A GOD IN DAN­GER

Scuba Diver Australasia + Ocean Planet - - Contents - Ale­jan­dro Pri­eto

By Ale­jan­dro Pri­eto

The Mex­i­can ax­olotl, an am­phib­ian with the abil­ity to re­gen­er­ate mu­ti­lated body parts, is highly sought-af­ter for its in­cred­i­ble power. Years of cap­ture and en­vi­ron­men­tal degra­da­tion have now brought this bi­o­log­i­cally-im­por­tant species to the brink of ex­tinc­tion. Could it be too late to save it?

The ax­olotl is a unique species en­demic to Mex­ico, ca­pa­ble of re­gen­er­at­ing al­most ev­ery part of its body. Thanks to this unique abil­ity, it has be­come one of the most stud­ied species in the world. The ax­olotl is a type of sala­man­der that uniquely spends its whole life in lar­val form. It is the only species that never un­der­goes meta­mor­pho­sis. As they age, ax­olotls sim­ply get big­ger and big­ger, like am­phibi­ous Peter Pans.

Un­for­tu­nately, the num­ber of ax­olotls in the wild has dropped dra­mat­i­cally through the years, and they are now con­sid­ered crit­i­cally en­dan­gered by the In­ter­na­tional Union for Con­ser­va­tion of Na­ture (IUCN). The main threats they face in­clude habi­tat loss, wa­ter con­tam­i­na­tion by in­dus­trial prac­tices, and the pres­ence of in­va­sive species in their habi­tat.

The long-term sur­vival of the ax­olotl in the wild has now be­come crit­i­cal, and de­mands ur­gent ac­tion to re­store the an­i­mal’s num­bers and habi­tat. The ax­olotl (Am­bystoma mex­i­canum) be­longs to the mole sala­man­ders, a group of around 30 species en­demic to North Amer­ica, par­tic­u­larly the US, south­ern Canada, Alaska and Mex­ico. The ax­olotl, how­ever, is only found in cen­tral Mex­ico, on the south­ern edge of Mex­ico City. It has now dis­ap­peared from most of its range and is clas­si­fied as “Crit­i­cally En­dan­gered”.

A MEX­I­CAN GOD

Be­sides the great bi­o­log­i­cal value of this species, there is a his­tor­i­cal value: The ax­olotl had a spe­cial im­por­tance in the cul­ture of the an­cient Mex­i­cans. The spirit of this an­i­mal was recog­nised by an­cient cul­tures, which saw it as a be­ing that de­fies death. In Aztec mythol­ogy, the ax­olotl (Nahu­atl: atl,

“wa­ter” and xolotl, “mon­ster”, aquatic mon­ster), is the aquatic equiv­a­lent of the god Xolotl, from which its name came.

Be­cause of its strange shape and char­ac­ter­is­tics, which the an­cient in­hab­i­tants of the Val­ley of Mex­ico at­trib­uted to mystical prop­er­ties, the ax­olotl has been used for medic­i­nal pur­poses in the treat­ment of asthma and bron­chi­tis

Brother of Quet­zal­coatl and mon­strous be­cause of the twin birth, Xolotl is as­so­ci­ated with the idea of move­ment and life, ac­cord­ing to the Legend of the Fifth Sun. Du­al­ity man­i­fests it­self in the trans­for­ma­tions to which it re­sorts to avoid sac­ri­fice. Bernardino de Sa­hagún, a Catholic mis­sion­ary pri­est, tells that Xolotl re­fused death, flee­ing the ex­e­cu­tioner by hid­ing in the corn­fields, where he mor­phed into a corn plant with two stalks. When he was dis­cov­ered, he ran again and took the form of a dou­ble maguey plant. Once again, the ex­e­cu­tioner found him and he es­caped into the wa­ter, trans­form­ing into an ax­olotl. This was the last meta­mor­pho­sis. Fi­nally, the ex­e­cu­tioner caught Xolotl and killed him.

In Aztec cul­ture, the ax­olotl is doc­u­mented in sev­eral codices, among which is the Floren­tine Codex. The first sci­en­tific ref­er­ence to the ax­olotl ap­pears in a book of nat­u­ral his­tory from 1615 From then on, nu­mer­ous works on the an­i­mal were pub­lished, but the sci­en­tific name was only given 200 years later.

