Ambystoma dumerilii

The Lake Patzcuaro Salamander (Ambystoma dumerilii)

The Lake Patzcuaro salamander, known locally as achoque and scientifically as Ambystoma dumerilii, is a remarkable species of mole salamander found exclusively in the high-altitude Lake Patzcuaro in the Mexican state of Michoacán. First described in 1870, this species is named in honor of French herpetologist Auguste Duméril. The achoque is most notable for its neotenic nature, retaining larval characteristics such as prominent, heavily filamented external gills and caudal fins throughout its adult life. This paedomorphic trait means it largely lives its adult life in an aquatic state, unlike many other salamander species that undergo complete metamorphosis.

Life and Habitat

Ambystoma dumerilii inhabits the alkaline freshwater environment of Lake Patzcuaro, situated at an elevation of 1,920 meters. The species has an average adult weight of 121 grams, with females typically weighing more than males. Adults can grow to impressive lengths, with some specimens exceeding 35 cm, placing them among the largest within the Ambystoma genus. Their skin texture varies from granular to smooth, and their coloration typically ranges from tan brown to green on the dorsum, often with dark spots, while the underside is pale grey. A unique characteristic for its genus is the retention of webbed feet on all four limbs into adulthood. The species is generally nocturnal but can be active during daylight hours.

Diet and Behavior

The achoque's diet in the wild primarily consists of the crustacean Cambarellus patzcuarensis, though they may incidentally consume plant matter and algae. In captivity, they are generalist carnivores, readily consuming aquatic invertebrates and small fish. They employ a unique feeding method using their gill rakers to create a sucking motion to draw food into their mouths. Behaviorally, they are known for their regenerative capabilities, able to regrow limbs. When threatened or needing to swim quickly, they pull their limbs close to their body and dive. While they do not typically vocalize, they can produce croaking or squeaking sounds when removed from water.

Reproduction and Life Cycle

Reproduction for Ambystoma dumerilii occurs in the winter and early spring. Unlike some tropical salamanders, their spermatogenesis follows an annual cycle. Males initiate courtship by displaying their cloaca to receptive females. Females can lay over 1,000 eggs in a single clutch, which are attached to vegetation or rocks. The larvae hatch at approximately 12 mm and develop their limbs and pigmentation as they grow. Sexual maturity is generally reached between 18 to 24 months of age. While the species can undergo metamorphosis in captivity, it is often incomplete, stressful, and significantly reduces lifespan.

Conservation Status and Threats

Ambystoma dumerilii is critically endangered, with estimates suggesting fewer than 100 individuals remain in the wild and a potential extinction within the next 20 to 30 years. The primary threats are severe pollution and habitat degradation of Lake Patzcuaro, stemming from human population growth, agricultural runoff, sewage, and deforestation. Invasive fish species introduced since the 1930s also prey on their eggs and larvae and compete for food resources. Despite its protected status, conservation efforts have been largely unsuccessful in reversing the lake's deteriorating conditions.

Historical and Cultural Significance

Historically, the achoque has been a significant part of the Purépecha culture, utilized for both food and traditional medicine since the Pre-Columbian era. 'Achoque soup' was believed to have medicinal properties for respiratory ailments, anemia, and as a source of energy for children and lactating women. The species was harvested extensively until the lake's environmental collapse in the late 1980s drastically reduced their numbers.