The Tailed Toad (genus Ascaphus) is a genus of small, inconspicuous toads that may be the most primitive of all modern anurans. Tailed toads are part of the genus, Ascaphus, which is the only taxon in the family Ascaphidae.
Classification and taxonomyEdit
The type species, Ascaphus montanus, has been known to science since 1899. It inhabits the mountain streams and ponds of the Rockies, in central North America. This species, the Mountain Tailed Toad, is smaller and colored differently than the other species often referred to as a tailed toad, which was discovered as a separate species in 1949. This species, Ascaphus truei, is commonly known as the Costal Tailed Toad. It is typically larger and coloured differently than A. montanus. Both species of tailed toads are also sometimes referred to as " tailed frogs"; being moist-skinned and frog-like in appearence. However, they are generally classified as toads due to the presence of paratoid glands that true frogs lack.
DescriptionEditThe existence of the visible "tail" appendage makes this genus of toad distinct from all other anurans. Thus its wider classification is difficult. It is usually classified in the Archaeobatrachia suborder of primitive toads, though some say it should be a sister group to 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, known as amplexus, rather than the external fertilisation found in other toads.
Ascaphus montanus, the Mountain Tailed Toad, is the type species. It is cryptically coloured for it lacks the poison secretions within its paratoid glands that all other toads have. A. montanus males average around 2.3 cm in length from nose to tail, and females about 2.6 cm in length. It is more robust in build than A. truei, and ranges in colour from pale brown to cocoa in colouration. Typically, A. montanus has a horizontal dark stripe running along its flank.
Ascaphus truei, on the other hand, is sometimes regarded as a subspecies of A. montanus. Like the Mountain Tailed Toad, the Costal Tailed Toad lacks toxic secretions in its paratoid glands and is cryptically coloured as a result. It ranges in colour from lime green to olive, and it is generally larger. Males of A. truei average around 3 cm long; as with the Mountain Tailed Toad, females of the Costal Tailed Toad are slightly bigger than the males. A. truei is more dependant on water than A. montanus.
Adults forage primarily terrestrially along stream banks but also occasionally feed underwater. A wide variety of food items taken, including both aquatic and terrestrial larval and adult insects, other arthropods (especially spiders), and snails. Tadpoles consume small quantities of filamentous green algae and desmids. Large quantities of conifer pollen are consumed seasonally by tadpoles.