Description
First described in 2005, Aplastodiscus eugenioi is a frog that typically has a snout-vent length range of 31 - 39 mm. Males range between 31 - 36 mm, and females are a bit larger at 36 - 39 mm. The head is roughly equal in length and girth, is 35% the length of the snout-vent length, and has a rounded snout that is less than half the length of the head. The nostrils are set close to the tip of the snout. The loreal region is slightly concave and oblique. The eyes are about 28% of the head length and apart from each other, about 57% of the width of the head. Aplastodiscus eugenioi has a mid-sized tympanum that is 66 - 70% the diameter of the eye. The tongue is small, cordiform, longer than it is wide, and is partly free on the posterior margin. Vocal slits can be found from the midlateral base of the tongue almost to the angle of jaw. The maxillary teeth run along the entire jaw. Its vomerine teeth are located between the large choanae and are in two groups that are slightly arched and almost touching each other. Aplastodiscus eugenioi has a single, subgular, internal vocal sac (Carvalho-e-Silva and Carvalho-e-Silva 2005).

This frog’s arms are slender. The forearm is more robust than the upper arm and has a fine, smooth crest that extends along the outer margin to the hand. The upper arm is 16% the length of the forearm and 17% of the snout-vent length. The hands are 31% of the snout-vent length and the phalanges have round, mid-sized adhesive disks with a robust inner carpal tubercle that is ovular and more than twice as long as it is wide. The subarticular tubercles are well-developed and round and the fingers have very small supernumerary tubercles. The relative finger lengths are I< II < IV< III. The webbing is rudimentary between I and II and is most developed between III and IV. There is some variation regarding the amount of webbing between fingers. The webbing formula is I - II (1 -1 ½) – (2 -2 1/3) III 2 – 2 – 1V (Carvalho-e-Silva and Carvalho-e-Silva 2005).

The combined lengths of the femur and tibia are longer than the snout-vent length. The femur is slightly shorter than the tibia, and the foot length is 42% of the snout-vent length and 82% of the tibia length. The calcar is well-developed and is about 65% of the disk of the fourth toe. The round toe disks are not significantly smaller than the finger disks. The external margin of the foot has a thin crest extending on the tarsus. The relative toe lengths I < II < V < III < IV. Webbing is most developed between IV and V, then III and IV, then II and III, and finally least developed between I and II. The webbing forumla is I (1 – 2-) – (2 – 2+) II (1 – 1+) - (2+ - 3-) III (1 – 1 ½) – (2+ - 2-) IV (2 – 2+) – (1 – 1+) V. The inner metatarsal tubercle is large and egg-shaped and the subarticular tubercles are well-developed and round. The supernumerary tubercles are reduced (Carvalho-e-Silva and Carvalho-e-Silva 2005).

Aplastodiscus eugenioi has a finely granular dorsal surface and a granular vent. There is a narrow, slightly interrupted supra-anal fold with well-developed granules (Carvalho-e-Silva and Carvalho-e-Silva 2005).

Aplastodicus eugenioi can be differentiated from A. arildae and A. weygoldti because it has a curved supratympanic fold that is short, lacks clear beige pigment, and just outlines the membrane. In the other species, the fold is straight. Additonally, A. eugenioi has a more developed calcar and is a bit smaller than A. arildae and A. weygoldti. Aplastodicus eugenioi differs from A. musica because the former has a well-developed calcar and a smaller snout-vent size. Aplastodicus eugenioi can be distinguished from A. ehrhardti by the length of the femur and tibia, the coloration of the inner eye, the supra-anal crest, call rate, and geographic range. Aplastodicus eugenioi’s combined femur and tibia lengths are longer than the total snout-vent lenght, while those of A. ehrhardti are shorter. The inner part of the eye is salmon in A. ehrhardti versus orange-red with cream in A. eugenioi. Additionally, the supra-anal crest is absent in A. ehrhardti, the call rate is faster, and the distribution is farther south. Aplastodicus eugenioi is smaller and has a more developed calcar than A. albofrenata, which also has a shorter combined tibia and femur length compared to its snout-vent length. Additonally, A. albofrenata has a clearer green dorsal color, a purple-wine colored iris, and its calls are faster (Carvalho-e-Silva and Carvalho-e-Silva 2005).

