Tailed frog
The tailed frogs are two species of frogs in the genus Ascaphus,[1] the only taxon in the family Ascaphidae /æˈskæfɪdiː/.[2] The "tail" in the name is actually an extension of the male cloaca. The tail is one of two distinctive anatomical features adapting the species to life in fast-flowing streams. These are the only North American frog species that reproduce by internal fertilization.[3]They are among the most primitive known families of frogs.
Its scientific names means 'without a spade', from the privative prefix a- and the Ancient Greek skaphís (σκαφίς, 'spade, shovel'), referring to the metatarsal spade, which these frogs do not have.[4][5]
Until 2001, the genus was believed to be monotypic, the single species being the tailed frog (Ascaphus truei Stejneger, 1899). However, in that year, Nielson, Lohman, and Sullivan published evidence that promoted the Rocky Mountain tailed frog (Ascaphus montanus) from a subspecies to its own species.[6] Since then, the former species has been formally called the coastal tailed frog.
The existence of the visible "tail" appendage makes this frog family distinct from all other frogs. Thus, its wider classification is difficult. It is usually classified in the ancient frog suborder Archaeobatrachia, though some say it should be a sister to all other frogs. The "tail" is found only in males, and is actually part of the cloaca, used to insert sperm into the female during mating. This anatomical feature improves breeding success by minimizing loss of sperm in the turbulent, fast-flowing streams inhabited by this species. Thus, the tailed frogs exhibit internal fertilisation, rather than the external fertilisation found in other frogs.[7]
These frogs are primitive in having a greater number of vertebrae than other frogs, in lacking the ability to vocalise, and in possessing free ribs. They are small – around 2.5 to 5.0 cm (0.98 to 1.97 in) long – and are found in steep, fast-flowing streams in Montana, Idaho, Washington, Oregon, and northern California in the northwest United States, and southeastern British Columbia (Rocky Mountain Tailed Frog) and coastal BC (Coastal Tailed Frog).
Another primitive trait that tailed frogs contain is a series of antimicrobial peptides called ascaphins. These peptides share minimal genetic characteristics with other peptides secreted by frogs, yet shows some similarities with antibacterial peptides found in African scorpions Pandinus imperator and Opistophtalmus carinatus. The ascaphin peptides are secreted through the skin and imperative in fighting bacteria such as E. coli and S. aureus.[8]