The strange an­i­mal greatly im­pressed Alexan­der von Hum­boldt, a Prus­sian nat­u­ral­ist and ex­plorer, who took two spec­i­mens from Mex­ico and brought them to Paris, giv­ing them to the nat­u­ral­ist Ge­orges Cu­vier to study. He de­scribed with sur­prise the pres­ence and per­sis­tence of the ex­ter­nal gills on the sides of the head, and high­lighted its anatom­i­cal re­sem­blance to the sala­man­der. Cu­vier, true to the logic of com­par­a­tive anatomy, con­cluded that the ax­olotl was no more than the larva of a large sala­man­der. How­ever, years later, in his fa­mous clas­si­fi­ca­tion of the an­i­mal king­dom, he was forced to clas­sify it as a peren­ni­branch, an am­phib­ian that re­tains its gills through­out its life.

VALUE IN THE MAR­KET

Within culi­nary cul­ture, and since pre-His­panic times, the ax­olotl has been used in a va­ri­ety of dishes, in­clud­ing tamales and broths. Up to a few years ago, it was still eas­ily ac­quired in the Mex­i­can mar­kets of Xochim­ilco, Toluca, Pátzcuaro and Zumpango.

Be­cause of its strange shape and char­ac­ter­is­tics, which the an­cient in­hab­i­tants of the Val­ley of Mex­ico at­trib­uted to mystical prop­er­ties, the ax­olotl has been used for medic­i­nal pur­poses in the treat­ment of asthma and bron­chi­tis. Its heal­ing prop­er­ties have af­forded it renown that still per­sists to this day, and a trip to Sonora Mar­ket in Mex­ico City will al­low you to get your hands on oint­ments and ton­ics with the Mex­i­can ax­olotl as the main in­gre­di­ent.

In Mex­ico, the ax­olotl is also val­ued as a unique aquar­ium pet, with the rare al­bino, gold and melanic va­ri­eties con­sid­ered the most sought af­ter. This over­ex­ploita­tion, to­gether with the dis­rup­tion and dis­ap­pear­ance of its ecosys­tem, has put great pres­sure on the ax­olotl, driv­ing the species steadily to­wards ex­tinc­tion.

THREATS TO SUR­VIVAL

EN­VI­RON­MEN­TAL POL­LU­TION

In Mex­ico, the main cause of en­vi­ron­men­tal pol­lu­tion is the exploitation of nat­u­ral re­sources by in­dus­trial, agri­cul­tural, eco­nomic, so­cial, po­lit­i­cal and cul­tural ac­tiv­i­ties. Such un­sus­tain­able prac­tices have al­tered the nat­u­ral con­di­tions of the air, wa­ter, and soils.

The ax­olotl breathes through its gills, mouth, skin and lungs. While this abil­ity has made the ax­olotl an evo­lu­tion­ary mon­ster, it has caused ax­olotls, and am­phib­ians in gen­eral, to be ex­tremely sen­si­tive to the pres­ence of pol­lu­tants as they en­ter the body via th­ese four routes.

HABI­TAT LOSS

Am­bystoma mex­i­canum in­hab­its the fa­mous canals of Xochim­ilco, one of Mex­ico City’s 16 bor­oughs. This area has been com­pletely in­vaded by ur­ban sprawl – only a few hectares re­main that haven’t been touched. Pop­u­la­tions of the ax­olotl are in de­cline as the de­mands ofthe city’s hu­man pop­u­la­tion have led to the drain­ing and con­tam­i­na­tion of the wa­ters of Xochim­ilco Lake.

PRES­ENCE OF AN IN­VA­SIVE SPECIES

About 20 years ago, African tilapia were in­tro­duced into Xochim­ilco’s canals in a mis­guided ef­fort to cre­ate fish­eries. To­gether with the Asian carp, the two species now dom­i­nate the ecosys­tem, fur­ther push­ing the ax­olotl to­wards ex­tinc­tion. This non­na­tive species not only eats the ax­olotl’s eggs, but also com­petes with it for food.

