Gephyromantis (Duboimantis) saturnini, D. & Mihaja, 2018

Gephyromantis (Duboimantis) saturnini View in CoL sp. nov.

( fig. 1–7 View Figure 1 View Figure 2 View Figure 3 View Figure 4 View Figure 5 View Figure 6 View Figure 7 , Table 1)

LSID: urn:lsid:zoobank.org:act:

Gephyromantis (Duboimantis) sp. Ca30 – ( Scherz et al. 2017 a, b)

Specimens allocated to new species

Holotype

ZSM 61/2016 ( MSZC 0123 ), an adult male collected in the eastern parcel of the Ampotsidy mountains ( 14.4133°S, 48.7175°E, 1450 m a.s.l.), District de Bealanana, Région Sofia, northern Madagascar, at 18 h 30 on 31 December 2015 by M. D. Scherz, J. Borrell, L. Ball, T. Starnes, E. Razafimandimby, D. H. Nomenjanahary and J. Rabearivony.

GoogleMaps

Paratypes

UADBA-A 61674 (ex-ZSM 66/2016, MSZC 0164), an adult male collected between 20 h 30 and 21 h 55 on 7 January 2016 in the western parcel of the Ampotsidy mountains ( 14.4123°S, 48.7118°E, 1481 m a.s.l.), GoogleMaps and ZSM 62/2016 ( MSZC 0153 ), an adult male collected at 23 h 50 on 6 January 2016 in the eastern parcel of the Ampotsidy mountains ( 14.4134°S, 48.7173°E, 1476 m a.s.l.), District de Bealanana, Région Sofia, northern Madagascar, by M. D. Scherz, J. Borrell, L. Ball, T. Starnes, E. Razafimandimby, D. H. Nomenjanahary and J. Rabearivony GoogleMaps .

Diagnosis

A Gephyromantis species assigned to the subgenus Duboimantis on the basis of its fairly smooth skin, interocular tubercles, large body size and presence of inner and outer dorsolateral folds. Gephyromantis saturnini is characterised by the following unique suite of characters: (1) large body size (SVL 39.4–42.8 mm in adult males), (2) paired subgular vocal sacs, (3) HIL/SVL 1.79–1.87, (4) TD/ED 0.48–0.56, (5) presence of inner and outer dorsolateral folds, (6) reticulated low ridges on the dorsum, (7) distinct interocular tubercles, (8) indistinct femoral glands consisting of 9–16 faint granules. It is furthermore characterised by advertisement calls consisting of 1–3 pulsatile notes, emitted in series of 7–8 calls.

Comparisons

Within the genus Gephyromantis , G. saturnini may be distinguished from all members of the subgenus Gephyromantis on the basis of much larger body size (SVL 39.4–42.8 mm vs. 20–33 mm); from all members of the subgenus Asperomantis on the basis of generally larger body size (SVL 39.4–42.8 mm vs. 26.6–40.7 mm); from all members of the subgenus Phylacomantis on the basis of the presence of distinct dorsolateral ridges (vs. absent or discontinuous), indistinct femoral glands (vs. distinct), more slender body shape and absence of outer metatarsal tubercle (vs. presence); from all members of the subgenus Laurentomantis on the basis of much larger body size (SVL 39.4–42.8 mm vs. 20–34 mm), smooth skin (vs. highly granular to rugose); and from all members of the subgenus Vatomantis on the basis of much larger body size (SVL 39.4–42.8 mm vs. 23–31 mm), lack of greenish skin colouration (vs. presence) and less slender limbs. Within the subgenus Duboimantis , it may be distinguished from G. (D.) cornutus ( Glaw & Vences, 1992) and G. (D.) redimitus ( Boulenger, 1889) by the possession of paired subgular vocal sacs (vs. single); from G. (D.) luteus ( Methuen & Hewitt, 1913) , G. (D.) sculpturatus ( Ahl, 1929) and G. (D.) plicifer ( Boulenger, 1882) by less webbed toes, lack of concave black suprascapular markings (vs. usually present) and presence of only diminutive heel spines (vs. distinct heel spines); from G. (D.) moseri ( Glaw & Vences, 2002) by the much less rugose dorsum and smaller supraocular tubercles; from G. (D.) salegy ( Andreone, Aprea, Vences & Odierna, 2003) and G. (D.) redimitus by considerably smaller body size (SVL 39.4–42.8 mm vs. 46–53 mm); from G. (D.) schilfi , G. (D.) tschenki ( Glaw & Vences, 2001) and G. (D). tohatra by much larger body size (SVL 39.4–42.8 mm vs. 27–36 mm); from G. (D.) zavona ( Vences, Andreone, Glaw & Randrianirina, 2003) , G. (D.) leucomaculatus ( Guibé, 1975) and G. (D.) granulatus ( Boettger, 1881) by the presence of distinct interocular tubercles (vs. absence). From the most similar species, G. (D.) tandroka , G. (D.) saturnini may be distinguished by generally larger adult male size (SVL 39.4–42.8 mm vs. 35.6–40.1 mm; see Table 1).

