Flea Frog

Psyllophryne hermogenesi is one of two species belonging to the genus, both of which occur in the Atlantic forests of southeastern Brazil. This small frog, like other diminutive amphibians, has morphological reductions and losses in digits and other osteological elements (see Giaretta and Sawaya 1998 for figures). In life, this small anuran is brownish yellow or palebrown on the dorsum. The dorsal surface of the thigh may show a pale pink pattern. 40% of preserved specimens display narrow stripes that form a dark X on the dorsum. Some individuals have large symmetrically paired dark spots on the dorsum and/or sacrum region. Some have the dorsum of the limbs crossed with a gray stripe. A narrow vertebral stripe may be present, and in some specimens, lateral coloration is darker than dorsum. Ventral surfaces are pale gray with many brown spots. Belly has many intersperced glandular areas on a uniformly dark with white spotted background. The other congener, P. didactyla, differs by having its glands concentrated onto one belly area and thus creating a black spot. The head is wider than it is long, and in dorsal view the snout is rounded. Nostrils closer to tip of snout than to the eyes. Tympanum indistinct but visible. Anterior border of nostrils and inferior border of eys are grooved. First and fourth fingers vestigial, third larger than second. First toe is absent and the second is larger than fith and smaller than third. Skin is smooth or slightly granular on upper eyelid and nostril. Osterodermal plate on the body is absent (found in the sister genus Brachycephalus). The presence of a functional 5th toe in P. hermogenesi is unique within not only this genus, but also in other diminutive frogs of the genus Brachycephalus and Euparkarella (Lynch 1971).

Known from 3 localities in the municipality of Ubatuba, Brazil: Picinguaba, Fazenda Capricornio, and Corcogado.

Males have an external vocal sac that extends from the gular region to midbelly. Females were frequently encountered with a bulk on one side of the body due to the presence of a single maturing oocyte.

Diagnosis A diminutive frog related to Brachycephalus didactylus. This species can be characterized by the presence of a functional fifth toe. With glands uniformly scattered throughout the ventral surface.

The species was originally described from Picinguaba, at the Parque Estadual da Serra do Mar, with distribution records restricted to Ubatuba municipality of the State of São Paulo, and Parati municipality in the adjacent State of Rio de Janeiro. The species was later collected in two new localities in the plateau of State of São Paulo: Estacão Biológica de Boracéia and Reserva Florestal de Morro Grande.

DescriptionIn dorsal view, snout rounded, head wider than long, and canthus rostralis well defined. In lateral view, nostrils closer to the tip of snout than to the eyes; tympanum indistinct, but visible; pupil horizontal and elliptic; anterior border of nostrils and inferior border of eyes grooved; tongue rounded and free behind; vomerine teeth absent; first and fourth fingers vestigial, third larger than second; first toe absent, second larger than fifth and smaller than third; third smaller than fourth; a single rounded metacarpal tubercle present; outer metatarsal tubercle rounded; subarticular tubercles undefined on hands and feet; tip of fingers and second, third, and fourth toes pointed, that of fifth round; no webs or disks on fingers or toes; skin smooth or slightly granular on upper eyelid and nostril; osteodermal plate on the body absent; males with an external vocal sac extending from the gular region to midbelly. Measurements (in millimeters) of the holotype and an adult male paratype (ZUEC 9716), are respectively: total length = 10.00/8.77; head width = 3.38/3.02; head length = 2.25/2.00, eyeostril distance = 1.00/0.75, thigh length = 4.31/3.85; shank length = 4.46/4.15; eye diameter = 1.23/1.08; foot length = 4.00/3.23, forearm length = 2.31/2.15; hand length = 1.85/1.54. Adult males average 8.7 mm (snout-vent length) (± 0.19 mm SD; n = 3) and adult females 10.5 mm (± 0.49 mm; n = 4). The new species is sexually dimorphic in size. No sexual dimorphism in shape is evident. For males, the mean body proportions (%), relative to mean snout-vent length (n = 3), are head width = 38, head length = 23, eyeostril distance = 8, thigh length = 46, shank length = 47, eye diameter = 13, foot length = 38, forearm length = 25, hand length = 17. Color: In life, brownish yellow or pale brown on the dorsum; the dorsal surface of the thigh may show a pale pink pattern. Preserved specimens with the dorsum pale gray or dark brown; 40% of them show narrow stripes that form a black X on the dorsum. Some individuals have large symmetrically paired dark spots on the dorsum and/or sacral region; some have the dorsum of each thigh, shank, and tarsus crossed by a dark gray stripe. A narrow, clear vertebral stripe may be present, and some specimens have the lateral portion of the body darker than the dorsum; the belly, throat, and ventral surfaces of the arms and legs are pale gray with many small brown spots. Belly with glandular skin, uniformly dark with many small white spots.

LC. Least Concern.

The flea-frog (Brachycephalus hermogenesi) is a species of frog in the family Brachycephalidae. It is endemic to Brazil and its distribution includes the states of São Paulo and Rio de Janeiro.

Its natural habitat is subtropical or tropical moist lowland forests. It is threatened by habitat loss.

Brachycephalus hermogenesi is part of the dull colored assemblage of the family Brachycephalidae and is distinguished from other species of the genus Brachycephalus by its complex calling activity.