Thursday, February 1, 2024

[Herpetology • 2024] Scinax juruena • A New snouted Treefrog (Anura: Hylidae: Scinax) from Fluvial Islands of the Juruena River, southern Brazilian Amazonia


Scinax juruena
Ferrão, Hanken, Oda, Campião, Penhacek, Anjos & Rodrigues. 2024

Southern Amazonia is one of the less-explored regions by anuran taxonomists. We describe small new species of snouted treefrog, genus Scinax, from this region, from a fluvial archipelago in the Juruena River, state of Mato Grosso, Brazil. The description is based on external morphology of adults and tadpoles, advertisement call and molecular data. The species is phylogenetically related to other snouted treefrogs of the Scinax cruentomma species group and shows the most southeastern distribution in Amazonia among its close relatives. It is distinguished from congeners mainly by its larger adult body size and bilobate vocal sac that reaches the level of the pectoral fold, a reddish-brown horizontal stripe on the iris, dark melanophores or blotches on the vocal sac and the throat of females, and the uniformly brown posterior portion of the thigh. The advertisement call comprises one pulsed note emitted at regular intervals, with a duration of 189–227 ms, 30–35 pulses/note and a dominant frequency of 2,250–2,344 Hz. The type locality is suffering several environmental impacts, including illegal mining, overfishing, unsustainable agriculture, uncontrolled logging and degradation associated with the construction of new hydroelectric dams. Further study of the biology and regional distribution of the new species is required to propose mitigation measures needed for its conservation.

Coloration in life of Scinax juruena sp. nov. from islands in the Juruena River, municipality of Cotriguaçu, state of Mato Grosso, Southern Amazonia, Brazil.
Nocturnal (A–D) and diurnal (E, F) color patterns.

Scinax juruena sp. nov.  
Generic placement. The new species is assigned to the snouted treefrog genus Scinax based on the phylogenetic position inferred from mitochondrial and nuclear genes (Fig 2).

Diagnosis: Scinax juruena sp. nov. is distinguished from congeners by the following combination of characters. SVL 24.1–27.6 mm (n = 14) in adult males; snout truncate in dorsal view; vocal sac bilobate and reaching the level of pectoral fold; dorsum covered by dark brown spots and irregularly distributed blotches, but lacking dorsal or dorsolateral dark stripes; absence of longitudinal stripe on thigh; reddish brown horizontal stripe on iris; vocal sac covered by dark melanophores or blotches; green bones. Tadpoles have LKRF 2(2)/3; upper lip unemarginated laterally; MPRF (1)/3/1; P-3 smaller than P-2 and P-1; and a dark brown horizontal bar on iris. Advertisement call is composed of one pulsed note with a call duration of 189–227 ms; a call rate of 68–89 calls/min; 30–35 pulses/note; and a dominant frequency of 2,250–2,344 Hz.

Etymology: The specific epithet juruena refers to the Juruena River, where the pristine type locality of the new species is located.

Phylogenetic relationships among Scinax juruena sp. nov. and closely related species of the S. cruentomma group.

Miquéias Ferrão, James Hanken, Fabrício H. Oda, Karla M. Campião, Marcos Penhacek, Samuel Anjos and Domingo J. Rodrigues. 2024. A New snouted Treefrog (Anura, Hylidae, Scinax) from fluvial Islands of the Juruena River, southern Brazilian Amazonia. PLoS ONE. 19(1): e0292441.  DOI: 10.1371/journal.pone.0292441