Gephyromantis (Phylacomantis) azzurrae, Mercurio & Andreone, 2007

Mercurio, Vincenzo & Andreone, Franco, 2007, Two new canyon-dwelling frogs from the arid sandstone Isalo Massif, central-southern Madagascar (Mantellidae, Mantellinae), Zootaxa 1574 (1), pp. 31-47 : 33-37

Gephyromantis (Phylacomantis) azzurrae n. sp.

( Fig. 1 )

Diagnosis. A species belonging to the genus Gephyromantis (sensu Glaw & Vences, 2006), according to genetic data, and recognizable by the following morphological and natural history characters: (1) medium size (SVL 36–43 mm), (2) webbing between toes present, (3) partly connected lateral metatarsalia, (4) inner and outer metatarsal tubercles present, (5) presence of femoral glands of type 2, (6) presence of a paired subgular vocal sac, (7) finger tips moderately enlarged, (8) nocturnal activity, (9) occurrence in gallery forest habitat of dry central western Madagascar. For comparisons to other Gephyromantis , see below.

Holotype. MRSN A5310 ( FAZC 12568 ), adult male, Andriamanero (22°22.40’S; 45°22.71’E; 640 m a.s.l.), Parc National de l’Isalo , Fianaratsoa Faritany, Ranohira Fivondronona, collected by F. Andreone, F. Mattioli, and V. Mercurio on 20 November 2004, fixed in 4% formalin.

Paratypes. MRSN A5309 ( FAZC 12567 ) and A5311 ( FAZC 12569 ), adult males, same locality, collectors and date as the holotype; MRSN A5312 ( FAZC 12910 ), juvenile, collected at Iambahatsy River (22°24.35’S, 45°16.13’E, 689 m a.s.l.), Parc National de l’Isalo , Fianarantsoa Faritany, Ranohira Fivondronona, by V. Mercurio and T.J. Razafindrabe on 15 December 2004, fixed in 4% formalin; MRSN A5313 ( FAZC 12951 ), adult male, collected at Sakamalio (22°26.09’S, 45°15.31’E, 649 m a.s.l.), Parc National de l’Isalo , Fianarantsoa Faritany, Ranohira Fivondronona, by V. Mercurio and T.J. Razafindrabe on 16 December 2004, fixed in 4% formalin; SMF 85859-60 ( FAZC 12979-12980 ) (ex MRSN A5314-5315), adult males, same locality, collectors and date as the MRSN A5313 .

Description of the holotype. Specimen in excellent state of preservation missing the left fourth toe (clipped for DNA analysis). Snout-vent length 41 mm, for other measurements see table 1. Body rather stout; head wider than long but not wider than body; snout pointed in dorsal view, rounded in lateral view; nostrils directed posterolaterally, slightly protuberant, nearer to tip of snout than eye; chantus rostralis distinct, straight; tympanum distinct, rounded, 65.5% of eye diameter; tongue ovoid, posteriorly bifid; maxillary and vomerine teeth present; choanae elliptical. Arms slender; fingers without webbing; distinct single subarticular tubercle; finger discs distinctly enlarged, trapezoidal. Hind limbs slender, tibiotarsal articulation reaches between eye and nostrils; lateral metatarsalia partly connected; inner and outer metatarsal tubercles distinct; webbing between toes 1(1), 2i(1.5), 2e(0.5), 3i(2), 3e(1), 4i(2), 4e(2), 5(1). Dorsal skin smooth without evident dorsolateral folds. Ventral skin smooth on throat and chest, granular on belly and limbs. Femoral glands of type 2 fairly distinct from external view; left gland elliptical of 6.3 mm length, 2.0 mm width with about 45 granules of 0.5 mm diameter. Dorsal colouration brownish-blackish with a dirty light broad vertebral band. Vertebral band with some dark mottlings and bordered by dark. Tympanic area brownish. Faint darker crossbands present on arms and limbs. Ventrally dark brown mottled by whitish irregular markings, being more abundant along the posterior margins of the arms and extending to axillary region. Brownish folds along lower jaw corresponding to vocal sacs. After one year in preservative the chromatic pattern are similar as in life but strongly faded, especially the lighter vertebral band.

Variation. Paratypes are similar to the holotype in morphology and colouration pattern. The main chromatic differences are the status of dorsal band (brightly visible in MRSN A5309 and A5311 vs. absent in MRSN A5313-5315), and the saturation of ventral colouration (heavily pigmented in MRSN A5309, and SMF 85859-60; pigmented in MRSN A5311; faintly pigmented with a whitish ventral colouration in MRSN A5313). Specimens lacking the vertebral stripe are usually darker with a uniform mottled dorsum without any pattern. Femoral glands are more or less defined and visible from external view in all the specimens. In MRSN A5313 the glands are less visible and reduced with only 29 granules (vs. about 40 in the other specimens) of 0.5 mm diameter of which five are enlarged (0.8 mm) on the posterior margin, while in SMF 85860 they are well visible with well defined margins (7.5 mm length, 2.7 mm width, about 42 granules of 0.5 mm diameter).

Etymology. F. Andreone dedicates this new species to his daughter Kintana Azzurra, with much love and wish of endless happiness.

