Petropedetes palmipes Boulenger 1905

Petropedetes palmipes Boulenger, 1905

Figs. 3 d, 4, 8d, 9d, 16

Petropedetes palmipes Boulenger, 1905, Ann. Mag. Nat. Hist., Ser. 7, 15: 282

Material examined. IRSNB-KBIN 13.840 (male), Gabon, Estuaire Province, Kango Department, 15 km north of Alen-Nkoma, right of route L107, 2004, coll. O.S.G. Pauwels; IRSNB-KBIN 14.936 (female), 14.937-14.939 (3 males), Gabon, Kinguélé, app. 80 m a.s.l., VI.2001, coll. O.S.G. Pauwels; IRSNB-KBIN 14.940 (male), Gabon, Province du Woleu-Ntem, Song, app. 360 m a.s.l., 25.VI.2001, coll. O.S.G. Pauwels; MHNG 961.68 (male), Cameroon, Mbikiliki, 18.I.1956, coll. J.-L. Perret; MHNG 1033.28-31 (4 males), 1033.32-33 (2 females), Cameroon, Mbikiliki, 1959, coll. J.-L. Perret; MHNG 1033.49-50 (2 males), 1033.51-52 (2 females), Cameroon, Bipindi, Abiete, 1969, coll. J.-L. Perret; ZFMK 28942 (female), Cameroon, Kribi, Efulen, 1906, coll. G.L. Rosenberg; ZFMK 73210-211 (2 females), Gabon, 18 km northeast of Barrage de Kinguélé, app. 165 m a.s.l., 25.-27.I.2000, coll. S. Lötters & V. Gossmann; ZMB 73891 Gabon (male), Province du Woleu-Ntem, Tchimbélé, app. 469 m a.s.l., 08.VI.2001, coll. O.S.G. Pauwels.

Diagnosis. Medium to large-sized Petropedetes; robust body shape; tympanum indistinct; breeding males without tympanic papilla; moderate forearm hypertrophy; carpal spike present; spinosities developed on whole body; moderate femoral glands prominent; toes fully webbed.

Description. Medium to large-sized Petropedetes with robust body; females growing slightly larger than males (SUL in males: 40.3–57.8 mm, in females: 37.5–54.7 mm); mean head width in males about 41% of SUL, in females about 37%; snout more pointed than in other species; canthus rostralis distinct but rounded, loreal region concave; eye diameter about 1.7 times eye-narial distance; nose closer to snout tip than eye; tympanum very small and indistinct (tympanum / eye in males: 0.18–0.23, in females: 0.20–0.25); no tympanic papilla; supratympanic fold distinct; fingers slender, with typically T-shaped fingertips; relative length of fingers: III> IV> II> I; manual subarticular tubercles single; manual webbing absent; palmar tubercle and thenar tubercle present, palmar tubercle sometimes indistinct; forearm hypertrophy moderately developed in males; carpal spike present in males; spinosities on whole body; dorsal surfaces with heterogeneous skin structure, some larger warts on flank and back, otherwise skin texture on flanks and dorsum similar (Fig. 8 d); ventral skin more granular than in other species; mean femur length in males 53% of SUL, in females 51%, mean tibia length in males 58% of SUL, in females 57%; mean foot length in males 73% of SUL, in females 72%; upper hind limbs of moderate size, lower hind limbs slender; femoral glands larger in males than in females (femoral gland / femur length in males: 0.26–0.38, in females: 0.22–0.31; Fig. 9 d); relative length of toes: IV> III> V> II> I; toes fully webbed, on 4th toe sometimes slightly less developed 4 (0.5-0.5).

Coloration. Dorsum uniformly dark; green and black with very few minuscule pale spots; throat whitish or dark marbled; upper hind limbs with pale, thin cross bars; coloration in preservation as in life, but pale. According to Lamotte et al. (1959) adults are of a glossy black colour in life, and therefore hard to find between stones. Boulenger (1905) describes them as dark olive above, spotted or marbled dark and light. Limbs bear broad dark bands and narrow light cross-bars, the ventral side is dirty whitish (Boulenger 1905).

Tadpole. Lamotte et al. (1959) describe the tadpoles of P. palmipes. Tadpoles were found in high numbers in small rocky pools at the foot of rapids. The general coloration of the tadpoles is grey on dorsum and flanks, a duller colour around eyes and nostrils; venter translucent, intestinal tract being visible (Fig. 3 d); overall body shape flat; large eyes situated in the first third of body; tail almost twice as long as body and tail tip pointed; jaw sheats small, narrow and serrated; keratodont formula in younger stages 4:3+3//1+1:5, in older ones 3+3//1+1:2 (Fig. 3 d). More developed tadpoles are darker than younger stages. Tadpoles do not exceed a total length of 35 mm (25 mm being tail; Lamotte et al. 1959).

Natural history. Very little data on the biology of this species has been published. Specimens were caught at night in primary forest among stones in a stream. Clutches were found glued to rocks (Fig. 16). Gossmann et al. (2002) explains that both eggs and larvae occur on submerged rocks. Lamotte et al. (1959) find tadpoles of P. palmipes in stagnant parts of rivers beneath small rapids. Schiøtz (1966) describes similarities in the morphology of advanced larval stages of P. palmipes and P. cameronensis, possessing identical teeth formulae. Schiøtz (1966) interprets the different tadpole mouth development as a change in biology, younger larvae being rheophilous and older ones semiterrestrial, scraping algae off stones. The full webbing of adults points to a more aquatic life history, at least in post-metamorphs. The call of P. palmipes is not known (Amiet 1989).

Distribution. Petropedetes palmipes occurs mainly in lowland areas (Fig. 4). It has been found in southern Cameroon (Perret 1966), in Equatorial Guinea (de la Riva 1994; Lasso et al. 2002) and Gabon (Lötters et al. 2001; Pauwels & Rödel 2007). The P. p a l m i p e s record from western Cameroon by Perret & Mertens (1957) is based on a P. perreti specimen (not known at that time).

Genetics. The genetic comparison for the uncorrected p-distances of the mitochondrial 16S rRNAfragment (Table 4) gave the following results for the single genetic voucher of Petropedetes palmipes which we could use for this gentic comparison: interspecific differences to P. palmipes and all other Central African Petropedetes taxa ranged between 7.80%-11.76%.

Systematic remarks. Petropedetes palmipes is one of two fully webbed Central African Petropedetes species; the other one being P. p e r re t i. By the amount of webbing it can easily be differentiated from the halfwebbed species P. cameronensis and P. juliawurstnerae sp. nov. and the rudimentary-webbed species P. euskircheni sp. nov., P. johnstoni, P. parkeri and P. vulpiae sp. nov. P. palmipes can be easily distinguished from the fully webbed species P. perreti by the size of the tympanum, which is very small and rather indistinct in both sexes of P. palmipes, while it is large and distinct in P. perreti (Figs. 8 a, 8d). In addition breeding males of P. p e r re t i possess a tympanic papilla, which is lacking in P. palmipes.