Description
Adelophryne michelin is a small frog whose snout-vent length is smaller than 11.5 mm, with males ranging between sizes of 7.6 mm and 9.1 mm, and females between 10.0 mm and 11.4 mm. The head is narrower than the body and does not have cranial crests. The snout appears rounded and slightly triangular in both the ventral and dorsal views. From the lateral view the snout appears truncated and slightly rounded. The round nostrils do not protrude. The internarial distance is larger than interorbital distance. The canthus is indistinct and the loreal region is somewhat concave. The pupil is horizontally oval and the upper eyelid is somewhat concave. The temporal region is vertical. The tympanum is indistinct without a visible membrane, and the tympanic annulus is absent. The hands have an oval inner metacarpal tubercle and a round outer metacarpal tubercle that is a little larger than the inner. The thin, short, unwebbed fingers lack terminal discs but have T-shaped terminal phalanges. Fingers I, II, and III have mucronate tips while the tip of finger IV is rounded. The relative finger lengths are IV < I < II < III and the phalangeal formula is 2 - 2 - 3 - 2. While the fingers do not have subarticular tubercles, they do have round subdigital pads with a formula of 1 - 2 - 2 - 1. These pads are not found on the most distal phalanges and there are no supernumerary tubercles. The foot has an oval inner metatarsal tubercle and a round, smaller outer metatarsal tubercle. The unwebbed, slightly flattened, cylindrical toes have a relative length of I < V < II < III < IV. Toes II, III, and IV have discs with circumferential grooves. Toe V also has circumferential grooves and mucronate tips, but Toe I only has a circumferential groove. The phalangeal formula for the toes is 2 - 2 - 3 - 4 - 3 and a subdigital pad formula of 0 - 0 - 2 - 1 - 0. Like the fingers there are no pads under the most distal phalanges and no supernumerary tubercles. The skin on both the belly and dorsum is smooth, but the flanks and ventral surface of the thighs are areolate. The cloaca opens horizontally, is positioned slightly below the level of the thighs on the dorsum, and has no anal flap (Lourenço-de-Moraes et al. 2018).

DIAGNOSIS:

Adelophryne michelin can be distinguished from species in the Phyzelaphryne genus by A. michelin having an indistinct tympanum and smaller size. From members of its own genus, A. adiastola, A. baturitensis, A. gutturosa, A. maranguapensis, A. mucronata, A. pachydactyla, and A. patamona all have distinct tympanums. Adelophryne michelin is smaller than A. baturitensis, A. gutturosa, A. maranguapensis, A. mucronata, and A. patamona. However, it can also be differentiated from A. baturitensis and A. maranguapensis by the lack of discs or circumferential grooves on the fingers in A. michelin. The absence of subarticular tubercles in A. michelin can also differentiate it from A. baturitensis. The absence in a distinct glandular ridge from the eye to the forelimb in A. michelin differentiate it from A. glandulata and A. gutturosa. Smooth skin in A. michelin differentiate it from A. adiastola, A. glandulata, A. mucronata, and A. patamona. Adelophryne michelin have more toes with circumferencial grooves than A. meridionalis. Lastly, the absence of an anal flap in A. michelin differentiate it from A. mucronata and A. maranguapensis (Lourenço-de-Moraes et al. 2018).

COLORATION:

In life, the dorsum is slightly golden with two dark brown stripes of various width in the middle region in an upside down “V” shape. There is a dark brown interorbital stripe in a “V” shape. The loreal region is dark brown. The flanks also have a dark brown stripe extending along the flanks to the groin with small white dots. The thigh and tibia have one or two dark band stripes. The forelimb can be red in some specimens. The venter can either be dark with scattered white spots or have a uniform coloration. The throat and underside of thighs and shanks are slightly golden. The iris is reddish brown with black reticulations (Lourenço-de-Moraes et al. 2018).

In preservative, A. michelin has a brown dorsum with numerous small white and black dots. The loreal region is black and has a black stripe extending along the flanks to the groin, with numerous white dots. The species also has a black interorbital stripe in a “V” shape, in which the lines don’t connect, and black upper eyelids. Both the thigh and tibia have numerous black dots that form lines. The venter is brown and the throat is dark brown (Lourenço-de-Moraes et al. 2018).

VARIATION:

The dorsal coloration varies in life, with most showing a very light, slightly golden pattern, but some individuals also show a bluish coloration. Formula of pads and discs varies in number. Males are smaller than females and have more depressed toes IV and V than females (Lourenço-de-Moraes et al. 2018).

Distribution and Habitat

Country distribution from AmphibiaWeb's database: Brazil

View distribution map in BerkeleyMapper.

Adelophryne michelin has only been found in Eastern Brazil, at the Reserva Ecológica Michelin, in the municipality of Igrapiuna, Bahia at an elevation between 170 and 270 m above sea level. Their habitat consists of leaf litter in the Atlantic Forest biome (Lourenço-de-Moraes et al. 2018).

Life History, Abundance, Activity, and Special Behaviors

The species lives in leaf litter habitat (Lourenço-de-Moraes et al. 2018).

The species was found to eat ants after examining stomach content (Lourenço-de-Moraes et al. 2018).

Trends and Threats
The area of occupancy for A. michelin is restricted to an area of less than 500 km² of preserved forest. Because of the small area of occupancy and lack of data on population status for A. michelin the species authority suggested the species be listed as “Near Threatened” on the IUCN Red List (Lourenço-de-Moraes et al. 2018).

Possible reasons for amphibian decline

General habitat alteration and loss

Comments

PHYLOGENETIC RELATIONSHIPS:

Bayesian Inference and Maximum Likelihood analyses on mitochondrial 16S rRNA found that A. michelin is a sister to a clade formed by two undescribed Adelophryne species. Together they are sister to a clade composed of A. baturitensis and A. maranguapensis. The five species form the North Atlantic Forest Clade (Lourenço-de-Moraes et al. 2018).

ETYMOLOGY:

Adelophryne michelin is named after the Reserva Ecológica Michelin where it was found (Lourenço-de-Moraes et al. 2018).

References

Lourenco-de-Moraes, R., Dias, I. R., Mira-Mendes, C. V., Oliveira, R. M. de, Barth, A., Ruas, D. S., Vences, M., Solé, M., Bastos, R. P. (2018). "Diversity of miniaturized frogs of the genus Adelophryne (Anura: Eleutherodactylidae): A new species from the Atlantic Forest of northeast Brazil." PLOS ONE, 13(9), e0201781. [link]

Species Account Citation: AmphibiaWeb 2023 Adelophryne michelin: Michelin Flea Frog; razinha-pulga-da-Michelin <https://amphibiaweb.org/species/8913> University of California, Berkeley, CA, USA. Accessed Oct 3, 2024.

Citation: AmphibiaWeb. 2024. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 3 Oct 2024.

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