Microhyla fissipes is a slender-bodied frog with the holotype having a snout vent length of 26 mm (Boulenger 1884). The average male snout-vent length is 22.5 mm and the average female is 25 mm. It has a truncated snout that is somewhat longer than the diameter of the eye. The canthus rostralis is rounded and the loreal region is somewhat oblique. The space between the eyes is longer than the width of the eyelid. The skin on the dorsum is smooth to somewhat tubercular. There is a longitudinal series of warts connecting the eye to the groin. There may also be an occipital fold connecting the posterior edge of the upper eyelid to the forelimb. There are small warts on the flanks. The ventrum is smooth with the exception of the anal region, which is granular. Males have a moderately distinct vocal sac fold across the chest. Like the body, the digits are slender, and the tips of the digits are not swollen or clefted. The subarticular tubercles of both the hands and the feet are distinct. The first finger of the hand is significantly smaller than the second. The second is subequal or slightly shorter than the fourth finger. The toes are unwebbed to slightly webbed and have no fringes to slight lateral fringe. When the leg is adpressed to the body, the tibio-tarsal articulation reaches between the shoulder and the eye. The feet have two small, obtuse metatarsal tubercles (Boulenger 1884, Parker 1934).
Tadpoles have a mean total length of 4.299 ± 0.263 mm when they hatch at Gosner stage 24. At stage 40, they reach their maximal total length of 22.267 ± 0.858 mm before tail reabsorption begins. Tadpoles have a dorso-terminal mouth, a singular mid-ventral spiracle, and a deep ventral tail fin (Wang et al. 2017).
Microhyla fissipes was previously thought to belong in the species M. ornata, however, in 2005 (Matsui et al.), M. ornata was split into three species with M. fissipes and M. okinavensis being elevated to full species. The three species are very similar but can be differentiated based on genetics and geography. Microhyla fissipes is found in Taiwan, Hainan Island, and north of the Red River in Vietnam and China (Yuan et al. 2016) whereas M. ornata is found in India and Bangladesh and M. okinavensis is found in the Ryukyu Archipelago of Japan. Microhyla fissipes can be further differentiated from M. okinavensis by morphology, and acoustics. Specifically, M. okinavensis has a different shaped loreal region, different proportions between the interocular distance and the eyelid width, different shaped toe tips along with other digit accessories, and a different relative tibio-tarsal articulation position when the leg is adpressed to the body (Matsui et al. 2005). In 2016 (Yuan et al.), M. fissipes was further split, by genetic analysis, into two species. This fourth species, M. mukhlesuri, is similar in appearance, but is only found in Southeast Asia - south of the Red River, and in Bangladesh. It also has different ecological requirements (Yuan et al. 2016).
The tadpoles of M. fissipes may have medial cloacal tails that would differentiate it from M. ornate’s dextral cloaca. They can also be differentiated by the latter having longer infralabial papillae, a membraneous ridge posterior to the nostrils, and more filter rows (Matsui et al. 2005). Tadpoles of M. fissipes are also very similar to M. pulchra but can be differentiated by being somewhat smaller and with a slightly shorter tail (Parker 1934).
In preservative, the dorsum of adults ranges in coloration from pinkish-olive, olive-brown, brown, or grey and the warts have a pale or red tinge. A dark lateral band runs from the tip of the snout, through the eye to the center of the side. Between the eyes, there is a dark, elongated X-shaped mark and in the sacral region there is an upside-down V-shape. These patterns may be ill-defined or interrupted. The dorsum also has undulating, dusky lines. The limbs have dark crossbars. The anal region and anterior surfaces of the thighs are darker. The ventrum is whitish and the throat and chest have brown stippling (Boulenger 1884, Parker 1934).
In life, tadpoles are transparent (Liu et al. 2016, Wang et al. 2017).
Distribution and Habitat
Country distribution from AmphibiaWeb's database: Cambodia, China, Hong Kong, Lao People's Democratic Republic, Malaysia, Singapore, Thailand, Viet Nam
Malaysian region distribution from AmphibiaWeb's database: Peninsular Malaysia
Microhyla fissipes is restricted to the north of the Red River, which runs through Vietnam and southern China, and extends up to Shangcheng, Henan, China. The species is also found on Taiwan and Hainan Island in the South China Sea (Yuan et al. 2016). The species can be found in elevations up to 2,000 m asl (Lau et al. 2008) in lowland scrub forest, grassland, agricultural land, pastureland, and urban areas (Yuan et al. 2016, Wang et al. 2017).
Life History, Abundance, Activity, and Special Behaviors
The species is somewhat fossorial but can also be found in the leaf litter of forest floors. It is primarily nocturnal but is known to be diurnal during breeding in the rainy season (Lau et al. 2008).
The species breeds in temporary pools or other still waters, including agricultural land that is not intensively farmed (Lau et al. 2008) from March to September with a peak from May to the end of June (Liu et al. 2016). Once amplexus has begun, multiple spawings occurs in the water and last about 10 minutes (Liu et al. 2016).