PET TRADE

The ax­olotl is a very pop­u­lar pet around the world, par­tic­u­larly in Ja­pan. They are also com­monly dis­trib­uted to labs for re­search, act­ing as the white mice of am­phib­ians thanks to their unique ge­netic pro­file. As long as the de­mand for cap­tive ax­olotls con­tin­ues, their num­bers will con­tinue to fall. In Mex­ico City, a black mar­ket of an­i­mals sells a va­ri­ety of il­le­gal species such as snakes, lizards, tur­tles, and dif­fer­ent types of am­phib­ians – in­clud­ing ax­olotls.l

IL­LE­GAL FISH­ING

Thou­sands of wild ax­olotls are fished ev­ery year in dif­fer­ent ar­eas of Mex­ico. This species has been present in Mex­i­can cul­ture from the time of the Aztec Em­pire till today, thus it has been caught for food and medicine for hun­dreds of years. Al­though the ax­olotl is now a pro­tected species, en­force­ment is lack­ing and il­le­gal fish­ing of the crit­i­cally-en­dan­gered species con­tin­ues.

A CURE FOR CAN­CER?

The ax­olotl is the most widely-re­searched sala­man­der in the world, mak­ing this am­phib­ian a per­ma­nent res­i­dent in lab­o­ra­to­ries. Re­gen­er­a­tion of limbs is not an un­com­mon trait in sev­eral am­phibi­ous species, but the ax­olotl can re­build its brain, spinal cord and heart – or­gans which can­not be re­built by other species. Sci­en­tists are con­duct­ing ex­per­i­ments in an at­tempt to har­ness the abil­ity of re­gen­er­a­tion for the treat­ment of hu­man dis­eases. The ax­olotl’s DNA could some­day aid in cur­ing can­cer.

A team of sci­en­tists has re­cently dis­cov­ered one of the ax­olotl’s se­crets: It has the largest genome that has been se­quenced so far, much larger than ours. The ax­olotl genome con­tains 32 bil­lion base pairs of DNA, 10 times larger than the hu­man genome, which has around 3 bil­lion base pairs. This find­ing will be a pow­er­ful tool to study the molec­u­lar ba­sis of limb re­gen­er­a­tion and other forms of re­gen­er­a­tion.

THE WORK OF THE DO­MINI­CAN NUNS

For the past 150 years, the Do­mini­can nuns in Patzcuaro, Mi­choa­can have been sus­tain­ably rais­ing ax­olotls, lo­cally known as achoques. The am­phib­ian is a cru­cial in­gre­di­ent in a mys­te­ri­ous medicine the con­vent makes. It is be­lieved to cure coughs, asthma and anaemia. The sisters breed the ax­olotls to keep the tra­di­tion alive. Th­ese nuns are one of var­i­ous dif­fer­ent groups con­tribut­ing their work to ax­olotl con­ser­va­tion. Through the devel­op­ment of an ex­per­i­men­tal cul­ture of the species, they en­cour­age the ac­tive par­tic­i­pa­tion of the lo­cal com­mu­nity and col­lab­o­rate with aca­demic, gov­ern­men­tal and com­mu­nity in­sti­tu­tions in­ter­ested in its con­ser­va­tion. This is the only re­li­gious or­gan­i­sa­tion that ac­tively par­tic­i­pates in con­ser­va­tion projects in Mex­ico.

Other con­ser­va­tion groups have been fo­cus­ing on restor­ing ax­olotl habi­tats through con­ser­va­tion ed­u­ca­tion and a na­ture tourism ini­tia­tive. Ground­work on habi­tat restora­tion and biore­me­di­a­tion has also been con­ducted.

RIGHT The sil­hou­ette of a wild ax­olotl found in Manant­lan Re­serve

ABOVE Ax­olotl served at Cinco de Mayo mar­ket in Pue­bla, Mex­ico. It has been a source of protein for the Mex­i­cans since an­cient times, and be­lieved to be a pow­er­ful rem­edy against many dis­eases TOP An ax­olotl mu­ral at Xochim­ilco mar­ket in Mex­ico City

BE­LOW The waste that is dis­charged il­le­gally in the rivers of Pue­bla causes great dam­age to the flora and fauna. This waste is gen­er­ated by ir­re­spon­si­ble com­pa­nies, and the Mex­i­can govern­ment rarely does any­thing to stop them

ABOVE In­side Mer­cado Mix­huca, the black mar­ket of an­i­mals lo­cated in Mex­ico City, you can find count­less il­le­gal species for sale, in­clud­ing ax­olotls

BE­LOW Be­sides the loss of thou­sands of ax­olotls in fish­er­men’s nets ev­ery year, the in­tro­duc­tion of non-na­tive species is push­ing this unique sala­man­der to the brink of ex­tinc­tion

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