Boophis arcanus, Glaw & Köhler & Riva & Vieites & Vences, 2010

Glaw, Frank, Köhler, Jörn, Riva, Ignacio De La, Vieites, David R. & Vences, Miguel, 2010, Integrative taxonomy of Malagasy treefrogs: combination of molecular genetics, bioacoustics and comparative morphology reveals twelve additional species of Boophis 2383, Zootaxa 2383 (1), pp. 1-82 : 16-19

Boophis arcanus sp. nov.

( Fig. 6 , Appendix 9)

Remark. This species has been referred to as Boophis sp. aff. miniatus "Mahakajy" by Glaw & Vences (2007:154–155) and as Boophis sp. 29 by Vieites et al. (2009). First data on this species were possibly given by Andreone (1994), who recorded a small brown Boophis from the Ranomafana area as B. miniatus . Glaw et al. (2001) gave further information on the corresponding voucher specimens from Ifanadiana, a locality not far from Mahakajy. These specimens may belong to B. arcanus , but since no reliable male specimens of B. arcanus are known, and no genetic data are available for the Ifanadiana specimens, this hypothesis cannot be tested at present.

Holotype. ZSM 298 /2006 ( ZCMV 3370 ), adult female, from Mahakajy , 21° 16.753' S, 47°31.823' E, 577 m a.s.l., southeastern Madagascar, collected on 1 March 2006 by T. Rajaofiarison, E. Rajeriarison and M. Vences.

Paratype. UADBA 24299 ( ZCMV 392 ) , adult female, Mahakajy reserve , 21°16.753'S, 47°31.823'E, 577 m a.s.l., collected on 1 February 2004 by E. Edwards and M. Vences .

Etymology. The specific name is derived from the Latin adjective "arcanus", meaning "hidden" or "secret". It refers to the fact that this cryptic species is extremely difficult to identify based on morphological characters only, and that we were unable to collect more than two specimens despite intensive searches during three visits to the type locality.

Diagnosis. Assigned to the genus Boophis based on the presence of an intercalary element between ultimate and penultimate phalanges of fingers and toes (verified by external examination), enlarged terminal discs of fingers and toes, lateral metatarsalia separated by webbing, absence of outer metatarsal tubercle, molecular phylogenetic relationships (see Vieites et al. 2009 for a complete molecular analysis of Boophis ), and overall similarity to other Boophis species. Assigned to the Boophis majori group based on the following combination of characters: small size (female SVL 34 mm); smooth dorsal skin without folds, spines or tubercles; presence of vomerine teeth; absence of distinct heel flaps or spines; presence of webbing between fingers; non-transparent ventral skin; brownish dorsal ground colour without green elements; occurrence of red colour on the hidden parts of the thighs and on the webbing of the feet; and molecular phylogenetic relationships ( Vieites et al. 2009). Boophis arcanus differs from all described species in the B. majori group by strong genetic differentiation (> 7.2% to all other species, see below). It furthermore differs from the three northern species of the Boophis majori group ( B. blommersae , B. marojezensis and B. vittatus ) by the presence of red colour on thighs and feet in preservative and distinctly from B. pyrrhus and B. haematopus by colouration in life and in preservative (both species with a dorsal hourglass marking; B. pyrrhus with a reddish brown and B. haematopus with a light greenish brown dorsum with many small spots; see photographs in Glaw & Vences 2007; vs. almost uniformly brown in B. arcanus ). It differs from B. majori by its larger female size (SVL 34.3 mm in B. arcanus vs. 29.0– 29.2 mm in B. majori ) and different colour in preservative (e. g. ground colour of back brown vs. reddish). It differs from B. miniatus and B. picturatus by having different iris colouration in life ( B. miniatus with red colour and B. picturatus often with bluish colour in the outer iris area; both species without a pattern of dark vertical stripes; see photographs in Glaw & Vences 2007; vs. uniform with distinct dark vertical stripes in B. arcanus ) and from B. feonnyala and B. piperatus by details of life colouration (a lighter ground colour and often with a pattern of fine dark spots especially in B. piperatus , vs. almost uniformly brown in B. arcanus ) and strong genetic differentiation.

