Hyperolius benguellensis (Bocage, 1893)

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 : 317-318

Hyperolius benguellensis (Bocage, 1893)

Benguella Long Reed Frog ( Fig. 4 )

Synonym. Hyperolius oxyrhynchus (Boulenger, 1901)

Genetic material. ZMB 77271–2, ZMB 77318 (Humpata, Angola); ZMB 77273–4 (Bicuar National Park, Angola); ZMB 77275 (Zootecnica Plateau, Humpata, Angola); AACRG 1030 (Kaparotta, Botswana); GenBank AF215224 , AF215442 (Rundu, Namibia) ( Fig. 1 ).

Diagnosis. The advertisement call ( Fig. 8 ) is a brief note consisting of five pulses, followed by 14 pulses at a slower rate, with a duration of 0.41 s. It can be distinguished from the brief calls consisting only of a single note, H. adspersus and H. lupiroensis sp. nov. and those consisting only of a series of pulses, H. acuticeps , H. jacobseni sp. nov., H. nasutus and H. dartevellei . The other species with advertisement calls consisting of an initial note followed by some discrete pulses can be distinguished either by their short duration, less than 0.2 s, as in H. friedemanni sp. nov., H. howelli sp. nov., H. igbettensis , H. poweri and H. rwandae sp. nov., or by the lower number of slow pulses, less than 10, as in H. inyangae and H. viridis . See Table 3 for a summary of call parameters. The snout is shark-like in profile, protruding forward of the mouth in a straight line, before forming a sharp tip. It can be distinguished from the truncated, sharply- or bluntly rounded snout profiles as in H. acuticeps , 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 .

Description of a Humpata specimen. Body long and slender, widest at mid-body, slightly tapering to groin; head comparatively small (HL/SUL 0.33, HW/SUL 0.30), not wider than trunk, longer than wide (HL/HW 1.11); snout long (SL/HL 0.42), bluntly rounded in dorsal view, acute, sharklike in profile ( Fig. 6 ), considerably projecting beyond lower jaw, wider than long (SL/EE 0.68); canthus rostralis distinct, moderately sharp, slightly concave from eye to just beyond nostril, slightly convex near tip of snout; loreal region almost vertical, slightly concave; nostril directed dorsolaterally; situated much closer to tip of snout than to eye (EN/NS 1.64), separated from each other by distance greater than distance between eye and nostril (NN/EN 1.11); eyes directed anterolaterally, moderately protruding, relatively small (ED/HL 0.33); eye diameter shorter than snout (ED/SL 0.78); interorbital distance much wider than upper eyelid (IO/EW 1.71), and greater than internarial distance (IO/ NN 2.1); 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 5.8, and narrow (2.7 at widest point), free for about three-fourths of length, bifurcated distally for about one-third of length; median lingual process absent; vocal sac single, median, subgular, mostly unpigmented and translucent when fully inflated; gular flap cream-coloured, granular; vocal sac aperture on each side of the mouth, situated lateral from and close to base of tongue, slit-like, long, directed posterolaterally.

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

Fore limbs slender; hand moderately large (HND/SUL 0.30); 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 2 –2.5 II 2– 3 III 2.5–2.5 IV (after Myers & Duellman [1982]); thenar tubercle absent; palmar tubercles absent; metacarpals without supernumerary tubercles; nuptial pads or asperities absent.

Hind limbs slender, moderately long (LEG/SUL 1.55); tibio-tarsal articulation reaching to level of snout tip when legs are adpressed to body; tibiofibula moderately long (TFL/SUL 0.53), shorter than thigh (TFL/THL 0.91); 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 0.83); 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– 1 II 0.75– 1 III 0– 1 IV 1– 1 V; inner metatarsal tubercle small, oval, prominent; outer one low, almost indistinct.

Colouration in life. Skin more or less translucent. Dorsum and dorsal surface of head and limbs dark green ( Fig 4 ); lateral sides of head and scapular region dark green; light, yellowish-white, moderately broad dorsolateral stripe running along each side of the body from snout tip, over the eye to vent; Pale paravertebral stripes originating on posterior of snout, diverging to level of eyes, and then running parallel to vent; small dark brown to black dots and on dorsum, most densely bordering both sides of dorsolateral stripes; distal portions of fingers and toes, especially the tips, yellow; ventral side and parts of dorsal side of thigh and upper arm largely unpigmented but with irregular dark spots, appearing bluish-green; peritoneum white, shining through the translucent belly skin. Iris reddish-brown. Colouration in preservative. All colours have faded to yellow; gular flap whitish-yellow.

Variation. The female ZMB 77271 is similar to the male in measurements (Appendix 2). The female is larger than the male (SUL 23.5). Colouration is variable; ZMB 77271 has a pale green dorsum with irregular darker marks, and yellow eyelids, with fingers and toes also yellow, and a white underside. AC 3073 has pale dorsolateral stripes on a dark green background.

Eggs and tadpoles. Unknown.

Habitat. We found the species only in open grassy habitats, along stream banks and man-made impoundments where sedges and other tall emergent vegetation were present (Humpata, Bicuar NP). Specimens were observed on leaves and stems of vegetation between 5 cm and 1.0 m above water level. Males called from elevated positions. The following species were found sympatrically or even syntopically with the new species: Hyperolius marmoratus and Xenopus laevis .

Remarks. The species is confirmed using molecular data from Rundu in the Caprivi Strip of Namibia, northern Botswana, and southern Angola.

The type locality of H. benguellensis is Caota, Angola. The type series (MBL 17.220-223; now Museu Bocage, National Museum of Natural History, University of Lisbon) has been destroyed (Frost 2011).

Our specimens agree with the original description of a sharp snout and small dorsal speckles. The specimens from Humpata show a range of colour patterns, from a uniform finely spotted dorsum, to pale dorsolateral stripes, to dorsolateral and paravertebral stripes. This variation was absent from the type description. The genetic material is from the same drainage basin as the type. Hyperolius oxyrhynchus is regarded as a synonym as the type description matches this species. The species is presently only confirmed from southern Angola, northern Namibia, and northern Botswana. We suggest that the conservation status Least Concern be maintained.

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 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 8. Advertisement calls of H. benguellensis Humpata (left) and H. friedemanni Karonga (right).