Axolotl

“ It would be easy for some of our scientifically inclined young Americans to secure specimens from Mexico, and rearing the young from the eggs, note all their changes. Nothing is more attractive than original investigation.
[Pg 252]
Some call the axolotl the “fish-formed siren,” as it has a fin-like membrane down the middle of the back, around the tail, and so on along part of the under portion of the body. This fin enables it to balance itself admirably in the water. Axolotls eat worms, snails, tadpoles, insects, bread-crumbs, bits of meat, or any small larvæ found in the water. ”

“ But at last a lady, Fraulein Marie von Chauvin, took some axolotls when they were full-grown, and kept them on land in wet moss, washing and feeding them every day, and thus succeeded in teaching them to breathe air, so that their gills shrivelled up and disappeared. Then there could no longer be any doubt that the axolotl is only the lower water-form of the amblystoma, which in the Mexican lakes, owing to the increased dryness of the surrounding country, has lost the habit of coming out on to the land, and remains in the water with its little ones all its life ”

“ It is true that the reversion is not complete, i.e. the present sexually mature Axolotl does not correspond in all details with its perennibranchiate ancestors. Since Wiedersheim has shown that the existing Axolotl possesses an intermaxillary gland, this can be safely asserted. This gland occurs only in land Amphibians, and therefore originated with the Amblystoma form, afterwards becoming transferred secondarily to the larval stage. ”

“ Some people smoke "mariguan" or Indian hemp, in their cigarritos.
Axolotl.—The most curious and incomprehensible superstition of the Mexican people, and one which has the widest dissemination, concerns the curious lizard called the axolotl, a name by which it was known to the Aztecs, although I do not feel prepared to say that they had the superstition concerning it.
The axolotl frequents damp, slimy places, near pools or tanks of water, and all kinds of refuse ("basura") .
It will enter the person of a woman, at certain times, and will remain just as long as would a human foetus. ”

“ As has already been mentioned above, the latest observations of Velasco furnish further confirmation that the Axolotl of the great lake is never met with in the Amblystoma condition, “although it (the Axolotl) is brought daily from Mexico into the market throughout the whole year.” I should not however regard it as a refutation of my view if prolonged investigation should show that this species also (Siredon Humboldtii) occasionally developed into an Amblystoma; on the contrary, it would not at all surprise me if such cases of reversion occurred in Mexico as well as in Europe. ”

“ The teeth are disposed in this species, as in all other Amblystomæ, in transverse series; whilst in Axolotl, as in Triton larvæ, they are arranged at the sides of the jaw in the form of a curved arch-like band beset with several rows of teeth.238 (Duméril. See his fig., loc. cit. p. 279) .
8. In Axolotl the lower jaw, in addition to the teeth on the upper edge of the bone, also bears “de très petites dents disposées sur plusieurs rangs;” these last disappear after metamorphosis (Duméril) . ”

“ If they are shut up in water and kept in a tank they never lose their gills, but continue through life in the lower stage of development, and reproduce themselves in other tritons with gills. Conversely the axolotl, a peculiar gilled salamander from the Lake of Mexico, has its normal course to live, die, and propagate its species in water, breathing by gills; but if an axolotl happens to stray from the water and take to living on dry land, the gills are modified into lungs and the animal gains a place in the class in the school of development. ”

“ A series of 34 larvae (JRD 5904-37) from 46 kilometers east of Morelia are tentatively referred to this species. These specimens are olive-brown above with cream-colored spots on the flanks; the dorsal tail-fin does not extend onto the body.
This species has been found only at elevations in excess of 2400 meters in pine and fir forests. At Rancho Axolotl James A. Peters collected larvae and neotenic individuals in a rocky stream and adults from beneath rocks and logs in the forest near the stream. ”

“ The present sexually mature form of the Axolotl has not arisen by the sexual maturity gradually receding in the ontogeny from generation to generation, but by the occurrence of single individuals which were sexually mature in the perennibranchiate stage, these having the advantage over the Amblystomæ in the struggle for existence under changed climatic conditions. ”

“ That the latter was produced under602 the influence of an aquatic life there can be no doubt, and thus, in accordance with my supposition, the hypothetical Amblystoma Mexicanum, the supposed ancestral form of the Axolotl of the Mexican Lake, might have been caused to revert to the perennibranchiate form by a reduction in the possibilities of its living upon land, and by its being compelled to frequent the water. ”

“ In the Axolotl some of these lamellae are further subdivided. In Necturus they are enormously increased in numbers, but are rather short, and they stand no longer in two rows, but are crowded into one. Those of Proteus form two rows of dendritic filaments; those of Siren are likewise much ramified.
The larvae of the Urodela have four clefts. In the adult Siren these are reduced to three, the first, namely, that between the hyoid and the first branchial arch, being closed up. ”

“ It has first to be established that Siredon Mexicanus never, as far as we know, undergoes metamorphosis in its native country. This Amphibian is there only known in the Siredon form, a statement which I have taken from De Saussure,225 who has himself observed the Axolotl in the Mexican lakes. This naturalist never found a single566 Amblystoma in the neighbourhood of the lakes, “nevertheless the larva (Axolotl) is so common there that it is brought into the market by thousands.” ”

“ Why should not a sudden change in all the conditions of life (transference from Mexico to Paris) have a direct action on the organization of the Axolotl, causing it suddenly to reach a higher stage of development, such as many of its allies have already attained, and which obviously lies in the nature of its organization—a stage which it would perhaps itself have572 reached, although later, in its native country? ”