Description of the holotype. Female, in relatively good state of preservation (a large tissue sample was taken from the right thigh and a smaller sample from the left thigh), SVL 34.3 mm. Body slender; head slightly longer than wide, wider than body; snout rounded in dorsal view, obtuse in lateral view, nostrils directed laterally, slightly nearer to tip of snout than to eye; canthus rostralis sharp in cross section, slightly concave in dorsal view, loreal region slightly concave; tympanum distinct, rounded, TD 44% of ED; supratympanic fold distinct; vomerine odontophores distinct, well separated in two round patches, positioned posteromedial to choanae; choanae medium-sized, rounded. Tongue bifid, free posteriorly. Arms slender, subarticular tubercles single, round; metacarpal tubercles not recognizable; fingers moderately webbed; webbing formula 1(1.5), 2i(1.25), 2e(1.25), 3i(2), 3e(1.25), 4(1); relative length of fingers 1<2<4<3 (finger 2 distinctly shorter than finger 4); finger discs distinctly enlarged. Hindlimbs slender; tibiotarsal articulation reaching snout tip when hindlimb is adpressed along body; lateral metatarsalia separated by webbing; inner metatarsal tubercle very small and indistinct; no outer metatarsal tubercle; webbing between toes well-developed, webbing formula 1(0), 2i(0.25), 2e(0), 3i(1), 3e(0), 4i(1), 4e(1), 5(0.25); relative length of toes 1<2<5=3<4; toe discs enlarged. Skin on dorsal surfaces smooth, very finely granular on throat and chest, coarsely granular on belly; few slightly enlarged tubercles ventrally under the cloacal opening.

Measurements (in mm): SVL 34.3, HW 12.3, HL 12.8, ED 5.0, END 3.1, NSD 2.6, NND 3.5, TD 2.2, TL 19.2, HAL 10.6, FOL 15.5, FOTL 26.6.

After 1.5 years in preservative, dorsal surfaces brown with fine red and black dots. Back with a large, but poorly developed, hourglass-like pattern that is slightly darker than the surrounding skin. Three distinct dark crossbands on forelimbs, two on hindlimbs. Concealed parts of thighs reddish. Terminal tips of fingers and toes partly red, dorsally as well as ventrally. Webbing between toes pink. Throat dirty white with a brownish band along the jaw. Chest cream white, belly yellowish. Lateral parts of fifth toe and tarsus dark brown.

Variation. The paratype (deposited in UADBA) was superficially similar to the holotype but was not available for a detailed morphological examination. Its dorsal life colouration (see Glaw & Vences 2007: 155, photo 5) was largely uniformly brown with few scattered black spots and dots on back and extremities. The inguinal region had a bluish shade. The iris was silvery with vessel-like lines and the iris periphery was blue. Ventral life colouration unknown.

Natural history. Two females of this species have been found at Mahakajy in 2004 and 2006. Despite repeated visits to the site, no unknown calls were heard, indicating either that reproduction takes place elsewhere or is seasonal. Specimens were sitting, at night, on leaves 1–2 m high in bushes at the edge of disturbed rainforest.

Molecular relationships. Boophis arcanus is placed in the B. majori group sensu stricto according to the mitochondrial phylogenetic analysis (see account of B. piperatus above). Its position within this lineage is not resolved ( Fig. 1 ), but its genetic divergences are remarkably high: 7.3% to B. miniatus , 8.2% to B. piperatus , 8.4% to B. feonnyala , and>9% to all other species.

Distribution. At present, Boophis arcanus is only reliably known from its type locality, Mahakajy Private Reserve in the southern-central east of Madagascar, along the road Ranomafana-Ifanadiana (Appendix 10).

Figures

FIGURE 1. Maximum parsimony 16S rRNA phylogram for species in the Boophis majori and B. microtympanum groups. From 480 total characters, 336 were constant and 129 parsimony informative. MP searches retained 39 trees of which a strict consensus is shown. Consensus support values higher than 50, from 2000 bootstrap replicates, are shown; an asterisk indicates Bayesian posterior probabilities equal or higher than 95%. Species newly described or resurrected herein are in bold.

FIGURE 6. Female paratype of Boophis arcanus sp. nov. (UADBA 24299) from Mahakajy.