Arthroleptis formosus, Rödel, Mark-Oliver, Kouamé, N’Goran Germain, Doumbia, Joseph & Sandberger, Laura, 2011

Rödel, Mark-Oliver, Kouamé, N’Goran Germain, Doumbia, Joseph & Sandberger, Laura, 2011, A new beautiful squeaker frog (Arthroleptidae: Arthroleptis) from West Africa, Zootaxa 3011, pp. 16-26 : 17-22

Arthroleptis formosus sp. nov.

Figs 1–3

Holotype. ZMB 75480 (field #: KD073, GenBank #: JN408725 ; female, 18.6 mm), western Guinea, Préfecture Télimélé, N 10.8549167, W -13.7417222, 286 m a.s.l., 9 October 2010, degraded gallery forest, small creak present, surrounding areas with corn, peanuts and rice fields, coll. N.G. Kouamé & J. Doumbia.

Paratypes. ZMB 75481 (field #: KD038, GenBank #: JN408726 ; male, 19.1 mm), ZMB 75482 (field#: KD049, GenBank #: JN408727 ; juvenile, 15.7 mm), N 10.8083611, W -13.8375833, 182 m a.s.l., 2 October 2010, tree and grass savanna, other data as holotype; ZMB 75483 (field #: KD048, male, 18.7 mm), N 10.8131667, W - 13.8350278, 359 m a.s.l., 3 October 2010, degraded gallery forest, river with waterfalls and rapids, other data as holotype; ZMB 75484 (field #: KD074, GenBank #: JN408728 ; female, 20.8 mm), ZMB 75485 (field #: KD075, male, 18.3 mm), data as holotype; ZMB 75486 (field #: KD132, GenBank #: JN408730 ; juvenile, 13.2 mm), ZMB 75487 (field #: KD133, GenBank #: JN408729 ; juvenile, 11.6 mm), N 11.0883333, W -13.6670278, 330 m a.s.l., 19 October 2010, tree and grass savanna, other data as holotype.

Diagnosis. The presence of a fine vertebral skin raphe, lack of webbing and tarsal tubercles ( Rödel 2000; Zimkus & Blackburn 2008), as well as molecular phylogenetic relationships (not shown), characterize the new species as a member of the genus Arthroleptis . From other Arthroleptis species it differs by small size and a unique colour pattern. From the most similar congener, A. aureoli , the species differs genetically by 4.5–5.1% in the investigated part of the 16S rRNA gene, smaller size, more enlarged toe and finger tips, the lack of hypertrophied third fingers and digital spines in males, and ventral colouration. The combination of small size and its unique colouration distinguishes it from all other African Arthroleptis . Genetically the new species differs from other African Arthroleptis by a minimum of 16.0%.

Description of the holotype (measures in mm). An adult female Arthroleptis with a slender almost parallel body shape; snout-vent length: 18.6; short snout, roundish in dorsal and pointed in lateral view; canthus rostralis indistinct and rounded; loreal region straight; head-width directly behind the eyes: 5.6; eye large, approximately equal to distance eye-nostril, eye-diameter: 1.9; pupil round; distance eye-nostril: 1.8; distance nostril-snout tip: 1.0, nostril much closer to snout than to eye; tympanum small but distinct, tympanum-diameter: 1.2, smaller than diameter of eye; tongue slender, about twice as long as wide, slightly diverging towards tip, distinctly notched, no lingual papillae; no vomerine teeth; long and slender extremities; femur: 8.6, distinctly shorter than tibio-fibula: 10.1; foot including toe IV: 13.9; hand with small, ovoid palmar and thenar tubercles; fingers with round to ovoid subarticular tubercles, additional tubercles on bases of fingers I–III ( Fig. 2 a); fingers without spines; relative finger length: I<II<IV<III; 2nd finger length: 2.6; 3rd finger length 4.2; palmar webbing absent; tarsal tubercle absent; small, ovoid inner metatarsal tubercle, approximately reaching one third of shortest toe length; outer metatarsal tubercle absent; relative toe length: I<II<V<III<IV; no pedal webbing; toe and finger tips slightly expanded without forming discs ( Fig. 2 ); dorsal skin slightly granular, almost smooth in preservation; ventral skin smooth; dorsum with fine vertebral skin raphe.

