Description Theloderma asperum is a small frog with a snout-vent length of 25 – 35 mm (Dever 2017). The head is wider than the body and slightly wider than long. The snout is rounded and slightly longer than the diameter of the eye. The nostrils are closer to the tip of the snout than the eye. The distance between the nostrils is smaller than the distance between the eyes. The canthus is indistinct and the loreal region is slightly concave and oblique. The interorbital space is longer than the upper eyelid. The tympanum is distinct and large, but slightly smaller than the eye, and located close to the eye. There is no supratympanic fold (Boulanger 1886, Taylor 1962).
The arms are moderate with hands that have rudimentary webbing at the base. There are three metacarpal tubercles with the outer two being fused and the inner being much smaller. Supernumerary tubercles are present and the subarticular tubercles are distinct but weak. The fingers have fringes or ridges along the edge to the well-developed, large discs that are smaller than the tympanum. The discs have grooves. The first finger is shorter than the second. The legs are also moderate. When adpressed along the body, the tibo-tarsal articulation reaches between the eye and the snout, almost to the snout tip. When held at right angles to the body, the heels overlap. There is no tarsal fold. The inner metatarsal tubercle is small. The toes are three-fourths or more webbed. The subarticular tubercles of the toes are strong. The skin on the dorsum and flanks are rough with small conical warts or tubercles. These warts can be arranged in lines or scattered. The ventrum is granular or areolate. The chin, throat, and ventral surface of the legs are smooth. There are also tubercles around the vent. The male does not have a vocal sac but males may have nuptial pads on the first finger (Boulanger 1886, Taylor 1962).
Theloderma asperum can usually be differentiated from other members of the genus by a combination of their small size, coloration, lacking vomerine teeth and vocal sac openings, but having an eye and tympanum that are about equal in size, dorsal asperites, granular ventrum, and unwebbed fingers (Dever 2017). Although T. asperum is physically similar to T. albopunctatum (Lau et al. 2004, Dever 2017) the two are genetically distinct (Poyarkov et al. 2015). Genetically, T. asperum is similar to T. pyaukkya, but the two can be differentiated by the former being significantly smaller and lacking vocal sack openings (Dever 2017). Both T. ryabovi and T. nagalandensis are also larger than T. asperum and can be further differentiated by T. ryabovi having vocal slits, a more pointed snout, different coloration, patterning that resembles lichen, and rudimentary webbing between fingers 3 and 4. Additional diagnostic characters from T. nagalandensis include the lack of vocal sacs, reticulation patterns on the abdomen, large ridges and warts on the dorsum, and small vomerine teeth in T. nagalandensis (Orlov et al. 2006). From the more similarly sized T. nebulosum, the focal species can be differentiated by their black background color and whitish patterning (vs. brown background with darker brown patterning) and by T. nebulosum having a bicolored iris (Rowley et al. 2011). From T. gordoni, the focal species can be differentiated by the lack of vomerine teeth and a smooth chin and throat. The presence of finger webbing in T. horridum and T. stellatum distinguish them from T. asperum (Taylor 1962). Theloderma asperum can be further differentiated from T. horridum by reproductive behavior with the latter making foam nests and the former attaching ova to surfaces without foam (Leong and Lim 2003).
In life, the dorsal and ventral background coloration is black or dark brown with white tipped warts on the dorsum. The belly has white marbling. The flanks, ventral surface of the limbs and posterior side of the thighs have irregular white reticulations (Boulanger 1886). In preservative, the dorsal coloration becomes grey to bluish gray. There is a small brown line between the eyes and some brown markings near the eye. Under the eye, there is a dark area that extends to the tympanum. There is an elongated brown marking that splits at the level posterior of the shoulder at which point it divides and continues along the sides to the level of the cloaca. Behind this area is a grey area that divides and ends at the base of the anterior thigh, which is typically brown with brown bars that have lighter centers and elongated fine cream flecks. The tibia, tarsus, and foot are also barred with the tibia barring typically encircling the limb. The chin is uniformly brown with small white flecks. The ventrum of the body is cream with strong brown marbling. The ventrum of the limbs is brownish (Taylor 1962).
