Lithodytes lineatus is a leaf-litter frog found primarily in the Amazon. Adult female L. lineatus are have a total length of 38.1 - 52.0 mm and significantly larger than adult males, who range from 34.9 - 47.0mm. When viewed from both the profile and above, its snout is rounded. The distinct tympanum is about the same diameter as its eye. The dorsum skin is finely speckled and the venter skin is smooth. Finger webbing is absent, and its first finger is longer than the second. The snout-vent length of juveniles collected in Rondonia state, northwestern Brazil between April 2001 and March 2002 ranged from 19.6 - 35.9 mm (Duellman 2005; Bernarde and Kokubum 2009).
Tadpoles in Gosner Stage 34 typically have a body length of 18.1 mm. In dorsal view their body is elongated ovoid and is the widest (wider than high) at one-third of its length. It’s a total length of 47.4mm. The snout is bluntly rounded in profile view, but truncate in dorsal view. Its eyes are situated dorsally, are slightly anterodorsally, and directed laterally. The nares are situated about midway between the eyes and the tip of the snout and the spiracle is sinistral below the midline of the body. The interorbital distance is about four times the diameter of the eye. The spiracular tube started slightly posterior to the mid-length of the body and is attached to the body in its entirety. The spiracular tube’s opening is directed posterodorsally. The vent tube is moderately long, medial, and attached to the ventral fin with its tip free. The caudal musculature is highest at about one-third of the length of the tail and is moderately robust. It gradually narrows posteriorly and it ends just before the rounded tip of the tail. The dorsal fin and ventral fin start at the bottom of the tail. The dorsal fin is highest around mid-length while the ventral fin is highest at about one-third the length of the tail and is equal to the height of the dorsal fin at this point. In the middle of the tail, both fins are shallower than the caudal musculature and gradually narrow to come to a rounded tip. The oral disc is anteroventral and the anterior labium is bare; everywhere else there is a single row of long marginal papillae. There are no submarginal papillae. It’s jaw sheaths are finely serrate, broadly arched and sender. The labial tooth row formula (LTRF) is 0/1; the LTRF and the presence of jaw sheaths are variable, 0/0 to 2(2)/3(1) (Duellman 2005).
Lithoydytes and Phyllobates fermoralis are two terrestrial species that may represent a case of amphibian (Batesian and Mullerian) mimicry. They both have yellow dorsolateral lines in almost the same position and have similar dorsal coloration and lash color. Lithodytes lineatus has wider dorsolateral lines than Phyllobates fermoralis (Dendrobatidae). Lithodytes Lineatus also has an orange stripe that starts at the groin and extends to its posterior face. It has dark tan limbs with dark spots on the proximal part of the thigh and black dorsal coloration with a slight tan coloring. Phyllobates femoralis has a black and white mottled venter and a cream ventro-lateral stripe that L. lineatus is missing. Pyllobates is known for having toxic skin secretions while L. lineatus has studded dorsal surfaces and granular tubercles which could suggest that it may also have dermal secretions used for protection (Nelson and Miller 1971).
In life, L. lineatus has a black dorsum and flanks with a thick yellow stripe that extends from their snout to their to the groin. The belly and ventral surfaces of the hind limbs are grey, throat and chest are brown, and the upper arms are tan. Lithodytes lineatus has red spots on the posterior surfaces of thighs and there is a large red spot on the groin. The iris is a dark coppery bronze and fine black reticulations are present (Duellman 2005; Nelson and Miller 1971).
Alive, the L. lineatus tadpole body is bright pink and has a short, white, metallic mid-dorsal stripe. Its fin is translucent pink and the color of the caudal musculature is similar to the body but is less intense distally (Duellman 2005).
Distribution and Habitat
Country distribution from AmphibiaWeb's database: Bolivia, Brazil, Colombia, Ecuador, French Guiana, Guyana, Peru, Suriname, Venezuela
Lithodytes lineatus is often considered too rare to find in many studies of anuran habitats, but it is known for being widely distributed in Amazonian forests of Ecuador, Eastern Peru, Brazil, Venezuela, and the Guianas. It is found in both terrestrial and freshwater habitats but is primarily found in tropical rainforests. It can be found below leaf-litter, logs, and other forest cover (La Marca et al. 2012).
