Marbled Tree Toad, Everett’s Asian Tree Toad
Species Description: Boulenger GA 1896. Descriptions of two new batrachians obtained by Mr. A. Everett on Mount Kina Balu, North Borneo. Annals and Magazine of Natural History, Series 6, 17: 449–450.
© 2020 Lars Fehlandt (1 of 5)
The lower arm is shorter than the head length and slightly less than a quarter of the snout-vent length. There are two palmar tubercles, with the outer being larger than the inner. The fingers have basal webbing that reaches the subarticular tubercle of finger I and past the basal subarticular tubercle of finger II. The relative finger lengths are III < IV < II < I and all the subarticular tubercles are rounded (Chandramouli and Amarasinghe 2016). Chandramouli and Amarasinghe (2016) describe the fingertips as sharp and smooth, however, Chan et al. (2016) describe the fingertips as “expanded into flat discs”. Nuptial pads can be found on the dorsal side of finger I (Chandramouli and Amarasinghe 2016).
The tibia is longer than the femur and foot. The foot is slightly longer than the femur. The hind limbs have a distinct tarsal ridge and tarsal folds. The outer metatarsal tubercle is rounded and the inner metatarsal tubercle is oval. The toes are fully webbed with the exception of toe IV and the toes end with expanded flat discs with round edges. The relative toe lengths are I < II < III < V < IV (Chan et al. 2016, Chandramouli and Amarasinghe 2016).
The dorsal skin is granular and further characterized by numerous round warts, especially on the middorsal, lateral, and posterior parts of the body that have larger warts. The head has numerous round warts on the snout and internarial region. The mouth is also surrounded by warts, however the distal margin of the lower and upper jaw is smooth. There is a symphysical knob at the anterior end of the mandible. The throat and belly have smooth skin. The flanks from the axila to the groin are also smooth. The dorsal and ventral sides of arms have small rough and sharp warts. The anterior and posterior surfaces of the thighs are relatively smooth as are the toes on both the dorsal and ventral surfaces (Chandramouli and Amarasinghe 2016).
Rentapia everetti is larger than the Asian bufoid genera Blythophryne, Pedostibes, and Phrynoidis. The lack of cephalic ridges in R. everetti differentiates it from some members of the genera Adenomus, Duttaphrynus, and Xanthophryne. The presence and shape of the parotid glands differentiate R. everetti from Blythophryne and Sabahphrynus. An externally visible tympanum in R. everetti distinguish it from Bufoides and Sabahphrynus. Expanded digit discs differentiate R. everetti from Phrynoidis. The presence of partial webbing on the fingers and complete webbing toes distinguish R. everetti from Phrynoidis and Sabahphrynus respectively. At eight, R. everetti has one more pre-sacral vertebrate than species in the genera Bufoides, and two more than species in the genera Blythophryne. The tarsal ridge present in R. everetti differentiates it from Bufoides and Pedostibes. Lastly, reproductive strategies differ between Pedostibes, which deposit medium-sized egg clutches expelled in a film, and Rentapia, which has a large clutch of eggs that are deposited in strings (Chan et al. 2016, Chandramouli and Amarasinghe 2016).
In preservative, the dorsal surface is blue-grey with several dark brown blotches. The lateral part of the head has wide dark brown bars. The legs and arms are light brown with the dorsal side having brown bars. The ventral side is completely cream-colored (Chandramouli and Amarasinghe 2016).
Distribution and Habitat
Country distribution from AmphibiaWeb's database: Indonesia, Malaysia
Life History, Abundance, Activity, and Special Behaviors
Adult R. everetti are arboreal (Chen et al. 2016) and found in hilly lowlands, submontane, moist tropical primary forest, and some secondary forest. Adults may have some tolerance to disturbance as they are found in recently disturbed, open areas in Kinabalu National Park and the Corcker Range National Park (IUCN 2018).
The breeding behavior of R. everetti is unknown. However, R. everetti egg clutches are deposited as strings. The ova themselves are small and pigmented (Chan et al. 2016). Breeding is speculated to occur in clear, rock-filled streams with slow paced water (IUCN 2018).
Trends and Threats
Rentapia everetti is a rare species. Its infrequent observations may be due to the species’ arboreal lifestyle. As a result, little is known about the population status of the species, but it is assumed to be decreasing in response to habitat loss or destruction due to a hydro-electric dam, logging concessions, small scale subsistence logging, palm plantations, and siltation of streams. The species is protected within at least two national parks. To further protect the species, lowland forest preservation and management of parks is necessary, as are more studies into the species distribution, population status, and natural history (IUCN 2018).
Relation to Humans
Possible reasons for amphibian decline
General habitat alteration and loss
Analysis of concatenated sequences of 16S mtDNA and the nuclear genes CXCR4 and NCX1 indicate that Rentapia is the sister genus to Phrynoidis, also known as the terrestrial river toad. Despite previously being assigned to the genus Pedostibes, Rentapia presents a 13 - 14% divergence from Pedostibes tuberculosus and a 12 - 13% divergence from genus Phrynoidis (Chan et al. 2016). As of 2020, R. everetti and R. hosii are the only member of the genus Rentapia as Chandramouli and Amarasinghe (2016) synonymized R. rugosa (also written as R. rugosus) with R. everetti, which was an older name, based on morphological analysis.
The genus name Rentapia refers to a warrior from the indigenous Bornean subgroup, the Iban, named Libau Rentap. Libau Rentap is considered a great war chief and Malaysian hero for leading the rebellion against the English monarchy (Chan et al. 2016).
The species epithet is presumably in honor of the collector of the first specimen, Mr. A. Everett.
Chan K.O., Grismer L.L., Zachariah A., Brown R.M., Abraham R.K. (2016). ''Polyphyly of Asian Tree Toads, Genus Pedostibes Günther, 1876 (Anura:Bufonidae), and the Description of a New Genus from Southeast Asia.'' PLoS One, 11(1), e0145903.
Chandramouli, S.R., Amarasinghe, A.A.T. (2016). ''Taxonomic Reassessment of the Arboreal Toad Genus Pedostibes Günther 1876 (Anura: Bufonidae) and Some Allied Oriental Bufonid Genera.'' Herpetologica, 72(2), 137-147.
IUCN SSC Amphibian Specialist Group. (2018). ''Rentapia everetti''. The IUCN Red List of Threatened Species 2018: e.T114108750A115741972. http://dx.doi.org/10.2305/IUCN.UK.2018- 2.RLTS.T114108750A115741972.en
Written by Elena Hausser (elenahausser AT berkeley.edu), UC Berkeley
First submitted 2020-06-23
Edited by Ann T. Chang (2020-06-23)
Species Account Citation: AmphibiaWeb 2020 Rentapia everetti: Marbled Tree Toad <http://amphibiaweb.org/species/9180> University of California, Berkeley, CA, USA. Accessed Jul 12, 2020.
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Citation: AmphibiaWeb. 2020. <http://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 12 Jul 2020.
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