Conraua sagyimase, NEIRA-SALAMEA, KARLA, OFORI-BOATENG, CALEB, KOUAMÉ, N’GORAN G., BLACKBURN, DAVID C., SEGNIAGBETO, GABRIEL H., HILLERS, ANNIKA, BAREJ, MICHAEL F., LEACHÉ, ADAM D. & RÖDEL, MARK-OLIVER, 2021

NEIRA-SALAMEA, KARLA, OFORI-BOATENG, CALEB, KOUAMÉ, N’GORAN G., BLACKBURN, DAVID C., SEGNIAGBETO, GABRIEL H., HILLERS, ANNIKA, BAREJ, MICHAEL F., LEACHÉ, ADAM D. & RÖDEL, MARK-OLIVER, 2021, A new critically endangered slippery frog (Amphibia, Conrauidae, Conraua) from the Atewa Range, central Ghana, Zootaxa 4995 (1), pp. 71-95 : 80-89

Conraua sagyimase sp. nov.

Figs. 4-7

Holotype. UWBM: Herp 5839 (field #: ADL 3858 , GenBank #: 16S: MT 669421 , DISP2 : MT 669442 , FICD: MT 669459 , KIAA2013 : MT 669477 , POMC: MT 669511 , SPEN: MT 669573 , SVEP: MT 669590 , TYR: MT 669624 ), adult male, Ghana, Eastern Region, Atewa Range Forest Reserve , 06º13’57.79” N, 0º33’07.08” W, 633 m asl; 11 May 2011, leg. Adam D. Leaché. & Caleb Ofori-Boateng.

Paratypes. Four females, one male, two subadults; all from Atewa Range Forest , Ghana ; ZMB 91136 (field #: JP 0041.1 ), adult female, Asiakwa South, 06º15’44.3” N, 0º33’18.8” W, 783 m asl, 11–16 June 2006, leg. N’goran Germain Kouamé & Caleb Ofori-Boateng ; ZMB 91137–91138 (field #: JP 0041.2 – 3 ), adult females, Asiakwa North, 06º16’16.1” N, 0º33’52.7” W, 814 m asl, 17–22 June 2006, leg. N’goran Germain Kouamé & Caleb Ofori-Boateng ; UWBM: Herp 5840 (field #: ADL 3859 ), adult male , UWBM: Herp 5841 (field #: ADL 3860 ), adult female , UWBM: Herp 5842 (field #: ADL 3861 ), subadult , UWBM: Herp 5843 (field #: ADL 3862 ), subadult, 25 May 2011, other data as holotype .

Diagnosis. The new species generally resembles other members of the genus Conraua Nieden, 1908 . Conraua sagyimase sp. nov. is the smallest species of its genus and a mid-sized (SVL of adults: 53–89 mm) aquatic frog, relative to other frog species (see Womack & Bell 2020). It has smooth dorsal skin, covered with scattered small, rounded warts; skin on belly smooth; large and protruding eyes, positioned latero-dorsally; three odontoid projections on lower jaw, one on the symphysis and one on each side of the central one on the dentary; fully webbed feet, i.e., webbing extends to the end of the last phalange of toe, disc remaining free of web.

Conraua sagyimase sp. nov. differs in the 16S sequences at least by 4% from other species in the genus, and its closest relative is C. derooi (see above and Blackburn et al. 2020). Adult body size varies substantially across species of Conraua (numbers reported are maximum values): Conraua sagyimase sp. nov. (females SVL = 66.7 mm, males SVL = 71.9 mm) is smaller than C. derooi (females 98 mm, males 100 mm), C. robusta (females 122 mm, males 140 mm), C. goliath (females 220 mm, males 340 mm), and C. beccarii (155 mm). The new species is similar in size to populations of the C. alleni (females 86.6 mm, males 91.9 mm) and C. crassipes (females 76 mm, males 81 mm) (see Channing & Rödel 2019). Conraua sagyimase sp. nov. can be distinguished from C. goliath by a more rounded snout (pointed in C. goliath ), the absence of short dorsal skin ridges (present in C. goliath ), a creamy venter with brown mottling (yellow venter in C. goliath ), by relatively larger odontoid projections on the lower jaw, the presence of a lateral line system (absent in C. goliath ), and an indistinct tympanum (distinct in C. goliath ). Conraua sagyimase sp. nov. differs from C. crassipes by a cream-colored belly with brown mottling (white or cream in C. crassipes ), an indistinct tympanum (distinct in C. crassipes ), the presence of a lateral line system (absent in C. crassipes ) and lacking a dermal fold near the elbow (present in C. crassipes ). Conraua sagyimase sp. nov. differs from C. beccarii by the absence of a transverse fold behind the eyes and across the interorbital region (present in C. beccarii ), and in having a head that is as wide as long (wider than long in C. beccarii ; adult C. beccarii males develop an extremely wide and flat skull, see Lamotte & Perret 1968, Largen & Spawls 2010, Paluh et al. 2020). Conraua sagyimase sp. nov. differs from C. robusta by having a head that is as wide as long (wider than long in C. robusta ; see Lamotte & Perret 1968), having non-expanded finger tips (slightly expanded in C. robusta ), and the presence of a lateral line system (absent in C. robusta ). Conraua sagyimase sp. nov. differs from individuals of C. alleni sensu lato by having a wider lateral dermal fringing along edges of fingers (narrower fringes in C. alleni sensu lato), and large and oval toe discs (small and rounded in C. alleni sensu lato). Finally, Conraua sagyimase sp. nov. differs from C. derooi by having a slimmer body and limbs (more robust body and limbs in C. derooi ), a slightly curved supratympanic fold (distinctly curved in C. derooi ), two subarticular tubercles on finger III (one in C. derooi ) and lacking a swollen postoccipital and suprascapular region in adult males (swollen in C. derooi ; Fig. 1a ).

