Experiments on the Axolotl 



D. F. LENEY, F. Z. S. 



Laboratory) of Comparative Anatoirvy, Oxford University 



The axolotl seems to attract attention 

 in Aquatic Life from time to time, so 

 perhaps a few notes on it may not come 

 amiss. 



It has been known for some time that 

 the axolotl or larval form of Ambly- 

 stoma tigrinum will give up its aquatic 

 life and take to a terrestrial one when 

 forced to breathe atmospheric air. This 

 external stimulus brings about complete 

 absorption of the feathery gills, and also 

 of the fin along the back and tail, while 

 the head becomes rounded and the eyes 

 more prominent. Figure i will give an 

 idea of the halfway stage, with gills 

 partly absorbed and the dorsal fin begin- 

 ning to be absorbed. In nature this 

 metamorphosis is brought about by the 

 gradual drying up of the pools where the 

 axolotl live, while in captivity the slow 

 evaporation of the water in which the 

 larvae are, will usually have the same ef- 

 fect (see Proc. Zool. Soc, 191 3 — 2, p. 

 403)- 



Goodenach fed young frog tadpoles on 

 the thyroid gland of the ox and found 

 that they turned into frogs in an excep- 

 tonally short time. Feeding with potas- 

 sium iodide mixed with flour did this 

 as well. And keeping them in a weak so- 

 lution of iodine crystals had the same ef- 

 fect. Does this answer with axolotl ? 



Last winter, at the Laboratory of Com- 

 parative Anatomy, of Oxford Univer- 

 sity, a pair of mature black axolotl were 

 fed twice a week, for seven weeks, on 

 pieces of ox thyroid. At the end of this 

 time both had left the water and had 



attained the perfect stage known as 

 Amblystoina tigrinum. Figure 2 is of 

 the male shortly after coming onto dry 

 land. The chief interest is that the axo- 

 lotl were sexually mature, hence the thy- 

 roid must have supplied the necessary 

 stimulant for the metamorphosis to take 

 place. 



Kendall has found that the thyroid 

 gland stores and secretes iodine, in some 

 form or other, into the blood, so that it 

 may be presumed that iodine is one of 

 the stimulating agents at work to bring 

 about metamorphosis. Accordingly a 

 young axolotl was put in a weak solu- 

 tion of iodine crystals. A visible reduc- 

 tion of the gills and tail fin took place, 

 but unfortunately the patient died soon 

 after Figure 3 was taken, where the very 

 reduced gills can be seen. 



Similarly the young of Salamandra 

 maculosa, the spotted salamander, have 

 been on thyroid gland and have meta- 

 morphosed in an abnormally short time, 

 but the iodine treatment appears to have 

 little or no effect on them, whereas when 

 small larvae of Triton vulgaris, the 

 smooth newt, are kept in weak solutions 

 of iodine, they rapidly metamorphose. 



Quite recently, in May, a white adult 

 axolotl, in a large aquarium, was observ- 

 ed to become covered with pink spots on 

 either side of its body ; a disease of some 

 kind. After this it was noticed to be 

 generally near the top of the water. 

 Three weeks later it was found to have 

 lost most of the filaments on its gills and 

 to be respiring with its lungs almost en- 



