Chiroleptes occidentalis, Anstis, Marion, Price, Luke C., Roberts, J. Dale, Catalano, Sarah R., Hines, Harry B., Doughty, Paul & Donnellan, Stephen C., 2016

Anstis, Marion, Price, Luke C., Roberts, J. Dale, Catalano, Sarah R., Hines, Harry B., Doughty, Paul & Donnellan, Stephen C., 2016, Revision of the water-holding frogs, Cyclorana platycephala (Anura: Hylidae), from arid Australia, including a description of a new species, Zootaxa 4126 (4), pp. 451-479 : 469-472

Cyclorana occidentalis sp. nov.

Western Water-holding Frog Figs. 6–9

Holotype. WAM R 111826, adult female collected 55 km E Newman, Pilbara, WA (23.4908°S, 120.3172°E) by P. Doughty on 4 October 2005.

Material examined. Details of the 41 specimens used to document variation are listed in Appendix 1.

Diagnosis. A medium to large robust burrowing species, SVL males 42–60 mm; females 44–66 mm. Clearly assigned to the Cyclorana by its phylogenetic placement in molecular genetic analyses ( Fig. 2 ) and a combination of its morphological characters, burrowing behaviour, tadpoles and call structure. Distinguished from all other species of Cyclorana except C. platycephala by the more dorsally-tilted eyes, fully webbed toes (no more than half-webbed in all other Cyclorana) and the oral disc of tadpoles ( Anstis 2013). Distinguished from C. platycephala by its western Australian distribution ( Fig. 1 ), the consistently greater number of tubercles and skin folds, yellow-brown dorsal colour (never green or pink as in C. platycephala ), by molecular genetic analyses and the call. The call of C. occidentalis increases in amplitude steadily over the first ¾ of the call, compared with amplitude peaking about mid-call in C. platycephala ). The only species of Cyclorana sympatric with C. occidentalis is C. maini from which C. occidentalis can be separated by a combination of larger body size, fully webbed toes (one-third webbed in C. maini ), more prominent dorsal tubercles and skin folds, broader head with more dorsally-tilted eyes, dorsum rarely with numerous darker patches (as in C. maini ), oral disc of the tadpoles and the call. Calls of C. maini , as described by Tyler & Martin (1976), have a higher pulse rate (244 pulse.s -1), higher frequency (1922 Hz) and the call is longer (814 ms) than the call of C occidentalis .

Description of holotype. Moderately large and robust in habitus (SVL 64 mm). Head broad, slightly flattened and slightly wider than long (HW/HL = 1.06); snout broadly rounded in dorsal view, obtusely rounded in profile; eyes prominent and dorsolateral in position, inclined anterolaterally with a dorsal tilt; eyelids granular; transverse diameter slightly greater than eye-to-nostril distance (ED/EN = 1.12). Canthus rostralis poorly defined and very slightly curved in anterior and lateral views ( Fig. 6 A, B); nostrils slightly closer to tip of snout than to eye, distance between them less than eye to nostril (IN/EN 0.74); tympanum distinct, in anterior view projecting dorsolaterally, annulus slightly raised, diameter slightly less than eye (TYMP/ED = 0.96); supratympanic fold distinct and sloping ventrally posterior to tympanum, terminating above forearm.

Tongue very broad, attached anteriorly and free behind; a prominent vomerine tooth plate either side of midline, each laterally adjacent to medial edges of choanae and narrowly separated; each tilting slightly posteriorly towards medial edge; ventral edges denticulate, with four to six small pointed tips; choana about equal in length to the width of a vomerine tooth plate; mouth could not be opened wide enough to photograph, so Fig. 8 shows features of mouth of WAM R165306, which agrees with description of holotype above.