Description of the holotype ( Figs. 4–5 ; measurements in mm). Adult male; slightly dorsoventrally flattened, short and rounded body; snout rounded in dorsal view, rounded in lateral view, with upper lip slightly projecting forward; SVL 71.9; head width 26.7, approximately equal to head length 25.6; head length 36% of SVL; snout length 7.9, 31% of head length; eye–nostril distance 4.6; eye–snout distance 9.0; internarial distance 5.2, slightly larger than interorbital distance; nostrils protuberant, directed dorsolaterally, visible in lateral and dorsal view; large protruding eyes, projecting laterally beyond margins of head in dorsal view; eyes projecting above dorsal margin of head in lateral view; eye diameter 8.1, twice as large as horizontal diameter of tympanum 3.9; upper eyelid width 5.7, 114% of interorbital distance; eye–tympanum distance 2.5; tympanum indistinct; interorbital distance 5.0, 62% of eye diameter; canthus rostralis distinct and rounded; loreal region concave; slightly curved supratympanic fold extending from posterior edge of eye to shoulder; upper lip slightly protruding; vocal sacs absent; premaxillary and maxillary teeth are slender and pointed, teeth are long and short in premaxilla and short in maxilla, three odontoid projections on lower jaw, one at symphysis and one to each side on dentaries.

Forelimbs moderately robust; forearm length 12.7, 73% of hand length, 17.4; outer and middle palmar tubercles barely visible, smaller than inner palmar tubercle; supernumerary tubercles absent; one subarticular tubercle on fingers I, II, two subarticular tubercles on fingers III and IV; subarticular tubercles absent on the base of fingers, tips of fingers non-expanded, rounded; lateral dermal fringing along edges of fingers, wider on finger III; relative length of fingers: III>IV>II≈I,, finger III length 11.1; no webbing between fingers.

Hind limbs moderately robust; crus length 32.4, 45% of SVL; foot including longest toe 43.4, 60% of SVL; elongated, prominent oval inner metatarsal tubercle; outer metatarsal tubercle absent; supernumerary plantar tubercles absent; subarticular basal tubercles absent; subarticular penultimate tubercles prominent, ovoid in dorsal view; subarticular distal tubercles present in toes III, IV and V; toe tips with large oval discs; relative lengths of toes: VI>III>V>II>I, toe IV length 26.7; webbing complete, i.e., to the end of the last phalanx of toe; dermal fringing on outer surfaces of toe I and V forming lateral skin folds.

Skin texture on dorsal parts of head, body, flanks, and limbs smooth with scattered, small, rounded warts; inner surface of upper arm smooth; dorsal surface of crus with 17 rows of longitudinal ridges; ventral skin smooth, throat with longitudinal folds; a post-gular (thoracic) fold extending to level of forelimbs insertion; tarsal fold distinct. The lateral line system comprises a jugular line, upper lateral line, lower lateral line, median lateral line, and caudal lateral line, all distinct; an infra-orbital line, and a supra-orbital line are present but indistinct.

