Description
Densropsophus arndti is a relatively large frog with a snout-vent length range of 28 - 33.2 mm. The body is as wide as the head, with the head being more broad than long. The snout is short and rounded when viewed dorsally and truncated when viewed laterally. The nostrils are slightly protuberant and are directed posterolaterally. The canthus rostralis is rounded and barely distinct. The internarial region is slightly depressed. The eyes are large and protuberant with a diameter about 1.4 times the diameter of the tympanic annulus. The tympanum is concealed and the tympanic annulus is visible below the skin. The dorsal skin is smooth and the ventral skin is granular on the head and thighs. The arms are slender with an auxiliary membrane reaching halfway to the elbows. The relative lengths of the fingers are I < II < IV < III, and they each have large oval discs. The subarticular tubercles are single, round to ovoid, and prominent. The distal tubercle of finger IV is bifid. There are supernumerary tubercles present and the palmar tubercle is indistinct. The webbing of fingers I is basal and the formula for the rest of the fingers is II1 ½ – 2 ½ III 2 ⅔ – 2 IV. The hind limbs are moderately long. The outer metatarsal tubercle is small, round, and poorly defined, and the inner metatarsal tubercle is large, elongated, and elliptical. The relative lengths of the toes are I < II < V < III < IV. The subarticular tubercles are single, round, and flat, and the supernumerary tubercles are only on the soles. The webbing formula for the toes is I 1+ – 2- II 1+ – 2- III 1+ – 2 IV 2+ – 1+ V. The toes have similar, but wider than long, discs as the fingers (Caminer et al. 2017).

Dendropsophus arndti can be differentiated from most other species in the genus by its larger size and wide, dorsolateral bands. From the two most similar species to it, D. leucophyllatus and D. triangulum, it can be differentiated by its rounded sacral mark with small dark spots and irregular edges. It also differs from these two species in its advertisement call; specifically by having a lower duration and number of pulses than D. leucophyllatus and a lower frequency bandwidth and dominant frequency than D. triangulum (Caminer et al. 2017).

Dendropsophus arndti can also be differentiated from D. reticulum by its advertisement call and larger size. Dendropsophus reticulum also has a more uniform dorsal color and a red ventral color, which further distinguishes it from D. arndti (Caminer et al. 2017).

In life, the background dorsal color is a brown or dark brown with white or bright yellow irregular dorsolateral bands extending to the head and a white or bright yellow circular sacral mark. There are one to two light irregular rounded spots on the dorsal surfaces of the forearms and one to three on the shanks. Some individuals also have a reticulated color pattern. The ventral side and the webbing vary in color from orange to orange-yellow to pink. The irises vary from a dull brown to a coppery bronze (Caminer et al. 2017).

In preservative, the dorsum is brown with white dorsolateral bands and a white sacral mark, both with irregular brown spots surrounding them. All of the spots on the limbs as well as the ventral side and the webbing are a dull, creamy white (Caminer et al. 2017).

There is some variation in coloration, and some size differences based on sex. The coloration of the ventral side and the webbing vary from orange to orange-yellow to pink, and the irises vary from a dull bronze to a coppery bronze. The number of white spots on the limbs also varies from one to three (Caminer et al. 2017).

There is sexual dimorphism, with the females being slightly larger (Caminer et al. 2017).

Distribution and Habitat

Country distribution from AmphibiaWeb's database: Bolivia

View distribution map in BerkeleyMapper.

Dendropsophus arndti is found in the Bolivian Amazon Basin, in the Beni and Santa Cruz departments. Its elevation ranges from 148 to 529 meters above sea level. They can be found at night along river shores, edges of forest, temporary swamplands, and artificial ponds on vegetation above the ground or water surface (Caminer et al. 2017).

Life History, Abundance, Activity, and Special Behaviors
Dendropsophus arndti is nocturnal and it has been observed as the prey of the spider, Ancylometes (Caminer et al. 2017).

The advertisement call is one pulsed, trill note that lasts approximately 0.19 seconds. Each note has 15 - 19 pulses with a mean dominant frequency of 2655.4 Hz. The mean rise time is 0.12 s and it has a frequency bandwidth of 487.67 Hz. The aggressive call is 3 - 4 pulsed notes with a short average duration of 0.14 s and has fewer pulses than the advertisement call. This call has a mean dominant frequency of 2668.76 Hz, mean rise time of 0.07 s, and a mean frequency bandwidth of 423.26 Hz (Caminer et al. 2017).

Larva
At Gosner stage 36, the larva have a total length of 31.6 mm and a body length of 9.6 mm. Their body is compressed when viewed laterally and violin-shaped when viewed dorsally. The snout is sloped when viewed laterally and rounded when viewed dorsally. The eyes are large and are positioned and directed laterally. The nostrils are globular, positioned anterolaterally, directed anteriorly, and on the same level as the eyes. The spiracle is sinistral, directed dorsally, and very short. The centripetal wall of the spiracle is completely fused to the body wall at the spiracle opening. The cloacal tube is dextral, attached to the ventral fin, and is covered by a fold. The tail is very long, over twice the length of the body, and is inclined slightly upward from the body. It has a short tail that smoothly transitions into the ventral fin and abruptly transitions into the dorsal fin. The dorsal fin emerges on the tail and is slightly taller than the body. The ventral fin is wider than the dorsal fin (Schulze et al. 2015).

In life, at Gosner stage 36, the larva is a light to reddish brown with dark brown speckles and large spots both dorsally and laterally. There is a broad, dark brown lateral stripe running from the snout through the eyes to the border between the body and the tail. It has a darker lower edge and a thinner, unpigmented line beneath it. The ventral coloration is a light silver with dark speckles. The tail and fins have the same coloration as the body, and the flagellum is a light brown to yellowish color with large, brown, and sub-rectangular spots with the margins transparent (Schulze et al. 2015).

Trends and Threats

This species has a very large range with a low proportion of it as degraded habitat, indicating that overall, there are not many threats to this species (Caminer et al. 2017).

Comments

Maximum Likelihood and Bayesian analyses on nucDNA and 16S mtDNA found that D. arndtiis sister to D. leucophyllatus, with the next most closely related species being D. reticulatus (Caminer et al. 2017).

References

Caminer, M. A., Milá, B., Jansen, M., Fouquet, A., Venegas, P. J., Chávez, G., Lougheed, S. C. and Ron, S. R. (2017). Systematics of the Dendropsophus leucophyllatus species complex (Anura: Hylidae): Cryptic diversity and the description of two new species. PLoS (Public Library of Science) One 12(3), e0171785 [link]

Gosner, K. L. (1960). A simplified table for staging anuran embryos and larvae with notes on identification. Herpetologists' League 16(3), 183 - 190. [link]

Schulze, A., Jansen, M., and Köhler, G. (2015). Tadpole diversity of Bolivia's lowland anuran communities: molecular identification, morphological characterisation, and ecological assignment. Zootaxa 4016(1), 001 - 111. [link]

Species Account Citation: AmphibiaWeb 2024 Dendropsophus arndti: Arndt's Tree Frog <https://amphibiaweb.org/species/8602> University of California, Berkeley, CA, USA. Accessed Sep 14, 2024.

Citation: AmphibiaWeb. 2024. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 14 Sep 2024.

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