Arms short (FA/SVL = 0.21); hindlimbs short and robust (TL/SVL = 0.37). Tips of fingers and toes slightly fleshy, no wider than digit, no circum-marginal grooves; fingers slender and unwebbed, decreasing in length in order 3˃4˃1˃2; thumb opposable; inner metacarpal tubercle large and prominent, palmar tubercle broad and flattened; subarticular tubercles distinct and projecting, especially on first finger; toes slender, decreasing in length in order of 4˃5˃3˃2˃1 and fully webbed to tips, tapering into broad lateral fringes towards tip of longest (fourth) toe; inner metatarsal tubercle prominent, shovel-shaped and medial edge free of attachment to foot beneath; outer metatarsal tubercle indistinct, broad and flat; subarticular tubercles very small and indistinct.

Dorsum with numerous smoothly rounded, low tubercles and a few short skin folds; a long dorsolateral skin fold extends from posterior of tympanum to more than midway along flanks; eyelids granular; ventral surface granular.

Colour in life. Dorsum yellow-ochre with diffuse, faintly darker yellow and grey flecks, increasing posteriorly and over legs ( Fig. 9 ). Dorsal colour merges into cream over sides of body. Undersurface white. Iris golden.

Colour in preservative. All yellow pigment is lost; dorsum grey, eyelids with subdued darker spots, eye to tympanum darker; limbs and flanks mottled; undersurface cream with light grey spots on throat.

Variation. Details of all specimens examined for this description of variation are presented in Appendix 1. See also morphological measurements of all preserved specimens ( Table 2) and details of morphological variation ( Table 3 ). SVL males 42–60 mm, females 46–70 mm. TibL/SVL range is 0.34–0.43 (mean 0.39±0.02). The dorsal skin of all but one frog (WAM R154929) bears tubercles to varying degrees (dense in 51%), and all but one (WAM R63834) have a long dorsolateral skin fold beginning posterior to the tympanum. Most (76%) have additional short skin folds ( Table 3 ). Ventral skin smooth (23%) to granular (77%). The snout is mostly rounded in dorsal view and in profile, 38% are truncate in dorsal view and in profile. The canthus rostralis is slightly curved or curved in anterior and lateral views ( Fig. 7 I, M), with a slight ridge from eye to naris in some.

Tadpoles. Maximum size in life: TL to 82 mm, BL to 32 mm (stage 39, Carnarvon, WA). Tadpoles of C. occidentalis are generalised pond-dwellers and have a moderately large to large, plump body with moderately arched fins ( Anstis 2013). Photographs of tadpoles in life and a drawing of the oral disc and morphometric comparisons are given in Fig. 9 and Table 3 . As tadpoles have a similar morphology to those of C. platycephala , no drawing of the tadpole is included. Photographs of tadpoles in life and a drawing of the oral disc are included ( Fig. 10 ), and morphometric comparisons of 10 tadpoles of C. occidentalis with samples of C. platycephala from eastern and northern populations ( Table 4; Fig. 4 ).

Colour in life. Tadpoles in earlier stages 25–26 are translucent gold with darker areas over naris to eye, brain and vertebral region. Dorsal tail muscle with alternating gold and black patches anteriorly (when first collected). As tadpoles grow, yellow-gold pigment increases in coverage and density over dorsum and merges into dense, opaque silver-white over sides of body and venter. Iris dense gold. Tail muscle in fully-grown tadpoles light golden, fins transparent, densely speckled with gold. Colour was similar in all specimens raised or freshly collected.

Colour in preservative. All gold and silver-white pigment is lost in preservative and tadpoles are dull and translucent with darker internal body areas visible.

Oral disc. As for C. platycephala , but the jaw sheaths may be slightly less robust.

Metamorphosis. Recorded in January, but probably occurs at any time from January to March in north-western Australia, depending on the timing of summer rains. Metamorphs strongly resemble the adult in colour and skin texture ( Fig. 10 ), but the tympanum is not distinct initially. Four had a mean SVL of 30 mm (26.0–32.0). Observations of recent metamorphs in the field indicated the SVL was relatively similar to those raised in captivity, but none was measured.

