Hyperolius dartevellei Laurent, 1943

Channing, A., Hillers, A., Lötters, S., Rödel, O., Schick, S., Conradie, W., Rödder, D., Wagner, P., Dehling, J. M., Du Preez, L. H., Kielgast, J. & Burger, M., 2013, Taxonomy of the super-cryptic Hyperolius nasutus group of long reed frogs of Africa (Anura: Hyperoliidae), with descriptions of six new species, Zootaxa 3620 (3), pp. 301-350 : 319-320

Hyperolius dartevellei Laurent, 1943

Dartevelle's Reed Frog ( Fig. 9 )

Synonomy. Hyperolius sagitta Laurent, 1943

Genetic material. ZMB 77303 Ikelenge, Zambia; USNM 576167–70 (Impongui, Republic of Congo); field numbers A27, CRT 3577-9, 3604-6 ( Congo River near Yekela, DRC); CRT 3730, 3798 ( Congo River, near Nganda Kona, DRC); CRT 3838-9 ( Congo River near Ngengele, DRC); CRT 3975–89 ( Congo River near Bomani, DRC); CRT 4024, 4027 ( Congo River, near Lulu, DRC); CRT 4205–10 ( Congo River, near Lieki, DRC) ( Fig. 1 ).

Diagnosis. A typical advertisement call ( Fig. 5 ) consists of 13 pulses in 0.1 s, with an emphasised frequency of 4.8 kHz. It differs from those species with a brief note consisting of a few initial pulses, followed by a number of pulses at a much slower pulse rate, such as H. benguellensis , H. friedemanni sp. nov., H. howelli sp. nov., H. igbettensis , H. inyangae sp. nov., H. rwandae sp. nov., H. viridis and H. poweri , and those with a longer call consisting of multiple pulses that may change tempo, such as H. acuticeps , H. jacobseni sp. nov., and H. nasutus . See Table 3 for a summary of call parameters. The advertisement call structure is similar to that of H. adspersus and H. lupiroensis sp. nov., while the 16S sequence of H. lupiroensis sp. nov. differs by more than 11%.

The snout is truncated, distinguishing it from the species with shark-like or rounded snout profiles: H. acuticeps , H. adspersus , H. benguellensis , H. friedemanni sp. nov., H. howelli sp. nov., H. igbettensis , H. inyangae sp. nov., H. jacobseni sp. nov., H. lupiroensis sp. nov., H. nasutus , H. poweri , H. rwandae sp. nov. and H. viridis . The webbing shows a phalanx free on the first, third and fifth toes, with half a phalanx free on the other two. It can be distinguished from the species that have less than a phalanx of the fifth toe free: H. adspersus , H. friedemanni sp. nov., H. igbettensis , H. jacobseni sp. nov., H. lupiroensis sp. nov., H. nasutus , H. poweri , H. rwandae sp. nov. and H. viridis . It differs from the species that have one phalanx or more of the fourth toe free of web: H. acuticeps , H. benguellensis , H. howelli sp. nov., and H. inyangae sp. nov.

Description of a Carumbo specimen. An adult male PEM A 10059 (measurements presented in Appendix 2) measuring 18.6 mm SUL; body long and slender, widest just behind orbital region, tapering to groin; head relatively small (HL/SUL 0.32, HW/SUL 0.34), not much wider than long (HL/HW 0.95); snout long (SL/HL 0.46), bluntly pointed in dorsal view ( Fig. 6 ), protruding just beyond lower jaw, wider than long (SL/EE 0.72); canthus rostralis distinct; loreal large and oval in shape; nostril directed dorsolaterally, moderately large vertical slit (0.4 mm in length), situated much closer to tip of snout than to eye (EN/NS 1.60), separated from each other by distance greater than distance between eye and nostril (NN/EN 1.60); eyes large (ED 1.8), directed anterolaterally, protruding outwards and forward, pupil is horizontal to circular, visible from below, eye diameter shorter than snout (ED/SL 0.64); interorbital distance much wider than upper eyelid (IO/EW 1.50), and greater than internarial distance (IO/NN 1.41); tympanum not visible externally; upper jaw with dentition; teeth on premaxilla larger than those on maxilla; choanae large, oval, vomer processes and teeth absent; tongue long 3.9 and broad 2.8, mostly free except for first quater, bifurcated distally for about one-fourth of length; median lingual process absent; vocal sac single, median, subgular; large granular gular flap covering thin vocal sac (5.9 wide)

Dorsal surfaces of head, trunk and limbs generally appearing smooth but with many densely and more or less evenly scattered tiny, asperities; ventral surface of limbs and gular smooth, chin and abdomen slightly more areolate; supratympanic fold absent.

