Description
Snout-vent length for males ranges from 36.4 – 52.2 millimeters while for females it ranges from 42.7 – 54.4 millimeters. It is a medium to small-sized frog and is generally smooth. It is overall brown with whitish spots on the back and a yellow triangular mark on the top of the head. The head tends to be slightly wider than it is long, with a rounded snout that can appear shortened. The canthus rostralis is prominent, with the loreal region sloping sharply to the lips, which don’t point out. The nostrils are lateral, and located closer to the snout tip than to the eye. The length of the eye is greater than the distance between the eye and the nostril. The distance between the eyes is greater than the distance between the nostrils (Formas 1981).

The forelimbs are slender. The relative length of each finger is as follows, from longest to shortest: 3 - 4 - 2 - 1. There is no webbing on the hands, and the fingertips are somewhat enlarged. It has a conspicuous elongate inner palmar tubercle, and a smaller, oval-shaped outer palmar tubercle. Subarticular tubercles are conical, modest, and medium-sized. It also has supernumerary palmar tubercles (Formas 1981).

The hind limbs are also slender. The toes are fairly long, and the relative length of each toe is as follows, from longest to shortes: 4 - (3,5) - 2 - 1. The outer metatarsal tubercle is low in profile and egg-shaped, while the inner metatarsal tubercle is conical and small. The subarticular tubercles are big and tapered, and tiny supernumerary tubercles are present. The tarsal fold, though visible, is reduced, and webbing between fifth and fourth toes is limited. The cloaca is slanted and discreet. The skin is generally smooth, with small tubercles present on the thighs, back, and head. The skin is somewhat bumpy underside of thighs towards the rear (Formas 1981).

This species can be distinguished with a combination of characters: the primitive webbing present between fifth and fourth toes, slender limbs, papillae that are present on its uneven tongue, and the yellow triangle on its head (Formas 1981).

In life, the back is brown, with whitish spotting in an uneven pattern. A yellow triangle is noticeable on the head. The underside is whitish up to the throat. The region between the eye and nostril is dark. A dark glandular fold is present behind the eyes. Limbs are striped dark brown (Formas 1981).

Juveniles have a darker belly that is mottled with black and retaining the whitish spotting of adults. Some adults show a white mid-dorsal stripe on the lower half of the dorsum. Snout-vent length proportions vary by approximately 8 mm to 12 mm, based on measurements of 28 adult specimens (Formas 1981).

Distribution and Habitat

Country distribution from AmphibiaWeb's database: Chile

View distribution map in BerkeleyMapper.

Distribution is restricted to a small area of southern Chile: Nahuelbuta Range, Ramadillas in the Biobiό region, Arauco Province. Few populations are known, and all are below 700 m elevation. The lowest population is at 25 m asl. Three of the known populations were found in small remnant patches of native forests (Nothofagus alpina, Aextoxicon punctatum), with leaf litter and small shady pools where specimens were most often observed. Exotic pine tree plantations are found in their habitat (Rabanal and Alarcón 2010, Veloso et al. 2010).

Life History, Abundance, Activity, and Special Behaviors
Adult specimens, though rarely encountered, have been seen in evening hours on leaf litter fairly distant from pools (Rabanal and Alarcón 2010).

It appears that the breeding season for this species is during January to February, as females collected during this time had eggs, while males had nuptial spines on their chest as well as on the thumb and second finger. Eggs collected were yellowish and about 2.33 mm in diameter (Formas 1981). Overall, behavioral information on this species is sparse since few field observations have been made (Formas and Brieva 2004, Rabanal and Alarcón 2010, Veloso et al. 2010).

Larva
The tadpole has a rounded snout, and its nostrils are ovoid and slightly depressed. The pupils are rounded, and the mouth is tapered. There is a rostral gap, but no ventral gap, and there are small fleshy projections that form a single row. The upper jaw extends past the lower jaw. The cloacal tube has a dorsal lip that covers the ventral lip. The tail is 62.2% of its whole length, with a straight tail axis. The back fin originates in a crest that reaches the spiracle, and the ventral fin originates at the end of the cloaca. The tip of the tail is slightly curved. It has a noticeable lateral line (Formas and Brieva 2004).

Preserved tadpole specimens have transparent dorsal and ventral fins, though unevenly permeated with dark specks. The underside is transparent, with internal organs visible. The jaws are dark for about half the width. Color in life is similar to those that have been formalin-fixed (Formas and Brieva 2004).