Life History, Abundance, Activity, and Special Behaviors
In the past, Lithodytes lineatus has appeared to be a mostly forest dwelling species. Although this species is relatively abundant in Amazonian forests, knowledge of it is limited. What is well known is L. lineatus’ association with leaf cutter ants, Atta cephalotes. This relationship has been suggested to be a true symbiosis, with ant nests having been observed as a breeding site of L. lineatus during the October to March breeding season. Such a relationship has never been reported before. This association often impedes visual encounter surveys because males call from the ant nest burrows.
Lithodytes lineatus, sports impressive yellow stripes along its back. Originally thought to be a Batesian mimic of other poison frogs, it turned out that this species is actually toxic, and hence likely to be a Mullerian co-mimic (Prates et al. 2012). Recent research on this species has revealed another fascinating component to its natural history – it chemically mimics ants. This species is typically found living in the nests of leaf-cutter ants (genus Atta), yet does not appear to suffer attacks from the ants, which are generally highly aggressive towards nest intruders. De Lima Barros et al. (2016) tested the hypothesis that the frogs use chemical mimicry, by producing or acquiring a coating of chemicals on their skin that deceives the ants into perceiving them as nest members rather than intruders. They tested individual L. lineatus against four similar species of frogs by confining them with leaf-cutter ants, and found that while all the other species were attacked, L. lineatus individuals were not and made no attempt to escape the ants. The researchers then prepared a skin extract from L. lineatus that they used to coat 10 individuals of another species (10 others were coated with purified water as a control). In contrast to the controls, the frogs coated with L. lineatus skin extract were not attacked by the ants. This provides experimental evidence that chemicals on the skin of L. lineatus provide an effective form of mimicry. Although chemical mimicry is more commonly found in parasitic insects, this is not the first time that such mimicry has been detected in frogs. For example, Rödel and Braun (1999) identified several species of African frogs that appear to chemically mimic ants, and Rödel et al. (2013) identified specific skin peptides that enable the African frog, Phrynomantis microps, to chemically mimic the ponerine ants that this species lives with. The benefits that these frog species derive from living with ants are not yet known, but obvious possibilities include protection from predators, access to a climatically optimal microenvironment inside ant nests, or even access to a food source.
Calls of synchronus Lithodytes lineatus males’ have been recorded from inside of the same large nest of these ants, with advertisement calls consisting of a series of short whistles that are produced at a continuous rate of about 90 notes/minute. The notes are in three distinct harmonics at 1300, 2600 (dominant), and 3900Hz and each last about 0.12 seconds long. Egg-bearing females and calling males are often found most frequently between September and February (Duellman 2005; Bernarde and Kokubum 2009; Schlüter et al. 2009).
An adult female that was collected in 1986 contained 211 unpigmented eggs with a diameter of 1.5 mm. Although, egg laying has not been observed, eggs have been found in foam nests on water, under pieces of bark in water on a terrarium, or at the mouth of a partially submerged burrow (Duellman 2005). Foam-nests adhere to the roots protruding from the otherwise smooth walls. Tadpoles in this type of nest have been found at all different developmental stages and leave the foam nests between 7-15 days after the nest was built. Tadpoles begin to feed about 3 days after they hatch, but their nutrition needs further investigation as most captive-raised tadpoles that were fed with commercial fish food died within a few weeks. Tadpoles have been found in water filled depressions at the end of a system of underwater burrows with a vertical tunnel directly above the pool that was around 25 cm in diameter. Adult frogs of this species have also been found in pathways in the forest or sitting in hollow logs that didn't show any obvious association to the ant nests (Duellman 2005; Schlüter et al.
It has been noted that all L. lineatus’ captured at the entrance of these Atta nests released an aromatic odor. It is suggested that this might be a chemical disguise or repellent to prevent ants, which usually try to kill intruders, from attacking. Experiments have been conducted in which specimens of L. lineatus did not have this odor and were immediately killed by the ants. Leptodctylus lineatus benefit from their association with leaf cutter ants because they can obtain suitable hiding places against predation, experience stable microclimates, and also possibly obtain food from these nests; it is unclear if L. lineatus feeds on invertebrate predators of leaf-cutter ants (Schlüter et al. 2009).
The stomach contents of two individuals included nineteen ants making up 54.3% of the number of prey accounting for 8.1% of the volume. Other stomach contents included a cricket (33.9%), an earthworm (22.0%), isopods (12.6%), and insect larvae (12.4%) (Duellman 2005).
Lithodytes lineatus has a seasonal recruitment pattern very similar to other species in the Central Amazon that depend on still water for larva development with juvenile recruitment occurring from February to June (the end of the rainy season and the beginning of the dry season). Females appear to reach sexual maturity at 38.1 mm. Mature ovarian egg sizes range from 1.50 to 1.92 mm and egg count ranges from 110 to 328. Egg count has a positive correlation with female snout-vent length (Bernarde and Kokubum 2009).