Coloration in preservative (after nine years in 75% ethanol). Dorsum brown with dark-brown spots and scattered small cream warts; abundant cream spots on dorsolateral surface, flanks, and shoulders; lateral surface of lips cream with brown spots, tip of snout mottled cream with brown; cream spots on interorbital region, shaping diffuse interorbital stripe; nostrils cream. Dorsal surface of arms and legs cream with brown spots; longitudinal ridges on legs cream; dorsal surface of fingers I and II cream; fingers III and IV mottled cream with brown; throat cream mottled in brown; belly cream with brown mottling on anterior part, cream on posterior part; ventral surface of hands brown, edges of fingers cream; ventral surface of legs, feet and toes cream with almost imperceptible mottled brown; toe IV and V with brown spots; discs brown; area surrounding cloaca brown with many cream warts.

Variation. Overall the paratypes are similar to the holotype in external appearance and coloration (see Table A1). Size ( SVL) of adult females ranges from 53.4–66.7 mm, thus being smaller than male SVL, ranging from 57.0– 71.9 mm. Additional field measures of 49 individuals, with unidentified age and sex, revealed a maximum SVL of 89 mm (range: 52–89 mm; x ± sd: 65.9 ± 10.5 mm). The color of dorsal surfaces varied from predominantly brown ( UWBM:Herp 5839) to dark brown ( UWBM:Herp 5841), with many dark spots ( UWBM:Herp 5840, 5841; ZMB 91136).All paratypes exhibited more dark spots and fewer cream dots on dorsum than the holotype. Some specimens exhibit a continuous and straight interorbital stripe ( UWBM:Herp 5840–5843; ZMB 91136), in other specimens the interorbital line was composed of many light spots ( UWBM:Herp 5839; ZMB 91137) and not perfectly straight. In some specimens the tympanum was distinct ( UWBM:Herp 5841, 5842), in others it was hidden and only visible under particular illumination ( UWBM:Herp 5839, 5840, 5843; ZMB 91136, 91137 ). This variation is probably due to preservation differences. Throat pigmentation varies among specimens, some ( ZMB 91136, 91137 ; UWBM:Herp 5841) have dark pigmentation and others are lighter; however, all specimens exhibited some throat pigmentation. The belly was generally uniform cream ( UWBM:Herp 5840–5843); however, two specimens ( ZMB 91136, 91137 ) exhibit darker pigmentation, and the holotype ( UWBM:Herp 5839) showed a slightly mottled brown .

The presence of vomerine teeth and shape of tongue was not possible to examine in the holotype without breaking the mandibles. However, we could check for these characters in two paratypes. ZMB 91136 and ZMB 91137 possess pointed vomerine teeth, and a tongue that bifurcates into rounding lobes, separated by a wide U-shaped indentation. The tongue is attached to the floor of the mouth along its anterior third. Compared to the holotype the lateral line system was more distinct in some paratypes ( UWBM:Herp 5841, ZMB 91136, ZMB 91137) .

Life coloration (based on photos of uncollected individuals, Figs. 6–7 ). Dorsum light to dark brown with light spots and scattered cream warts; lips with same coloration as dorsum or lighter; flanks light to dark brown with lighter mottling; dorsal surfaces of arms and legs with scattered cream warts; rows of parallel longitudinal ridges on legs cream, lighter than body; iris gold; throat cream, mottled in brown; belly cream with brown mottling; ventral surfaces of legs and feet brown with cream mottling; ventral surface of hands brown; edges of fingers cream; ventral surface of toes brown.

Acoustics. The advertisement of Conraua sagyimase sp. nov. consist of a whistle-like tonal call with ascending frequency modulation 0.69 – 1.38 kHz (mean ± sd, 0.92 ± 0.4 kHz, N = 3; Fig. 3 ). The call has a duration of 0.42 – 0.58 seconds (mean ± sd, 0.5 ± 0.08 s, N = 3). Dominant frequency ranges from 2.24 – 2.58 kHz (mean ± sd, 2.47 ± 0.2 kHz, N = 3), minimum frequency 1.12 – 1.66 kHz (mean ± sd, 1.47 ± 0.31 kHz, N = 3) kHz, and maximum frequency 3.16 – 3.48 kHz (mean ± sd, 3.36 ± 0.17 kHz, N = 3). The bandwidth 90% ranges from 0.69 – 0.86 kHz, (mean ± sd, 0.75 ± 0.1 kHz, N = 3) ( Fig. 3 ). Call parameters are summarized in Table 3.

Range. Conraua sagyimase sp. nov. is so far known from only five streams in the northern part of the Atewa Range Forest Reserve in eastern Ghana ( Fig. 8 ). However, we suppose that populations may also exist in the southern part of the Atewa Range Forest Reserve. Lowland forest areas in Ghana west of Atewa are inhabited by Conraua alleni senso lato, the region east of the Volta River is inhabited by C. derooi . We thus assume that the new species is endemic to the Atewa Range.

