Litoria dux, Richards, Stephen J. & Oliver, Paul M., 2006

Richards, Stephen J. & Oliver, Paul M., 2006, Two new species of large green canopy­dwelling frogs (Anura: Hylidae: Litoria) from Papua New Guinea, Zootaxa 1295, pp. 41-60 : 50-55

Litoria dux sp. nov. ( Figs 5 –9)

Holotype. SAMA R60725 adult male with nuptial pads and vocal slits, calling when collected, Yuwong Village, Huon Peninsula, Morobe Province, Papua New Guinea, (5°51.263'S, 146°44.057'E, ~ 400 m asl) collected by Stephen Richards on 13th Jan 2003.

Paratypes. UPNG 9986 adult male with nuptial pads and vocal slits, collected on 15 January 2003, SAMA R60726, adult female with eggs, collected 16 January 2003, both with same collection data as holotype.

Diagnosis

Litoria dux sp. nov. can be distinguished from all congeners by the following combination of characters 1) green dorsal colouration 2) large adult size (two mature males with nuptial pads 67.0 and 70.3 mm, a female 75.0 mm SV) 3) prominent white dermal folds on the arms and legs 4) absence of white labial stripe 5) hands extensively webbed 6) iris red and white, without mottling or black pigmentation 7) sclera of eye black and 8) edge of upper eyelid lacking a white edge.

Description of holotype

Adult male with following measurements (mm) SVL 70.3; EN 6.7; HW 24.1; EYE 7.6; TL 37.7; IN 6.2; HL 24.4; EAR 4.5; 4TD 4.6; 4TP 3.7; 3FD 5.4; 3FP 3.4. Habitus moderately slender; head marginally wider than long (HW/HL 1.029), not wider than body in dorsal view; snout truncate in dorsal and lateral view; labial region slightly flared; loreal region steeply sloping, marginally concave; canthus rostralis moderately distinct, curved; nares much closer to tip of snout than to eyes, oriented laterally and only marginally visible in both dorsal and anterior views.

Choanae large, roughly circular, separated by a distance approximately three times their width; prominent clumps of about ten very low triangular vomerine teeth positioned along the posterior ridge of two triangular, posteriorly directed elevations located medially to choanae. Eyes moderately small but prominent (EYE/SVL 0.108), clearly visible in both dorsal and lateral views, pupil horizontal, thin band of dense small white pigment flecks extends across dorsal edge of nictitating membrane, very sparse scattered pigment flecks elsewhere on membrane, especially around anterior corner. Tympanum moderate (E AR/SVL 0.046), annulus distinct, dorsal edge obscured by thick, fleshy, curved supratympanic fold that runs from posterior edge of eye to axillary junction. In preservative skin on dorsal surfaces of body and limbs smooth; ventrally throat, forelimbs and most of hindlimbs smooth, abdomen and lateral edge of femur coarsely granular.

Arms robust; prominent white dermal fold extends from penultimate phalanx of finger IV along upper arm to elbow; relative lengths of fingers III>IV>II>I; terminal discs of all fingers significantly wider than penultimate phalanx (3FP/3FD 0.630), with circummarginal grooves; subarticular tubercles prominent, conical; two tubercles on digits I and II, three tubercles (medial tubercle distinctly larger) on digits III and IV; one rounded supranumerary tubercle on digit I, three or more on digits II to IV; a single large (one third length of digit I), ovoid inner metacarpal tubercle and a small rounded nuptial excresence at base of digit I. All digits webbed, webbing extends to level of proximal subarticular tubercle between digits I and II, and on both sides of digit III; and to disc on outer side of digit two and inner side of digit IV.

Legs moderately long (TL/SVL = 0.537); prominent white dermal fold along tarsus extends from lateral edge of toe V to heel. Relative lengths of toes IV>V>III>II>1; discs expanded, with circum­marginal grooves (4TP/4TD = 0.804), subarticular tubercles prominent, rounded or conical, two tubercles on digits I and II, three on digits III and V, and four on digit IV; numerous small round supranumerary tubercles on basal phalanges of digits II­V; inner metatarsal tubercle small, oval shaped. All digits webbed, webbing extends halfway along penultimate phalanx on both sides of digit IV, and to base of disc on all other digits.

In life dorsum and dorsal surfaces of arms and legs pale leaf green with scattered faint patches of yellowish green. Ventral surfaces, including hidden surfaces of both limbs, yellow to yellowish white. Yellowish­green horseshoe shaped marking on the tympanic membrane. Dorsal surfaces of outer toes and fingers leaf green; of inner toes and webbing yellow. Prominent off­white dermal ridges on outer edge of arms and legs. Pupil horizontal, iris with distinctive outer red rim surrounding inner ring of grey around pupil, a further thin reddish line is present just above the pupil; sclera black.

In preservative dorsal surfaces pale slate blue with widely scattered very small patches of darker slate blue; ventral surfaces off­white, abdomen with very slight brownish tinge. Dorsal surface of legs, lower arms, finger IV and toe V largely slate blue. Remaining digits largely white with varying levels of faint brown spotting, especially toe IV and finger III which appear faintly tinted with brown. Tympanic membrane with distinct area of clear skin in the shape of an inverted horseshoe. Dermal ridge on edge of legs and arms white. Nuptial excresence very faint brown.

Va r i a t i o n

The type series is rather uniform. The male UPNG 9986 is the smallest specimen and is significantly darker than the other types, especially in the anterior dorsal region. The single female paratype (SAMA R60726) is the largest specimen (SVL 75.0 mm) but this size difference is not unusual for Litoria species (e.g, Tyler 1968). Both paratypes have slightly more brown spotting on the hands and feet than the holotype.

Comparison with other species

Litoria dux differs from all New Guinean Litoria except L. graminea and L. sauroni in the characters used to diagnose L. graminea (above). It differs from L. graminea in having a narrower head (0.34 Vs 0.38­0.40), an iris without extensive black and orange reticulations and in having a small round (vs elongate) nuptial pad. It is most similar to L. sauroni but differs notably in a number of characters related to eye colouration, including iris without extensive and heavy black and red pigmentation, sclera black (vs blue), and pigment flecking largely restricted to a band across the dorsal edge of the nictitating membrane (vs dense stippling across membrane). It can also be distinguished from both the species mentioned above by the absence of a white distal edge to the upper eyelid.

Etymology

From the Latin dux , meaning leader, alluding to the bright colouration and impressive appearance of the species (particularly the red iris) which make it prominent within a genus that is already replete with spectacular species.

Natural history

Litoria dux were calling from high in the canopy on ridges adjacent to the Tarona River during January 2003. One specimen was in a tree adjacent to a forest garden and two specimens were collected from primary rainforest in trees overhanging puddles that had formed in a previously dry rocky creek bed after torrential rain. One male descended to within three metres of the pools during observation, suggesting that this species may breed in pools on the forest floor. Descending to the ground after torrential rain to breed is a behaviour typical of several groups of unrelated tropical arboreal frogs e.g Rhacophorus ( Inger & Stuebing 1997) and Agalychnis (Savage 2002)) .

Female specimens for all L.graminea­ complex species are very rarely collected. SAMA R60726 is larger than the two male L. dux , and contains small, pigmented eggs.

FIGURE 9. Advertisement calls of A. Litoria dux sp. nov. (UPNG 9986) and B. L. sauroni sp. nov. (SAMA R60727) recorded at 25o C and 27o C respectively.

Figures

FIGURE 5. Lateral view of head of holotype of Litoria dux (SAMA R 60725). Note the limited pigmentation on the nictitating membrane. Scale = 10 mm.