Tadpoles have been collected from the bottoms of small pools in shady areas. They are free-swimming and probably feed on material that they scrape off of plants and rocks under the water’s surface (Rabanal and Alarcón 2010).

Trends and Threats
The population numbers of this species are declining at a high rate due to destruction of their habitat from the expansion of nearby pine plantations. The population is estimated to have declined by 80% over the last ten years. Alsodes vanzolinii is intolerant of habitat modification, and their range has been almost completely destroyed in the last 10 years. In addition, plantation management actions like herbicides, application of fertilizer, or tree harvesting may be adversely affecting the population. In fact, Ramadillas, the area of the species’ original discovery, was home to high human activity and disturbance (Veloso et al. 2010, Ramadan and Alarcón 2010).

Possible reasons for amphibian decline

General habitat alteration and loss
Habitat modification from deforestation, or logging related activities
Intensified agriculture or grazing

Comments

Alsodes is sister to Eupsophus, the genus to which A. vanzolinii was originally ascribed; together, they form a strong monophyly within Alsodidae (Blotto et al. 2013). Alsodidae is nested within the superfamily Hyloidea, within the Neobatrachians (Pyron and Wiens 2011).

Alsodes vanzolinii is synonymous with Eupsophus vanzolinii.

Alsodes vanzolinii is named for Dr. Paulo Emilio Vanzolini, a herpetologist from Brazil who put together one of the largest herpetological collections of the Americas (Beolens et al. 2013).

This species was most recently sighted in 2008, and determination was based almost exclusively on tadpoles. Three populations were found, but only two adult specimens—both female—were seen (Rabanal and Alarcón 2010).

The original species description, by Donoso-Barros in 1974, was based on 15 adult males and 13 adult females (Formas 1981).

A karyotype comparison refers to 8 male specimens used as samples, but most likely refers to the specimens collected by Donoso-Barros. Since this original discovery, there have been no adult male sightings referred to in the literature (Formas and Vera 1983).

References

Beolens, B., Watkins, M., Grayson, M. (2013). The Eponym Dictionary of Amphibians. Pelagic Publishing

Blotto, B. L., Nunez, J. J., Basso, N. G., Ubeda, C. A., Wheeler, W. C., Faivovich, J. (2013). Phylogenetic relationships of a Patagonian frog radiation, the Alsodes + Eupsophus clade (Anura: Alsodidae), with comments on the supposed paraphyly of Eupsophus. Cladistics: 113-131.

Formas, J.R. (1981). The Identity of the Frog Eupsophus vanzolinii From Ramadillas, Nahuelbuta Range, Southern Chile. Proceedings of the Biological Society of Washington 93:920-927.

Formas, J.R. and L. Brieva (2004). The tadpoles of Alsodes vanzolinii and A. verrucosus (Anura: Leptodactylidae) with descriptions of their internal oral and chondrocranial morphology. Amphibia-Reptilia 24: 151-164.

Formas, J.R. and M.I. Vera (1983). Karyological Relationships among Frogs of the Genus Alsodes, with Description of the Karyotypes of A. vanzolinii and A. verrucosus. Copeia 1983(4): 1104-1107.

Pyron, R.A., Wiens, J. (2011). ''A large-scale phylogeny of Amphibia including over 2800 species, and a revised classification of extant frogs, salamanders, and caecilians.'' Molecular Phylogenetics and Evolution, 61(2), 543-583.

Rabanal, F. E., Alarcon, D. (2010). Amphibia, Anura, Cycloramphidae, Alsodes vanzolinii (Donoso-Barros, 1974): Rediscovery in Nature, latitudinal and altitudinal extension in Naheulbuta Range, southern Chile. Check List, Journal of species lists and distribution. Online edition ISSN 1809-127X.

Veloso A., Nunez, H., Ortiz, J.C. (2010). Alsodes vanzolinii. The IUCN Red List of Threatened Species. Version 2014.3. www.iucnredlist.org. Accessed 5 March 2015.

Species Account Citation: AmphibiaWeb 2023 Alsodes vanzolinii: Vanzolini's Spiny-Chest Frog <https://amphibiaweb.org/species/2560> University of California, Berkeley, CA, USA. Accessed Nov 27, 2024.

Citation: AmphibiaWeb. 2024. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 27 Nov 2024.

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