Ptychadena delphina, Goutte & Reyes-Velasco * & Freilich & Kassie & Boissinot, 2021

Goutte, Sandra, Reyes-Velasco *, Jacobo, Freilich, Xenia, Kassie, Abeje & Boissinot, Stephane, 2021, Taxonomic revision of grass frogs (Ptychadenidae, Ptychadena) endemic to the Ethiopian highlands, ZooKeys 1016, pp. 77-141 : 77

Ptychadena delphina sp. nov.

Type material.

Holotype. Adult male (SB310) collected on 7 June 2018 by S. Goutte and J. Reyes-Velasco between Dembi and Gechi, Oromia, Ethiopia (8.2195°N, 36.446°E, 2064 m a.s.l.). Paratypes. One female (16-242) and one male (16-241) collected 22 July 2016 by X. Freilich, J. Reyes-Velasco and S. Boissinot west of Bedele (8.3746°N, 36.2596°E, 1876 m a.s.l.), one female (SB295) collected on 6 June 2018 by S. Goutte and J. Reyes-Velasco west of Bedele (8.4330°N, 36.3176°E, 1942 m a.s.l.), two males (SB313 and SB314) collected on 7 June 2018 by S. Goutte and J. Reyes-Velasco between Dembi and Gechi (8.2195°N, 36.4460°E, 2064 m a.s.l.), one female (SB341) collected on 9 June 2018 by S. Goutte and J. Reyes-Velasco west of Gore (8.1769°N, 35.3627°E, 1612 m a.s.l.), 3 females(SB355, SB356 and SB357) and two males (SB354 and SB363) collected on 10 June 2018 by S. Goutte and J. Reyes-Velasco south of Gore (8.0802°N, 35.5239°E, 1903 m a.s.l.). All specimens are deposited at ZNHM.

Diagnosis.

Large member (male (6) SVL 40.1 ± 2.9 mm, female (6) SVL 47.2 ± 2.3 mm) of the Ptychadena neumanni species group (Fig. 19 ) distinguished by the following combination of characters: (1) moderately long hind limbs (male TL/SVL 0.53 ± 0.02, female TL/SVL 0.55 ± 0.03), (2) long forearms (FLL/SVL 0.20 ± 0.01), (3) eye close to one another (male IOD/HW 0.17 ± 0.02, female IOD/HW 0.20 ± 0.03), (4) light vertical stripe on the tympanum, (5) vocal sacs are dark grey or dark grey posteriorly and lighter anteriorly.

Comparison.

Ptychadena delphina sp. nov. is smaller than P. cooperi and larger than P. nana , P. erlangeri , P. levenorum , and P. robeensis sp. nov. This species has shorter hind limbs and feet than P. goweri but longer than P. beka sp. nov. and P. amharensis (see Suppl. material 3: Table S2). The length of its forearms is also greater than in P. beka sp. nov. and P. amharensis . Ptychadena delphina sp. nov. can be distinguished from P. goweri by shorter hands, shorter snout, and pigmented vocal sacs in adult males. Eyes are closer to one-another than P. goweri , but further apart than in P. amharensis . Tympanum larger than P. doro sp. nov.

Description of the holotype.

Relatively large (SVL 44.2 mm) male (Fig. 19 ). Head wider than long (HL/HW 0.87). Snout projecting beyond the lower jaw. Interorbital distance 0.54 × eye diameter. Internarial distance 1.68 × interorbital distance. Tympanum 0.71 × eye diameter. Finger tips not expanded but rounded, with small subarticular tubercles.

Finger formula: I<II<IV<III. Hand free of webbing. Hindlimbs elongated, with tibia length 0.55 × snout-vent length. Foot longer than thigh (FL/THL 1.27) and slightly longer than tibia (FL/TL 1.02). Toe tips rounded. Subarticular tubercles small and round. Inner metatarsal tubercle present, external absent. Fourth toe on the left foot amputated. Toe formula: I<II<V<III<IV. Foot webbing formula: Ie(minimal), IIi/e(minimal-1), IIIi/e(2-2), IVi/e(2-2), Vi(2). Two light lateral ridges, continuous on the right side and discontinuous on the left side. Two continuous dorsal ridges and two interrupted dorsolateral ridges. No vertebral nor sacral ridges. Body and eyelids covered with minute transparent warts. Nuptial pad developed along finger I. Tongue longer than wide, free for half of its length, bifurcated at the end. Vomerine, maxillary and premaxillary teeth present.

Coloration of the holotype in life.

Dorsal ground color brown with elongated dark brown blotches symmetrically distributed on the dorsal ridges. Wide light grey-brown vertebral stripe, doubled with a thin, clearer stripe from the tip of the snout to the vent. Dark brown canthal stripe from the tip of the snout to the back of the jaw. Light vertical blotch on the otherwise brown tympanum. Upper and lower lip cream to light brown with irregular brown markings. Iris dark brown on the lower two thirds, light golden brown above, separated by a cream horizontal stripe.

A few irregular dark brown blotches on the light grey flanks. Throat and ventrum cream with a few small light grey dots under the chin. Two small symmetrical dark brown blotches on the antero-ventral side of the shoulders. Thin light longitudinal stripe on the tibias and lower half of the thighs. Hind limbs brown with dark bars over the thighs, tibias, and feet. A few small round white dots around the groin. Back of the thighs dark brown irregularly molted with yellow. Vocal sacs uniformly dark grey.

