Gephyromantis oelkrugi sp. nov. (lineage C)

Vences, Miguel, Koehler, Joern, Crottini, Angelica, Hofreiter, Michael, Hutter, Carl R., du Preez, Louis, Preick, Michaela, Rakotoarison, Andolalao, Rancilhac, Lois, Raselimanana, Achille P., Rosa, Goncalo M., Scherz, Mark D. & Glaw, Frank, 2022, An integrative taxonomic revision and redefinition of Gephyromantis (Laurentomantis) malagasius based on archival DNA analysis reveals four new mantellid frog species from Madagascar, Vertebrate Zoology 72, pp. 271-309 : 271

Gephyromantis oelkrugi sp. nov. (lineage C)

Holotype.

ZSM 314/2010 (FGZC 4220), adult male (call voucher), from Ambodivoangy, near Makira Reserve (15.2899°S, 049.6203°E, ca. 100 m a.s.l.), Analanjirofo Region, northeastern Madagascar, collected on 31 March 2010 by F. Glaw, J. Köhler, P.-S. Gehring, M. Pabijan, and F.M. Ratsoavina.

Paratypes.

ZSM 315/2010 (no field number), adult male, with same collection data as holotype except for being collected on 02 April 2010; ZSM 271/2016 (FGZC 5300), probably an adult female, from Masoala Peninsula, near "Eco-Lodge chez Arol" hotel (ca. 15.7122°S, 49.9640°E, 21 m a.s.l.), Analanjirofo Region, northeastern Madagascar, collected on 09 August 2016 by F. Glaw, D. Prötzel, J. Forster, K. Glaw, and T. Glaw; MRSN A5475 (no field number), adult female, from an unspecified locality in the Masoala region, date unspecified, collected by J.E. Randrianirina; MRSN A1991 (FN 7905) and MRSN A1992 (FN 7910), adult individuals (unsexed), from Masoala Peninsula near Andasin’i Governera (campsite Ambatoledama ca. 15.2833°S, 50.0208°E), around the border between Analanjirofo and Sava Regions, northeastern Madagascar, collected on 09 December 1998 by F. Andreone and J.E. Randrianirina; MRSN A2844 (RJS 528), adult individual (unsexed), from Masoala Peninsula, near Mahalevona (campsite Amparihy, ca. 15.4177°S, 49.9403°E, ca. 770 m a.s.l.), Analanjirofo Region, northeastern Madagascar, collected on 09 February 2002 by J.E. Randrianirina; UADBA uncatalogued (FGZC 4201 and 4244), two adult specimens from the type locality Ambodivoangy collected on 31 March and 2 April 2010 by the same collectors as holotype; UADBA uncatalogued (APR 11885), from Sahabe Antanamahalana (15.5604°S, 050.2818°E, 45 m a.s.l.), Masoala National Park, Sava Region, northeastern Madagascar, collected in 2015 by A.P. Raselimanana; UADBA uncatalogued (APR 12006), from Ambohitsitondroina (15.5694°S, 050.0034°E, 550 m a.s.l.), Masoala National Park, Analanjirofo Region, northeastern Madagascar, collected in 2015 by A.P. Raselimanana.

Etymology.

The specific epithet is a patronym for Christopher Roland Oelkrug in recognition of his support for biodiversity research and nature conservation through the BIOPAT initiative.

Diagnosis.

A member of the subfamily Mantellinae based on the presence of intercalary elements between terminal and subterminal phalanges of fingers and toes (verified externally), and on the absence of nuptial pads and presence of femoral glands in males. Assigned to the subgenus Gephyromantis Laurentomantis in the genus Gephyromantis based on the strongly tubercular dorsal skin, absence of foot webbing, completely connected lateral metatarsalia, and molecular phylogenetic relationships. The new species differs from all nominal species of the subgenus Gephyromantis Laurentomantis as follows: From G. horridus by smaller body size (male SVL 21.6-21.9 mm vs. 33.5 mm), and absence of a dorsal pattern of two blackish transverse patches (vs. presence); from G. ranjomavo by the absence of light brown to orange-brown color covering limbs dorsally (vs. presence), a slightly smaller body size (male SVL 21.6-21.9 mm vs. 23.5-28.1 mm) and absence of a tibial gland (vs. presence); from G. striatus by absence of a vertebral stripe posteriorly on dorsum (vs. presence); from G. malagasius (as redefined herein) by absence of a distinct bluish gray pattern on a dark venter (vs. presence); from G. marokoroko by a more coarsely tubercular dorsal skin, presence of red color ventrally on limbs (vs. absence), absence of orange spots and vermiculations on dorsum (vs. presence), and absence of gray to whitish color on vocal sac (vs. presence). Furthermore, differing from all the aforementioned species by the presence of bright red color in the inguinal region and ventrally on limbs and on a small portion of posterior belly in life (vs. absence), and by a substantial genetic divergence (>6% uncorrected pairwise distance in the 16S gene).

According to the molecular phylogeny, G. oelkrugi is closely related to G. fiharimpe and G. matsilo described above. It differs from G. fiharimpe by the absence of a tibial gland (vs. presence), a more strongly tubercular dorsal skin, and brighter red ventral color that appears not to extend much on posterior belly (vs. less bright light red color extending onto posterior belly), probably by a faster note repetition rate in advertisement calls (43.5-54.1 vs. 14.9-37.4 notes/second in most recordings; but up to 54.1 in one recording of G. fiharimpe ), and an uncorrected 16S genetic distance of 4.3-5.5%. The new species is morphologically most similar to G. matsilo but differs by a faster note repetition rate (43.5-54.1 vs. 20.8-21.6 notes/second) and a shorter note duration (3-10 ms vs. 13-21 ms) in advertisement calls, and an uncorrected 16S genetic distance of 4.3-5.5%.

