Phrynomedusa dryade Baêta, Giasson, Pombal & Haddad, 2016
|Species Description: Baeta D, Giasson LOM, Pombal Jr JP, Haddad CFB 2016 Review of the rare genus Phrynomedusa Miranda-Ribeiro, 1923 (Anura: Phyllomedusidae) with description of a new species. Herpetological Monographs 30: 49-78.|
Phrynomedusa dryade is a slender, colorful, small-sized frog. The snout-vent length range in male is between 28.4 – 31.7 mm and one female specimen measured 36.1 mm. The rounded snout has small medial protrusions in both the dorsal and lateral views. The canthus rostralis and loreal region are relatively straight. The lips do not flare and do not have a fringe. The nostrils are positioned laterally upon the slight projection nearest to the tip of the snout; however, the nostrils themselves do not protrude. The distance between the nostrils is slightly smaller than the distance between the eyes. Phrynomedusa dryade has large eyes (only slightly smaller than the distance between the eyes) with a vertically shaped pupil and a non-reticulated palpebral membrane. The rounded tympanums' anterior margin touches its eyes’ posterior margin. There is a supratympanic fold beginning from the eyes’ posterior margin, over the tympanum and then obliquely, connecting to the arm insertion (Baeta et al. 2016).
The arms are not particularly muscular. The forearm has as series of small tubercles on the postaxial margins. The fingers are slender and the order of finger lengths in descending order is: 3, 4, 2, 1. The adhesive discs on the fingers are oval and their width is larger than their length, with the disc on finger one being the smallest and rounded. In addition, the webbing between fingers is reduced with the following formula: I absent – absent II 2+ - 3 1/3 III 3- - 2+ IV. The fingers have single, round subarticular tubercles and supernumerary tubercles. The inner metacarpal tubercle is elliptical, equal in length to the metacarpus and half the width of the metacarpus. There is no outer metacarpal tubercle. When keratinized nuptial pads are present, they cover Finger I from the dorsal side, across the preaxial surface, to the metacarpal and proximal tubercle on the ventral side up to the base of the disc (Baeta et al. 2016).
This species has robust hind limbs with a tibia that is almost half of the length of the snout-vent. There are no tarsal folds. The toes are slender and their lengths as as follows, in descending order: 4, 5, 3, 2, 1. Like the fingers, the toes have round adhesive discs. The webbing formula on the toes is: I2 – 2 II 2 – 3 II 2- - 3 IV 21/2 - 2 + V. They have single, round subarticular tubercles. Smaller scattered supernumerary tubercles are located on the ventral surfaces of the toes and foot. The inner metatarsal tubercle is elliptical and the outer is absent. The skin is relatively smooth on the limbs and on the dorsum of the body. The ventrum and gular region are areolate. There are granular tubercles where the femur inserts in the body. The skin is more granular with small tubercles near the cloaca. The anterior edge of the cloaca is located at the upper area of the thighs (Baeta et al. 2016).
At Gosner Stage 36, the depressed tadpole body is elliptical in dorsal view and oval in lateral view. The width of the body is slightly larger than the height, and the height of the body is about 60% of the length. In both the dorsal and lateral views, the snout is rounded. The nostrils are positioned closer to the tip of the snout than to the eyes. The eyes are directed in a lateral position. The interorbital distance is half of the body width but twice the eye diameter. The oral disc is on the underside of the front of the head and has a width that is 40% of the body width. The upper and lower lips have two rows of marginal papillae. There is no dorsal gap in the marginal papillae. The ventrolateral sides of the posterior labium have some scattered submarginal papillae. The labial tooth row formula is 2 (2)/3(1). The upper jaw sheath is U-shaped lower jaw sheath is V-shaped. The posteriorly directed spiracle is sinstral and located in the middle third of the body on the ventrum. The opening is visible as a small, crescent-shaped slit. The spiracle lacks an inner wall and is expanded externally. The short and narrow vent tube is located medially at the posterior end of the body and attached to the vent fin by a fleshy membrane. It is directed posteriorly. The tadpole’s tail length is 70% of the total body length and has well-developed musculature. The dorsal fin starts at the first third of the caudal musculature while the ventral fin starts at the vent tube. The lateral line system can be difficult to see, but appear as a series of oval-shaped, vertical, white stitches. There is an irregular series of neuromasts that form supraorbital lines from the anterior region between the nostrils, to the posteromedial region of body. There is also an infraorbital line that starts from the anterolateral region going over the dorsum, curving above the nares to the insertion of the posterior limbs and going down on the ventrum to the spiracle opening (Baeta et al. 2016).
