Description
Alsodes cantillanensis is a medium-sized frog with a sturdy build that was described from two individuals, a male (holotype) and a female. The male has a snout-vent length of 45.9 mm and the female 44.2 mm. The head length constitutes 34.4% of the snout-vent length and is wider than long. The snout is slightly truncated from a lateral view. Their nostrils have a dorsolateral orientation and are located midway between the tip of the snout and the anterior border of the eye. They have a well developed canthus rostralis. The eyes are bulging. The supratympanic fold covers the tympanum. The tympanic ring is not visible from the outside of the animal. This species has smooth skin in dorsum, arms, legs, and ventral surface while having granular flanks. Males have two round thorny nuptial patches, one on either side of their chest. The fingers and toes lack webbed and both have rounded tips. The order of increasing length of the fingers is II, I, IV, III, and males have thorny nuptial pads on fingers one and two. The order of increasing length of the toes is I, II, V, III, IV (Charrier et al. 2015).

DIAGNOSIS:

Alsodes cantillanensis is differentiated from other Alsodes by the thorny patches seen on the chests of males with spines uniformly distributed, a triangular marking on the top of the head with contrasting color from the rest of the body, and smooth dorsal skin. Alsodes cantillanensis is found in sympatry with A. nodosus but the two do not share similarities in all of their morphological characteristics. Alsodes cantillanensis has uniformly distributed chest spines, yellow on the upper portion of its iris, a light triangle on its head, and smooth skin. These morphological characteristics are more similar to southern Chilean and Argentinian Alsodes species than to A. nodosus (Charrier et al. 2015).

COLORATION:

In life, the males are yellow to ochre to dark grey with a lighter triangle and females are red to orange with a red-orange triangle. The triangle on their head is between the posterior border of their eyes and the tip of their snout, and there is dark coloration under the canthus. They have a thin vertebral yellow line on the posterior half of their dorsum. The ventral coloration is white with white spines on the chest. The tips of the fingers and toes are white. The dorsal portion of the iris is gold-yellow while the rest is dark brown or black (Charrier et al. 2015, Charrier 2019).

VARIATION:

Because the species was only described from one male and one female, it is difficult to extrapolate if variation between them is from individual variation or sexual dimorphism. Physically, the male specimen has spiny patches on the chest and thicker arms than the female. In terms of color, the male is yellow to dark gray with a lighter triangle and the female is red to orange with a red-orange triangle (Charrier et al. 2015, Charrier 2019).

Distribution and Habitat

Country distribution from AmphibiaWeb's database: Chile

View distribution map in BerkeleyMapper.

Alsodes cantillanensis is described as being distributed in central-southern Chile as well as the eastern Andes Mountain range of Argentina. This species is specifically found in the Altos de Cantillana mountains, which has a temperate climate, wetland environment, and where the average temperature is 10°C. They inhabit the forests of the western slopes of the mountain range and are found close to water sources, such as streams and creeks (Charrier et al. 2015). The elevation range ranges from 729 meters to 850 meters above sea level while the geographical range is estimated to be 20 - 21 square kilometers (IUCN 2015).

Life History, Abundance, Activity, and Special Behaviors
This species is found between rocks on the main banks of river shores, hidden under logs and stones. Some members of the species have been seen walking up to several meters away from the water. In the warmer months, this species is commonly found under layers of leaves between large stones (Charrier et al. 2015).

The larvae of this species are commonly found under shaded areas of rivers or small streams, as well as calm, stagnant waters and ponds adjacent to the main riverbed. This habitat provides cool waters with little current and a rocky substrate. The larvae are commonly hidden beneath and between the crevices of the rocks found in these stagnant waters. The average number of eggs laid at a time is approximately 60 (Charrier 2019).

They commonly inhibit rivers with similar amphibians, including Alsodes nodosus and Pleurodema thaul, invertebrates, including those of the genus Aegla, and fish in the genus Trichomycterus (Charrier et al. 2015).

Alsodes cantillanensis shares breeding sites with A. nodosus. As of 2021, it’s unknown what reproductive mechanisms are used by to maintain reproductive isolation between these closely related species (Charrier et al. 2015).

Trends and Threats
This species and other closely related species in the same area are living in “islands of biodiversity” that are completely surrounded by land used by humans. Because this species is located in the Altos de Cantillana mountain range, it has been impacted by human activities, such as charcoal and gold mining, increased land use, and livestock and agricultural production, as well as natural disasters, including fires (Charrier et al. 2015). Climate change is also changing the rates of precipitation and increasing fire risk during the warm season (Charrier 2019). Little is known about the current population size or trends (IUCN 2015).

The species is not known in any official protected area (Charrier 2019). Quebrada Infiernillo and another creek where this species was found are located on private property, which means that a large portion of the population is now somewhat territorially protected. However, the sanctuary does not have the legal right to exclude potential mining projects, as there is a history of this kind of activity there (Charrier et al. 2015).

Possible reasons for amphibian decline

General habitat alteration and loss
Intensified agriculture or grazing
Mining

Comments

PHYLOGENETIC RELATIONSHIPS:

The phylogenetic relationships of 14 Alsodes species were determined using Bayesian and Maximum Parsimony analyses of 359 parsimony-informative characteristics from mtDNA and nDNA. That tree has two main clades; one clade includes A. cantillanensis, A. nodosus, and A. vanzolinii. The other clade is composed of the remaining Alsodes species. Alsodes nodosus is the sister lineage of A. cantillanensis. The two species have significant geographic overlap, even living and reproducing in some of the same water bodies (Charrier et al. 2015).

ETYMOLOGY

The genus Alsodes is made up of various spiny chest frog species found in Chile. The species name “cantillanensis” comes from the Latin variation of the word “Cantillana”, the mountainous region near Santiago, Chile known as Altos de Cantillana (Charrier et al. 2015).

OTHER INTERESTING INFORMATION:

A video of the frog and its habitat can be found on Vimeo by Andres Charrier, the lead author of the species description.

References

Charrier, A. (2019). Anfibios de los Bosques de la Zona Centro Sur y Patagonia de Chile. Corporación Chilena de la Madera, Madera, Chile.

Charrier, A., Castro-Carrasco, C., Correa, C.L., Mendez, M.A. (2015). "A new species of Alsodes (Anura: Alsodidae) from Altos de Cantillana, central Chile." Zootaxa, 3915(4), 540-550. [link]

IUCN SSC Amphibian Specialist Group. (2015). "Alsodes cantillanensis." The IUCN Red List of Threatened Species 2015: e.T76338143A76338146. https://dx.doi.org/10.2305/IUCN.UK.2015-4.RLTS.T76338143A76338146.en. Downloaded on 25 January 2021.

National inventory of Chilean species. (2016). “Alsodes cantillanensis (Charrier, Correa, Castro & Mendez, 2015)”. Ministry of Environment. Accessed 16 February 2021 from http://especies.mma.gob.cl/CNMWeb/Web/WebCiudadana/ficha_indepen.aspx?EspecieId=5691&Version=1.

Species Account Citation: AmphibiaWeb 2021 Alsodes cantillanensis: Cantillana Spiny-Chest Frog <https://amphibiaweb.org/species/8311> University of California, Berkeley, CA, USA. Accessed Jan 7, 2025.

Citation: AmphibiaWeb. 2025. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 7 Jan 2025.

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