Trends and Threats
Currently there is not enough information to distinguish proper threats to this species. According to the IUCN, L. lineatus is listed as Least Concern due to its wide distribution, presumably large population, and a possible ability to tolerate a degree of habitat alteration. Its ability to adapt over a long period of time is unknown. There are no current conservation measures being undertaken for this species because it is classified as Least Concern and it is found in many protected areas. In order to know if conservation measures need to be taken, more studies are needed to thoroughly understand this species and what it needs to maintain its stability (La Marca et al. 2012).
Lithodytes lineatus was previously known under the genus Lithodytes (Bernarde and Kokubum 2009). It was also first described as Rana lineata (Schneider 1799).
This species is often considered to be a mimic of some Aromobatids and Dendrobatids because of its coloration and juvenile diurnal activity. The largest male of this species was found in Espigão do Oeste while the largest female was found in Cecília, Ecuador (Bernarde and Kokubum 2009).
Lithodytes lineatus is synonomous with Leptodactylus lineatus (Kwet 2007)
Featured in Amazing Amphibians on 1 April 2013
Bernarde, P.S., Kokubum, M.N. de C. (2009). ''Seasonality, age structure and reproduction of Lithodytes (Lithodytes) lineatus (Anura, Leptodactylidae) in Rondônia state, southwestern Amazon, Brazil.'' Iheringia. Série Zoologia, 99(4), 368-372.
Duellman, W.E. (2005). Cusco Amazónico: The Lives of Amphibians and Reptiles in an Amazonian Rainforest. Comstock Pub. Associates, Ithaca.
Kwet, A. 2007. Bioacoustic variation in the genus Adenomera in southern Brazil, with revalidation of Leptodactylus nanus Müller, 1922 (Anura, Leptodactylidae). Mitt. Mus. Nat.kd. Berl., Zool. Reihe 83(Supplement): 56–68
La Marca, E., Azevedo-Ramos, C., Coloma, L.A., Ron, S., Hardy, J. 2010. Lithodytes lineatus. In: IUCN 2012. IUCN Red List of Threatened Species. Version 2012.2. Downloaded on 05 February 2013.
Nelson, C., Miller, G.A. 1971. A possible case of mimicry in frogs. Herptelogical Review. 3(6):109
Rödel, M.-O. and Braun, U. (1999). ''Associations between anurans and ants in a West African savanna (Anura: Microhylidae, Hyperoliidae and Hymenoptera: Formicidae).'' Biotropica, 31(1), 178-183.
Rödel, M.O., Brede, C., Hirschfeld, M., Schmitt, T., Favreau, P., Stöcklin, R., Wunder, C., Mebs, D. (2013). ''Chemical camouflage – a frog’s strategy to coexist with aggressive ants.'' PLOS One, 8, e81950.
Schluter, A. Regos, J. 1996. The tadpole of Lithodytes lineatus - with notes on the frog resistance to leaf-cutting ants (Amphibia: Leptodactylidae). Stuttgarter Beitrage zur Naturkunde Ser. A, 536: 1-4
Schlüter, A., Löttker, P., and Mebert, K. (2009). ''Use of an active nest of the leaf cutter ant Atta cephalotes (Hymenoptera: Formicidae) as a breeding site of Lithodytes lineatus (Anura: Leptodactylidae).'' Herpetology Notes, 2, 101-105.
Schneider, J.G. 1799. Historiae Amphibiorum Naturalis et Literariae, volume 1. Friedrich Frommann, Jena.
de Lima Barros, A., López-Lozano, J.L., Lima, A.P. (2016). ''The frog Lithodytes lineatus (Anura: Leptodactylidae) uses chemical recognition to live in colonies of leaf-cutting ants of the genus Atta (Hymenoptera: Formicidae).'' Behavioral Ecology and Sociobiology, 70, 2195-2201.
Written by Amanda Chiachi (achiachi AT berkeley.edu), UC Berkeley
First submitted 2013-06-26
Edited by Ann T. Chang (2017-01-30)
Species Account Citation: AmphibiaWeb 2017 Lithodytes lineatus: Painted Ant-nest Frog <http://amphibiaweb.org/species/3376> University of California, Berkeley, CA, USA. Accessed Feb 27, 2017.
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Citation: AmphibiaWeb. 2017. <http://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 27 Feb 2017.
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