Zhangixalus minimus (Rao, Wilkinson & Liu, 2006)
Guangxi Diminutive Treefrog
|Species Description: Rao, Wilkinson & Liu 2006 A new species of Rhacophorus (Anura: Rhacophoridae) from Guangxi Province, China. Zootaxa 1258: 17-31|
The forelimbs are short with slender forearms and large hands. The inner metacarpal tubercle is indistinct, low, and oval. The outer metacarpal tubercle is also indistinct and low, but is distally cleft. The relative length of the basally webbed fingers is 3 > 4 > 2 > 1. The webbing formula is I 2.5 – 2.5 II 2 – 3 III 2.5 – 2.25 IV. The subarticular tubercles are well developed and round. Additional supernumery tubercles can be found on each finger, proximal to the subarticular tubercles closest to the fingertips. The fingertips are rounded, have well-developed discs with oval circummarginal grooves, and have Y-shaped distal phalanges. The hind limbs are short and when adpressed to the body, the tibiotarsal articulation only reaches the posterior half of the eye. The heels do not meet when held at right angles to the body. The foot does not have an outer metatarsal tubercle but the inner metatarsal tubercle is distally raised and oval. The relative length of the webbed toes is 4 > 5 = 3 > 2 > 1. The webbing formula is I 1.5 – 2 II 1.5 – 2.5 III 2 – 2.5 IV 2.5 – 1.5 V. There is one subarticular tubercle on toes 1 and 2 and two on the other toes. The proximal tubercles are smaller than the distal tubercles. There are no supernumerary tubercles. Like the fingers, the toes have oval discs with circummarginal grooves (Rao et al. 2006).
Polypedates and Rhacophorus are the only genera in the family, Rhacophoridae, that have bright green coloration on the dorsum, hand webbing, and have foam nests. Rhacophorus minimus is distinguishable from the other green species in these genera by having a green dorsal surface that has no pattern and smooth texture, as well as having the smallest snout-vent length among species in its genus. It also has a white stripe that extends laterally from the snout tip, across the upper labial surface and to the hip joint. The digits of its forelimbs have less webbing than other Rhacophorus species and the tympanum is larger in diameter than the disc on the third finger. More specifically, the lack of any fully webbed digits distinguishes R. minimus from R. angulirostris, R. bipunctatus, R. dulitensis, R. edentulus, R. monticola, and R. turpes. The lack of tubercles on the dorsum distinguishes R. minimus from R. appendiculatus, R. everetti, and R. kajau. The absence of a brown pattern on the dorsum distinguishes R. minimus from Polypedates dugritei and P. zhaojuensis. The absence of dark spots on the lateral surfaces of the body distinguishes R. minimus from P. dorsoviridis and P. nigropunctatus. The small size and slenderness of the body distinguishes R. minimus from P. chenfui, P. hungfuensis, R. schlegelii, R. taipeianus, and P. yaoshanensis. The lateral white stripe beginning at the tip of the snout and traveling along the upper lip to the hip joint, the absence of dorsal tubercles, and webbing that extends less than 33% of the length of the digits distinguishes R. minimus from P. chenfui, P. hungfuensis, and P. yaoshanensis. The tympanum being larger than the disc of the third finger distinguishes Rhacophorus minimus from P. chenfui and P. hungfuensis. The absence of white dots, the presence of a mottled pattern on the lateral surfaces of the body and thighs, brown hands and yellow-green coloration on the digital discs distinguishes R. minimus from P. hungfuensis. The snout of P. yaoshanensis is shaper than that of R. minimus, and P. yaoshanensis has red coloration on the thighs (Rao et al. 2006).
In life, Rhacophorus minimus is bright green on its dorsal side with speckling and a white line that extends laterally from the snout tip, across the upper labial surface under the eye, to the hip joint. The hands and feet are mostly light brown with a darker mottled pattern. The finger- and toe-tips are yellow-green. The iris is brown close to the pupil and yellow further away from it, especially on the top quarter of the pupil (Rao et al. 2006).