Habitat. The light yellow-golden colour of C. occidentalis tadpoles found in the Wooramel and Carnarvon districts of WA is consistent with the yellow-brown opaque muddy water of the large claypans and floodplains where they occurred.

Comparisons with tadpoles of other species. Tadpoles of C. occidentalis could be confused with those of C. maini and Neobatrachus because of similarities in maximum size and colour. Cyclorana occidentalis tadpoles have less heavily keratinised jaw sheaths (robust) with a more broadly arched upper jaw sheath than those of C. maini , which have very heavily keratinised jaw sheaths (massive) and a more narrowly arched upper jaw sheath ( Anstis 2013). Neobatrachus tadpoles differ from Cyclorana in having three or four anterior tooth rows (two in Cyclorana), dorsal eyes and massive jaw sheaths. From stage 38, C. occidentalis have more extensive webbing between the toes than any of the other sympatric species above.

Etymology. The species epithet is Latin for ‘western’ and refers to its distribution in the western third of the Australian continent.

Distribution and habitat. This species inhabits arid or semi-arid areas of central WA, south from about Karratha in the north to the Kalgoorlie area, and from the coast inland to Well 26 on the Canning Stock Route in the north and Mavis Rock in the south ( Fig. 1 ). Most specimens are from the Pilbara, Murchison, Gascoyne, Yalgoo and Carnarvon IBRA regions (Department of the Environment 2012; Atlas of Living Australia website at www.ala.org.au ̗ accessed 1 Sep 2015). Several specimens from Barrow Island, eastern WA and the south-western and north-western NT fall outside of the distribution we present in Fig. 1 . WAM R40026 from Barrow Island could not be located in the WAM collection, and with no subsequent sightings or calls of this species recorded from the island despite extensive survey work, we view this record as suspect. NTM R30138 from the “Victoria River District” could not be located at the NTM so we have not been able to confirm its identity. We assessed specimens attributed to ‘ C. platycephala ’, WAM R21320 from Warburton, WAM R21535 and R96360–8 from Palm Valley, AMS R21117 from 240 km W Alice Springs, but all are either C. maini Tyler & Martin or Platyplectrum spenceri Parker. These records were not included in Fig. 1 . Based on records of frogs from museum collections viewable on line (Atlas of Living Australia 2015), the absence of C. occidentalis or C. platycephala from the intervening area of these species ranges is not readily explained by lack of sampling, as other arid frogs such as Neobatrachus Peters , Notaden Günther , Platyplectrum spenceri and other Cyclorana species are recorded from much of this area. Therefore we view the geographic separation between taxa to be real, possibly caused by differences in soil type or historical factors, for example, relatively recent range expansion, as evidenced by lack of mitochondrial phylogeographic structure within C. occidentalis , and C. verrucosa relative to that observed in C. platycephala ( Fig. 2 ).

Within its broad range in the western deserts, C. occidentalis appears to have a preference for areas with heavy clay soils and has been encountered in ephemeral pools along creek lines. It avoids desiccation by aestivating underground and forming a cocoon of sloughed skin ( Withers 1995).

Advertisement call. The call is a nasal ‘waaaaaaaaah” increasing in amplitude over the first ¾ of the call, decreasing rapidly after that, and repeated ≈ every 1.5 seconds—often in long calling sequences (see details Table 5, Fig. 5 ). A call can be heard at: http://museum.wa.gov.au/explore/frogwatch/frogs/water-holding-frog.

Breeding behaviour. MA observed males and gravid females at night beside water bodies at Carnarvon WA on 12 January 2011 and also found tadpoles in stages 26–28 at this time. JDR observed calling males in a pool in a drainage line following heavy rains near Meekatharra, December 19–20, 1988 where calls were recorded.

Figures

FIGURE 1. Map showing museum records (small symbols) and sites sampled for the molecular genetic analysis (large symbols) of Cyclorana platycephala sensu lato populations. Black = eastern populations, red = northern populations (C. platycephala sensu stricto), blue = western populations (C. occidentalis sp. nov).

