Description

Diagnosis: Leptodactylus simonstuarti can be distinguished from other congeners by a relatively large SVL (maximum 26.2 mm for males and 25.2 mm for females), dark dorsal coloration, dark stripes on the ventral surfaces of the arms, and a unique advertisement call (Angulo and Icochea 2010).

Description: Small robust body with maximum SVL of 26.2 mm for males and 25.2 mm for females. Snout is rounded when viewed from above and nearly acuminate when viewed laterally. Canthus rostralis is indistinct. Nares are dorsolaterally oriented and are equidistant between the snout tip and the eye. Tympanum is distinct. Supratympanic fold extends from the posterior of the eye to the arm insertion. An oval cream-colored gland is present below the angle of the jaw. Vomerine teeth present in parallel transverse series, posterior to choanae. Arms are robust and short. Fingers are slender with rounded but not expanded tips. Relative finger lengths are III>I=II>IV. Fingers have rounded cream-colored subarticular tubercles. Hind limbs are robust and the tibia is longer than the thigh. Relative toe lengths are IV>III>V>II>I. Toes have dark lines on the undersides and do not have fringes. Metatarsal tubercles are quite distinct. The dorsum has small scattered tubercles distributed from around the shoulder down to vent. The venter is smooth. Thighs are mostly smooth. Shanks have very small white-tipped tubercles (Angulo and Icochea 2010).

Coloration: Leptodactylus simonstuarti, in life, has a grayish/dark brown dorsum with irregular dark markings from mid-dorsum to the groin. A dorsolateral, discontinuous, tan-orange glandular line extends on each side of the body from behind the eye to just anterior to the groin. The supratympanic fold is edged by a dark stripe that runs from the dark brown tympanum to the arm insertion, then continues irregularly from the posterior of the arm to the groin. A lighter stripe runs roughly parallel and ventral to the dark stripe. A small orange-colored gland is visible beneath each supratympanic fold, between the tympanum and the anterior of the arm. Below each eye, there are two dark bars that lie somewhat diagonal to the anterior and posterior angles of the eye. Upper and lower lips have some white spotting. Dorsal surfaces of arms and heels are orange-red, and the arm bears two incomplete crossbars. A dark, nearly continuous stripe extends along the underside of the arm beginning at the wrist, slightly narrowing at the elbow, and continuing to the arm insertion. Hind limbs have dorsal surfaces with irregular dark crossbars, and shanks with white-tipped tubercles. The venter is grayish-white. A dark gland is present on either side of the cloaca (Angulo and Icochea 2010).

Variation: In Peru, some paratypes had slightly lighter dorsal coloration; others had short, dark spots or lines on the palms. The Bolivian paratypes (two females) lacked diagonal dark bars underneath the eye; one of them also had a thin mid-dorsal light stripe extending from the lumbar region down to the vent. Bolivian paratypes also had very well-developed supratympanic folds running from behind the eye to the arm insertion, and less lower lip mottling than the Peruvian paratypes (Angulo and Icochea 2010).

Similar species: Leptodactylus simonstuarti can be distinguished from Amazon-associated congeners as follows. In comparison to Leptodactylus heyeri, L. simonstuarti lacks two distinct pairs of dorsolateral folds, and L. simonstuarti males lack yellow coloration on their throat and belly. In comparison to Leptodactylus lutzi, L. simonstuarti has a smaller maximum body size (26.2 mm SVL for L. simonstuarti males vs. 30 mm SVL for L. lutzi males), and lacks distinct spots on the posterior thigh. This species differs from Leptodactylus andreae, Leptodactylus diptyx and Leptodactylus hylaedactylus by having a larger SVL (26.2 mm SVL vs. L. andreae, 21 mm SVL, L. diptyx, 22 mm SVL and L. hylaedactylus, 24.6 mm SVL), dark dorsum, and a very dark stripe that runs along the underside of the arm from the wrist to the arm insertion. Leptodactylus simonstuarti also differs from Leptodactylus coca in having a relatively more developed inner metacarpal tubercle, dark dorsum, and a dark, continuous stripe that runs along the underside length of the arm (Angulo and Icochea 2010).