Adult P. dryade can be morphologically differentiated from all other Phyrnomedusa by having a calcar that is at an oblique angle to the tarsus sagittal axis at the postaxial margin instead of a parallel calcar and by having a larger nuptial pad that reaches the subarticular tubercles. More specifically, it can be differentiated from P. appendiculata by the latter having an acuminate snout in the dorsal view and an oblique snout in the lateral view, a curved canthus rostralis, an oblique loreal region, having a green head, and lacking tubercles and folds on the postaxial margins of the forearm and tarsus. It can be differentiated from P. bokermanni by the latter having an acuminate snout in the dorsal view and an oblique snout in the lateral view, a curved canthus rostralis, an oblique loreal region, having a cream white snout, a dentigerous processes of the vomer, a calcar that covers a third of the heel, and, in males only, a larger snout-vent length and hypertrophied arms and fingers. It differs from P. fimbriata by the latter having an acuminate snout in the dorsal view and a markedly oblique snout in the lateral view, an oblique loreal region, a dermal fringe on the upper lip, sparse papillae on the postaxial margin of the forearm and tarsus, a calcar that covers the whole heel, and a larger female snout-vent length. It can be differentiated from P. marginata by the latter having a mottled black and white strip on the third posterior portion of the dorsum, lacking tubercles or folds on the postaxial margins of the forearm and tarsus, the calcar only covering a third of the heel, a longer call interval (2.0 – 9.0 s), and a smaller female snout-vent length. Lastly, it can be differentiated from P. vanzolinii by the latter having an acuminate snout in the dorsal view and an oblique snout in the lateral view, a curved canthus rostralis, an oblique loreal region, having an oblique orange stripe from the eye to the arm, a dentigerous process of the vomer, a calcar that covers one third of the heel, and lacking tubercles and folds on the postaxial margins of the forearm and tarsus (Baeta et al. 2016).
The dorsal fin of P. dryade tadpoles, which starts at the first third of the tail musculature, is diagnostic and can help differentiate it from P. vanzolinii, whose tail fin starts at the junction with the body (Baeta et al. 2016).
In life, the adult P. dryade is brightly colored. Defined by a white line, the dorsal surfaces of the head, body, forearm, and tibia are green. The gular, pectoral region, and venter are a cream white, with tiny gray spots on the anterior gular region. The iris is bicolored, containing dark yellow in the upper and lower areas, with a horizontal dark stripe in the middle of the eye. Beginning from the snout and extending to the groin area, there is a marbled black and white lateral white stripe, with the color becoming lighter and less dark near the dorsal region. Fingers I – III are light orange, finger IV is marbled black and white from the adhesive disc to forearm, and the hands are light orange. Toes I – IV are vibrant orange and toe V is mottled black and white. The dorsum and postaxial margin of the tarsus is marbled black and white, and the ventral surface of the tarsus is shaded dark brown from heel to Toe V. The dorsal areas of the femur are bright orange, with white tubercles focused near the marbled black and white cloacal region. The marbling is continuous with the color of the flanks followed by a white line below the cloacal opening. Metamorphs are of similar color and pattern as adults, but with more muted colors (Baeta et al. 2016).
In preservation, the colors of the adult P. dryade become much duller. Originally green regions fade to light blue and vibrant orange areas fade to a pastel orange (Baeta et al. 2016).
In preserved tadpoles, the body and tail has a marbled appearance that is predominantly brown and irregular small white spots. This coloration follows into the abdomen, excluding the unpigmented region of the visceral mass. The coloration is also more explicit in Stage 39 and later tadpoles whereas stage 25 - 36 tadpoles may be transparent. Starting from the middle area of the body, there is a distinct medial lateral brown line extending posteriorly to the end of the tail. A dorsal brown line on the tail from the junction with the body to the tip of the tail may also be present in some individuals. Dorsal and ventral fins are unpigmented, and the iris is black (Baeta et al. 2016).