In life, the dorsal and lateral surfaces, including the tail, of the tadpole is dark ashy grey. The ventrum is unpigmented in the abdominal area and vent tube. The jaw sheaths are partially black. When the limbs emerge, they have dark bars. The dark interorbital bar and mid-scapular patch on adults is evident at stage 41. As the tail is reabsorbed the musculature turns to a buff, cream color. In preservative, the grey background color is muted (Leong and Lim 2003).
Younger specimens may have fewer and less elevated tubercles. The white tips of the warts maybe lost, resulting in a crater-like structure in its place. Patterning may also vary slightly (Taylor 1962).
Theloderma asperum is thought to be the most widely distributed Theloderma with a disjointed range that includes a thin strip of forest along the Aruachai Pradesh and Assam State boarder in India, areas around Longrui and Diwangling in Guangxi Province, China, and a larger area extending from Vietnam and the Cardamom Mountains of Cambodia in the east, through Laos and Thailand to Myanmar, and south along Peninsular Malaysia into one site on West Sumatra, Indonesia. They are found up to 1400 m asl in tropical and subtropical forests (Leong and Lim 2003, Lau et al. 2004, Dever 2017).
Life History, Abundance, Activity, and Special Behaviors Little is known about this rare species because of its cryptic appearance and arboreal lifestyle. They have been observed in small aggregations at breeding sites, which include water-filled tree cavities, small rainwater pools, or in artificial water containers (Leong and Lim 2003, Lau et al. 2004, Dever 2017).
During breeding, eggs, measuring 8.0 mm, are attached 2 – 3 cm above the water surface in pairs by a clear, viscous gelatin. There was no evidence of a foam nest, which can be found in T. horridum. Egg deposition of T asperum appears similar to T. corticale (Leong and Lim 2003).
Larva Larval T. asperum have the distinctly depressed body form of benthic larvae. Larvae hatch at stage 23 with a body length of about 4.1 mm and tail length of about 12.7 mm. During this stage they still have paired cement glands located posterior to the oral disc but have a fully developed operculum. At stage 25 the body length ranges from 5.8 – 7.8 mm and the tail length ranges form 15.5 – 20.1 mm. At stage 27 the body length is about 10.5 mm and the tail length is about 25.6. At stage 28 the body length is 13.2 mm and the tail length is 33.0 mm From stages 29 – 35 the body lengths range from 15.3 -16.8 mm and tail lengths range from 37.4 – 45.0 mm. At stage 43 the body length is 19.3 mm and the tail length is 25.5 mm. The bodies are longer than wide and wider than high. The snout is broadly rounded with the nostrils located dorsally, closer to the snout tip than eyes. The dorso-laterally directed eyes are located dorsally and not visible from below. The oral disc is subterminal and antero-ventral with 1 - 2 rows of rounded marginal papillae starting at the corners of anterior labium and fully enclosing the posterior labium. The labial tooth row formula is 3(2-3)/3(1). The first anterior row is continuous and gently arched. The second and third are divided by the upper jaw sheath with the third being shorter than the second. The first posterior tooth row is divided narrowly by the lower jaw sheath but is otherwise parallel and of similar length to the second and third posterior tooth rows. The lower jaw sheath has fine serrations in the early stages that wear with age. The upper jaw sheath is not convex in the middle. The body reaches its maximum width at the mid-body and has a fine row of lateral line pores that are visible under a microscope. The sinistral spiracle is located ventro-laterally and 2/3rd to 4/5th of the body length from the snout. The spiracle does not extend into a tube, instead opening in a vertical, oval slit. The medial anal tube tapers toward the tip, is continuous with the ventral tail fin and extends slightly beyond the fin margin. The elongated tail has strong musculature that is deeper than both fins. The dorsal fin begins at the body-tail junction. The dorsal and ventral fins are of approximately equal depth and are sub-parallel, only tapering near the end of the broadly rounded tail tip. At stage 41, tuberculated textured hind limbs are present and the reabsorption of both fins begins. When forearms erupt, they are also tuberculated. At metamorphosis, froglets are about 19.3 mm (Leong and Lim 2003).