FIGURE 2. Maximum likelihood mitochondrial ND 4 gene tree of Cyclorana. Grey branches had ML bootstrap proportions ≥ 70 % and Bayesian posterior probabilities ≥ 95 %. Letter prefixes of voucher numbers: A = AMS, Q = QM, S = SAMA, W = WAM.

FIGURE 4. Discriminant Function Analysis (DFA) of morphometric characters of tadpoles of Cyclorana platycephala sensu lato. Blue = western populations, red = northern populations; black = eastern populations. LD 1 and LD 2 are linear discriminant functions.

FIGURE 5. Calls of C. platycephala and C. occidentalis: upper traces of a complete call (left) and, showing details of pulse structure (right). Bars indicate relevant time scales. Lower traces are a power spectrum display of the whole call demonstrating peak frequencies and the absence of any harmonic structure (see text for further discussion about presenting frequency information in calls with a pulsed structure).

FIGURE 6. Holotype of Chiroleptes platycephalus, BMNH 1947.2. 18.42. A = dorsal view of snout; B = snout in profile; C = palmar view of left hand; D = left foot.

FIGURE 7. Comparisons of head and body of preserved specimens of Cyclorana platycephala and C. occidentalis: Dorsal and ventral views of body, and dorsal and lateral views of head. A, D, G, J: male C. platycephala (eastern), AMS R 152847; B, E, H, L: female C. platycephala (northern), SAMA R 46608; C, F, I, M: female C. occidentalis, holotype WAM R 111826. Bar represents 5 mm.

FIGURE 8. Vomerine teeth (top row), foot (middle row) and hand (bottom row) of Cyclorana species. A, D, G: C. platycephala (eastern), A = SAMA 46801, D, C = AMS R 152847; B, E, H: C. platycephala (northern), B = AMS R 60331, E, H = SAMA 46608; C, F, I: C. occidentalis. C = WAM R 165306, F, I = Holotype, WAM R 111826. Bar represents 5 mm.

FIGURE 9. Comparisons of live adults of eastern and northern representatives of Cyclorana platycephala and C. occidentalis. Cyclorana platycephala (eastern): A = male AMS R 175496, lateral view, 6.6 km N Bourke, NSW; D = dorsal view, same specimen; G = male no voucher, dorsal view in habitat, 16 km NE Warren, NSW; J = female QM J 85400, lateral view, Craven Peak, 143 km SW Boulia, Qld; M = male no voucher, anterolateral view, 143 km SW Boulia, Qld. Cyclorana platycephala (northern): B = male AMS R 175498, lateral view, 47 km N Barkly Homestead, NT; E = dorsal view, same specimen as B; H = female AMS R 175499, lateral view, 49 km N Barkly Homestead, NT; K = dorsal view, same specimen as H; N = no voucher, anterior view, 86 km N Barkly Homestead, NT. Cyclorana occidentalis. C = lateral view, holotype female WAM R 111826; F = dorsal view, same specimen; I = anterior view, same specimen; L = female no voucher, lateral view, Carnarvon, WA; O = male no voucher, lateral view, Carnarvon, WA.

FIGURE 10. Comparisons of tadpoles of Cyclorana taxa in life (A – F) and preserved (G – H) and features of the oral disc (I – K). Lateral and dorsal views of live tadpoles: A, B = C. platycephala (eastern), stage 39, Gulargambone, NSW; C, D = C. platycephala (northern) stage 39, 86 km N Barkly Homestead, NT; E, F = C. occidentalis, stage 37, Carnarvon, WA. Preserved tadpoles: G = C. platycephala (eastern), stage 37, Gulargambone, NSW; H = C. platycephala (northern) stage 39, 86 km N Barkly Homestead, NT. Oral discs: I = C. platycephala (eastern), stage 40, Boomi, NSW; J = C. platycephala (northern)., stage 39, 86 km N Barkly Homestead, NT; K = C. occidentalis, stage 35, Carnarvon, WA. Bars for G and H = 5 mm, I – K = 1 mm.