Life history. The new species occupies relatively pristine upland evergreen forest habitats within an elevation range of ~ 500–750 m asl. The frogs occur in rocky, clear, generally fast-flowing streams and waterfalls, although some individuals have been recorded in slow-flowing streams. Stream widths range from one meter to over six meters ( Figs. 9–10 ).

Conraua sagyimase sp. nov. is highly aquatic, spending over 95% of the time in water.Some individuals however, have been found at the banks of streams both day and night. One individual was recorded nine meters away from the nearest stream. Along the streams, individuals perch on logs, rocks, sand, and in some cases on artificial drainage systems such as culverts. Although usually solitary and patchily distributed, adult frogs occasionally congregate in small but deep pools (> 2 m) within streams, probably for feeding or mating. Habitat preferences are probably related to prey availability (as prey may also be specialized to these habitats) or microclimatic conditions, but this requires further investigation. Tadpoles have usually been found in shallow pools within streams, co-existing sometimes with tiny fishes. We have found higher number of frogs in streams bordered by large trees (diameter at breast height> 20 cm), and dense canopy coverage (> 70%), but we have also recorded individuals in streams with overgrown bushes, suggesting the species could thrive in moderately degraded habitats.

In a recent population assessment in two streams (COB, unpubl. data), 433 individuals were marked over approximately 5 km river lengths. Most streams did not have enough individuals to make estimates of population feasible based on mark-recapture techniques. Based on the field counts we assume that more than 1000 individuals could occur throughout the Atewa Hills Forest Reserve.

The female paratypes contain large ovarian eggs with a diameter of 1.5 mm ( ZMB 91136), 3.2 mm ( ZMB 91137) and 2.5 mm ( ZMB 91136). The eggs have a yellowish and dark pole. We assume deposition of aquatic eggs .

Threat status. The new species, although not yet officially assessed for the IUCN Red List, should be regarded as Critically Endangered (CR), compare discussion and IUCN (2012).

Etymology. The name of the new species has been chosen in order to honor the people of the Sagyimase community. This small community has supported the research of COB and the anti-mining campaigns during the early 2006–2007. We hope that the naming of this endemic species will further encourage this community in their fight for an intact Atewa Range. The species epithet is used as an invariable noun in apposition to the generic name. As English common name, we suggest Atewa Slippery Frog, and as Akan common name we suggest kwaeɛ mu nsutene apɔnkyerɛne, meaning the frog of the forest streams.

Figures

FIGURE 1. Conraua derooi from the type locality Misahöhe, Togo (a – c) and Biakpa in the Volta area (d), Ghana; a: adult male, note bulging neck and posterior part of head, b & c: adult females; d: half-grown specimen. Specimens not collected.

FIGURE 3. a) Spectrogram and oscillogram of advertisement call of male Conraua sagyimase sp. nov. from Atewa Range Forest, individual not collected (call 1); b) Spectrogram and oscillogram of advertisement call of male Conraua derooi from Biakpa, Ghana, individual not collected. FFT = 256 points.

FIGURE 4. Conraua sagyimase sp. nov., male holotype (UWBM:Herp 5839) in lateral, dorsal, and ventral view. Scale = distance between two small strokes: 1 mm.

FIGURE 5. Conraua sagyimase sp. nov. male holotype (UWBM:Herp 5839) ventral views of throat and arms, right hand; and right foot. Scale = distance between two small strokes: 1 mm.

FIGURE 6. Four individuals of Conraua sagyimase sp. nov. from the Atewa Range Forest Reserve, southern Ghana (a: photo by Piotr Naskrecki); specimens not collected.

FIGURE 7. Conraua sagyimase sp. nov. from the Atewa Range Forest Reserve, southern Ghana (photos by Alan Channing); specimen not collected.

FIGURE 8. Inset shows a map of West Africa showing the location of the Atewa Range in Ghana (upper left), known localities of Conraua sagyimase sp. nov. are shown in red and know localities of Conraua derooi in yellow. Stars indicate type localities. Altitudinal range is indicated with shading from lowlands (light) to high elevation (dark). Sources: OpenStreetMap (2020), U.S. Geological Survey (2020).

FIGURE 9. Habitat from Conraua sagyimase sp. nov. in the Atewa Range Forest Reserve (a–b), southern Ghana (photos: courtesy of Piotr Naskrecki); and type locality of Conraua derooi, Misahöhe, Togo (c–d).

FIGURE 10. Habitat from Conraua sagyimase sp. nov. in the Atewa Range Forest Reserve, southern Ghana.