I don't recall clearly so that's certainly possible, but it seems the Axolotl does have the capability of spontaneous metamorphosis. Here are quotes from some publications I found.
First, regarding the first individuals imported in Europe [1]:
"In November 1865, Duméril issued another report to the Académie des sciences. One of the axolotls had started to become “markedly different from the other axolotls of the same age.” Soon, others followed. The external gills disappeared, and the form of their heads and bodies changed along with their coloration. Several animals that were born in the Collection had left the water and had transformed into a land-dwelling form. They had become what Duméril called “ambystomes.”"
Then this extract of a Master's thesis [2]:
"Six A. mexicanum were transferred to Paris where Dumeril (1870) subsequently
reported that individuals reproduced in an aquatic, larval state and that some
of the resulting offspring underwent a metamorphosis. Smith (1989) suggests
that some of the original stock that arrived in Paris included closely related
members of the Tiger salamander species complex, that are capable of expressing
a paedomorphic or metamorphic life history. However, it seems likely that
domestication altered the penetrance for expressing paedomorphosis and the
original axolotl stock was pure A. mexicanum that maintained a higher
propensity to express metamorphosis in nature (Voss & Shaffer, 2000). Even
though metamorphic forms have been culled from the Ambystoma Genetic Stock
Center axolotl collection for decades, the frequency of spontaneous
metamorphosis is only 1–2%, with a 10% frequency observed if A. mexicanum
experience stressful conditions (Randal Voss, unpublished data)."
And this from a book chapter [3]:
"The modern axolotl strain used in most laboratories is a highly inbred population that most likely arose from a donation of seven wild axolotls (six wild-type and one white mutant) between 1863 and 1866 to the Paris Natural History Museum [6]
. In fact, most modern-day laboratory axolotls likely have a direct lineage to these founders, and all white mutants are descendants from this single white animal [7]. A few wild-caught axolotls were introduced into the colony strain in the 1960s including an albino tiger salamander (Ambystoma tigrinum) [8], but overall the present-day laboratory strain is likely one of the most long-running inbred strains of any laboratory species. The 150-year history of laboratory breeding seems to have selected against spontaneous metamorphosis (currently <1 % frequency), as it is more prevalent in wild strains than the lab strain [7, 9]. The most extensive colony of laboratory axolotls is maintained at the Ambystoma Genetic Stock Center (AGSC)"
In particular this part: "The 150-year history of laboratory breeding seems to have selected against spontaneous metamorphosis (currently <1 % frequency), as it is more prevalent in wild strains than the lab strain."
i think some of the recent posts are about a batch of salamander/axolotl hybrids, but if you scroll further down, there's more of the morphed axolotls they have.
First, regarding the first individuals imported in Europe [1]:
"In November 1865, Duméril issued another report to the Académie des sciences. One of the axolotls had started to become “markedly different from the other axolotls of the same age.” Soon, others followed. The external gills disappeared, and the form of their heads and bodies changed along with their coloration. Several animals that were born in the Collection had left the water and had transformed into a land-dwelling form. They had become what Duméril called “ambystomes.”"
Then this extract of a Master's thesis [2]:
"Six A. mexicanum were transferred to Paris where Dumeril (1870) subsequently reported that individuals reproduced in an aquatic, larval state and that some of the resulting offspring underwent a metamorphosis. Smith (1989) suggests that some of the original stock that arrived in Paris included closely related members of the Tiger salamander species complex, that are capable of expressing a paedomorphic or metamorphic life history. However, it seems likely that domestication altered the penetrance for expressing paedomorphosis and the original axolotl stock was pure A. mexicanum that maintained a higher propensity to express metamorphosis in nature (Voss & Shaffer, 2000). Even though metamorphic forms have been culled from the Ambystoma Genetic Stock Center axolotl collection for decades, the frequency of spontaneous metamorphosis is only 1–2%, with a 10% frequency observed if A. mexicanum experience stressful conditions (Randal Voss, unpublished data)."
And this from a book chapter [3]:
"The modern axolotl strain used in most laboratories is a highly inbred population that most likely arose from a donation of seven wild axolotls (six wild-type and one white mutant) between 1863 and 1866 to the Paris Natural History Museum [6] . In fact, most modern-day laboratory axolotls likely have a direct lineage to these founders, and all white mutants are descendants from this single white animal [7]. A few wild-caught axolotls were introduced into the colony strain in the 1960s including an albino tiger salamander (Ambystoma tigrinum) [8], but overall the present-day laboratory strain is likely one of the most long-running inbred strains of any laboratory species. The 150-year history of laboratory breeding seems to have selected against spontaneous metamorphosis (currently <1 % frequency), as it is more prevalent in wild strains than the lab strain [7, 9]. The most extensive colony of laboratory axolotls is maintained at the Ambystoma Genetic Stock Center (AGSC)"
In particular this part: "The 150-year history of laboratory breeding seems to have selected against spontaneous metamorphosis (currently <1 % frequency), as it is more prevalent in wild strains than the lab strain."
[1] https://www.brepolsonline.net/doi/full/10.1484/J.CNT.5.13210...
[2] https://uknowledge.uky.edu/biology_etds/13/
[3] https://link.springer.com/protocol/10.1007/978-1-4939-2495-0...