Coloration of the holotype in preservative.

Dorsal ground color dark brown with a few small, oval dark brown blotches symmetrically distributed on the dorsolateral ridges. Wide lighter brown vertebral stripe, doubled with a thin, clearer line from the tip of the snout to the vent. Dark brown canthal stripe from the tip of the snout to the back of the jaw. Light vertical stripe on the otherwise brown tympanum. Upper lip grey on the anterior half and cream on posterior half. Lower lip grey with irregular cream spots. Flanks brown with a few irregular small dark brown blotches. Throat, ventrum, ventral side of the thighs and tibias uniformly cream with the throat and chest lightly dusted with grey. Two symmetrical dark brown blotches on the ventral side of the shoulders. Thin, light longitudinal stripe on the tibias. Faint brown bars on the thighs. Back of thighs molted light grey and brown. Vocal sacs dark grey. Nuptial pads cream.

Variations.

In life, background color varies from light to dark brown. Dorsal ridges vary in number and definition. Median ridges may be continuous from eye level to the groin, or interrupted and be present only along half the back. Postpalpebral fold interrupted in the middle of the back, sometimes continuing on the lower back. Short laterodorsal fold almost always present. Lateral ridges generally non-interrupted until the lower third of the back and from orange to cream. All specimens examined had small dark brown or black blotches distributed symmetrically on the dorsal ridges. Inguinal area more or less conspicuously yellow. Vertebral stripe may be thin or wide, generally around a lighter thin stripe. Tympanum blotch may be more or less conspicuous depending on the individual.

The thin cream longitudinal stripe on the tibia may be extended to the thigh or half of the thigh and the foot in some individuals. Tibias, thighs, and feet posteriorly barred with more or less defined brown or light brown markings. Thighs posteriorly marbled with light to dark brown and yellow. Ventrum and throat uniformly white to light yellow. Vocal sacs grey to dark grey or bicolored cream and grey. Small warts over the back and flanks in ca. 20% of adult males.

Etymology.

The specific name originates from the Latin delphinus, dolphin, in reference to the advertisement call of the species resembling a dolphin’s clicking sound. We have Latinized delphinus into the adjective Ptychadena delphina to be in accordance with the gender of genus Ptychadena . The advertisement call best distinguishes P. delphina sp. nov. from P. doro sp. nov.

Habitat, distribution, and natural history.

The distribution range of Ptychadena delphina sp. nov. is mostly restricted to mid-elevation forests (1612 to 2064 m a.s.l.), west of the GRV and north of the Geba River (tributary of the Baro River). However, two individuals (XF13-283 and XF13-285) collected in 2013 by X. Freilich and S. Boissinot in Asgori, between Addis Ababa and Ambo (8.9799°N, 38.0241°E, 2370 m a.s.l.) clustered with Ptychadena delphina in phylogenetic analyses based on four molecular markers ( Freilich et al. 2016). If the molecular results are not caused by introgression between P. delphina sp. nov. and P. beka sp. nov, which occurs in the area, and if these two individuals represent a real population, this is the easternmost and highest known population of P. delphina sp. nov. The habitat at this locality is also quite different from the rest of P. delphina sp. nov. distribution range, as it is composed of open agricultural fields and not forest. No other individual of the species was collected in the multiple sampling campaigns subsequently conducted, and this population remains to be confirmed. Beside these two individuals, the easternmost populations have been found south of Bedele, while, in the west, Individuals have been collected by Uka, west of Gore. The southernmost individuals were found in Bichano, just north of the Geba River.

Males of P. delphina sp. nov. call at night in flooded grassland ponds or puddles, or in rainwater-filled holes on the road. Within the genus, P. delphina sp. nov. is found in sympatry with P. beka sp. nov., P. doro sp. nov., and P. neumanni . Males of P. delphina sp. nov. have been found calling jointly with P. doro sp. nov.

Advertisement call.

To the human ear, the call of Ptychadena delphina sp. nov. (4 males, 33 calls) resembles a dolphin’s series of clicks. It is composed of a single note of 504 ± 92 ms in duration, containing 8.4 ± 1.4 pulses, which are clearly distinct and at regular intervals. Amplitude increases regularly within the note until 384 ± 129 ms, where it decreases. As in other Ethiopian Ptychadena species, call repetition rate is highly variable and dependent of the social context. Call dominant frequency is 2327 ± 147 Hz, with a gradual increase in dominant frequency within the call.

The call of Ptychadena delphina sp. nov. is easily distinguishable from the calls of all other Ptychadena from the Ethiopian highland by its well defined and regularly spaced pulses, except for the call of P. robeensis , which presents a similar structure. The call P. robeensis can however be distinguished by its higher dominant frequency (2876 ± 74 Hz), related to the species’ smaller body size. It is worth noting that the call of the closely related syntopic species P. doro sp. nov. is remarkably different both in temporal and spectral features, while the two species are morphologically extremely similar. The two species were thus named after their respective calls, which constitute their most distinguishable traits.

Figures

Figure 19. Ptychadena delphina sp. nov. A live male holotype (SB 310; left) and female paratype (SB 341, right) B dorsal and ventral views of the same individuals (male left, female right) after euthanasia and before fixation.