In life, adult A. eugenioi have a lime green dorsal surface that is sometimes darker, with clear, dark spottings that are beige to brown. The concentration of these patterns varies based on the animal’s environement. There is a line of beige running from the canthal stripe to the border of the upper eyelid, and a curved supratympanic stripe that extends from the posterior corner of the eye to behind the arm. The ventral coloration is a clear yellow. A bluish color runs from the throat to the first third of the abdomen and within the inner parts of the legs. The calcar is beige, like the outer parts of the feet and tarsus. The webbing is clear green. The supra-anal fold is beige. They have a bright orange iris with cream-colored rays extending outwards. In general, females are more yellow in areas of their abdomen and flanks (Carvalho-e-Silva and Carvalho-e-Silva 2005).

In preservative, the adult body’s green color starts to fade after two days in preservative. After that, the dorsal surface is cream with brown and white punctuation that varies in number. There are whitish crests that are present on the external surface of the forearm, hand, tarsus, and foot. The subanal tubercles, supra-anal fold, calcar, canthal stripe, and the edge of the top eyelid are whitish, as well (Carvalho-e-Silva and Carvalho-e-Silva 2005).

The dark dorsal punctuations that are beige and brown vary in their concentration depending on environment (Carvalho-e-Silva and Carvalho-e-Silva 2005).

Distribution and Habitat

Country distribution from AmphibiaWeb's database: Brazil

View distribution map in BerkeleyMapper.

This species can be found from 0 to 300 m along the coasts of the states of northeastern Sao Paulo and southwestern Rio de Janeiro in southeast Brazil (Carvalho-e-Silva and Carvalho-e-Silva 2005). In 2012, Salles et al. determined that the range extended 50 km to the east. The area of occurrence is estimated to be 5590 km². Aplastodiscus eugenioi is found in three reserves - Reserva Ecológica de Rio das Pedras, Parque Natural Municipal da Taquara, and Reserva Ecológica de Guapiaçu (Salles et al. 2012).

Life History, Abundance, Activity, and Special Behaviors
During the day, mature frogs hide in bromeliads that are high up in the trees, or in coiled leaves of Marantaceae or Musaceae (Carvalho-e-Silva and Carvalho-e-Silva 2005).

At night, single males call from the leaves of trees, from bromeliads located high in trees, or from bushes throughout the year. Their calling positions are always near straight streams with flowing water. The call of A. eugenioi is a single note repeated about 40 times a minute and sounds “like drops of water falling into an empty bottle”. The breeding period is mostly within the months of August to January, but sometimes occurs after cold fronts pass during other months (Carvalho-e-Silva and Carvalho-e-Silva 2005).

Larva
At gosner stage 28, the tadpole body is elongate and elliptical in the dorsal view. It has a round snout. The eyes are dorsolateral, have a diameter of about 10% of the body length, and are separated from each other by roughly 53% of the width of the body. The nostrils are reniform and are located about halfway between the tip of the snout. The tadpole’s eyes have a small projection on the inner border. The mouth is ventral and includes a well-developed oral disk with two rows of papillae. From above, the papillae is broadly interrupted and has a small interruption on the posterior margin. There are three apparent indentations and one of the inner rows of papillae is present on the sides. The mouth also includes two series of upper labial teeth with the second one being broadly interrupted. There are four lower series with the first one being interrupted. The tooth row formula is 2(2)/4(1). The mouth also has a hard, black, keratinous beak composed of a finely serrated, rounded maxilla and an open, V-shaped jaw. The posteriorly-directed, sinstral spirical is located about 58% further from the snout than from the anus and has an opening that is slightly smaller than the narial openings. The anal tube is attached to the ventral fin on the right side and has a wide opening. The tail has strong musculature, makes up 74% of the total tadpole length, and has a larger maximal depth than the body. The slightly arched dorsal fin gradually rises and reaches its highest depth at the last third of the tail. The ventral fin is nearly straight and has a larger depth than the dorsal fin. The tip of the tail is pointed and has slightly rounded end. Tadopoles have visible, robust lateral lines located on the dorsal, middle, supraorbital, infraorbital, anterior oral, angular, and ventral regions (Carvalho-e-Silva and Carvalho-e-Silva 2005).

Aplastodiscus eugenioi tadpoles can be distingushed from A. albofrenata by the former’s larger size, narrower tail, the dental formula, and coloration. More specifically, the marginal papillae have a broad interruption on the anterior edge and lateral internal papillae in A. eugenioi. Additionally, larvae of the focal species have irises that are golden brown while A. albofrenata’s are dark red. Lastly, the tail of A. eugenioi is darker with a dark longitudinal strip vs the clear brown and beige dorsal areas in A. albofrenata (Carvalho-e-Silva and Carvalho-e-Silva 2005).