Bioacoustically, G. (D.) saturnini most strongly resembles G. (D.) tandroka to the human ear, but differs consistently in call series structure (1–3 notes per call vs. always single-note calls). Its call series structure resembles more strongly G. (D.) leucomaculatus and G. (D.) zavona in this respect, but it differs from G. (D.) zavona in having a maximum of three notes per call (vs. up to five) and a lower dominant frequency (2497–2670 Hz vs. 3171–3785 Hz); and from G. (D.) leucomaculatus in having a longer inter-note interval within two-note calls (150–237 ms vs. 83–116 ms) and a lower dominant frequency (2497–2670 Hz vs. 2917–3168 Hz). To compare the calls by ear to other members of the subgenus Duboimantis , the reader is referred to our deposited calls and those available from Vences et al. (2006), which are also available online at www.fonozoo.com.

Genetically, the species is distinguished from all other species of Gephyromantis by uncorrected p-distances of at least 5.1 % in the analysed 16S rRNA gene fragment.

Description of holotype ZSM 61/2016, adult male

Specimen in a good state of preservation, a tissue sample taken from the left thigh. SVL 39.4 mm. For other measurements see Table 1. Body somewhat gracile; head longer than wide, not as wide as body (body is somewhat inflated in preservative); snout pointed in dorsal and lateral view; nostrils directed laterally, protruding slightly, much nearer to tip of snout than to eye; canthus rostralis distinct, straight; loreal region concave and weakly oblique; tympanum distinct, oval, its horizontal diameter 56 % of eye diameter; supratympanic fold distinct, weakly curved, from the posterior corner of the eye to above the insertion of the arm; tongue fairly broad, posteriorly bifid; vomerine teeth clearly distinct, arranged in two small aggregations on either side of the midline of the palate at the level of the anterior edge of the eye, posteromedial to choanae; choanae small and rounded and laterally displaced. Dark, translucent dermal fold below each jaw starting at the level of the anterior edge of the eye. Arms slender, subarticular tubercles single, highly distinct; outer metacarpal tubercle small and oval and inner metacarpal tubercle small; fingers without webbing; relative length of fingers 1 <2 <4 <3, second finger distinctly shorter than fourth; finger discs distinctly enlarged, round, nuptial pads absent. Hindlimbs slender; lateral metatarsalia slightly separated distally with webbing; subarticular tubercles highly distinct; inner metatarsal tubercle distinct, anteriorly oriented, outer metatarsal tubercle absent; webbing formula of foot according to the scheme of Blommers-Schlösser (1979) 1(1), 2i(1.5), 2e(1), 3i(2), 3e(1.25), 4i(2.5), 4e(2.25), 5(1); relative toe length 1 <2 <3 <5 <4, third toe much shorter than fifth; toe discs distinctly enlarged. Skin dorsally granular, with two pairs of distinct dorsolateral ridges, corresponding to the inner and outer ridges of Vences & Glaw (2001), one pair running from the posterior of the eye to the suprascapular region, and the other pair along the dorsolateral ridge of the body; between these ridges over the dorsum posterior to the head is a reticulated pattern of fine ridges; a small pair of interocular spines is present, and each eye is adorned with two small supraocular spines; a diminutive dermal flap is present on the heel; ventral skin smooth on chin and forelimbs, but highly granular on the abdomen and ventral thighs. Femoral glands indistinguishable in the fixed specimen, but visible from images of the specimen in life ( fig. 4 View Figure 4 ): type 2 sensu Glaw et al. (2000), 4.6 mm long, 2.2 mm wide (measured in internal view), consisting of 16 granules on the right thigh and 15 on the left thigh.

