Bioacoustics of Gephyromantis corvus

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 ). Catalogue number Rank Sex SVL HW HL TD ED END NSD NND MRSN A5317 HT M 34.8 13.5 15.0 4.0 4.9 3.3 2.5 3.7 MRSN A5036 PT M 35.5 12.9 14.8 4.2 5.2 3.0 2.3 3.7 MRSN A5319 PT M 33.4 12.2 13.0 3.8 4.0 3.2 1.8 3.6 SMF 85861 PT M 32.8 13.5 12.8 3.2 5.1 3.4 2.3 3.7 MRSN A5035 PT F 35.8 13.8 15.6 3.1 4.6 3.9 2.2 4.0 MRSN A5254 PT F 37.7 13.3 14.5 3.4 5.5 3.4 3.3 4.4 MRSN A5318 PT F 38.5 15.2 16.3 3.6 5.6 3.2 2.8 4.3 MRSN A5252 PT F 38.8 14.5 16.6 3.4 5.5 4.4 2.2 4.5 SMF 85862 PT F 37.8 14.1 14.7 3.3 5.9 3.2 2.8 3.9 SMF 85863 PT F 35.5 13.3 14.5 3.2 4.4 3.3 3.3 4.4 SMF 85864 PT F 40.0 15.5 15.5 3.4 5.6 4.4 2.2 3.4 Catalogue number HAL FORL HIL FOTL FOL IMTL IMTW FGL FGW NG GD MRSN A5317 10.0 17.8 36.2 25.9 18.7 2.0 1.2 2.2 2.5 8 0.7 MRSN A5036 11.5 19.8 35.6 29.8 19.3 2.0 1.0 2.0 1.7 8 0.5 MRSN A5319 11.0 18.3 35.6 28.3 18.3 1.6 0.9 2.5 2.0 9 0.6 SMF 85861 9.1 14.9 35.6 28.6 18.3 2.0 1.0 2.0 2.0 4 0.8 MRSN A5035 10.3 18.3 39.1 27.5 19.2 2.0 1.0 - - - - MRSN A5254 11.1 18.8 39.8 26.7 19.9 2.2 1.0 - - - - MRSN A5318 11.5 19.8 40.0 30.5 20.5 2.0 1.0 - - - - MRSN A5252 11.0 18.8 39.8 27.8 19.9 2.2 1.0 - - - - SMF 85862 9.6 17.5 38.2 29.1 18.8 1.7 0.9 - - - - SMF 85863 11.1 18.8 37.5 27.0 19.6 2.3 1.0 - - - - SMF 85864 11.1 20.0 42.2 31.1 21.1 2.2 0.7 - - - - HT ( holotype ), PT ( paratype ), M (male). F (female). Other abbreviations are given in the text. 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 .

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.