In life, the dorsal and lateral sides of the tadpole body is a “raw umber” color mixed with slightly lighter colors. There is also a dark umber triangular spot between the eyes. The area surrounding the spiracle is a clear beige, and the body has two lighter stains at its posterior end, one on each side and close to the start of the tail. The tail itself is the same color as the rest of the body with some lighter markings on the dorsal aspects. The sides are brown in a marbled pattern with some lighter areas. There is a dark brown stripe running down the middle of the tail musculature longitudinally, which loses its thickness as it runs towards the very tip of the tail. Both the dorsal and the ventral fins are marbled with transparent borders. The lateral line pores are easy to see, as the lines are stippled whitish and are as developed on the body as they are on the tail. The tadpole irises are a clear beige color with golden flecks and dark, small peripheral dots (Carvalho-e-Silva and Carvalho-e-Silva 2005).

The body of the tadpole in preservative is tan and lighter from the nostrils towards the snout and around the spiracle. The characteristic markings such as the triangle on the head, the tail marbling, the two clear beige spots, the dark lateral stripe, and the lateral line system remain clearly visible (Carvalho-e-Silva and Carvalho-e-Silva 2005).

Tadpoles can be found between pebbles and stones in the lotic-benthic zone with sandy ground. They eat material that has been deposited on leaves and scrape it off while feeding. They are largely nocturnal and usually occur in narrow streams with a pH of about 6.0. They often occur sympatrically with tadpoles of the species Hylodes phyllodes (Leptodactylidae) (Carvalho-e-Silva and Carvalho-e-Silva 2005).

Trends and Threats
This species is known from ten locations. Its habitat has been decreasing in quality. There are historical and current logging operations that threaten the Atlantic Forest in which it is found. Its population trend is unknown, but it is listed as "Near Threatened" on the IUCN Red List of Threatened Species. Increased habitat protection is needed for the species survival (Carvalho-e-Silva 2006).

Possible reasons for amphibian decline

General habitat alteration and loss
Habitat modification from deforestation, or logging related activities
Intensified agriculture or grazing
Urbanization
Habitat fragmentation
Local pesticides, fertilizers, and pollutants
Disease

Comments
Based on Bayesian Inference analysis of 6642 base pairs of mitochondrial and nuclear gene fragment sequences, A. sibilatus was found to be the sister taxon of the rest of the genus. A. eugenioi is in the A. albofrenatus group that includes five other species (A. ehrhardti, A. arildae, A. weydoldti, A. albofrenatus, and one unnamed species). Aplastodiscus albofrenatus is the closest known relative to A. eugenioi (Berneck et al. 2016).

Based on analyses conducted in 2016, the genus Aplastodiscus (family: Hylidae) consisted of 15 species plus an additional six unnamed species, that are usually diagnosed by cloacal morphology. The monophyly of this genus is strongly supported by recent phylogenetic analysis (Berneck et al. 2016).

This species is named after Eugenio Izecksohn for his contributions in Brazilian amphibian research (Carvalho-e-Silva and Carvalho-e-Silva 2005).

This species was formerly in the genus Hyla before being moved to Aplastodiscus (Faivovich et al. 2005).

References

Berneck, B.V.M., Haddad, C.F.B., Lyra, M.L., Cruz, C.A.G., Faivovich, J. (2016). ''The Green Clade grows: A phylogenetic analysis of Aplastodiscus (Anura; Hylidae).'' Molecular Phylogenetics and Evolution, 97, 213-223.

Carvalho-e-Silva, A.M.P.T., Carvalho-e-Silva, S.P. (2005). ''New Species of the Hyla albofrenata Group, from the States of Rio de Janeiro and Sao Paulo, Brazil (Anura, Hylidae).'' Journal of Herpetology, 39(1), 73-81.

Carvalho-e-Silva, S.P. (2006). Aplastodiscus eugenioi. The IUCN Red List of Threatened Species 2006, e.T61770A12537909. Downloaded 12 April 2018.

Faivovich, J., Haddad, C. F. B., Garcia, P. C. A., Frost, D. R., Campbell, J. A., Wheeler, W. C. (2005). ''Systematic review of the frog family Hylidae, with special reference to Hylinae: phylogenetic analysis and taxonomic revision.'' Bulletin of the American Museum of Natural History, (294), 1-240. [link]

Salles, R.O.L., Pontes, R.C., Silva-Soares, T. (2012). ''New records and geographic distribution of Aplastodiscus eugenioi (Anura: Hylidae) in southeastern Brazil.'' Herpetology Notes, 5, 431-433.

Species Account Citation: AmphibiaWeb 2023 Aplastodiscus eugenioi <https://amphibiaweb.org/species/6445> University of California, Berkeley, CA, USA. Accessed Nov 7, 2024.

Citation: AmphibiaWeb. 2024. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 7 Nov 2024.

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