Fore limbs slender; hand moderately large (HND/SUL 0.26); tips of fingers enlarged into broad oval disks, no circummarginal groove; relative length of fingers: I<II<IV<III; subarticular tubercles rounded, well developed, with one per phalange; webbing formula of the hand I 1.5–0.25 II 0.25–0.25 III 0.25–0.25 IV (after Myers & Duellman 1982) thenar tubercle indistinct; palmar tubercles absent.

Hind limbs slender, moderately long (LEG/SUL 1.50); tibio-tarsal articulation reaching to level of tip of snout when legs are adpressed to body; tibiofibula moderately long (TFL/SUL 0.52), longer than thigh (TFL/THL 1.07); heels overlapping each other considerably when knees are flexed and thighs are held laterally at right angle to body; foot shorter than tibiofibula (FOT/TFL 0.77); relative length of toes: I<II<III<V<IV; discs of toes similar in size to those of fingers; subarticular tubercles: one on toes I and II, two on toes III and V, and three on toe IV; pedal webbing formula ( Fig. 7 ) I 0.25– 1 II 0.25– 1 III 0.25– 1 IV 1–0.25 V; inner metatarsal absent; outer metatarsal tubercle large, almost circular, low and not distinct.

Colouration in life. Below translucent silvery-white, above uniform translucent green to brown, scattered darker spots, clear yellow-white dorsolateral line from snout to vent, forming a light canthus on the snout, darker pigmentation anterior-lateral from snout tip to above eye, upper jaw nearly free of any pigmentation, eye iris is yellow to brown; dorsal surface of arms and legs with scattered dark spots, inner thighs unmarked. Colouration in preservative. All colours have faded to a beige yellow with brown dorsal spots still visible.

Eggs and tadpoles. Unknown.

Habitat: Specimens were collected in the grassland floodplain wetlands surrounding a large natural lake (350 ha) at daytime. Specimens were found half a meter to a meter above water level on vegetation. The only other amphibians found were Phrynobatrachus mababiensis . Additional material was collected at a small pond (<0.5 ha) covered by tick marginal vegetation. Specimens were calling low down on the edge of the open water. Two other Hyperolius species were present in the same area, Hyperolius angolensis and Hyperolius cf. cinereus , both species were calling further away and higher up the vegetation. Hoplobatrachus occipitalis was present in the pond.

Distribution. Southern Cameroon, east and south through Gabon to the lower Congo Basin and the most northern parts of Angola, and the north-western Zambian highlands.

Remarks: The synonomy of H. granulatus (the holotype RMCA-152 was examined) is supported by the absence of dorso-lateral stripes and a short rounded snout. The species is presently only confirmed from northern Angola, the Cabinda enclave, and Gabon. There is little doubt that existing records refer to this species, and we suggest that its conservation status of Least Concern remains unchanged.

Figures

FIGURE 1. Map showing the distribution of the sequenced specimens of recognised species in the Hyperolius nasutus group plus H. lamottei. Species numbers represent the following: 1 — H. acuticeps, 2 — H. adspersus, 3 — H. benguellensis, 4 — H. friedemanni sp. nov., 5 — H. howelli sp. nov., 6 — H. igbettensis, 7 — H. inyangae sp. nov., 8 — H. jacobseni sp. nov., 9 — H. lamottei, 10 — H. lupiroensis sp. nov., 11 — H. nasutus, 12 — H. poweri, 13 — H. rwandae sp. nov., 14 — H. dartevellei, 15 — H. viridis, 16 — H. nasicus.

FIGURE 5. Advertisement calls of H. acuticeps Kaningina (left), H. adspersus Bateka Nature Reserve (center) and H. dartevellei Carumbo (right).

FIGURE 6. Snout profiles of representatives of the species in the Hyperolius nasutus group.

FIGURE 7. Webbing diagrams of representatives of the species in the Hyperolius nasutus group.

FIGURE 9 Hyperolius nasutus, Calandula, Angola, ZMB 77311, photo A. Channing (A); Hyperolius poweri, Mkambati NR, South Africa, photo W. Conradie (B); Hyperolius rwandae sp. nov., Butare, Rwanda, ZMB 77221, holotype, photo J. M. Dehling (C); Hyperolius viridis, Kaningina, Malawi, photo V. Mercurio (D), Hyperolius rwandae sp. nov, female paratype ZMB 77223, photo J. M Dehling (E), Hyperolius dartevellei, Carumbo, Angola, PEM A 10035, photo W. Conradie (F).