It thus, though at first sight looking as helpless as can be, is well able to defend itself.
The diodon has been known to be swallowed alive by a shark, in whose stomach it was found floating, probably supported by the air with which it had become inflated. It is asserted that it also frequently eats its way, not only through the coats of the shark’s stomach, but through the sides of the monster, which is thus killed. Probably the little diodon of the Amazon has a similar means of revenging itself on the voracious monsters to whom it falls a prey; and though it might not be able to liberate itself through the scaly back of an alligator, it would inevitably kill the monster, or cause him such pain as to make him repent having swallowed so indigestible a morsel.
The magnificent pirarucú or anatto, of vast size, with its ornamental coat of mail, and broad large scales margined with bright red, peoples the waters in immense numbers. It is most frequently caught by the native fishermen; and when salted, forms the staple food of all classes on the banks of the Lower Amazon. It swims at great speed, and attains the length of eight feet when full-grown, and five feet in girth. The Indian name of pirarucú is given to it from the native words pira, fish, and urucú, red; in allusion, says Mr Bates, to the red colour of the borders of its scales.
Among the other fish most frequently caught are the surubim and piraepiéua (species of Pimelodus); very handsome fishes, four feet in length, with flat spoon-shaped heads, and prettily spotted and striped skins—two long feelers hanging from each side of their jaws like trailing moustaches.
The Acara.
The larger animals which inhabit the mighty river and the network of streams and pools which surround it on both sides, have been described; but numerous smaller creatures dwell within it, equally curious, and many totally unlike those to be found in other parts of the world. It has generally been supposed that, of all creatures, fish are the most destitute of parental feelings, and that from the moment the eggs have been deposited in the sand or mud, they are allowed to struggle into existence as best they can, to do battle with their foes, and the numerous dangers to which they are exposed. In the acara, however, we have an example of parental care and watchfulness unrivalled by any terrestrial animal.
The male of this curious fish has a conspicuous protuberance on the forehead, wholly awanting in the female and the young. Somehow or other, the eggs of the female are conveyed into the mouth of the male, the bottom of which is lined by them, between the inner appendages of the branchial arches, and especially into a pouch formed by the upper pharyngeals, which they completely fill. They are there hatched; and the little ones, freed from the egg, are developed until they are in a condition to provide for their own existence. In their head there is a special lobe of the brain, similar to those of the triglas, which sends large nerves to that part of the gills protecting the young, thus connecting the care of the offspring with the organ of intelligence. In this curious cavity of the father’s head the young fish are found in all stages of development,—the more advanced, a quarter of an inch long, and able to swim about, full of life and activity. These appear to exist outside the gills, within the cavity formed by the gill-coverts and the wide branchiostigal membrane. The eggs remain in the back part of the gills.
The parent’s care does not appear to cease even when the young are fully developed, but he allows them to swim in and out, and try their powers, if not to search for food; and when danger appears, opens his mouth, when they all swim back again in a shoal, for safety. The natives assert that some species, at all events, are not actually developed in the parent’s head, but are laid and hatched in the sand, the male and female watching carefully over them; and that the father only takes charge of them when they are hatched, and receives them within his mouth to protect them from danger. From the observations of Professor Agassiz, however, there is no doubt that in some species, at least, the whole process of development is begun and completed in the gill cavity.
The species which lay their eggs in the sand belong to the genera Hydrogonus and Choetobranchus. They build a kind of flat nest in the sand or mud, in which they deposit their eggs, hovering over them until the young are hatched.
Curious also is the little bill-fish—the lymnobellus—with its long beak.