Hyperolius acuticeps Ahl, 1931

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 : 310-314

Hyperolius acuticeps Ahl, 1931

Sharp-headed Long Reed Frog ( Fig. 4 )

Genetic material. MCZ A-137085–86 (Chelinda Camp, Nyika Plateau, Malawi); ZMB 76103, 76107, 76109 (Chongoni Forest Reserve, Malawi); ZMB 76097–98 (Kaningina Forest Reserve, Malawi) ( Fig. 1 ).

Diagnosis. The illustrated advertisement call ( Fig. 5 ) has a duration of 0.22 s,

consisting of 25 pulses, with a slower pulse rate at the end. This differs from the brief single notes of H. adspersus , H. lupiroensis sp. nov., and the 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 . The structure of the call of H. jacobseni sp. nov. and H. nasutus is similar to that of H. acuticeps , but the former consists of only five pulses with a duration of 0.07 s, while the latter consists of eight pulses in 0.1 s. The call of H. dartevellei consists of 13 pulses in 0.1 s. See Table 3 for a summary of call parameters. The snout is sharply rounded in profile and from above, differing from the truncated snout of H. dartevellei and the sharp, shark-like profile of H. benguellensis , H. inyangae sp. nov. or the bluntly rounded snout profile of H. adspersus , H. igbettensis , H. jacobseni sp. nov. and H. poweri . Although the webbing is variable, a typical specimen has one phalanx of the fifth toe free, while the fourth toe is webbed with half to just more than the first phalanx free, and the third toe likewise. It can be distinguished from species with less than one phalanx of the fifth toe free, such as H. adspersus , H. friedemanni sp. nov., H. igbettensis , H. jacobseni sp. nov., H. lupiroensis sp. nov., H. poweri , H. rwandae sp. nov. and H. viridis . It differs from those species with more than one phalanx free; H. howelli sp. nov. and H. inyangae sp. nov. It differs from H. benguellensis which has webbing on the third toe extending to the disc, from H. nasutus which has webbing on the fourth toe reaching the disc, and from H. dartevellei which has half a phalanx of the fourth toe free.

Description of a Chelinda specimen. This description is based on a female MCZ A-137085 from Chelinda on Nyika Plateau. Body long and slender, widest at temporal region, slightly tapering to groin; head comparatively small (HL/SUL 0.33, HW/SUL 0.30), not wider than trunk, longer than wide (HL/HW 1.10)although slightly wider than long in specimen MCZ A-137086; snout long (SL/HL 0.43), pointed in dorsal view, acute in profile ( Fig. 6 ), considerably projecting beyond lower jaw, wider than long (SL/EE 0.72); canthus rostralis distinct, rounded, slightly concave from eye to nostril, concave near tip of snout; loreal region almost vertical, slightly concave; nostril directed laterally; situated much closer to tip of snout than to eye (EN/NS 1.43), separated from each other by distance less than distance between eye and nostril (NN/EN 0.9); eyes directed anterolaterally, moderately protruding, relatively small (ED/HL 0.26); eye diameter shorter than snout (ED/SL 0.61); interorbital distance as wide as upper eyelid (IO/EW 1.0), and greater than internarial distance (IO/NN 1.67); tympanum not visible externally; upper jaw with dentition; teeth on premaxilla larger than those on maxilla; choanae small, oval, located far anterolaterally at margins of roof of the mouth; vomer processes and teeth absent; tongue long 4.8, and wide (3.7 at widest point), free for about three-fourths of length, bifurcated distally for about one-fourth of length; median lingual process absent.

Dorsal surfaces of head, trunk and limbs smooth; ventral surface of limbs and gular smooth, chin and abdomen slightly more areolatet.

Fore limbs slender; hand moderately large (HND/SUL 0.27); tips of fingers enlarged into broad oval disks, each with circummarginal groove; relative length of fingers: I<II<IV<III; subarticular tubercles rounded, well developed, with one on fingers I and II, two on fingers III and IV, with proximal tubercle on finger IV hardly discernible; webbing formula of the hand I 1– 2 II 1–2.5 III 2– 1 IV (after Myers & Duellman [1982]); thenar tubercle indistinct, low; palmar tubercles absent; inner metacarpal tubercle small, rounded, outer metacarpal tubercle absent.

Hind limbs slender, moderately long (LEG/SUL 1.45); tibio-tarsal articulation reaching to level of tip of snout when legs are adpressed to body; tibiofibula moderately long (TFL/SUL 0.49), 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 0.82); relative length of toes: I<II<III<V<IV; discs of toes smaller than 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 1.5– 2 II 1– 2 III 1– 2 IV 2–1.5 V; inner metatarsal tubercle small, oval, prominent; outer one larger, almost circular, low and almost indistinct. Measurements of a second specimen from Chelinda MCZ A- 137086 are included in Appendix 2.

Colouration in preservative. The pattern elements that remain after the green has faded are a dark vertebral stripe made up of a single row of chromatophores, with pale lateral bands bordered by irregular dark spots, and a row of dark chromatophores forming a dorsolateral stripe. A male is illustrated in Fig. 4 .

Eggs and tadpoles. Unknown.

Distribution. This species is presently only confirmed from northern Malawi on the Nyika Plateau and Chongoni and Kaningina Forest Reserves, and the type locality in southern Tanzania.

Remarks. This study restricts the distribution of the species from the wide range presently attributed to it (Schiøtz et al. 2004), suggesting that its conservation status should be changed from Least Concern to Data Deficient, pending the collection of more data.

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 4. Hyperolius acuticeps Chongoni, Malawi, photo V. Mercurio (A); H. adspersus Bateka Nature Reserve, Gabon, photo G. Jongsma (B); H. benguellensis, Humpata, Angola, photo A. Channing (C); H. friedemanni sp. nov., Karonga, Malawi, photo V. Mercurio (D); H. howelli sp. nov. holotype, SAIAB 118979, Arusha, Tanzania, photo A. Channing (E); H. howelli sp. nov. female paratype, SAIAB 118980 - 1, Arusha, Tanzania, photo A. Channing (F).

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.