Theloderma asperum (Boulenger)

Leong, T. M. & Lim, Kelvin K. P., 2003, Herpetofaunal Records From Fraser’S Hill, Peninsular Malaysia, With Larval Descriptions Of Limnonectes Nitidus And Theloderma Asperum (Amphibia: Ranidae And Rhacophoridae), Raffles Bulletin of Zoology 51 (1), pp. 123-136 : 128-130

Theloderma asperum (Boulenger)

( Figs. 5-7 )

Distribution. – NE. India (Arunachal Pradesh), S. China, Myanmar, Vietnam, W. and N. Thailand, Peninsular Malaysia, Sumatra ( Dutta, 1997; Iskandar & Colijn, 2000; Taylor, 1962b). In Peninsular Malaysia, previously recorded from Bukit Itam and Bukit Belachan, Selangor ( Berry, 1975). Type locality: Peninsular Malaysia; Perak, Maxwell’s Hill (Bukit Larut), elevation ca. 1, 000 m asl.

Microhabitat. – Although it may be safely presumed that members within this genus are generally phytothelm breeders ( Taylor, 1962b), tadpoles of T. asperum were found in an artificial water container. Adults (DWNP.A.1185, ZRC.1.9321, Fig. 4 ), embryos (ZRC.1.9372-9375), and larvae (ZRC.1.9376-9390) were found within a large (1m x 1m x 1m), black, plastic drum used for collection of rainwater runoff. This covered drum was within private residence along the Telecom’s Loop (ca. 1, 400 m asl), adjacent to montane forest. The commensal rhacophorid, Polypedates leucomystax , was also sharing this artificial breeding site. Adults (DWNP.A.1184, ZRC.1.8042) and larvae (ZRC.1.9368-9371) of P. leucomystax were collected as vouchers. The embryos of T. asperum were found attached in pairs ca. 2-3cm above the water surface, via a clear, viscous gelatin. The earliest embryos (ZRC.1.9372-9373, Stage 20) were still bound within their transparent egg membranes (diameter 8.0mm), while a more advanced pair (ZRC.1.9374- 9375, Stage 21) was wriggling inside a slightly larger egg membrane (diameter 9.3mm). The gelatinous remains of previously hatched ova were observed along the inner rim of this container as well. There were no signs of any foam nest formations. Larval T. asperum were predominantly swimming around the bottom of the container, occasionally surfacing cautiously for gulps of air, then rapidly diving down again.

Diagnosis. – A benthic larval form, with distinctly depressed body; eyes and nostrils set dorsally; oral disc subterminal; LTRF 3(2-3)/3(1); upper jaw sheath without median convexity; spiracle sinistral, ventrolateral, not projecting as a free tube; anal tube median; tail musculature strong; body and tail dark ashy grey.

Morphology. – ( Figs. 5 , 6 ) Body ovoid, snout broadly rounded, BW 0.70-0.84 of BL; clearly depressed, BH 0.64- 0.80 of BW, maximum width at mid-body; eyes dorsal, directed dorso-laterally, not visible from below, IOD 0.32- 0.37 of BW, 0.91-1.22 of oral disc width; nostrils dorsal, nearer to snout tip than eye; IND 0.47-0.66 of IOD; spiracle sinistral, ventro-lateral position, not extended as a tube, spiracular opening a vertical, oval slit, snout-spiracle 0.62- 0.83 of BL; anal tube median, tapering towards the tip, continuous with ventral fin, projecting slightly beyond ventral fin margin. Tail elongate, dorsal and ventral fin margins sub-parallel, tapering only towards the end to a broadly rounded tip; TAL 1.32-1.79 of BL, MTH 0.26-0.43 of TAL; caudal muscle deeper than both fins for proximal _ of tail; dorsal fin originating at body-tail junction, depth comparable with ventral fin. Fine rows of lateral line pores visible dorsally under microscope.

Colour and markings. – (In life) Dorsum and sides of body dark ashy grey, tail muscle and fins uniformly pigmented ashy grey, venters unpigmented around abdominal region. Anal tube unpigmented. In preservative, the intensity of the grey colouration is slightly reduced.

Oral disc morphology. – ( Fig. 7 ) Mouth antero-ventral, subterminal, width 0.30-0.37 of BW, marginal papillae of anterior labium confined to lateral corners, consisting of 1- 2 rows of short, rounded papillae; lower labium with continuous margin of 1-2 rows of similarly shaped papillae. Jaw sheaths finely serrated in early stages, but margins increasingly worn smooth in more advanced (Stage 35 onwards) larvae; upper jaw sheath without median convexity; both jaw sheaths partially pigmented black. LTRF: 3(2-3)/ 3(1); A-1 continuous and gently arched, A-2 and A-3 broadly divided by upper jaw sheath, A-3 shorter than A-2. P-1 narrowly divided in the middle, P-1 to P-3 almost parallel and of similar lengths (0.75 width of oral disc).

