Leptobrachella brevicrus

Oberhummer, Evelyne, Barten, Catherin, Schweizer, Manuel, Das, Indraneil, Haas, Alexander & Hertwig, Stefan T., 2014, Description of the tadpoles of three rare species of megophryid frogs (Amphibia: Anura: Megophryidae) from Gunung Mulu, Sarawak, Malaysia, Zootaxa 3835 (1), pp. 59-79 : 66-69

Leptobrachella brevicrus

Colour in life and preservation (stage 25)

The following description is based on five specimens at Stage 25 whose total length ranged from 16.50 to 46.50 mm ( Tables 2 and 3 ).

The skin of the head, body and tail is translucent brown. Dorsally ( Fig. 2 C), the head and body are uniformly brown with small brown melanocytes. The colour of the snout is darker coffee brown, getting slightly lighter behind the ocular region. During ontogenesis the brown pigmentation changes from a light yellowish brown in smaller tadpoles to darker brown in larger specimens. In lateral view ( Fig. 2 A), the brown pigmentation of the trunk changes from brown to an iridescent bluish-white colour. The spiracle is translucent and therefore difficult to distinguish from the body wall in lateral view. The lateral line system is clearly visible against the background colour. The nares have a beige interior surrounded by darker coffee brown pigmentation. The oral funnel is translucent. The eyes are black, with dark grey pupils in larger specimens. The pigmentation of the tail is light yellowish brown and the myotomes and myosepta are visible.

Stage n BL BH BS BW ED ES IND IOD LFH MTH The dorsal and ventral fins are both unpigmented and opaque, pale yellowish brown. The tip of the tail is translucent. In ventral view ( Fig. 2 B), the skin has a bluish–white sheen which is particularly intense between the oral disk and the hyobranchial apparatus. The skin of the dorsum and tail is translucent. In lateral and ventral views, the reddish gills, the pale yellowish liver and the gut coil are clearly visible through the skin.

In preserved specimens ( Fig. 2 F) the red colour of the gills and the brown pigmentation of head, body and tail disappear. The skin is transparent with a slightly darker bluish sheen. Myotomes and myosepta become more prominent. The oral funnel becomes translucent. The vena caudalis ventralis and vena caudalis lateralis are visible in ventral and lateral views. The eyes are uniformly black.

External morphological features. The body shape is vermiform, the head and trunk are elongated and slender ( Fig. 2 A). The trunk and head are subcylindrical. The head and belly are slightly depressed. The anterior tip of the head is rounded in lateral and dorsal views. The nares are closer to the snout than to the eyes ( Fig. 2 C). The nares are round and open antero–laterally with a short dorsal projection. The internarial distance is subequal to the interorbital distance ( Table 2 ). The eyes are positioned dorsolaterally. They are small and sunken and do not protrude beyond the body wall, the iris is uniformly black. The spiracle is sinistral, long and conical in shape and has a pointed end ( Fig. 2 C). The spiracular tube protrudes from the body wall and opens laterally. The opening of the spiracle is positioned at 48–52% of the head–trunk length. The tail makes up 70% of the total body length. The dorsal fin is low in the proximal half of the tail, only broadening slightly in the posterior half. The height of the ventral fin is constant in the proximal half of the tail and only increases slightly in the posterior half. The upper and lower fin each contributes 25% to the maximum tail height. The tip of the tail is rounded. The muscles are visible through the transparent skin. The width of the base of the tail is 70–80% of the maximal trunk width. The anal siphon is short and dextral.

The subterminal, antero-ventrally protruding oral disc can be seen from the both ventral and lateral aspects. The width of the funnel-shaped oral disc makes up 80% of the maximal width of the trunk ( Fig. 2 A). The upper and lower lips each have deep medial emarginations ( Fig. 2 E). The short and moderately pointed marginal papillae are arranged in a single row. Submarginal papillae are present on both sides between the oral orifice and the emarginations of the upper and lower lip and around the oral orifice. Below the submarginal papillae on the upper lip, two parallel parasagittal ridges emerge, run towards the upper jaw sheath and diverge laterally. On the lower lip a medial broad pad of thickened skin, parallel narrow ridges and isolated papillae are present. Keratodonts are absent. The beak is black and well keratinized with sharp serrations. The upper beak is arched in ventral view whereas the lower jaw is V-shaped.

At Stage 39 the eyes protrude beyond the contour of the body. The oral disk and spiracle are reduced. All five toes are fully separated. Toe pads and subarticular tubercles are present. The tail is elongate and shows thick caudal muscles, the dorsal and ventral fins are not yet reduced.

Figures

FIGURE 2. Leptobrachella brevicrus. A) Tadpole at Stage 25 in lateral view showing the vermiform body shape and the protruding funnel shaped oral disks. B) Same individual in ventral view, note the spiracular tube that protrudes from the body wall and opens laterally, and the translucent venter. C) Same individual in dorsal view, note the slender trunk. D) Adult individual. E) Ventral view of the mouthparts of Leptobrachella brevicrus in preservation at Stage 25. The marginal papillae are arranged in a uniserial line on the margin of the oral disc and keratodonts are absent. F) Preserved tadpole at Stage 25 in lateral view showing an faded pigmentation in contrast to living specimens. G) Drawing of tadpole at Stage 25 in lateral view.

