Bioacoustics of Afrixalus lacustris

Description of holotype . Measurements of the holotype are provided in Table 2 . Body very slender, widest at temporal region, slightly tapering to groin ( Fig. 8D–F ); head small (HL/SVL 0.31, HW/SVL 0.31), about as long as wide (HW/HL 0.99); snout relatively long, rounded in dorsal view and in lateral profile, slightly wider than long; canthus rostralis hardly discernible, slightly concave between eye and nostril in dorsal view; loreal region oblique; nostrils rounded, directed anterolaterally and slightly dorsally; situated much closer to tip of snout and to eye, separated from each other by distance about equal to distance between eye and nostril (IN/EN 1.02); eye directed anterolaterally, strongly protruding, very large (ED/HL 0.39), its diameter shorter than snout (ED/SL 0.90); interorbital distance much wider than upper eyelid (IO/EW 1.61) and wider than internarial distance (IO/IN 1.31); tympanum covered by skin, not visible externally; upper jaw with dentition; teeth on premaxilla larger than teeth on maxilla; choanae small, located far anterolaterally at margins of roof of mouth, its anterior edge covered by maxillary bone, therefore appearing semicircular in ventral view; vomer ridges and teeth absent; tongue heartshaped, longer than broad, bilobed for about one-fourth of its length, free distally for about two-thirds its length; densely covered with minute papillae; median lingual process absent. Dorsal surfaces of head, trunk, and limbs and lateral surfaces of trunk finely shagreened; tiny pointed, widely scattered tubercles on dorsum, more numerous posteriorly than anteriorly; supratympanic fold absent; few tubercles at rear end of mandible without pointed tips; ventral side of head smooth; vocal sac present; gular gland of vocal sac smooth, large and wide, covering about 70 percent of throat width ( Fig. 8E ); chest smooth, abdomen weakly areolate; ventral side of limbs smooth; short transverse fold above vent. Forelimbs slender; hand large (HaL/SVL 0.28); tips of fingers enlarged into large disks, each with circummarginal groove; relative length of fingers: I <II <IV <III; subarticular tubercles well developed, numbering one on Fingers I and II, two on Fingers III and IV, proximal tubercles on Fingers III and IV and tubercles on Fingers I and II singular, rounded; distal tubercles on Fingers III and IV indistinctly bipartite; webbing formula of the hand I 2-/2 II 2-/3- III 2.25/2 IV ; thenar tubercle oval, small and very low, about one-fourth length of metacarpal of Finger I; inner palmar tubercle and outer palmar tubercle very low, small, rounded, almost indiscernible. Hind limbs slender, moderately long; heel reaching to level of eye when legs adpressed forwardly to body; crus moderately long (TibL/SVL 0.44), slightly shorter than thigh; heels not touching each other when knees flexed and thighs held perpendicularly to median plane; foot subequal in length to crus (FoL/TibL 0.94); relative length of toes: I <II <III <V <IV; toe tips rounded, enlarged into large disks, each with circummarginal groove; subarticular tubercles singular, numbering one on Toes I and II, two on Toes III and V, and three on Toe IV; pedal webbing formula I 1.5/2+ II 1+/2+ III 1+/2+ IV 2/1+ V ( Fig. 8E ); inner metatarsal tubercle moderately prominent, elongated, about half length of metatarsus of Toe I; outer metatarsal tubercle small, rounded. Coloration in life. During night, skin on dorsal side of head, trunk, forelimbs, crus and tarsus light brown with more or less regular, locally more densely clustered dark brown speckling; distinct dark brown transverse stripe between upper eyelids, another less distinct one in scapula region, and another narrow one at level of anterior end of pelvis; dorsal skin of thigh largely unpigmented with only a broad stripe of widely scattered brown pigmentation; distinct dark brown band along canthus, continuing behind eye on both sides of trunk to level of pelvis; tubercles below eye and in tympanic region at rear end of jaw white; dark brown stripe running diagonally on middle of tibia, forming interrupted, inverted U-shaped band together with pelvic spots when legs folded against body; skin of ventral side of head, trunk and limbs largely unpigmented and translucent; gular gland bright yellow; fingers and toes yellow ( Fig. 12 ). During day, basic dorsal coloration light brown; dark brown dorsal speckles, spots and stripes in more pronounced contrast to basic coloration, more distinctly visible. Coloration in preservative. Dorsal basic coloration largely faded to light brown; darker dorsal pattern elements dark brown, clearly visible; color of gular gland, fingers and toes faded to white ( Fig. 8D–F ). Variation. The paratypes match the holotype in general appearance and proportions. Coloration and color pattern varies from light-cream to yellowish-orange with a few relatively large and darker blotches and vermiculation, light speckling and indistinct dorsolateral stripe to an almost reticulated pattern of contrasting bright and dark elements with a broad and conspicuous brown dorsolateral band ( Fig. 12 ). Pedal webbing variation is I 1.5[100]/2+[100] II 1+[100]/2+[100] III 1 +[50],1.25[50]/2+[100] IV 2 [100]/1+[100] V . Bioacoustics. The advertisement call and other vocalizations are unknown.

Ecology and natural history. We collected males and females in swamps in forest openings and near forest edges ( Fig. 11B ), from vegetation at the edge of streams (or on vegetation overhanging them) in forest, and from non-forest vegetation near the shore of Lake Tanganyika. Egg deposition has not been observed and tadpoles are unknown. An adult male (CAS 256035) was found in Bwindi Impenetrable National Park ( Uganda ) ca. 2 m above ground in a tree fern “either calling or moving to a calling site (similar to ‘running’ of Kassina )” (D. Blackburn, in litt., 22 July 2021 ). Laurent (1955) noted the species from transitional forest. In his paper on amphibians of Virunga National Park, Laurent (1972) noted the species is most commonly found in swamps with herbaceous vegetation in secondary forest, and more rarely, in primary forest. Laurent (1982) noted that, in general, the species is common in the foliage of shrubs in dense forests. He also recorded it from “une mare sombre” (i.e., a dark pond) in syntopy with Chiromantis at Kitutu ( DRC ), marshes where it reproduces by sticking its eggs under the leaves of fountain grass ( Pennisetum , Shabunda , DRC ), a shaded bank of a pond in syntopy with Hyperolius “ tuberculatus ” (likely H . hutsebauti sensu Bell et al . 2017 ) and H . frontalis ; the center of this pond had reeds harboring H . kivuensis and Afrixalus orophilus (Shabunda, DRC ). Laurent (1983:352) listed the species (along with Phrynobatrachus petropedetoides and Hyperolius frontalis ) from “shadowy puddles of the thick transition forest.”