Description
Allobates olfersioides is small frog with a snout-vent length range of 11.5 - 18.8 mm. The head is slightly wider than it is long with a slightly rounded snout in both the dorsal and lateral views. There are prominent external nares that are positioned laterally. The canthus rostralis is rounded and the area between the eyes is slightly indented, but mostly flat. The tympanum is less than half the eye diameter. The skin of the dorsal and ventral areas, including the limbs, is generally smooth with some small protrusions present across the lower body but no enlarged tubercles near the anus. The forelimbs are slender. There is a nearly round outer metacarpal tubercle and a smaller, elliptical inner metatarsal tubercle. The fingers have relative lengths of III > II = I > IV and lack webbing between fingers. Tips of fingers are expanded into discs that are about 25% larger compared to width of fingers. The tibia is 44% of the snout-vent length and the foot has a rounded outer metatarsal tubercle and an elliptical inner metatarsal tubercle. The toes have relative lengths of IV > III > V > II > I, expand into disc like the fingers, and are not fringed. For a more comprehensive description please see Verdade and Rodrigues 2007.

One tadpole at Gosner stage 36 has a total length of 23.3 mm and a body length of 7.8 mm. It had a depressed, elliptical body in the dorsal view and an oval body in the lateral view. The snout is widely rounded in both the dorsal and ventral views, and oval in the lateral view. The nares are located dorsolaterally, closer to the snout tip than eyes, and have a round opening. The dorsal eyes are directed dorsolaterally. The oral disc is transversally elliptical and positioned antroventrally with lateral emargination. The anterior labium has 10 papillae separated by a dorsal gap and the posterior labium has 24 papillae with no gap. The papillae have pointed tips and are in an uniserial row. The labial tooth row formula is 2(1)/3. They have a single, lateral, sinistral spiracle with a lateral aperture. The vent tube is located slightly to the side of medial with a dextral opening. The tail is long with low fins. The dorsal fin begins just before the body ends, while the ventral fin begins just after the body ends. The tail tip is narrowly rounded (Verdade and Rodrigues 2007).

Allobates olfersioides is similar to all species of Allobates, Anomaloglossus, and Hyloxalus found in Brazil. Allobates brunneus, A. marchesianus, and A. masniger have dark spots on the dorsum that are among the characters that differentiate them from A. olfersioides. Allobates caerulodactylus has blue digits and toe discs. Reduced fringes on the toes of A. conspicuus, A. crombiei, A. gasconi, and A. sumtuosus differentiate them. Swollen third fingers in A. gasconi, A. fuscellus, and A. trilineatus distinguish them. An anal flap in A. granti along with other characters prevent confusion with the focal species. Allobates olfersioides is smaller than Allobates nidicola and A. vanzolinius. From the Brazilian Anomaloglossus, A. olfersioides can be differentiated by the former having a median lingual process. The only Hyloxalus in the area, H. peruvianus is larger and has fringed and webbed fingers. For a more comprehensive diagnosis please see Verdade and Rodrigues 2007.

In life, the frogs have a belly that ranges from off-white to cream colored, with a dark stripe across their side beginning around the nares and eyes. At the eyes, the stripe is narrow, extending towards the groin, where it widens. The thighs and upper legs are brown with a pair of darkened stripes that align when legs are in their natural position. The dorsal area matches the brown tone of the legs, with intercrossing dark brown X-shapes. When preserved, the color is generally similar, although a pattern of dark brown Xs may form along the dorsal area. Moreover, white spots might be seen along the frog's dark brown lateral stripe. For a more comprehensive description please see Verdade and Rodrigues 2007.

In preservative, the larvae are faded with some brown reticulations that become blotches towards the tail. In life, the body is blackish with a white spot near the snout (Verdade and Rodrigues 2007).

Geographic variation in this species is limited to length of snout-vent and pattern of color. Color pattern is highly variable, some individuals have Xs across their dorsal area that do not intersect. Variation in snout-vent length is less obvious and may be the result of limited sampling. There is slight sexual dimorphism with females exhibiting slightly larger size and a more frequently immaculately colored belly (Verdade and Rodrigues 2007).

Distribution and Habitat

Country distribution from AmphibiaWeb's database: Brazil

	View distribution map in BerkeleyMapper.
	View Bd and Bsal data (3 records).

The frog is endemic to the Atlantic Forest on the northeastern coast of the Brazilian state of Rio de Janeiro (Lutz 1925). They dwell on the floors of undisturbed and partially disturbed forest (Verdade 2010).

Life History, Abundance, Activity, and Special Behaviors
Allobates olfersioides is diurnal and lives on the forest floor. When threatened, it escapes into the leaf litter (Verdade and Rodrigues 2007).

Reproduction in this species is thought to occur throughout all months of the year. Females lay an average of eight eggs at a time that are roughly 1 - 2 mm in size. The mature eggs hatch in moist terrestrial nests and tadpoles are carried to small bodies of water on the forest floor by their parents, most often the male, when they are in Gosner stage 25 (Verdade and Rodrigues 2007).

Their call has been described as an acute or shrewd trill (Izekhson and Carvalho-e-Silva 2001, Verdade and Rodrigues 2007).

Trends and Threats
Allobates olfersioides population is in decline and is now missing from many areas in Rio de Janeiro that it previously inhabited. Threats include environmental conversion and degradation due to residential and commercial development, agriculture, and logging. Genetic disease and chytridiomycosis may also be playing a role in population decline (Verdade 2010).

Comments
The species authority is: Lutz, B. (1925). "Batraciens du Brésil." Comptes Rendus Societe Biologie Paris XCIII, 137-139.

Formerly identified as Eupemphix olfersioides (Lutz, 1925).

The holotype only currently exists as a piece of flesh (Verdade and Rodrigues 2007).

References

Bokermann, W. C. A. (1966). Lista anotada das localidades tipo de anfíbios brasileiros. Serviço de Documentação-RUSP, São Paulo, Brazil.

Izecksohn, E., and Carvalho-e-Silva, S. P. (2001). Anfí­bios do Municí­pio do Rio de Janeiro. Editora UFRJ, Rio de Janeiro.

Lutz, B. (1925). "Batraciens du Brésil." Comptes Rendus Societe Biologie Paris XCIII, 137-139.

Verdade, V. 2010. "Allobates olfersioides." The IUCN Red List of Threatened Species 2010 : e.T55122A11255268. https://dx.doi.org/10.2305/IUCN.UK.2010-2.RLTS.T55122A11255268.en. Downloaded in 2018

Verdade, V., Rodrigues, M. (2007). "Taxonomic review of Allobates (Anura, Aromobatidae) from the Atlantic Forest, Brazil." Journal of Herpetology, 41(4), 566-580. [link]

Species Account Citation: AmphibiaWeb 2021 Allobates olfersioides: Rio Rocket Frog <https://amphibiaweb.org/species/1592> University of California, Berkeley, CA, USA. Accessed Dec 21, 2024.

Citation: AmphibiaWeb. 2024. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 21 Dec 2024.

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