The karyotype, C-bands and AgNO3-bands of a lungless salamander from Korea:Onychodactylus fischeri (Boulenger) (Amphibia, Urodela)

Effect of arsenic on p53 mutation and occurrence of teratogenic salamanders: their potential as ecological indicators for arsenic contamination

The p53 mutation in salamanders can be used as an indicator of arsenic contamination. The influence of arsenic exposure was studied on mutation of tumor suppressor gene in salamanders collected from several As-contaminated mine areas in Korea. Salamander eggs and larvae were exposed to arsenic in a toxicity test, and teratogenic salamanders found in heavy metal- and As-contaminated water from As-Bi mines were evaluated using PCR-SSCP to determine if they would be useful as an ecological indicator species. Changes in amino acids were shown to have occurred as a result of an arsenic-accumulating event that occurred after the DNA damage. In addition, both of the Hynobius leechii exposed groups were primarily affected by forms of skin damage, changes in the lateral tail/dorsal flexure and/or abnormality teratogenesis. Single-base sense mutation in codons 346 (AAG: Lys to ATG: Met), 224 (TTT: Phe to TTA: Leu), 211 (ATG: Met to AAG: Lys), 244 (TTT: Phe to TTTG: insertion), 245 (Glu GAG to Gln CAG) and 249 (TGT Cys to TGA stop) of the p53 gene were simultaneously found in mutated salamanders. Based on the results of our data illustrating the effect of arsenic exposure on the p53 mutation of salamanders in arsenic-contaminated mine areas, these mutated salamanders can be used as potential ecological indicators in the arsenic-contaminated ecosystems.

Evolutionary cytogenetics in salamanders

Salamanders (Amphibia: Caudata/Urodela) have been the subject of numerous cytogenetic studies, and data on karyotypes and genome sizes are available for most groups. Salamanders show a more-or-less distinct dichotomy between families with large chromosome numbers and interspecific variation in chromosome number, relative size, and shape (i.e. position of the centromere), and those that exhibit very little variation in these karyological features. This dichotomy is the basis of a major model of karyotype evolution in salamanders involving a kind of 'karyotypic orthoselection'. Salamanders are also characterized by extremely large genomes (in terms of absolute mass of nuclear DNA) and extensive variation in genome size (and overall size of the chromosomes), which transcends variation in chromosome number and shape. The biological significance and evolution of chromosome number and shape within the karyotype is not yet understood, but genome size variation has been found to have strong phenotypic, biogeographic, and phylogenetic correlates that reveal information about the biological significance of this cytogenetic variable. Urodeles also present the advantage of only 10 families and less than 600 species, which facilitates the analysis of patterns within the entire order. The purpose of this review is to present a summary of what is currently known about overall patterns of variation in karyology and genome size in salamanders. These patterns are discussed within an evolutionary context.