Raqescar

Cascades Frog
Conservation status
Near Threatened (IUCN 3.1)
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Amphibia
Order:	Anura
Family:	Ranidae
Genus:	Rana
Species:	R. cascadae
Binomial name
Rana cascadae Slater, 1939

The Cascades Frog (Rana cascadae) is a species of frog in the Ranidae family. It is found in western United States and possibly Canada, mainly in the Cascade Range and Olympic Mountains. Its natural habitats are temperate forests, temperate grassland, rivers, swamps, freshwater lakes, intermittent freshwater lakes, freshwater marshes, and intermittent freshwater marches generally between 665 m (2,180 ft) and 2,450 m (8,040 ft) elevation. The range may extend lower in Washington.

Physical Description

The cascades frog has a green to brown color on its back and a light yellow on its throat and belly. There can be a range from just a couple to about fifty gray spots located on its back. Depending on the situation, the spots may change color from the lighter gray/brown to a darker black spot. The colors on the frog’s back are also used to attract mates. The shape of the frog’s head is most commonly an oval with the mouth coming out to a slight point. Adult frogs will range anywhere from fifty to sixty five millimeters in length

Cascadae eggs are gelatinous and have a dark color on top with a creamy bottom. The tadpoles range within thirty-four to fourty millimeters. They have two upper rows of teeth and four lower rows, and there is a small gap in the upper rows located in the center.

Sound

The advertisement call of Rana Cascadae is a faint series of low grating clucking noises. Calls are produced at night and during the day from above and under the water

Breeding

Cascades Frogs lay their eggs May 20th through July 10th, depending on when the snow melts and creates ponds for the eggs to hatch in. First egg masses are deposited in comparatively warm water along gradually sloping shorelines, often over soft substrates protected from severe wave action. A single female will lay up to 425 eggs at a time. Females breed no more than once/year, but whether they skip years remains unknown. Very few tadpoles will live past their first year. The placement of clusters of egg masses in shallow water soon after first thaw can make them susceptible to freezing mortality and pathogen transmission between adjacent masses. The eggs hatch within eight to twenty days. They then have a larval period which lasts eighty to ninety-five days. Most frogs will reach their full size after three years, after which they become fertile and can begin mating. Adults appear to be strongly philopatric, using the same breeding sites for several years.

Habitat

The Cascade frog was first discovered in the Cascade Mountains in the California regions. It can be found throughout the Cascade Mountains ranging from Washington through Oregon, and California. They concentrate heavily around the volcanic area of the peaks. They also inhabit wetland habitats at higher elevations and moist meadows. They can be found in relatively small permanent and temporary ponds also found along streams in summer. The adults generally stay close to water, particularly along sunny shores, under dry summer conditions, but can be found traversing uplands during high humidity.

Diet

Larvae are thought to be primarily benthic feeders, but specific preferences are not well known The diet of the Cascade frogs is poorly known, but adults are thought to consume a variety of invertebrate prey and will occasionally consume conspecifics Taxonomy

Population

Females have a higher mortality rate than the male Cascade, but both are believed to live over five years, sometime reaching up to seven. (Briggs 297)

Causes of the Cascade frog's recent decline in population are not fully known, but introduced trout, UV-B radiation, fungal pathogens, and loss of open meadow habitat due to fire suppression have been suggested. Fertilizers such as urea may also pose a threat to Cascade frogs, as juveniles do not appear capable of sensing and avoiding toxic levels in laboratory studies.

Predation

The main predators of the cascade frogs are the, raccoon, mink coyote, water bugs (Belostomatidae), garter snakes (Thamnophis sirtalis), and several bird species such as the sharp shinned hawks, owls, gray jays, and robins. The long toed salamander and adult cascadae frogs are predators to the eggs and tadpoles as well (Briggs 289).

Fun facts

To guard itself from other microorganisms that live in the environment, the cascade frog produces high concentrations of antimicrobial peptides that it secretes from its skin in response to infection or stress (Blaustein 43). These antimicrobial peptides are also its main source of protection from larger predators such as birds and snakes. In studies done by Conlon, it has been found that “Frogs belonging to the genus Rana represent a particularly rich source of peptides with diverse structures and specificities against micro organisms” (1271). He began testing the frog secretions in order to determine whether or not the peptides would have an effect on bacterium that attack human cells. His discovery was that the chemical Ranatuerin-2CSa, which is produced by the R. cascadae, impeded the growth of Ecoli and S aureus in humans (“Conformational analysis” 924). These anti-infective agents give the Cascade frogs “therapeutic potential for the future” according to Conlon (926). One of the pitfalls of the Cascadae’s peptides, however, is that it also works as a blood thinner for humans and decreases the supply of oxygen that flows in the bloodstream (Case 301). To try and counteract this problem there are tests currently being undergone on the peptides in which amino acids are added to help decrease the toxicity to the human cells(Case 302). The goal is to still keep the peptide’s ability to fight against the bacteria but stop it from attacking already healthy cells. 

A breakthrough in research was recently found by Conlon called D-lysine (“Conformational analysis” 928). It is a substitute for Ranatuerin-2CSa which makes analogues of naturally occurring peptides that lack significant hemolytic activity (Conlon, “Conformational analysis” 928). This significantly reduces the strength of the blood thinning properties, and makes the chemical almost harmless to humans.

References

• Hammerson, G & Pearl, C. 2004. Rana cascadae.
• Hillis, D.M. & Wilcox, T.P. (2005): Phylogeny of the New World true frogs (Rana). Mol. Phylogenet. Evol. 34(2): 299–314. doi:10.1016/j.ympev.2004.10.007 PDF fulltext.
• Hillis, D. M. (2007) Constraints in naming parts of the Tree of Life. Mol. Phylogenet. Evol. 42: 331–338.
• 2006 IUCN Red List of Threatened Species. Downloaded on 23 July 2007.