In life ( fig. 4 View Figure 4 ) the dorsum was a light mocha, with rust markings on the upper flanks, in a W-shaped marking on the mid-dorsum, on the lateral head and posterior surface of the eyes, and in an oblong patch over the hips. The light colouration of the dorsal surface of the head continued as a medial rostral stripe visible in ventral and anterior view. The inner and outer dorsolateral folds were not remarkably coloured. A mottled dark line was present between the eyes, with black around the interocular tubercles. The larger of the two supraocular spines was also surrounded in black. A thin black stripe was present from the nostril to the eye along the canthus rostralis, and the lower edge of the supratympanic fold and the tympanum itself were dark brown. A further dark brown marking was present on the upper lip below the eye. The limbs exhibited extensive crossbanding: the forelimb had one faint crossband on the upper arm, and three crossbands on the lower arm, each of the rust colour of the dorsum, with black on the inner surface; the fingers lacked crossbands but had black flecks, without any distinctive colouration of the distal discs. The hindlimbs had five crossbands of dark brown tinged with rust and black on the thigh, six on the shank, three on the tibiotarsus, and two on the foot. The chin was mottled translucent and light yellow ventrally, only slightly darker on the vocal sacs, becoming translucent over the pectoral region, and then cream over the abdomen, in turn fading to egg-yolk yellow near the hip and over the surface of the thighs. The thighs were distally flecked with brown, the lower legs mottled yellow, beige and brown. The foot was mocha brown ventrally with tinges of rust on the subarticular tubercles. The hand was also brown ventrally, but its tubercles were cream in colour.

After roughly two years in preservative, the colour pattern is unchanged, but the colour itself has faded ( fig. 5 View Figure 5 ). Dorsally, areas that were light mocha have become grey to silver, with light grey dorsolateral ridges, while areas that were rust in life are now mauve. Both the chin and the pectoral region have lost their translucence and the colouration on the chin has become darker, and the W-shaped marking on the mid-dorsum has faded but is still visible. All traces of yellow in the ventral colouration has been replaced by a dirty cream.

Morphological and chromatic variation

In morphology, the paratypes strongly resemble the holotype; for variation in measurements, see Table 1. Webbing formula varies in 3e ( 1 in the paratypes vs. 1.25 in the holotype) and 5i ( 0.75–1 in the paratypes). The femoral glands are equally poorly distinguishable in all specimens, but can be identified with strong magnification ( fig 6 View Figure 6 ); the number of granules varies from 9–16, but they are always indistinct.

Although they are consistently brown in overall colour, the colour patterns of the type specimens are highly varied ( fig. 4 View Figure 4 ), and only a few characteristics are consistent: the dark canthal stripe is consistently present in the type series, though much thicker in UADBA-A 61674 than the other paratypes. Crossbands are always present on the limbs, but the number is variable. The ventral abdomen is consistently cream in colour, and the mottling of the thighs distally is also fairly consistent among the specimens. The rostral stripe is present in all of the type series.