“ But enough of supposition. We must not complain that we are unable from afar to discover with precision the causes which compelled the Axolotl to abandon the Amblystoma stage, as long as we are not able to explain the much nearer cases of reversion in Filippi’s and Jullien’s Tritons; nevertheless, in these cases also, the causes affecting the whole colony of Tritons must be general, since—at least in the case noticed by Filippi—the greater majority of the individuals remained in the larval condition. Experiments with Triton larvæ could throw greater light upon this subject ”

“ I may here interpolate a fact not generally, if at all, known to Europeans: that these chinampas (of which I hope some day to give an account) are in existence at the present time.
Several species of very small fish inhabit lakes Chalco and Xochimilco; indeed, the fish marker of the Mexican capital is chiefly supplied from them. But I have never heard of the axolotl being taken, or observed in either ”

“ Marie von Chauvin [54] undertook, at the University of Freiburg, long and carefully conducted experiments, showing (1) that little Axolotls can comparatively easily be caused to develop further into the perfect Amblystoma if they are induced to breathe air more frequently than usual; shallow vessels, perhaps also insufficiently aerated water, will produce the desired result; (2) that the commencing metamorphosis can again be checked, the shrinking gills then undergoing fresh development; (3) that they can be forced to remain Axolotls ”

“ We are all of us to-day evolutionists, if some of us still with a certain amount of reservation,{192} and to the evolutionist tadpoles must always prove interesting acquaintances. They provide us with at least an inkling as to the fashion in which your unadulterated water-breather may have been converted into an air-breather, and by means of no process more recondite than that of losing its gills. That such conversions do take place, and under certain circumstances remain permanent, has been proved in the well-known case of the axolotl, or Mexican gilled salamander. ”

“ Thus we see that in our aquariums most of the axolotls remain in the branchiate condition, transformed individuals being on the whole very exceptional. Now it has been stated that in the lakes near Mexico City, where it was first discovered, the axolotl never transforms into an Amblystoma. This the present writer is inclined to doubt, considering that he has received examples of the normal Amblystoma tigrinum from various parts of Mexico, and that Alfred Dugès has described an Amblystoma from mountains near Mexico City ”

“ The fact, however, that Axolotls require special treatment to induce metamorphosis seems to show that they have distinctly less congenital tendency to metamorphosis than larvae of the same species, Amblystoma tigrinum, in other parts of North America, and this difference must be attributed to the inherited effect of the conditions. The most important of these conditions seems to be abundance of oxygen in solution in the water, and the next in importance abundance of food in the water. Recently it has been shown that the metamorphosis may be induced by feeding Axolotls on thyroid gland. ”

“ One of the largest and most widely distributed species of this genus, which includes about twenty, is the Amblystoma tigrinum, an inhabitant of both the east and west of the United States and of a considerable part of the cooler parts of Mexico. It varies much in colour, but it may be described as usually brown or blackish, with more or less numerous yellow spots, sometimes arranged in transverse bands. It rarely exceeds a length of nine inches. This is the Amblystoma into which the axolotl has been ascertained to transform. ”

“ The skin becomes yellowish white, irregularly spotted on the sides and back (Duméril) , whilst at the same time its former grey-black ground-colour changes into a shining greenish black (Weismann) ; it loses, moreover, the slimy secretion of the skin, and the cutaneous glands become insignificant (Kölliker) .
5. The eyes become prominent and the pupils narrow (Kölliker) , and eyelids capable of completely covering the eyes are formed; in Axolotl only a narrow annular fold surrounds the eyes, so that these cannot be closed (Weismann) . ”

“ Though in a sense the sole inhabitant of Tezcoco, the axolotl is not left to peaceful or undisputed possession of the lake. It has its enemies in the predatory aquatic birds—herons, cranes, and cormorants—while man is also among them. To the “Lake Indian” its capture is a matter of economic industry, its flesh being a saleable commodity in the market. It is not absolutely relished as an article of food, except by the Indians themselves; who, as is well known, will eat anything and everything that lives, moves, and has being, be it fish, fowl, reptile, or insect. ”

“ Just as in the case of seasonal dimorphism it is possible to compel the summer generation to abandon the summer form, and to assume the winter guise by the action of cold; so in the present case we are able to induce the Axolotl to adopt the Amblystoma form by making aërial respiration compulsory at a certain stage of life; and further, just as in seasonal dimorphism it can583 be shown that this artificially produced change is only apparently an abrupt transformation, and is actually a reversion to the much older winter form ”

“ Dorfmeister, G.; experiments with A. levana, 11. Duponchel; figures of larvæ referred to, 207, 208, 218, 253. Duméril; experiments with Axolotl, 555, 564, 566, 593; characters of Axolotl, 375, 576. E. Edwards, W. H., seasonal dimorphism of P. pseudargiolus and P. violecea, 4; of P. Tharos and P. Marcia, 4; of P. Ajax, 30; of L. Artemis and L. Proserpina, 32; experiments with P. Ajax and P. Tharos, 33, 126, 140; pupal period of winter forms of P. Ajax, 36; experiments with G. interrogationis, 149; early stages of larvæ of N. American butterflies, 165 ”

“ In Gadow’s opinion, the reason why there are only perennibranchiate axolotls in these lakes is obvious. The constant abundance of food, stable amount of water, innumerable hiding-places in the mud, under the banks, amongst the reeds and roots of the floating islands which are scattered all over them,—all these points are inducements or attractions so great that the creatures remain in their paradise and consequently retain all those larval features which are not directly connected with sexual maturity. ”

“ They fear neither heat nor light, and do very well under damp sea-weed while waiting for the return of the tide. They run and swim with the same facility. When in the condition of Ancei, they lose their agility, and, under this form, all denotes their sedentary habits. They appear to live in holes, at the bottom of which they defend themselves with their powerful mandibles. It has been observed that fecundation is accomplished, as in the Axolotls, before the evolution is complete, but that the eggs are not laid until the animal assumes the form of Anceus. ”