Basic dorsal colour pattern: red with large black spots and patches; a black spot in the centre of the snout; a black irregularly bordered interorbital line; followed posteriorly by a black U open towards snout tip; from scapular region towards urostyle a black long, goblet shaped blotch; large black inguinal blotches; further smaller roundish black spots, in particular along dorsolateral areas of dorsum; two transversal black bars on thighs and two to three black bars on lower legs; side of head, temporal region and region dorsal from forearm bases black; upper arms reddish; lower arms with very broad transversal black bars; hands and feet blackish with small white spots; many very small yellow-whitish spots within the reddish coloured dorsal and lateral surfaces; upper and lower mandible almost uniform black with a few very small white dots; iris dark golden with many small black points; throat, chest and belly, a swell as ventral parts of upper arms and lower legs dark grey; throat and chest with small white spots. Coloration in preservation: red colours turn into light brown; the yellowish small points turn white; large black spots and blotches persist; ventral colour persist with the exception of dark grey ventral parts of legs, which turn lighter than in life.

Variation. The paratypes very closely resemble the holotype in most characters. Adult males may be slightly smaller (18.3–19.1 mm; N= 3) than adult females (18.6–20.8 mm, N= 2), have narrower heads and shorter tibiofibulae ( Table 1 ). However, the sample sizes are too small to test the significance of this. Whereas both adult females had slightly lighter bellies and throats with comparatively many white spots ( Fig. 1 e), males have dark brown almost blackish ventral surfaces with no or only very few white spots ( Fig. 1 f). Females may have more and lighter reddish parts on dorsal surfaces than males ( Fig. 1 a, b, d). In males the flanks were almost uniform black and the many small yellowish-white dorsal points of the females have a more bluish-greenish tinge; especially the light spots on the flanks seem to be mostly blue. From the pictures of live animals, males have slightly more granular skin on the dorsum than females. This is not visible in preserved specimens. Measurements and indices of measurements of adult specimens of the new species are summarized in Tab. 1 .

Genetics. When aligning the sequences of the new species to the data provided by Blackburn (2008b), and further sequences generated for this study ( Table 2) A. formosus sp. nov. clustered together with other species, currently placed within Arthroleptis (tree not shown). Based on the 402 investigated base pairs of the 16S rRNA gene A. formosus sp. nov. was genetically most similar to A. aureoli . From this species the new species differed by a mean 4.7% sequence divergence ( Table 2). The genetic distance to other African Arthroleptis ranged from 16.0– 23.4% ( Table 2).

continued.

ZMB # sex SVL/HW SVL/FL SVL/TL SVL/FTL FL/TL LSF/LTF 75480 f 3.3 2.2 1.8 1.3 0.9 0.6 75484 f 3.3 2.4 1.9 1.5 0.8 0.6 75481 m 3.4 2.4 2.1 1.4 0.9 0.6 75483 m 3.6 2.3 2.1 1.5 0.9 0.6 75485 m 3.5 2.3 2.2 1.5 1.0 0.6 nov. (for GenBank accession numbers see type series) and the sequences of 20 other African arthrolpetid species. Given are

mean and range of sequence divergence.

