© 2009 Richard D. Sage (1 of 3)
Variation: An aquatic form and littoral form exists. The aquatic form has well developed cutaneous folds, extensive interdigital menbranes and an orange venter, whereas the littoral form has little cutaneous folds, little interdigital membranes and a grayish venter (Cei 1980; Cuello et al. 2006).
Coloration: The dorsum is either grayish or olive-brown with dark spots or fine speckles. The venter is orange and is slightly mottled on the chest and throat in the aquatic form (Cei 1980).
Tadpole morphology: Tadpoles have a flattened body. The skin is transparent. Its viscera are visible. The head is not as wide as the body. It has visible eyes and nostrils, which are positioned dorsally. Its upper tooth rows are equal in length or longer than the upper beak. The spiracle is sinistral and the spiracular tube is not easily visible. The tail is longer than the head and body. The tail musculature is well developed. It has a rounded tail tip (Cei 1965; Cei 1980).
Tadpole coloration: The dorsum is a pale golden-brown and dotted with small brown spots. The tail is also golden-yellow. The caudal fin is transparent with brown markings that are not as prominent in the ventral fin. In preserved specimens, the dorsum is brown with brown spots on the posterior part of the body, dorsal fin and dorsal part of the tail. The venter is transparent. The snout is slightly pigmented(Cei 1965).
Distribution and Habitat
This species inhabits isolated lagoons, rocky and volcanic areas bordering Laguna Blanca. It can be found up to 1200 m in elevation (Cei 1965; Úbeda et al. 2010). Breeding is known to take place in ponds (Úbeda et al. 2010).
Life History, Abundance, Activity, and Special Behaviors
Larvae tend to swim in shallow waters rather than open water and also feed on small animals and algae (Cei 1965). In the winter, frogs will remain submerged underwater (Cuello et al. 2009).
Calls are characterized by a deep voice (Cei 1965).
Egg laying is hypothesized to occur in January and the breeding cycle extends from spring to summer. Gelatinous clutches, which have heavily pigmented eggs, are attached to submerged stalks (Cei 1965; Cei 1980).
Based on environmental variables, such as water levels, the morphology of A. patagonicus changes between that of a littoral form and an aquatic form. These changes do not seem to correspond to an annual pattern (Cuello et al. 2008).
The different morphotypes have different diets. The aquatic form feeds on mostly naiads, benthic arthropods and amphipods (Cuello et al. 2006; Cuello et al. 2009a). Some studies found that the species also consumed algae. On the other hand, the littoral form mainly subsists on small arthropods such as ants, beetles, mites and spiders (Cuello et al. 2006). Its diet, in general, includes mainly amphipods and because the frogs are the only permanent vertebrates of the area, A. patagonicus is considered a key species of the ecosystem (Cei 1965; Cei 1980; Cuello et al. 2009a).
Diet choices between the morphotypes possibly contribute to the morphotype changes since amphipods in the pools have carotenoids which give the aquatic form its ventral orange color and the diet of the littoral form contributes to its grayish color (Cuello et al. 2008).
Trends and Threats
Introduced fish may be a threat to A. patagonicus since they overlap in diet choice. Other threats include habitat disturbance, eutrophication of its lake habitat due to livestock, disease and alteration of diet (Cuello et al. 2006; Cuello et al. 2009b; Úbeda et al. 2010).
The species is susceptible to both the ranavirus and the chytrid fungus. However, the ranavirus occurs at a higher incidence than Batrachochytridium dendrobatidis. Symptoms of the ranavirus manifests itself in the tadpoles and metamorphs of this species instead of adults. Infected tadpoles exhibit hemorrhages in the tail, abdomen, back legs and throat. Although it is not known if the ranavirus is the cause of the decline, this particular occurrence of the disease is the first documented case of significant mortality that it is associated with in South America (Fox et al 2006).
A conservation project to restore populations and educate the local human population was started and an effort to prevent introduction of fish has been suggested (Cuello et al. 2009b; Úbeda et al. 2010).
Possible reasons for amphibian decline
General habitat alteration and loss
The two morphotypes were hypothesized to be two cryptic species, but some studies suggested that the morphotypes are reversible based on environmental variables (Cei 1980; Cuello 2008). A recent genetic study confirmed the hypothesis that the two morphotypes were the result of reversible phenotypes (Martinazzo et al. 2011).
Carmen Úbeda, Esteban Lavilla, Néstor Basso 2010. Atelognathus patagonicus. IUCN (2011). 2011 IUCN Red List of Threatened Species. www.iucnredlist.org. Downloaded on 23 April 2012.
Cei, J. M. (1965). ''The tadpole of Batrachophyrus patagonicus Gallardo .'' Herpetologica, 20, 242-245.
Cei, J. M. (1980). ''Amphibians of Argentina.'' Monitore Zoologica Italiano, New Series Monografia, Firenze, 2, 1-609.
Cuello, M. E., C. A. Úbeda, and M. T. Bello (2008). ''Relationships between morphotypes of Atelognathus patagonicus (Anura, Neotrachia) and environmental conditions: evidence and possible explanation.'' Phyllomedusa, 7, 35-44.
Cuello, M. E., M. T. Bello, M. Kun, and C. A. Úbeda (2006). ''Feeding habits and their implications for the conservation of the endangered semiaquatic frog Atelognathus patagonicus (Anura, Neobatrachia) in a northwestern Patagonian pond.'' Phyllomedusa, 5(1), 67-76.
Cuello, M. E., Úbeda, C. A., Bello, M. T., Kun, Marcelo (2009). ''Seasonal trophic activity of the aquatic morphotype of Atelognathus patagonicus (Anura, Neobatrachia) and prey availability in the littoral benthos of a permanent pond in Argentinean Patagonia .'' Phyllomedusa, 8(2), 135-146.
Cuello, Maria E., Perotti, M. G. Iglesias, G. J. (2009). ''Dramatic decline and range contraction of the Endangered Patagonian frog Atelognathus patagonicus (Anura, Leptodactylidae).'' ORYX, 43(3), 443-446.
Fox, Stanley F., Greer, Amy L., Torres-Cervantes, Ricardo, Collins, James P. (2006). ''First case of ranavirus-associated morbidity and mortality in natural populations of the South American frog Atelognathus patagonicus.'' Diseases of Aquatic Organisms, 72(1), 87-92.
Frost, D. (2011). Amphibian Species of the World: an Online Reference. Version 5.5.
Martinazzo Liza B., Basso Nestor G., Ubeda Carmen A. (2011). ''The aquatic and littoral forms of the Patagonian frog Atelognathus patagonicus (Batrachylinae): new molecular evidence.'' Zootaxa, (3129), 62-68.
Written by Mingna (Vicky) Zhuang (mz.aerochild AT gmail.com), UC Berkeley
First submitted 2012-05-11
Edited by Michelle S. Koo (2012-05-11)
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