A retrospective study of diseases in Ambystoma mexicanum: a report of 97 cases

Identification of enterobacteriaceae causing septicemia in the axolotl Ambystoma mexicanum

The Ambystoma mexicanum axolotl is a highly threatened amphibian and a valuable research model, with very little information about bacterial diseases affecting it. The aim of this study was to perform an identification of bacteria responsible for septicemia in three individuals. For all of them, necropsies were made, bacteria classification was performed by traditional and DNA-based molecular methods and tissues were histologically examined. All animals showed edema and ascites, and other tissues such as the lungs, spleen, liver, and kidney were also affected, dermatitis also occurred, in one case, the dermatitis was severe. Two bacterial isolates showed genetic identities of 99% with Aeromonas veronii, one with Citrobacter freundii, and another with 100% identity with Citrobacter portucalensis. These and other Enterobacteriaceae species of Aeromonas genus have been reported to produce septicemia in Anura amphibians and fish, pointing out that they are a health hazard for aquatic animals. Future endeavors to determine these bacteria prevalence, the search for antibiotic resistance/susceptibility, factors that can trigger the pathology, and the development of early diagnostic tools should be done to improve our understanding.

Ultrasound description of the coelomic cavity of the axolotl (Ambystoma mexicanum) in a clinically healthy population: a pilot study

Axolotls (Ambystoma mexicanum) are extensively studied for their relevance in human medical research. Despite being critically endangered in the wild, they have gained popularity as household pets. Although they have been kept in captivity for over a century, detailed descriptions of their coelomic organ anatomy remain limited. Also, this species exhibits significant variations compared to other amphibians. Ultrasound is a non-invasive and painless medical imaging technique, ideally suited for investigating internal organs or structures. This study focused on describing the ultrasound appearance of the axolotl coelomic cavity. It details the identification, localization and parenchymal description of major organs in 28 neotenic axolotls using ultrasound frequencies ranging from 7 to 15 MHz. The accuracy of the results was validated by comparing ultrasound findings with necropsy results from one male and one female axolotl. The heart, lung surface, liver and reproductive tracts were visualized. Measurements, along with confidence intervals, were calculated for the spleen, kidneys, testicles, gastric wall, gallbladder, and pylorus. Occasional detection of hyperechoic millimetric particles in the gallbladder or ascites was noted. However, visualization of the pancreas and bladder was not possible. This research outcomes involve the development of a comprehensive atlas comprising images obtained throughout the study. Additionally, the experiment established a reproducible and readily accessible protocol for conducting anatomy-morphological assessments in axolotl medicine. This protocol stands as a crucial preliminary stage before advancing to lesion identification.

GROSS AND ULTRASONOGRAPHIC ANATOMY OF THE COELOMIC ORGANS OF HEALTHY AXOLOTLS (AMBYSTOMA MEXICANUM)

The objectives of this study were to describe the gross anatomy and ultrasonographic appearance of coelomic organs in subadult and adult axolotls (Ambystoma mexicanum), to describe an ultrasound technique, and to test correlations of ultrasonographic measurement with body length, width, and weight. Necropsies of coelomic organs were conducted on 10 axolotls (females = 5; males = 5) and ultrasound on 11 (males = 5; females = 6). Animals were kept in water and maintained conscious during ultrasound. The heart, caudal vena cava, liver, gallbladder, spleen, esophagus, stomach, colon, kidneys, ovaries, and fat bodies were identified in all study subjects, although testicles were identified in only 6/7 subjects. The pancreas and adrenal glands could not be identified in any animals, either during necropsy or ultrasonography. Coelomic and pericardial effusion was present in all animals. Ultrasonographic measurements of the liver, spleen, myocardial thickness, and right and left kidney length were highly repeatable (correlation value [CV] < 5%) and the esophagus, spleen, caudal vena cava, fat bodies, gallbladder, colon thickness, right kidney height and width, and right testicle diameter were statistically repeatable (CV < 10%).

Establishing a New Research Axolotl Colony

The field of regenerative biology has taken a keen interest in the Mexican axolotl (Ambystoma mexicanum) over the past few decades, as this salamander successfully regenerates amputated limbs and injured body parts. Recent progress in research tool development has also made possible axolotl genetic manipulation and single-cell analysis, which will help understand the molecular mechanisms of complex tissue regeneration. To support the growing popularity of this model, we describe how to set up a new axolotl housing facility at a research laboratory. We also review husbandry practices for raising axolotls and using them in biological research, with a focus on diet, water quality, breeding, and anesthesia.