Ischnocnema guentheri is a small direct-developing frog (19-40mm SVL, belonging to the I. guentheri species series of Hedges et al. (2008) and closely related to I. parva (Heinicke et al. 2007). The snout is fairly long and acuminate in dorsal view. Nostrils lateral. Eyes large, fairly prominent, with the diameter about 1.5 times the snout length. The tympanum is distinct, with the diameter about 1/5 that of the eye. Single vocal sac weakly indicated, males with vocal slits. The first finger is about the same length as the second. Fingers free, without webbing, fairly long, all with dilated tips, a pronounced rounded tubercle at the base of the first finger; metacarpal tubercles well developed. Legs and toes long, with enlarged discs, fifth toe longest. Outer metatarsal tubercle rounded. Dorsal texture smooth or very finely granular. Ventral texture smooth.
Dorsal color can vary greatly from dark brown, uniform dark, brick red, green or pale cream. Posterior surface of the thigh almost uniform brown. Dark sacral spots present. Most individuals bear an interrupted or complete dark stripe in the anterior surface of the tibia. The belly is smooth and can vary from light yellow to golden yellow or cream, just like the inner side of the tibia. Heel with tubercles (Cochran 1955; Heyer 1984; Heyer et al. 1990). The species exhibits sexual size dimorphism, with males being smaller than females (Heyer 1984). Mean body mass is 1.77g (Rocha et al. 2007).
Distribution and Habitat
Country distribution from AmphibiaWeb's database: Brazil
Ischnocnema guentheri is found in the Atlantic Rain Forest of Brazil from southern Bahia to western Paraná and northeastern Santa Catarina, above 1,200m (Kwet and Solé 2005; Hedges et al. 2008). This species lives on the forest floor.
Life History, Abundance, Activity, and Special Behaviors
Ischnocnema guentheri is a forest ground dweller and is commonly found on the leaf litter during the day or night. This is a species with low mobility. Although it mainly inhabits forest habitats it can also be encountered near the forest edge in surrounding vegetation (Heyer et al. 1990; Pombal 1997; Ramos and Gasparini 2004; Ribeiro et al. 2005).
Males call at late afternoon and early night from low vegetation (20-60 cm) in the rainy season from October to February away from water bodies, but inactive individuals can be found from the very end August throught June (Heyer et al. 1990; Haddad and Sazima 1992; Pombal and Gordo 2004). The advertisement call was described by Heyer et al. (1984; 1990) and can be heard on Haddad et al. (2003). The call is given sporadically, beginning quietly and ending loudly; call duration 1.10-1.75s. Some variations in call structure within the geographic range of I. guentheri and its taxonomic implications are discussed in Kwet and Solé (2005).
This species has direct development, laying small clutches (usually 20-30 eggs) in small hollows, like miniature roofed caves, in banks of earth (Lynn and Lutz 1946; Lutz 1947; Izecksohn and Carvalho-e-Silva 2001; mode 23 of Haddad and Prado 2005).
Dixo and Verdade (2006) reported that they found 12 individuals during 32 days in their study site. Van Sluys et al. (2007) found 6 individuals during one year of sampling, at a density of 1.3 individuals/100m2 using small plots. Rocha et al. (2007) found similar results; I. guentheri was the dominant species within the leaf-litter frog fauna in their study site, comprising 29.5% of the anuran fauna, with a density of 2.71 ind/100m2. Steinicke (2008) found 383 specimens in four forest fragments during two rainy season sampling periods in southeastern Brazil. Additionally, I. guentheri was more commonly found inside small forest fragments, compared with a control site (a forest reserve). Furthermore, it tended to have a higher survival rate in fragmented habitats, demonstrating to be an intermediate habitat specialist. Giaretta et al. (1997) found that I. guentheri was more common at a higher altitude locality in their study site, due to more leaf-litter accumulation and humidity, moreover, I. guentheri comprised 83% of the individuals caught, being the dominant species at this site.
There are reports of infection by nematodes in a population of I. guentheri from Rio de Janeiro. Five species of worms infected the frogs and were found in the lungs and intestine (Martins and Fabio 2005).
An analysis of food items ingested by the pirapitinga do sul (Brycon opalinus, an endangered fish in rivers of the Atlantic Forest of the Serra do Mar, in southeastern Brazil) revealed the occurrence of Ischnocnema guentheri as a prey item, but the authors pointed out that this fish is an opportunistic omnivore (Gomiero et al. 2006).
The defense strategy is death feigning (Haddad et al. 2008).
Trends and Threats
Its range is within protected areas, like the Nova Baden State Park, at Lambari-MG, Ibitipoca State Park, at Lima Duarte-MG, Parque Nacional da Serra da Bocaina, São José do Barreiro-SP, Parque Nacional da Tijuca, in Rio de Janeiro-RJ, Parque Nacional da Serra dos Órgãos, at Teresópolis-RJ, Reserva Ecológica do Guapiaçu, Parque Estadual da Serra do Mar, Parque Nacional do Caparaó, Estação Biológica da Boracéia, at Salesópolis-SP, Parque Estadual de Intervales, Estação Ecológica Juréia-Itains and Serra do Japi. It is little abundant in Ilha Grande. Declining according to IUCN. This species seems to have experienced a local decline at Boracéia between 1983 and 1984, compared with data from 1979, but recently appeared to be abundant again, as new data has been collected at the site, but there are no records of declines in another localities along the range of this species (Heyer et al. 1988; Eterovick et al. 2005). Ischnocnema guentheri is a common species within its range.
Possible reasons for amphibian decline
General habitat alteration and loss
Habitat modification from deforestation, or logging related activities
Intensified agriculture or grazing
Deformity-causing parasitic worm (trematode) larvae
The species has a diploid chromosomal number of 2n = 22 (Beçak 1968; Siqueira et al. 2004).
The name of the genus comes from the Greek words ischnos, meaning slender or weak, and kneme, meaning calf of the leg (Hedges et al. 2008). The species is named for Albrecht Karl Ludwig Gotthilf Günther (October 3, 1830 - February 1, 1914), a German-born British zoologist. A photo of the holotype is available in Kwet and Solé (2005). A table with distinctive traits that can differentiate I. guentheri from other members of the group from southeastern Brazil is available from Heyer (1984: 21).
Kwet and Solé (2005) stated that there are at least three cryptic species under the name of I. guentheri, revealing the necessity of taxonomic clarification.
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Written by: Diogo B. Provete (2008-09-12)
Edited by: Kellie Whittaker (2009-01-20)
Species Account Citation: AmphibiaWeb 2009 Ischnocnema guentheri: Steindachner's Robber Frog; ra-da-mata <https://amphibiaweb.org/species/2952> University of California, Berkeley, CA, USA. Accessed Apr 13, 2021.
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Citation: AmphibiaWeb. 2021. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 13 Apr 2021.
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