Choerophryne multisyllaba, Guenther, Rainer & Richards, Stephen, 2017

Guenther, Rainer & Richards, Stephen, 2017, Three new species of the microhylid frog genus Choerophryne (Amphibia, Anura, Microhylidae) from Papua New Guinea, Zoosystematics and Evolution 93 (2), pp. 265-279 : 268-270

Choerophryne multisyllaba sp. n.

Holotype.

SAMA R70322 (FN SJR 2322), adult male, Iagifu Ridge near Moro, Southern Highlands Province, Papua New Guinea (06°26.4864'S, 143°13.1040'E; 1,413 m asl) collected on 21-10-2001 by S.J. Richards.

Paratypes.

SAMA R70323-70325 (FN SJR 2070, 2286, 2325), PNGNM unregistered (FN SJR 2137), ZMB 84337-84338 (FN SJR 2323 & 2324), all details same as holotype except PNGNM collected on 28-05-2002 and SAMA R70324 collected on 19-10-2001 by S.J. Richards.

Diagnosis.

A species of the genus Choerophryne lacking an elongated snout. Snout-urostyle length in males (n=7) from 14.0-15.2 mm (mean 14.4 ± 0.45 mm). No webs between fingers or toes; fifth toe longer than third; finger discs wider than toe discs (ratio T4D/F3D 0.67-0.89); shanks medium-length (TL/SUL 0.43-0.47). Eyes fairly large (ED/SUL 0.126-0.143), eye-naris distance greater than internarial distance (END/IND 1.00-1.17). Almost all specimens with a yellowish (whitish in preservative) interocular stripe, an irregular longitudinal mark of the same colour in the scapular region and a narrow streak between corner of the mouth and tympanum. No brown hour-glass mark on dorsum and no light cross on head. Best diagnostic character is the advertisement call: a rattle of 0.7-1.0 s duration with a dominant frequency of 3.5 kHz.

Description of the holotype.

Adult male with a SUL of 14.9 mm. Additional measurements and ratios are listed in Table 2. Head broader than long (HL/HW 0.86); tip of snout subelliptical with a small median protuberance in dorsal view and slightly protruding in lateral view; nostrils near tip of snout, directed laterally and not visible from above, distance between nares less than distance between eye and naris (END/IND 1.15); canthus rostralis rounded, loreal region slightly sloped and with some elongate pits; tongue strongly widened posteriorly, with a weak indentation and its posterior part nearly half free; one prepharyngeal ridge without denticles; fairly long vocal slits on both sides of mouth floor. Tympanum medium-sized (TyD/ED 0.42) and well visible, no supratympanic fold. Shanks medium sized (TL/SUL 0.44). Fingers unwebbed and with semi-circular or truncate, grooved terminal discs, their relative lengths 3>4>2>1 (Fig. 5a, b); disc of third finger substantially more than twice width of penultimate phalanx, metacarpal and subarticular tubercles absent. All toes with wide and grooved terminal discs, those of fourth toe clearly narrower than those of third finger; no webs between toes, no metatarsal tubercles, subarticular tubercles weakly developed; relative lengths of toes 4>5>3>2>1 (Fig. 5a, b). A group of distinct tubercles dorsolateral of the tympanum and some tubercles also on flanks; throat and chest with small tubercles, abdomen and ventral surfaces of extremities smooth.

Colour of the holotype in preservative.

Colour of holotype in life unknown. In preservative ground colour of dorsal surfaces of head, body, upper arm, forearm, thigh and shank light-grey, that of hands and feet yellowish. All dorsal surfaces more or less densely dotted with tiny dark brown dots: less so on hands, feet, between eyes, on tibiotarsal joint and on sacral region continued on to thighs; more so on all other dorsal surfaces. A scarcely visible pale interocular stripe and a pale, irregular stripe(s) in the scapular region; a similarly inconspicuous pale, irregular stripe along the upper flanks and a pale lumbar “eye-spots” (Fig. 5a). Ground colour of all ventral surfaces yellowish and covered with more or less dense brown punctations. Underside of hands and feet with least punctations (Fig. 5b).

Morphological variation in the paratypes. Measurements and body ratios of the type specimens are presented in Table 2.

Colour in preservative of the type series: The pale inter-ocular stripe is more strongly expressed in the paratypes than in the holotype. The pale and irregularly shaped longitudinal line in the scapular region is also more strongly developed in most paratypes, and in some specimens it reaches the inguinal region. Ground colour of the dorsal surfaces in all specimens is off-white. Tiny, clearly demarcated brown dots are distributed on all dorsal surfaces. These dots form clusters of small circles on various body parts. In addition there are light or dark brown spots of different shape on various parts of the dorsal and lateral surfaces. Paler areas occur mostly on the snout, extremities, sacral region and upper flanks. Ground colour of ventral surfaces is also off-white and covered by many tiny brown dots. Their distribution ventrally is more homogenous than on dorsal surfaces, and larger spots are rare. Small and inconspicuous white spots occur on ventral surfaces of all specimens.

