AmphibiaWeb - Hylodes japi


(Translations may not be accurate.)

Hylodes japi de Sá, Canedo, Lyra & Haddad, 2015
family: Hylodidae
genus: Hylodes
Species Description: de Sa FP, Canedo C, Lyra ML, Haddad CFB 2015 A new species of Hylodes (Anura, Hylodidae) and its secretive underwater breeding behavior. Herpetologica 71: 58-71.
Hylodes japi
© 1989 Celio Haddad (1 of 1)
Conservation Status (definitions)
IUCN Red List Status Account
National Status None
Regional Status None


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Hylodes japi is relatively small frog with a snout vent length for males between 22.9 - 25.8 mm and for females between 26.4 – 28.0 mm. Its head is longer than it is wide and overall it is a slender bodied frog. The elliptical nares are flat on the body and directed to the side. The canthus rostralis is distinct and nearly straight. The loreal region is concave. The tympanum is medium sized − about half the diameter of the eye, and nearly round. There is a weak supratympanic fold and an oblique lateral fold that is continuous from the supratympanic fold to the groin. In males the laterally positioned, paired vocal sacs widely expand externally. A many-lobed berry like medial gland is also visible on the gular region. The skin is nearly smooth on the dorsum and flanks as well as on the ventral surfaces. Slightly textured areas appear near the vent, on ventral surfaces of the thighs, and on the posterior region of the body (De Sá et al. 2015).

The arms and forearms are slender. The hands have singular, round, subarticular tubercles; small, almost oval fingertips discs; a larger, round outer metacarpal tubercle; a medium-sized, elliptical inner metacarpal tubercle; and weakly developed paired scutes on the dorsal surfaces of the fingers; and lateral fringes on both sides that are more prominenton the fingers than thumb. The thumbs do not have nuptial asperities, spines, or tubercles. The relative finger lengths are: 2 < 1 ≈ 4 < 3. The legs are robust with the foot having an elongated, oval inner metatarsal tubercle; a smaller, round outer metatarsal tubercle, and single subarticular tubercles.. There is extensive lateral fringe on both sides of each toe. Fringe on the digits of fore and hind limbs is more pronounced in males than females. An extensive tarsal flap runs contiuously with the fringe on the inner side of toe 1. Toes end in nearly round discs with the disc of toe 5 being smaller than the other toes. Scutes are present on the toes as on the fingers. The relative toe lengths are: 1 < 2 < 3 ≈ 4 < 5 (De Sá et al. 2015).

This species can be distinguished from other members in the Hylodes nasus group due to the presence of smoother dorsal surfaces as well as the fact that there are no of tubercles ventral to the oblique lateral fold. The presence of a continuous oblique lateral fold and a prominent, lightly colored, oblique lateral stripe are also diagnostic. This frog can be distinguished from H. amincola, H. ornatus, H. perere, and H. sazimai by comparing the advertisement call and further from H. ornatus ventral coloration of the two species (De Sá et al. 2015).

In life Hylodes japi has an overall silver whitish coloration. The venter is light in color with small, weakly defined, dark spots. There is a light colored region on the ventral half of the lateral side of the head. The lips are pale brown and the iris is copper. There are variable shaped, dark blotches on the interocular region. Light, oblique lateral stripes are normally apparent from the shoulder to the groin but become more pronounced towards the posterior part of the body. Brown, transverse bars may be present on the thigh, tibia, foot, and tarsus. There also may be a reddish brown color present on the frog’s dorsum as well as the dorsal regions of the foot, tarsus, tibia, and thigh. In preservative the colors are nearly the same as in life, just much less vivid and with the oranges and browns becoming pale and gray. The iris’s become gray, as well (De Sá et al. 2015).

In preservative, there is variation in patterning in the interocular region and dorsum. The number of transverse bars on the thigh varies as do bar thickness. Color on the coccygeal region ranges from blackish to grey and the color and patterning on the ventrum varies from cream to whitish with brown to grey blotches. The snout varies from a more subovoid shape a more pointed shape in the dorsal view. Females also tend to be larger than males and lack vocal slits and sacs (De Sá et al. 2015).