Developmental changes. – A recently hatched larva (ZRC.1.9376, Stage 23) still possessed a pair of cement glands immediately posterior to the oral disc, yet operculum development was already complete. An advanced twolimbed larva (Stage 41) collected from the container had already exhibited dark barrings on its well developed hind

23 1 4.1 12.7

25 7 5.8-7.8 15.5-20.1

27 1 10.5 25.6

28 1 13.2 33.0

29 1 15.3 37.4

31 1 15.6 40.0

33 1 15.5 36.0

35 1 16.8 45.0

43 1 19.3 25.5

limbs. The dark inter-orbital bar and mid-scapular patch was already noticeable. The tuberculated texture of the back and hind-limbs were also visible at this stage. Both dorsal and ventral fins had begun resorption, accompanied by a lightening of the tail muscle to a buff, cream colour. After four days, the fore-limbs eventually erupted, exhibiting characteristic dark bands on the fore-arms and fingers. Fingers with very rudimentary webbing, as in the adults. Tuberculation on fore-limbs distinct, as in the hind limbs. After live photographs were taken, it was preserved at Stage 43 ( Fig. 6 ). Upon complete tail resorption, the individual (ZRC.1.9390) would have an SVL of 19.3mm. Measurements of BL and TL of the developmental series are reflected in Table 2.

Interspecific comparisons. – Within the genus Theloderma Tschudi , nine species are currently recognised (Iskandar & Colijn, 2000), of which three already have detailed tadpole descriptions. The larval identity of T. horridum ( Boulenger, 1903) was revealed together with the first description of the adults, and clearly illustrated with excellent lithographs ( Boulenger, 1903: Pl. VI, Fig. 2a, b ). The second species whose larvae have been well described is T. stellatum Taylor, 1962b . Its tadpole was first described from Thailand by Wassersug et al. (1981) and even included detailed characteristics of the buccal area. Larval specimens of the same species from Vietnam were also briefly described subsequently ( Inger et al., 1999). The third species, T. molloch ( Annandale, 1912) was also described and illustrated with remarkable detail ( Annandale, 1912: Pl. IV, Fig. 6 ). One other species, T. corticale ( Boulenger, 1903) , has been successfully bred and raised in captivity (Orlov & Rybaltovsky, 1999), but unfortunately, no detailed larval descriptions were provided.

Larvae of T. asperum may be distinguished from those of T. horridum , T. molloch and T. stellatum by examining their LTRF, which is 3(2-3)/3(1), instead of 4(2-4)/3 ( Boulenger, 1903; Annandale, 1912) for T. horridum and T. molloch , or 4(2-4)/3(1) ( Wassersug et al., 1981), 4(2-4)/3 ( Inger et al., 1999) for T. stellatum . In addition, the upper jaw sheath of T. asperum lacks a median convexity, which is present in T. horridum , T. molloch and T. stellatum . In terms of colouration, T. horridum is a uniform dark brown or blackish ( Boulenger, 1903); T. molloch is uniformly black or dark grey; T. stellatum can be dark brown ( Wassersug et al., 1981) or black ( Inger et al., 1999), whereas T. asperum tends towards an ashy grey. All known larval forms, however, share the common characters of a distinctly flattened body, with dorsally positioned eyes and nostrils. It is interesting to note that although the anal tube of T. asperum , T. molloch and T. stellatum are consistently median in position, that of T. horridum was reported to be dextral (‘anus towards the right’, Boulenger, 1903). This seems to be a departure from the apparently predominant median position and may either have been an (a) artefact of the preservation process, or (b) observational error.

There is also another inconsistency in the reproduction mode of T. horridum , which was reported to deposit ova in foam nests ( Boulenger, 1903), while in T. corticale , the ova were merely attached onto plants with the help of their viscous, sticky membranes (Orlov & Rybaltovsky, 1999). Taylor (1962b) found the eggs of T. stellatum in ‘two masses attached to the trunk of a forest tree, about two feet from the ground, some five inches directly above a small hole in the trunk containing a quantity of black-brown water, coloured by rotting wood and leaves’. However, there were no indications as to whether the egg ‘masses’ were in the form of a foam nest or clear gelatin. Egg deposition in T. asperum appears to be similar to that in T. corticale , without any construction of a foam nest.

Figures

Fig. 5. Lateral (a) and dorsal (b) aspects of early (Stage 25) larval Theloderma asperum.

Fig. 6. Lateral (a) and dorsal (b) aspects of late (Stage 43) larval Theloderma asperum.

Fig. 7. Oral disc of larval Theloderma asperum (Stage 35).

Fig. 4. Adult female Theloderma asperum (ZRC.1.9321, SVL 33.1mm).

Fig. 2. Lateral (a) and dorsal (b) aspects of Stage 40 larval Limnonectes nitidus.