Tubercles are generally few and inconspicuous on dorsal surfaces but more conspicuous on flanks. Striking in all specimens studied is a tubercle directly behind the angle of the jaw and several tubercles in the postocular region.

Colour in life of two paratypes (PNGNM unreg. and SAMA R70324): Dorsal surfaces of the former (Fig. 6) and of the latter (Fig. 7) exhibit a mixture of different colours and spots. Brownish colours with yellow marks dominate in the former, and reddish areas in the latter. One additional, unvouchered specimen for which an image in life is available has a more uniform grey-brown dorsal colouration.

Distribution and ecological notes.

Choerophryne multisyllaba is currently known from two locations: the vicinity of the type locality at elevations between about 1,300-1,400 m asl on Iagifu Ridge in the Agogo Range, Southern Highlands Province, and at 1,600 m asl at Sawetau Camp in the Muller Range, Western Province (05°39.397'S, 142°18.277'E; Richards and Dahl (2011)), both in the central mountains of Papua New Guinea. Males call from hidden positions, often within curled leaves, between 1-3 m above the ground in extremely wet, mossy forest.

Vocalisation.

Forty-six calls from the male holotype (SAMA R70322), recorded at an air temperature of 21.5 °C, were analysed. The advertisement call sounds like a quick rattle comparable to the rattling calls of various Oreophryne -species. These calls follow one another at short intervals of about two seconds (Fig. 8). Mean call length is 0.85 ± 0.07 s, range 0.71-0.96 s. The calls contain 18-23 notes, mean 20.1 ± 1.30 notes/call. Mean interval length between calls 2.11 ± 0.67 s, range 1.48-4.75 s, n=42. Call notes are unpulsed and without frequency modulation (Fig. 9). Mean note length 5.6 ± 1.31 ms, range 2-9 ms, n=174; mean internote length 34.6 ± 9.8 ms, range 6-63 ms, n=162. Mean note repetition rate 23.8 ± 2.02, range 21.3-31.1 notes/s, n=46. Frequencies scatter mostly between 2.5 and 4.5 kHz. The dominant frequency is at 3.75 kHz (Fig. 10).

Etymology.

The specific epithet multisyllaba is a Latin feminine adjective meaning polysyllabic and refers to the polysyllabic advertisement call.

Comparisons with other species.

With its short snout Choerophryne multisyllaba differs from all twelve Choerophryne with an elongated snout. Most short-snouted Choerophryne utter buzzing, squeaking or clicking advertisement calls. Choerophryne multisyllaba is the first whose call sounds like a rattle (similar to the rattle calls of various Oreophryne -species).

Choerophryne crucifer differs significantly from C. multisyllaba in the following body ratios: HW/SUL (p=0.005), ED/SUL (p=0.009), TyD/SUL (p=0.015), T1D/F1D (p=0.018) and F3D/SUL (p=0.022). Moreover, note repetition rate ranges from 4.4 to 5.2/s in the former and from 21 to 31 notes/s in the latter.

Choerophryne gudrunae has a higher ratio END/IND than C. multisyllaba (1.20-1.50 vs. 1.00-1.17). The advertisement call of the former consists of about 10 clicks, those of the new species of 18-23. Note repetition rate in C. gudrunae is about 5 notes/s and in C. multisyllaba of more than 20 notes/s.

Choerophryne gunnari has a higher ratio END/IND (1.25-1.45 vs. 1.00-1.17) and conspicuous blue pigmentation on the belly and hind limbs, which is absent in C. multisyllaba . Note repetition rate of the advertisement call of C. gunnari is, according to the spectrograms published by Menzies (1999, 2006), not more than 4 clicks per second vs. 20-30 clicks per second in C. multisyllaba .

Choerophryne sanguinopicta is larger than C. multisyllaba (SVL 15.4-17.4 mm vs. SUL 14.0-15.2 mm); its dorsum has a pale blue or green ground colour (off-white in C. multisyllaba ) and its advertisement call is a very long series (several minutes) of clicks with a note (=call) repetition rate of less than three calls/s and a dominant frequency of around 4.0 kHz vs. much shorter series of clicks (each series lasting less than one second) with a repetition rate of more than 20 notes per second and a lower dominant frequency (at 3.5 kHz) in C. multisyllaba .

Choerophryne valkuriarum has shorter shanks (TL/SVL 0.37-0.44 vs. 0.43-0.47 in C. multisyllaba ) and strongly different advertisement calls. Menzies (1999) mentioned the fastest rate as two clicks (=notes) per s uttered in irregular series. C. multisyllaba call series are fairly regular and clicks are uttered at a rate of 20-30 per second.

Choerophryne variegata is known from a single specimen and its advertisement call is unknown. According to measurements by Menzies (1999) the holotype of this species differs from the new one by the ratios TL/SVL (0.47 vs. 0.43-0.47) and END/IND (1.38 vs. 1.00-1.17) as well as by the presence of webbing between toes 4 and 5 vs. no webbing at all in C. multisyllaba .

This new species differs by its polysyllabic calls clearly from the next new species which utters disyllabic calls.