Genome size in salamanders is extreme by vertebrate standards, and Amphiuma means sits near the top, with a haploid genome commonly cited at around 25 times that of humans in DNA content. The bulk is not extra genes but repetitive sequence, particularly transposable elements that salamander lineages appear poor at purging.
Large genomes have physical consequences. Cell size scales with DNA content, so amphiuma cells are correspondingly huge, and their erythrocytes are large enough that the species is used as a teaching and research standard in cell biology. Bigger cells mean lower surface-to-volume ratio, which is thought to constrain metabolic rate and slow development.
Amphiumas attract misidentification. They are salamanders rather than eels or snakes, they retain four vestigial legs with one to three toes depending on species, and they lose their external gills as adults while keeping a single gill slit on each side. They are not venomous, but a large one can bite hard.