In preservative, the dorsum is light blue, including midway down the flanks and onto the limbs. Dark blotches are present around the nares, the tympanum, and sparsely across the dorsum. The dorsal surfaces of the hands and feet are olive to light cream and mottled with dark brown. A white line extends from the snout to the hip joint, separating the blue of the dorsum from the ventral coloration. The ventral side of the entire body is cream colored with some dark mottling, especially on the thigh. On the posterior margin of the tarsus and supracloacal fringe is a white ventral line that is bordered with black. The hands and feet are dark on the ventral side (Rao et al. 2006).
Rhacophorus minimus has variation in coloration, skin texture, and displays several sexually dimorphic characters. Nares can vary in the amount of light brown they exhibit. The intensity of the dark brown mottled pattern of the thigh and the lateral white line on the body is variable. Individuals may also have a scattering of asperities on the head or upper eyelid. Females are larger than males. Male heads have a length equal to that of its width (the head is slightly wider than long in female) and the slope of the snout is less steep anterior to the nostrils than that of a female (Rao et al. 2006).
Distribution and Habitat
Life History, Abundance, Activity, and Special Behaviors
This species is terrestrial (Rao et al. 2006).
Males can be found calling in grass near shallow, freshwater ponds and from perches in broad-leaf trees. The males call mostly during the night but were also heard calling throughout the day. The males use axillary amplexus (Rao et al. 2006).
Rhacophorus minimis is oviparous and builds foam nests, which it attaches to objects outside of the water, to contain protect eggs. The frogs have been observed using artificial water trays for breeding (Rao et al. 2006).
In life, the tadpoles of R. minimus are black during the early stages of metamorphosis. As the limbs develop and the tail is reabsorbed, the juvenile become green. In preservative, The dorsum is brownish grey from dense brown chromatophores scattered across the skin. The ventrum is transparent and has fewer chromatophores. The lateral regions of the tadpoles have an intermediate number of chromatophores. The tail musculature is light cream with brown reticulations that extend onto the dorsal fin but not onto the ventral fin (Rao et al. 2006).
Trends and Threats
Possible reasons for amphibian decline
General habitat alteration and loss
Rhacophorus minimus was placed in the genus Rhacophorus, based on findings that green dorsum Asian rhacophorids formerly in Polypedates are more closely related to species in Rhacophorus (Rao et al. 2006). Further phylogenetic analyses, using Bayesian Inference, Maximum Likelihood, and Maximum Parsimony methods, on partial fragments of mitochondrial and nuclear genes show that R. minimus is sister to the clade composed of R. hungfuensis and R. wui. The clade composed of those three species is sister to the clade formed by R. dugritei and R. hui (Li et al. 2012).
The species epithet “minimus,” meaning “smallest” in Latin, is a reference to the species’ small size (Rao et al. 2006).
Li, J.-T., Liu, J., Chen, Y.-Y., Wu, J.-W., Murphy, R.W., Zhao, E.-M., Wang, Y.-Z., Zhang, Y.-P. (2012). ''Molecular phylogeny of treefrogs in the Rhacophorus dugritei species complex (Anura: Rhacophoridae), with descriptions of two new species.'' Zoological Journal of the Linnean Society, 165, 143-162.
Rao D., Wilkinson, J. A. Liu, H. (2006). ''A new species of Rhacophorus (Anura: Rhacophoridae) from Guangxi Province, China.'' Zootaxa, 1258, 17-31.
Rao Ding-Qi. 2008. Rhacophorus minimus. The IUCN Red List of Threatened Species 2008: e.T135910A4219717. http://dx.doi.org/10.2305/IUCN.UK.2008.RLTS.T135910A4219717.en. Downloaded on 28 April 2018.
Originally submitted by: Erik A. Sathe (first posted 2018-06-21)
Edited by: Ann T. Chang, Michelle S. Koo (2022-08-18)
Species Account Citation: AmphibiaWeb 2022 Zhangixalus minimus: Guangxi Diminutive Treefrog <https://amphibiaweb.org/species/6779> University of California, Berkeley, CA, USA. Accessed Sep 21, 2023.
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Citation: AmphibiaWeb. 2023. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 21 Sep 2023.
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