species GenBank accession numbers distance

mean range

Arthroleptis adelphus FJ 151092 ( Cameroon) 0.181 0.176–0.184

A. aureoli EF640989 , EF640990 , FJ 151117 ( Sierra Leone), JN408731 0.047 0.045–0.051 ( Guinea)

A. poecilonotus FJ 151119 ( Sierra Leone), FJ 151111 ( Ghana), HM238192 0.196 0.190–0.202 ( Nigeria)

Natural history. Between 2nd to 19th October 2010, which is the end of the rainy season, we found nine individuals (ZMB 75480-75487, 1 specimen NGK) of the new species at four sites in the Telimélé region. All sites (see type series for exact geographic data) consisted of lowland habitats (180–360 m a.s.l.) which were strongly altered by human activities, i.e. timber extraction and agriculture ( Fig. 3 ). Two sites were gallery forests with small rivers; the two others comprised humid grass and tree savanna. Five individuals were collected in grasses on rocky ground, one was recorded on a large rock in a disturbed gallery forest and three individuals were observed on dead wood in a gallery forest which was highly impacted by logging activities (type locality; Fig. 3 c & d). All savanna habitats were close to forest, indicating that A. formosus sp. nov. may migrate between the two habitat types. Similar to other frogs in West Africa ( Arthroleptis spp., Phrynobatrachus gutturosus , P. tokba , Rödel 2000, 2003, own unpubl. data), this species may live in humid savanna during the rainy season and in nearby forests during the dry season. All individuals were encountered during twilight or at night, while being active as well while being hidden.

The female holotype had a large, but completely empty ovarium. The largest female (ZMB 75484) carried only very small, unripe egg. It thus seems that, during the period of our survey, the reproductive period was already finished. This is in line with our failure to detect any calling males of the new species. ZMB 75483, however, had very well-developed testis and fat bodies.

Distribution. Arthroleptis formosus sp. nov. is known from a total of four sites ( Fig. 4 ) in the Télimélé region in western Guinea. Its occurrence in further forests and forested savannas within this region is likely. So far it is not known from any protected area.

Etymology. The species name is a Latin adjective meaning “beautiful” and refers to the colour pattern of the new species. As English name we propose “Beautiful Squeaker”.

Figures

FIGURE 1. Life colour of male and female Arthroleptis formosus sp. nov. Dorsal (a) and ventral (e) view of female holotype (ZMB 75480); dorsal views of ZMB 75483 (b, male paratype), a specimen which was not collected (c) and ZMB 75481 (d, male paratype); ventral view of the juvenile paratype ZMB 75486 (f).

FIGURE 2. Ventral views of left hand (a) and left foot (b) of female Arthroleptis formosus sp. nov. (ZMB 75480, holotype).

FIGURE 3. Habitats of Arthroleptis formosus sp. nov.; a) & b) habitat of ZMB 75483, (paratype), a degraded gallery forest with a fast flowing small river; c) the type locality, a degraded gallery forest where intensive logging activities where observed; d) female at the type locality.

FIGURE 4. Geographic position of the four known sites (white symbols) of Arthroleptis formosus sp. nov. in western Guinea, and the known distribution of A. aureoli in Sierra Leone and Guinea (black triangles). The two westernmost sites of the new species are very close to each other. The type locality is indicated by a star. The range of the new species is also indicated as black square in the inlet figure of Africa (map based on the ASTER Global Digital Elevation Model: www. ersdac. or. jp.).

Tables

TABLE 1. Measurements (mm) and indices of measurements of adult frogs of the type series of Arthroleptis formosus sp. nov. Given are accession number, sex (f = female; m = male), snout-vent length (SVL), head width measured directly behind the eyes (HW), femur length (FL), tibio-fibula length (TL), foot length including longest toe (FTL), length of second (LSF) and third finger (LTF), horizontal eye-diameter (ED), horizontal tympanum diameter (TD), distance from anterior corner of the eye to nostril (EN) and distance from nostril to snout-tip (NS).

ZMB #	sex	SVL	HW	FL	TL	FTL	LSF	LTF	ED	TD	EN	NS
75480	f	18.6	5.6	8.6	10.1	13.9	2.6	4.2	1.9	1.2	1.8	1
75484	f	20.8	6.3	8.8	10.7	14.3	2.7	4.4	2.2	1.2	2	1.2
75481	m	19.1	5.6	8.1	9.3	13.4	2.6	4.5	1.8	1	1.7	0.9
75483	m	18.7	5.2	8	8.8	12.1	2.2	3.6	2.1	0.9	1.5	0.8
75485	m	18.3	5.3	8.1	8.5	12.6	2.2	3.7	1.9	0.9	1.3	0.8