Distribution and Habitat

Country distribution from AmphibiaWeb's database: Bolivia, Peru

View distribution map in BerkeleyMapper.

Found in Southern Peru (four localities near each other in the District of Echarate, Province of La Convención, Region of Cusco, ranging in elevation from 280-694 m asl: (1) the type locality, Campamento Segakiato, Río Camisea, at 340 m asl; (2) Campamento Konkariari, Río Urubamba, 280 m asl; (3) Cashiriari II, 469 m asl; (4) Cashiriari III, 694 m asl) and northern Bolivia (San Sebastián, near Río Tahuamanu, Department of Pando, 280 m asl). It may occur more widely. The type locality in Peru is located 407 km away from the locality in Bolivia. This species occurs mainly in lowland Amazonian primary and secondary forests, but can also be found in disturbed habitat such as regenerating cacao plantations. It inhabits the leaf litter (Angulo and Icochea 2010).

Life History, Abundance, Activity, and Special Behaviors
In a cacao plantation with some secondary growth, the male holotype was found calling under leaf litter next to a rotting log. Calling activity is initiated at dusk. The call was first described by Angulo (2004) (as Adenomera "Camisea I"). The dominant frequency is the same as the fundamental frequency, ranging from 1813 to 2035 Hz, and at least two other lower-intensity harmonics may be present at 3707-4049.5 Hz and 4956-6024 Hz. Frequency rises slightly during the call (171-430 Hz, and there are 3-4 strong, pulse-like amplitude modulations in the call. Leptodactylus simonstuarti has a shorter mean call duration (65 msec) and a higher call rate (216-246 calls/min) compared to other species in the Leptodactylus marmoratus group. Only L. hylaedactylus (Tambopata, Peru) has a comparable call rate (162-252 calls/min) (Angulo and Icochea 2010).

Adult males have a projecting, callus-like ridge on the snout, just above the upper lip. This ridge is believed to be used to excavate nesting chambers since a similar ridge is known to be used for nest construction in Leptodactylus fuscus (Angulo and Icochea 2010).

Trends and Threats
This species is clearly capable of tolerating some degree of habitat disturbance since it has been found in abandoned cacao plantations with some secondary regrowth. The four Peruvian localities are all located within the boundaries of Camisea Natural Gas Project's Block 88. This project presents a tangible threat to flora, fauna, and indigenous communities, as the pipeline has already ruptured several times since 2004 (Angulo and Icochea 2010).

Possible reasons for amphibian decline

General habitat alteration and loss
Urbanization
Mining

Comments
Species authority: This species was first described by Angulo and Icochea (2010).

Etymology: Leptodactylus simonstuarti was named for Dr. Simon N. Stuart, in recognition of his considerable efforts to highlight the global amphibian crisis and to encourage amphibian research and conservation efforts across the world (Angulo and Icochea 2010).

References

Angulo, A. (2004). The Evolution of the Acoustic Communication System in Members of the Genus Adenomera (Anura Leptodactylidae): A Comparative Approach. Unpublished Ph.D. thesis, University of Toronto, Canada.

Angulo, A. and Icochea, J. (2010). ''Cryptic species complexes, widespread species and conservation: lessons from Amazonian frogs of the Leptodactylus marmoratus group (Anura: Leptodactylidae).'' Systematics and Biodiversity, 8(3), 357-370.

Species Account Citation: AmphibiaWeb 2010 Adenomera simonstuarti <https://amphibiaweb.org/species/7546> University of California, Berkeley, CA, USA. Accessed Oct 11, 2024.

Citation: AmphibiaWeb. 2024. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 11 Oct 2024.

AmphibiaWeb's policy on data use.