Distribution and Habitat
Phyrynomedusa drayade was first found in a single shaded pond located in a forest in the municipality of Sao Luiz do Paraitinga. The pond was located off of the Ipiranga River trail at the Angelim River crossing. The pond’s water level varies depending on the season and amount of rainfall. The pond has a rocky floor that is covered by leaf litter (Baeta et al. 2016).
Life History, Abundance, Activity, and Special Behaviors
The call of P. dryade contains a series of 6 - 12 pulses. Each note lasts between 0.079 - 0.148 seconds, and each pulse lasts from 0.003 - 0.026 seconds. The amplitude of the pulses gradually increases, with the last pulse being 3 - 15 times greater in frequency than the first. The most intense calls have been when the males are perched at lower heights, specifically 0.4 – 2.0 meters from the ground (Baeta et al. 2016).
Eggs are laid in rows in rock crevices just above water. Post-hatching the tadpoles develop in these water bodies until they metamorphose. There are also eggless capsules present in the egg clutch (Baeta et al. 2016).
Tadpoles are present for most of the year. They typically swim in a nearly vertical position, with their head facing upwards. Their movement is due to vibrations of the end of their tail near the surface of the water (Baeta et al. 2016).
The species co-exists with Physalaemus olfersii, Aplastodiscus leucopygius, Dendropsophus microps, and Scinax hayii (Baeta et al. 2016).
Trends and Threats
The chytrid fungus, Batrachochytrium dendrobatidis, occurs in areas where the genus Phrynomedusa likely disappeared from, so there may be threats posed by B. dendrobatidis that require further study (Jenkinson et al. 2016).
Possible reasons for amphibian decline
General habitat alteration and loss
This species belongs to the Hylidae family and is a part of the genus Phrynomedusa. Phrynomedusa was formerly considered a part of the Phyllomedusa genus, however, they have now been distinguished as two separate genera (Baeta et al. 2016).
The name “dryade” is from the Ancient Greek word “dryas”, meaning “tree”, and the suffix “ades”, meaning “from”. Powerful protectors and guardians of forests were called “Dryads” in Greek mythology and K.F.P. Martius, the German Naturalist, used Dryads to refer to the floristic region of the Atlantic Coastal Forest . The name of P. dryade refers to its occurrence in the Atlantic Coastal Forest (Baeta et al. 2016).
This genus is so rare that Phrynomedusa are only known from 61 specimens since 1898 (Baeta et al. 2016). It is possible that there are other undescribed species within this genus that may be imperiled due to habitat loss in the Brazilian Atlantic Forest.
Baeta D., Giasson L.O.M., Pombal Jr J.P., Haddad C.F.B. (2016). ''Review of the rare genus Phrynomedusa Miranda-Ribeiro, 1923 (Anura: Phyllomedusidae) with description of a new species.'' Herpetological Monographs, 30(1), 49-78.
Jenkinson, T. S., Betancourt Román, C. M., Lambertini, C., Valencia-Aguilar, A., Rodriguez, D., Nunes-de-Almeida, C. H. L., Ruggeri, J., Belasen, A. M., da Silva Leite, D., Zamudio, K. R., Longcore, J. E., Toledo, L. F. and James, T. Y. (2016). ''Amphibian-killing chytrid in Brazil comprises both locally endemic and globally expanding populations.'' Molecular Ecology, 25, 2978–2996.
Silvano D. L., Segalla, M. V. (2005). ''Conservation of Brazilian Amphibians.'' Conservation Biology, 19, 653-658.
Originally submitted by: Pearl Holmes, Emily Kotcher, Christina Torres (first posted 2018-02-06)
Edited by: Ann T. Chang (2018-02-07)
Species Account Citation: AmphibiaWeb 2018 Phrynomedusa dryade: Monkey Frog <https://amphibiaweb.org/species/8565> University of California, Berkeley, CA, USA. Accessed Oct 4, 2023.
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Citation: AmphibiaWeb. 2023. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 4 Oct 2023.
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