Bioacoustics

The calls of two recorded individuals consisted of pulsatile notes, which were arranged in note groups of 1–3 notes, and these note groups emitted in a finite series of 7–8 note groups. We here define each note group as a call. In this definition, calls are thus arranged in call series consisting of 7–8 calls, and each call consists of 1–3 notes. In the holotype ZSM 61/2016 (recorded on 31 December 2015 at 18 h 30, air temperature unknown), two call series contained calls with 1–2 notes, and lasted 22.7 s (7 calls) and 27.3 s (8 calls). Note duration was 56–78 ms (63 ± 6 ms; N = 10), and each note consisted of 12–18 very poorly distinguishable pulses (16 ± 2; N = 10), without silent intervals between them. Inter-call interval duration was 2054–8436 ms (3912 ± 2246 ms; N = 10) and decreased toward the end of the call series, i.e., calls were repeated faster and contained more notes towards the end of a call series. Within two-note calls, the interval duration between notes was 150–181 ms (165 ± 12 ms; N = 8). Dominant frequency was between 3057–3227 Hz (3100 ± 57 Hz; N = 10), approximate prevalent bandwidth is between 1000–4500 Hz.

The calls of paratype ZSM 62/2016 (recorded on 6 January 2016 at 23 h 45 at an air temperature of 15.9°C) were very similar; one call series of 7 calls was available for analysis. Of these, the first two calls had 1 note, the third and fourth call had two notes and the last three calls had three notes each. As in the holotype, inter-call interval duration decreased toward the end of the call series. Temporal and spectral measurements were as follows: Note duration 87–100 ms (91 ± 5 ms; N = 12), inter-call interval duration 2158–5944 ms (3500 ± 1385 ms; N = 6), inter-note interval within one call 199–237 ms (209 ± 13 ms; N = 8), dominant frequency 2497–2670 Hz (2583 ± 45 Hz; N = 10), approximate prevalent bandwidth 1000–5000 Hz.

Natural history and conservation status

Very little is known of the ecology of this species. Male specimens were collected at night, sitting on leaves in primary rainforest at 1.1–3 m above the ground. ZSM 61/2016 was collected 20 m from a small stream on a steep slope. The confirmed elevational range of the collected specimens is 1450–1481 m a.s.l. and we did not encounter them below 1400 m a.s.l. Our survey work above 1500 m a.s.l. was insufficient to be conclusive as to the upper ranges of the distribution of this species, but the Ampotsidy mountains have a maximum elevation of ca. 1860 m a.s.l.

At present this species is known from just three collected specimens, though several others were heard in the vicinity of the collected individuals at low density (MDS pers. obs.). It is known from one area of fragmented forests, which are in an active state of decline due to ongoing slash-and-burn agriculture, cattle grazing and logging. However, like other species collected in Ampotsidy (e.g. Gephyromantis [ Asperomantis ] angano, Scherz et al. 2017 b; Calumma gehringi, Prötzel et al. 2017 ; Uroplatus fotsivava, Ratsoavina et al. 2017 ), we suspect that the species will occur more broadly within the poorly surveyed District de Bealanana. As such, any evaluation of its conservation status based on current knowledge is liable to dramatically overestimate its threat status: at present it qualifies as Critically Endangered under IUCN (2012) criterion B1ab(iii) due to its range of below 100 km 2 (B1) from one threat-defined location (a) undergoing active decline in extent and quality of its habitat (b[iii]). To avoid being inflationary, we recommend that the species be considered Data Deficient until further survey work has been conducted in the District de Bealanana.

Etymology

We dedicate this species of Duboimantis to Saturnin Pojarski, a pseudonym of Alain Dubois during his time as a late-night radio presenter on Radio Carbone 14, a ‘pirate’ station that was part of the free radio movement in France in the 1980s. Saturnin also makes an appearance in a children's book ( Dubois & Ohler 2010) as a grandfather transmitting the enthusiasm for and knowledge of amphibian biology to his grandson, Augustin.