Tables

TABLE 2. Body measurements of Leptobrachella brevicrus, Leptolalax dringi and Megophrys drinig larvae in mm. Stages according to Gosner (1960). For details and abbreviations see Material & Methods.

Leptobrachella 25 brevicrus	5	5.28– 14.88	1.61– 2.32– 3.81 7.06	2.04– 5.14	0.16– 1.10– 0.85– 0.43 2.91 1.91	0.82– 2.10	0.58– 1.13	2.20– 5.44
mean		9.16	2.60 4.86	3.17	0.29 1.77 1.22	1.26	0.79	3.40
SD		3.93	0.80 2.02	1.18	0.13 0.72 0.42	0.51	0.21	1.23
39	1	11.6	3.6 na	4.39	0.83 2.11 2.01	2.82	1.76	4.53
Leptolalax 25 dringi	2	3.78– 8.87	1.61– 1.95– 3.45 3.72	1.98– 3.95	0.19– 1.13– 0.56– 0.27 2.16 1.67	0.84– 1.56	0.47– 0.9	2.03– 4.03
mean		6.33	2.53 2.83	2.96	0.23 1.65 1.12	1.2	0.69	3.03
SD		3.60	1.31 1.26	1.39	0.05 0.73 0.79	0.51	0.3	1.42
25	1	19.13	5.28 9.68	7.24	0.52 4.18 3.07	2.78	na	na
Megophrys 25 dringi	4	6.74– 11.35	2.80– 3.53– 4.54 5.75	3.26– 5.50	0.50– 2.00– 1.81– 1.01 3.72 3.18	2.25– 4.14	0.87– 1.2	3.44– 5.69
mean		9.11	3.86 4.30	4.85	0.80 3.18 2.71	3.48	1.09	4.99
SD		1.89	0.75 1.03	1.07	0.25 0.83 0.61	0.84	0.15	1.04
TABLE 2. (Continued)
Stage	n	NE	ODW SN	SS	TAL TMH	TMW	TTL	UFH

TABLE 3. Characters of Leptobrachella brevicrus, Leptolalax dringi and Megophrys dringi at Stage 25.

Characters	Leptobrachella brevicrus (N=5)	Leptolalax dringi (N=2)	Megophrys dringi (N=4)
TTL (mm)	Range: 16.94–46.12 Mean: 29.16 SD: 11.42	Range: 14.40–31.28 Mean: 22.84 SD: 11.94	Range: 23.23–37.63 Mean: 31.28 SD: 6.05
TAL/TTL	Range: 0.66–0.71 Mean: 0.69 SD: 0.02	Range: 0.72–0.74 Mean: 0.73 SD: 0.01	Range: 0.69–0.73 Mean: 0.71 SD: 0.02
TMH/BH	Range: 0.68–0.79 Mean: 0.77 SD: 0.09	Range: 0.69 Mean: 0.69 SD: 0	Range: 0.72–0.86 Mean: 0.8 SD: 0.06
TMH/MTH	Range: 0.54–0.64 Mean: 0.59 SD: 0.04	Range: 0.55–0.59 Mean: 0.57 SD: 0.03	Range: 0.58–0.65 Mean: 0.62 SD: 0.03
IND/IOD	Range: 0.95–1.07 Mean: 0.99 SD: 0.06	Range: 0.66–1.07 Mean: 0.87 SD: 0.29	Range: 0.77–0.81 Mean: 0.78 SD: 0.02
SS/BL	Range: 0.42–0.60 Mean: 0.51 SD: 0.07	Range: 0.48–0.58 Mean: 0.53 SD: 0.07	Range: 0.48–0.62 Mean: 0.53 SD: 0.06
ODW/BW	Range: 0.45–2.19 Mean: 0.83 SD: 0.76	Range: 2.14–2.36 Mean: 2.25 SD: 0.15	Range: 0.75–0.79 Mean: 0.77 SD: 0.02
N/ES	Range: 0.09–0.23 Mean: 0.16 SD: 0.06	Range: 0.16–0.46 Mean: 0.31 SD: 0.21	Range: 0.65–0.70 Mean: 0.67 SD: 0.02
ES/BL	Range: 0.15–0.25 Mean: 0.20 SD: 0.04	Range: 0.24–0.30 Mean: 0.27 SD: 0.04	Range: 0.29–0.39 Mean: 0.35 SD: 0.05
UFH/MTH	Range: 0.20–0.30 Mean: 0.24 SD: 0.04	Range: 0.23–0.26 Mean: 0.25 SD: 0.03	Range: 0.16–0.26 Mean: 0.19 SD: 0.05
LFH/MTH	Range: 0.21–0.26 Mean: 0.24 SD: 0.02	Range: 0.22–0.23 Mean: 0.23 SD: 0.01	Range: 0.19–0.25 Mean: 0.22 SD: 0.03
Oral disc orientation	Anteroventral	Ventral	Dorsal