Clutch size ranges between 209 and 564 eggs and have a diameter range of 0.9 - 1.0 mm. Initially, eggs are yellow. Eggs observed in captivity were free floating in water and covered in a jelly coat. Embryos have a displaced radical, holoblastic cleavage pattern, and rotate so that the animal hemisphere is on the top. The animal hemisphere is brown and vegetal hemisphere is brown. Egg development is rapid with hatching occurring after 54 hours in captive settings with water temperatures between 23 - 25°C and tadpoles completing metamorphosis on day 43, post-fertilization (Wang et al. 2017).
Trends and Threats
The species is widespread, common, and can be found in a wide range of habitats including lowland scrub forest, grasslands, pasturelands, agricultural fields and urban areas. As a result, the species has a status of “Least Concern”. However, the species is still threatened by pollution, specifically agrochemical, and habitat loss (Lau et al. 2008).
Possible reasons for amphibian decline
General habitat alteration and loss
Local pesticides, fertilizers, and pollutants
The species authority is: Boulenger, G. A. (1884). "Descriptions of new species of reptiles and batrachians in the British Museum.—Part. II." Annals and Magazine of Natural History, Series 5, 13: 396–398.
In 2005, Maximum Parsimony, Maximum Likelihood, and Neighbor-joining analyses of 629 base pairs of CytB showed a deep divergence in M. ornata with populations from South Asia being split from populations from Southeast Asia, China, Taiwan, and Japan. Populations from Southeast Asia, China, and Taiwan were thus named M. fissipes and the Japanese populations were name M. okinavensis. Further analyses on 1752 base pairs of 12 S and 16 S rRNA supported these findings and further found that M. fissipes was most closely related to M. okinavensis. The two species also formed a clade with M. heymonsi and M. pulchra and this clade is sister to a clade formed by M. ornata and M. rubra (Matsui et al. 2005). Later analyses in 2016, using Bayesian and Maximum Likelihood methods on CytB mitochondrial DNA and Rag-2 nuclear DNA, showed an additional north-south divergence in M. fissipes. Populations from China - north of the Red River, Taiwan, and Hainan Island were thus considered M. fissipes while populations in Southeast Asia - south of the Red River were renamed M. mukhlesuri. The 2016 analyses also showed that M. fissipes is sister to M. mukhlesuri and the clade forming those two species was most closely related to M. mymensinghensis. Microhyla okinavensis, M. mixtura, and M. heymonsi are equally related to the clade formed by M. fissipes, M. mukhlesuri, and M. mymensinghensis (Yuan et al. 2016).
The species epithet, “fissipes” is a resurrected name first proposed by Boulenger in 1884. However in 1934, H.W. Parker synonymized M. fissipes with M. ornata based on morphology. Microhyla fissipes was resurrected after molecular analysis by Matsui et al. (2005) showed that it was indeed a different species.
Boulenger, G. A. (1884). ''Descriptions of new species of reptiles and batrachians in the British Museum. Part II.'' Annals and Magazine of Natural History, series 5, 13, 77396-77398.
Lau, M.W.N., Baorong, G., van Dijk, P.P., Iskandar, D. (2008). “Microhyla fissipes”. The IUCN Red List of Threatened Species 2008: e.T135848A4210760. http://dx.doi.org/10.2305/IUCN.UK.2008.RLTS.T135848A4210760.en. Downloaded on 02 October 2018.
Liu, L.-S., Zhao, L.-Y., Wang, S.-H., Jiang, J.-P. (2016). ''Research proceedings on amphibian model organisms.'' Zoological Research, 37(4), 237-245.
Matsui, M, Ito, H, Shimada, T, Ota, H, Saidapur, SK, Khonsue, W, Tanaka-Ueno, T, Wu, G-F (2005). ''Taxonomic relationships within the Pan-Oriental narrow-mouth toad Microhyla ornata as revealed by mtDNA analysis (Amphibia, Anura, Microhylidae).'' Zool. Sci., 22, 489-495.
Parker, H.W. (1934). A Monograph of the Frogs of the Family Microhylidae. British Museum, London.
Wang, S., Zhao, L., Liu, L., Yang, D., Khatiwada, J.R., Wang, B., Jiang, J. (2017). ''A Complete Embryonic Developmental Table of Microhyla fissipes (Amphibia, Anura, Microhylidae).'' Asian Herpetological Research, 8(2), 108-117.
Yuan, Z.-H., Suwannapoom, C., Yan, F., Poyarkov Jr., N.A., Nguyen, SN, Chen, H.-M., Chomde, S., Murphy, R.W., Che, J. (2016). ''Red River barrier and Pleistocene climatic fluctuations shaped the genetic structure of Microhyla fissipes complex (Anura: Microhylidae) in southern China and Indochina.'' Current Zoology, 62(6), 531-543.
Written by Ann T. Chang (anntchang AT berkeley.edu), UC Berkeley
First submitted 2018-10-02
Edited by Ann T. Chang (2018-10-17)
Species Account Citation: AmphibiaWeb 2018 Microhyla fissipes: Ornate Chorus Frog <http://amphibiaweb.org/species/6459> University of California, Berkeley, CA, USA. Accessed Oct 18, 2019.
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Citation: AmphibiaWeb. 2019. <http://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 18 Oct 2019.
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