more striking in appearance than the Cephalopods. Moreover, among them are found the largest of all invertebrates, —the giant squids.
The most familiar of the group are the squids and octopus, commonly called "Devil-fishes." As the name implies the Octopus has eight arms. These are usually about equal in length, surrounding the mouth (in which are situated the beak-like jaws) and equipped along their inner surface with a great number of suckers for seizing their prey. The food consists almost entirely of crustaceans which are readily torn to pieces by the powerful jaws, while held in the strong, muscular arms. The body of the octopus is short and rounded, pulpy, and highly muscular and contractile. The head is small and joined directly to the body except on the under side where a slit occurs, from which projects the siphon tube.
The octopus possesses perhaps in greater degree than any other creature the power of changing color at will. Ordinarily the color of the common Octopus granulosus, of the southern states and West Indies, is pale flesh-color, mottled with minute greenish-red and yellow spots. When disturbed, the color instantly changes; waves of red, blue, green or purple surging over the animal, sometimes in blotches, sometimes completely covering the surface. When exceedingly angry the color is a deep purplish-red. Aside from this power the octopus, in common with all cephalopods, has a peculiar habit of ejecting a purplish or black fluid or "ink" in order to conceal itself, and it is from this fluid that the true "India Ink" is prepared. An old jest is that a disputant in print may hide himself in a cloud of ink.
On the Pacific coasts the octopus attains a very large size, specimens measuring ten or twelve feet from tip to tip being not unusual. In the Atlantic the largest specimens seldom reach a spread of more than five feet. An octopus of this size, however, can put up a good fight, and it is by no means an easy matter to capture them by hand. They are often seen,—where common as in Bermuda,—hiding beneath ledges or in crevices of the rocks between high and low-water mark. If grasped firmly just back of the head there is no danger of getting bitten, but the long tentacles instantly twist and curl about the hands and arm, sticking uncomfortably tight with the multitude of sharp-edged suckers. They are remarkably strong, and a specimen weighing five or six pounds is almost a match for any man. They are lively, too, and manage to travel about on rocks or sand at quite a rapid pace. These peculiarities, combined with their remarkable contractile power (which enables them to slip between one's fingers in a most amazing way), renders them very difficult to hold. Moreover, wherever the arms touch they stick, and I have frequently worked for half an hour before getting a small octopus safely stowed in the collecting pail.
Besides the genus Octopus there are a number of deep-sea genera allied and much resembling it in form and habits. Closely allied to Octopus are the "paper-sailors," or Argonauts, belonging to the genus Argonauta. These animals, famed in song and story, are so much like an octopus in appearance that a description of one would serve almost as well for the other. The main difference consists in one pair of the argonaut's arms being specially formed for grasping and holding in place the delicate shell with which the beautiful creatures are provided. From the inner surface of these specialized arms the shell is secreted. The shell serves as a receptacle for carrying the eggs and is present only in the female.
The true Nautilus has a much heavier and brighter-colored shell, and it is, moreover, constructed with a series of internal chambers or partitions, the body of the animal occupying only the outermost chamber. The animal of the Nautilus is much like an octopus, but the arms are much shorter and the body specialized for living within the spacious shell. The main interest in the Nautilus lies in the fact that it is very closely allied to the fossil Ammonites, which grew to an immense size. The Nautilus is a native of the Indian and western Pacific Oceans, while the Argonauts are Gulf Stream and Mediterranean inhabitants. Neither of them possesses the power of sailing on the surface, however,—the traditional belief being based on the paddle-shaped arms of the latter, whose purpose was for many years unknown.
Akin to the Octopus, and forming a sort of connecting link between them and the squids, are the true Cuttlefishes, of the genus Sepia. The body in this genus is shorter and more rounded than in the squids, but much longer and broader than in the octopus. Moreover it is provided with a thin fin-like edge all around its circumference. The resemblance of the arms to the squids is very strong, there being eight short stout ones, and two longer ones,—the latter with but a few small suckers, except at the broadened spear-shaped tips. It is from the various species of Sepia that the best India ink is prepared, and the internal "pen" or bone forms the "cuttlefish bone" found in every well-regulated canary's cage.
The true squids contain a number of genera, the commonest and best known of which is Loligo. The squids are rather slender-bodied and are almost cylindrical. The tail is provided with broad flaps or fins and in some cases these extend almost the entire length of the body. There are ten arms,—eight short and almost equal and two longer—usually widened at the tip. Unlike the octopus, which lives in holes and seldom swims far from home, the squids are pelagic and swim swiftly and readily, having no fixed abode. Whereas, the octopus possesses no internal skeleton, the squids have a pen or rudimentary skeleton which in some species is merely a thin, horny, plate, and in others calcareous and strong.
The squids are very abundant on the Atlantic coast and are much used for bait. The "flying squids" of the Gulf Stream are more tropical species and have a peculiar habit of projecting themselves from the water,—not infrequently jumping or "flying" so high as to land on the deck of vessels. The squids of the genus Architeuthis are the largest of invertebrates and sometimes attain a length of 40 feet. These huge creatures are natives of the northern seas, and most of the known specimens were obtained on the coast of Newfoundland, where they were found washed ashore after heavy storms. Remains of others have been found in the stomachs of sperm whales, and they are supposed to form a good portion of the food of these marine mammals. Without doubt the old stories of sea monsters, such as the fabulous "kraken," were based on these giant cephalopods. The little Spirulas are perhaps the least known of any of the cephalopod group. Although the empty, coiled shells are found washed up by thousands in many tropical parts of the world, less than a dozen specimens of the animal are in collections, and only two or three of these are anywhere near perfect. The animal is much like a miniature octopus but the shell, instead of being external as in the Argonauts, is situated within the posterior portion of the body. At the extreme end of the animal is a small sucker. All the perfect specimens have been obtained from a depth of 900 fathoms or more, and they are supposed to live upon the ocean bottom, adhering to stones or other objects by means of the sucker. Other specimens have been obtained from the stomachs of dolphins, and during the past year several were found by the writer on the coast of Bermuda, with the animal matter adhering, proving beyond a doubt that the little known creatures live in the immediate vicinity of the Bermuda islands.