Natural history. We found individuals of this species inside large canyons with running water in the river bed between stones, as well as in the gallery forest. Calling males were observed at night on leaves in the forest at about 50–150 cm above the ground. Although we do not have quantitative data they appear to be distributed inside the forest at distances of 10–20 m each other. We were also unable to locate tadpoles of G. azzurrae : we suspect that they are similar to the ones of G. pseudoasper Guibé or G. corvus Glaw & Vences. Only two specimens were collected after opportunistic search during the day, while the other specimens by locating calling males during the night. After the dissection of five specimens the stomach contents contained 12 prey items divided as follows (number of prey item/percentage of the sampling): Hymenoptera , Formicidae (3, 25.0%); Aranea (3, 25.0%); Lepidoptera larvae (2, 16.6%); Coleoptera (2, 16.6%); Brachycera (1, 8.3%), and Heteroptera (1, 8.3%).

Advertisement call. Calling male MRSN A5313 recorded at Sakamalio, Parc National de l’Isalo, on 16 December 2004, c. 20:00, 22°C. The call consisted of a series of 15–21 almost identical complex notes each of which is composed of seven-ten clearly identifiable sub-units arranged in a regular pattern ( Fig. 2 , table 3). The first two sub-units are longer and, in some cases, separated from each other by a very short time interval (1 ms), and they are followed by 7–8 in amplitude decreasing sub-units ( Fig. 3 ). The frequency spectrum of the call is harmonic. Fundamental frequency is around 1000 Hz followed by five-six well tuned harmonics of which the dominant frequency is about 3000 Hz. Frequency ranges from 800 to 6500 Hz. The temporal structure is periodic with single note of similar amplitude repeated at regular intervals of about 570 ms. We opted for the term “sub-unit” instead of “pulse” to emphasize his unusual complex harmonic structure probably not homologous with that of other Gephyromantis and closely related Mantidactylus species.

Morphological comparison with other species. Gephyromantis azzurrae bears clear overall morphological similarities to the other two species currently known in the subgenus Phylacomantis ( G. pseudoasper and G. corvus ), and appears to be genetically closest to these. The new species can be distinguished from G. pseudoasper by: (a) darker dorsal and ventral colouration, (b) skin on the back comparatively smoother, (c) larger size (maximum SVL in males in mm: 43 vs. 33–34), (d) advertisement call (15–21 vs. 3 notes per call and lower dominant frequency, 3000–3200 Hz vs. 3400–5000 Hz). Gephyromantis azzurrae differs from the sympatric G.corvus by: (a) different dorsal colouration (dark brownish with a dirty vertebral stripe vs. brownish to olive grey with lighter brown patches), (b) different ventral colouration (heavily brown marbled vs. dirty white), (c) comparatively larger eyes and larger tympanum (ratio tympanum/eye diameter 66.7% vs. 60%), (d) body shape (quite stout vs. slender), (e) larger maximum SVL in males in (43 mm vs. 38 mm corvus ), and (f) advertisement call (see Table 3 ).

Mitochondrial differentiation. Accession numbers of newly obtained sequences: MRSN A5309, EF222300 ; MRSN A5310, EF222301 ; MRSN A5311, EF222302 ; SMF 85860, EF222303 ; MRSN A5312, EF222304 ; SMF 85859, EF222305 ). In the mitochondrial 16S rRNA gene, the uncorrected pairwise sequence divergence of Gephyromantis azzurrae compared to that of G.corvus from Isalo is 7.5%. Concerning the other closely related species, G. azzurrae sequence divergences range respectively from 12.4% to 12.9%, for G. sp. aff. corvus from Bemaraha, and 15.8%-16.2% for G. pseudoasper from Manongarivo (data kindly provided by M. Vences). These divergences are comparatively very high among mantelline species (see Vences et al. 2005), and therefore corroborate the species status of G. azzurrae .

Conservation. Gephyromantis azzurrae is currently known from only three localities in the northern part of the Isalo Massif (Andriamanero, Iamabahatsy, Sakamalio). One of them (Andriamanero) is not included within the boundaries of the Parc National de l’Isalo. Threats affecting this area include the extensive prairie burning and the alteration due to the excavation of mines for searching sapphires, an activity that has a great potential of long-term persistence and is thus seriously threatening the Isalo biodiversity ( Duffy, 2006). Therefore and according to the IUCN (2006) we preliminarily classify G. azzurrae as Critically Endangered, following the geographic criteria B2ab(iii). This categorisation could be re-evaluated if all sites of presence will be included within the protected area and/or some other localities will be discovered in the future.

Figures

FIGURE 1. Gephyromantis azzurrae n.sp. in life: A) dorso-lateral and B) ventral view of the holotype MRSN A5310 (male) from Andriamanero, Isalo Massif.

FIGURE 2. Sonagram (above) and oscillogram (below) of the advertisement calls with 4 notes of Gephryromantis azzurrae n.sp. rom Sakamalio, Isalo Massif.

FIGURE 3. Sonagram (above) and oscillogram (below) of one note with eight sub-units of a call of Gephryromantis azzurrae n.sp. from Sakamalio, Isalo Massif.