Distribution and Habitat

Country distribution from AmphibiaWeb's database: Brazil

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This species occurs in eastern Brazil in the state of Sao Palo, just west of the Atlantic Plateau in the mountains of Serra do Japi. The habitat is 850 to 1050 m above sea level and consists of fast flowing streams located within a forest of semideciduous, mesophytic trees (De Sá et al. 2015).

Life History, Abundance, Activity, and Special Behaviors
This frog is found between 850 and 1050 m above sea level along fast flowing streams. It is diurnal but can be found calling at nighttime during the breeding season.

Males call sporadically, with a harmonically structured advertisement call. Only the third harmonic is apparent. At 24oC air temperature and 19.5oC water temperature,the call duration can range from 1.36 to 3.83 seconds and can have between 38 and 60 notes per call with 5.91 – 19.42 second intervals. Each note is comprised of a rising frequency-modulated whistle with the dominant frequency of 5.8 – 6.6 kHz occurring in the third harmonic. The first note has a dominant frequency range between 4.9 – 6.4 Hz (De Sá et al. 2015).

Courtship can be observed during the daytime or at night. This unique underwater breeding behavior begins with males calling from the water’s edge waiting for a female to engage. Once the female engages, they both decide on a suitable oviposition site at the river floor and at this point the female decides whether or not to accept his courtship offer. Once she accepts, the male excavates an underwater tunnel and chamber in the sand that is just big enough for the two frogs. The female follows the male through the tunnel into the chamber. After courtship and oviposition, the frogs leave the chamber and the male conceals the tunnel entrance by covering the hole with sand from the bottom of the river (De Sá et al. 2015).

Underwater breeding behavior occurs in other members within this same genus as well as members within Crossodactylus (De Sá et al. 2015).

Deposited eggs are a whitish cream color and are unpigmented. The diameter of an egg may range from 2.48 mm to 3.47 mm and the average diameter of the gelatinous capsule may range from 7.81 mm to 8.16 mm (De Sá et al. 2015).

Tadpoles can be found in high abundance between February and May. The tadpoles feed during the day and more actively, at night. These benthic tadpoles are omnivorous, and perhaps cannibalistic. The tadpoles are also exotrophic. It is thought that tadpoles remain inside of the breeding chamber for the early stages of development. They can be found freely swimming in fast streams as early as stage 25 of development (De Sá et al. 2015).

Hylodes japi tadpoles have small dorsolateral eyes and nostrils that are dorsolaterally positioned halfway between the tip of the snout and the eyes. The spiracle is sinistral and the oral disc is directed ventrally with strongly developed jaw sheaths and a V-shaped posterior jaw sheath (De Sá et al. 2015).

In life, tadpoles are brown with tones of yellow in the region located on the dorsal side from the posterior part of the body to the anterior of the tail. In preservative the ventral surfaces are brownish gray and the dorsum and flanks are a darker brown color. The iris and the edge of the nostril are black (De Sá et al. 2015).

Trends and Threats
While some populations of Hylodes japi are stable, it is susceptible to environmental degradation due to its association with fast moving streams. The area this species occurs in, Serra do Japi, faces strong developmental pressure from humans and is considered a protected area of Brazil (De Sá et al. 2015).

Possible reasons for amphibian decline

General habitat alteration and loss
Habitat modification from deforestation, or logging related activities
Habitat fragmentation

Hylodes japi belongs to the family Hylodidae. Based on Bayesian inference analysis of COI, 16S and RAG1, it is sister to H. sazimai, H. ornatus, H. perere, and H. aminicola (De Sá et al. 2015).

The specific epithet, japi, came from an indigenous Tupi word that means “springs”. This refers to the transparent rivulets that are abundant in this species’ breeding habitat (De Sá et al. 2015).


De Sá, F. P., Canedo, C., Lyra, M. L., Haddad, C. F. B. (2015). ''A new Species of Hylodes (Anura, Hylodidae) and its Secretive Underwater Breeding Behavior.'' Herpetologica, 71(1), 58-71.

Originally submitted by: Jillian Capdevielle (first posted 2015-05-26)
Edited by: Gordon Lau, Michelle S. Koo (2023-03-15)

Species Account Citation: AmphibiaWeb 2023 Hylodes japi <> University of California, Berkeley, CA, USA. Accessed Jun 18, 2024.

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Citation: AmphibiaWeb. 2024. <> University of California, Berkeley, CA, USA. Accessed 18 Jun 2024.

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