Few larvae of the genus Theloderma have been identified. However, the larvae of T. asperum can be differentiated from T. horridum, T. molloch, T. stellatum and T. nebulosum by the focal species’ labial tooth row formula, lack of a median convexity in the upper jaw, and ashy grey coloration in life and in preservative. More specifically, T. asperum has a labial tooth row formula of 3(2-3)/3(1), while the other species have formulas of 4(2-4)/3 or , 4(2-4)/3(1) and respective body colorations of dark brown or blackish (in life), black or dark gray (in life), dark brown (in life), and dark brown (in preservative). Theloderma asperum can be further differentiated from T. horridum by the later having a dextral anal tube (Leong and Lim 2003, Rowley et al. 2011).
Trends and Threats Theloderma asperum is listed on the IUCN Red list as a “Least Concern” species because it is found in several protected areas, has a presumed large population, and because it is unlikely to be quickly declining. However, the species is still threatened by habitat loss (Lau et al. 2004).
Possible reasons for amphibian decline
General habitat alteration and loss Habitat modification from deforestation, or logging related activities
Comments The species authority is: Boulenger, G. A. (1886). “First report on additions to the batrachian collection in the Natural-History Museum.” Proceedings of the Zoological Society of London 1886: 411–416.
Based on Bayesian Inference of 1987 base pairs of 12S – 16S rRNA mtDNA sequences, T. asperum is sister to T. licin (Poyarkov et al. 2015). These sister species along with T. albopunctatum, T. petilum, T. pyaukkya and T. ryabovi form the T. asperum species group, with T. ryabovi being the most distantly related lineage. Theloderma phrynoderma is also likely a member of the T. asperum species group (Poyarkov et al. 2015, Dever 2017).
Because of its splattered brown/black and white dorsal patterning, T. asperum is colloquially known as the “bird poop frog.” This patterning helps the frog stay camouflaged in its tropical and subtropical forest habitat (Dever 2017).
A video by Alexandre Herbin below shows calling behavior of Theloderma asperum.
Boulenger, G. A. (1886). ''First report on additions to the batrachian collection in the Natural-History Museum.'' Proceedings of the Zoological Society of London, 1886, 411-416. [link]
Dever, J.A. (2017). ''A new cryptic species of the Theloderma asperum complex (Anura: Rhacophoridae) from Myanmar.'' Journal of Herpetology, 51(3), 425-436.
Lau, M.W.N., Ermi, Z., van Dijk, P.P., Ming, L., Dutta, S., Bordoloi, S., Borah, M. (2004). ''Theloderma asperum (errata version published in 2016).'' The IUCN Red List of Threatened Species 2004: e.T59031A86241488. http://dx.doi.org/10.2305/IUCN.UK.2004.RLTS.T59031A11872564.en. Downloaded on 05 August 2019
Leong, T.M., Lim, K.K.P. (2003). ''Herpetofaunal records from Fraser's Hill, Peninsular Malaysia with larval descriptions of Limnonectes nitidus and Thelmoderma asperum (Amphibia: Ranidae and Rhacophoridae). .'' The Raffles Bulletin of Zoology, 51(1), 123-136. [link]
Orlov, N.L., Dutta, S.K., Ghate, H.V., Kent, Y. (2006). ''New species of Theloderma from Kon Tum Province (Vietnam) and Nagaland State (India) [Anura: Rhacophoridae]. .'' Russian Journal of Herpetology, 13(2), 135-154. [link]
Poyarkov, N. A., Jr., N. L. Orlov, A. V. Moiseeva, P. Pawangkhanant, T. Ruangsuwan, A. B. Vassilieva, E. A. Galoyan, T. T. Nguyen, Gogoleva, S. I. (2015). ''Sorting out Moss Frogs: mtDNA data on taxonomic diversity and phylogenetic relationships of the Indochinese species of the genus Theloderma (Anura, Rhacophoridae).'' Russian Journal of Herpetology, 22(4), 241–280. [link]
Rowley, J.L., Le, D.T.T., Hoang, H.D., Dau, V.Q., Cao, T.T. (2011). ''Two new species of Theloderma (Anura: Rhacophoridae) from Vietnam.'' Zootaxa, 3098, 1-20. [link]
Taylor, E.H. (1962). ''The amphibian fauna of Thailand.'' University of Kansas Scientific Bulletin, 43(8), 265-599.