For a distinction from the fourth new species described in the following (lineage D), see the diagnosis in the respective species account below.

Description of the holotype.

Adult male in good state of preservation (Fig. 18 ), tongue removed as tissue sample for molecular analysis. SVL 22.0 mm, for other measurements see Table 1 . Body slender; head as wide as long, and as wide as body; snout rounded in dorsal view, truncate in lateral view; nostrils directed laterally, slightly protuberant, much nearer to tip of snout than to eye; canthus rostralis rather indistinct but strongly concave; loreal region slightly concave; tympanum distinct, rounded, 50% of eye diameter; no supratympanic fold; tongue removed and thus not available for examination; vomerine teeth absent; choanae rounded; maxillary teeth present. Dermal fold along the posterior part of the lower jaws (the inflatable parts of the vocal sac) not recognizable. Arms slender, subarticular tubercles single; outer and inner metacarpal tubercles moderately expressed, well recognizable; fingers without webbing; relative length of fingers 1 <2 <4 <3, second finger distinctly shorter than fourth finger; finger discs enlarged; nuptial pads absent. Hindlimbs slender; tibiotarsal articulation reaching between eye and nostril when hindlimb is adpressed along body; lateral metatarsalia connected; inner metatarsal tubercle distinct, outer metatarsal tubercle small but recognizable; webbing between fingers and toes absent; relative toe length 1 <2 <5 <3 <4. Third toe slightly longer than fifth toe. Toe discs enlarged. Skin on upper surface strongly granular but without distinct ridges; many smaller irregularly distributed tubercles on head, eyes and dorsum. Ventral skin smooth on throat, chest and limbs, slightly granular on posterior belly. Femoral glands well delimited and distinctly recognizable from external view. No tibial glands.

After eleven years in preservative, dorsal coloration of head and body uniformly dark brown, with darker crossbands on hind- and forelimbs. Posterodorsal surface of thigh with a large pigmentless patch in its distal part, this area presumably corresponding to reddish color in life. Ventrally, whitish, with some dark spotting along the lower lip, two symmetrical brown patches on chest, and brown pigment on distal part of thighs.

Variation.

The coloration in life of several specimens is shown in Fig. 22 . The examined specimens of G. oelkrugi as well as the additional specimens photographed are morphologically quite similar to each other. The two measured males agree in body size (SVL 21.6-21.9 mm; Table 1 ). The only known female is slightly smaller (SVL 21.1 mm) but has no oocytes visible through the belly skin, and we hypothesize it is rather a subadult or young adult. The femoral glands of the males appear to consist of 3-5 granules arranged in a somewhat circular manner around a central depression (Fig. 22C, E ).

Call.

The advertisement call (Fig. 23 ) was recorded on 31 March 2010 at Ambodivoangy (estimated air temperature 25°C) from the holotype (ZSM 314/2010, FGZC 4220). It consists of a series of very short pulsed notes. There is considerable amplidude modulation within each call, with call energy constantly increasing from the beginning of the call reaching the maximum amplitude at about 60% of its duration and from there decreasing towards its end. Within calls, notes are repeated at a high rate and at regular intervals. Numerical parameters of 10 analyzed calls are as follows (range followed by mean ± standard deviation in parentheses): call duration 279-504 ms (350.9 ± 88.4 ms); note duration 3-10 ms (6.8 ± 1.3 ms); number of notes per call 13-25 (16.9 ± 4.4); note repetition rate within calls 43.5-54.1 notes/second (46.5 ± 4.0 notes/second); pulses per note 1-4 (2.9 ± 0.7); dominant frequency 3266-3882 Hz (3539 ± 190 Hz); prevalent bandwidth 2100-4500 Hz. Calls were usually emitted isolated at rather irregular intervals, except for one short call series recorded. This series contained 3 calls repeated at a rate of approximately 34 calls/minute.

Distribution and natural history.

Based on genetically verified records, the distribution area is restricted to (1) Ambodivoangy close to the Makira Reserve, and the Masoala Peninsula where it has been found at various sites, including (2) Andasin’i Governera, (3) Andranobe, (4) Ambatoledama, (5) Amparihy, (6) Antanamahalana, (7) Ambohitsitondroina, and (8) near hotel "Eco-Lodge chez Arol". A species apparently restricted to lowland rainforest habitat. The holotype was found calling sitting on a twig of a shrub plant approximately 30 cm above the ground.

Figures

Figure 18. Preserved holotype specimens of the four new Gephyromantis species in dorsal and ventral view. A, B G. matsilo sp. nov. (lineage A), ZSM 711 / 2009 (ZCMV 7234) from Ambatoroma, Befanjana Forest. C, D G. fiharimpe sp. nov. (lineage B), ZSM 164 / 2016 (FGZC 5181) from Mandraka. E, F G. oelkrugi sp. nov., ZSM 314 / 2010 (FGZC 4220) from Ambodivoangy. G, H G. portonae sp. nov. (lineage D), ZSM 115 / 2021 (ACZCV 0032) from Betampona.

Figure 22. Specimens of Gephyromantis oelkrugi sp. nov. (lineage C) from the type locality, Ambodivoangy, in life. A, B, C Adult male (FGZC 4201) in frontal, dorsolateral and ventral view. D, E Adult male holotype (ZSM 314 / 2010, field number FGZC 4220) in dorsolateral and ventral view. Not to scale.

Figure 23. Audiospectrogram and corresponding oscillogram of one advertisement call of the holotype of Gephyromantis oelkrugi sp. nov. (ZSM 314 / 2010) recorded on 31 March 2010 at Ambodivoangy. The oscillogram below shows a 100 ms section of the call figured above, showing four notes and their repective pulse structure. Recording band-pass filtered at 2000 - 8000 Hz.