Amnirana fonensis, (Rodel & Bangoura, 2004)

Griesbaum, Frederic, Jongsma, Gregory F. M., Penner, Johannes, Kouamé, N’Goran Germain, Doumbia, Joseph, Gonwouo, Nono L., Hillers, Annika, Glos, Julian, Blackburn, David C. & Rödel, Mark-Oliver, 2023, The smallest of its kind: Description of a new cryptic Amnirana species (Amphibia, Anura, Ranidae) from West African rainforests, Zootaxa 5254 (3), pp. 301-339 : 319-322

Redescription of A. fonensis ( Rödel & Bangoura, 2004)

Figs. 12–14

Holotype. SMNS 11788 , adult male, Guinea, Simandou Range , northwest flank of Pic de Fon, 8°36′N, 8°51′W; 6 November 2002, leg. M.A. Bangoura.

Paratypes. SMNS 11790 , adult male, Guinea, Simandou Range , village situated to the northwest of Pic de Fon, 3 November 2002, leg. M.A. Bangoura ; ZFMK 64481–64482 , adult males, Guinea, Park National du Haut Niger, November 1996 – February 1997, leg. G. Nikolaus.

Referenced specimens. Six males, one female; ZMB 79185 (field #: TI 60 , GenBank #: 16S: MG552336 ), adult female, Sierra Leone, Tingi Hills, 8°52′2.1″N, 10°47′32.1612″W, 4 June 2007, leg. J. Johnny & A. Hillers ; ZMB 79203 & 84733 (field #: SI 032–033, GenBank #: 16S: MG552334 & MG552340 ), two adult males, Guinea, Korombadou, 9°16′49.62″N, 9°6′ 52.0812″W, 5 October 2008, leg. J. Doumbia & A. Hillers ; ZMB 79208 (field #: TI 020 , GenBank #: 16S: MG552335 ), adult male, Sierra Leone, Tingi Hills, 8°53′25.44″N, 10°47′24.7812″W, 1 June 2007, leg. J. Johnny & A. Hillers ; ZMB 90058 (field #: N044, 09-609), adult male, Guinea, N’Zérékore , 7°35′33.3″N, 8°28′5.4″W, 24 October 2009, leg. J. Doumbia, L. Sandberger, K. Camara & F. Gbêmou ; ZMB 90158 (field #: LI10 088), adult male, Liberia, Tokadeh , 7°26′40.704″N, 8°39′27.972″W; 22 November 2010, leg. J. Penner & N.L. Gonwouo ; ZMB 90160 (field #: PG.L. 15/041), adult male, Ivory Coast, 7°0′15.1488″N, 5°34′37.0344″W, 7 May 2015, leg. J. Penner & N.L. Gonwouo.

For diagnostic differences to A. parva sp. nov., please see the diagnosis of the new species above.

Description (based on the type series and seven additional specimens; measurements in mm, see Table 5). Medium-sized, slender frog, SVL of males range from 48.7 to 65.3 (mean ± sd: 57.2 ± 5.2, N= 10); a female measured 68.0; head slightly longer than broad, approximately one third of SVL; snout acuminate with rounded tip in dorsal view, narrowly rounded in lateral view; tympanum diameter around 85% of eye diameter, in two type specimens (SMNS 11788 & 11790) tympanum slightly larger than eye; inter-orbital distance slightly smaller than eye diameter; nostril closer to snout than to eye; canthus rostralis distinct and rounded; loreal region concave; dorsolateral ridge broad and protruding, only two male individuals show slight discontinuities in the posterior third of the ridge; males with large humeral glands on anterocraniad part of upper arms; area of humeral gland spans between 13.5–26.4 mm 2 (20.5 ± 4.86, N= 10); fingers long and thin, without webbing; tips rounded, forming small discs; finger formula: II<I<IV<III; large nuptial pads on anteroventral surface of first finger; hind limbs slender and long; thigh length approximately half SVL; crus slightly more than half of SVL; foot length including longest toe around 75% of SVL; single inner metatarsal tubercle large and elongated; single outer metatarsal tubercle small and round; toes long and slender, tips only marginally broader than subarticular tubercles; toe formula I<II<V<III<IV; webbing formula in males: I(0) II(1-0) III(1-0) IV(2-1) V(0), and for one female: I(0) II(1-0) III(1-0) IV(1-1) V(0); dorsal skin with pronounced tubercles, spiny in male type specimens, less spiny and less conspicuous tubercles in other males; tubercles largest in center of dorsum, getting smaller and more flattened towards head and groin; dorsal tubercles in female much flatter and not spiny ( Figs. 12b , 13e, f ).

All dorsal surfaces in males chocolate-brown to light brown, with few darker spots; pale brown dorsum with small dark markings in female; flanks in both sexes similar to dorsal coloration along upper half, turning paler towards venter; female with whitish spots in groin; ventral coloration highly variable in males, from yellowish brown belly and dark throat in holotype to pale cream or white ventral colors in paratypes and additional material; female venter plain white; ventral part of hind limbs yellowish with darker speckles in males, uniformly yellow in female; dorsal part of front limbs with irregular dark markings; hind limbs with inconspicuous to distinct transverse dark bars; both sexes with bright cream or white lip, extending to posterior end of tympanum (in some females, white color not extending across entire lip; Fig. 13e ); iris golden or light brown.

Life coloration of males in breeding condition bright yellow ( Fig. 13a – d ), dark spots on dorsum and bands on hind limbs visible but paler; limbs and yellowish brown; flanks yellow, lighter towards cream belly; lip and throat bright yellow; dorsolateral ridge yellow to reddish brown; tympanum of breeding males with yellow center bordered by pale brown ring; tympanum of females dark or reddish brown ( Fig. 13e, f ).

Acoustics. The advertisement call of male A. fonensis consists of a whiny-voiced croaking sound with an ascending frequency modulation of 548–723 Hz (mean ± sd: 633 ± 87, N= 3). The sound comprises up to five harmonics of which the lowest is the dominant one (see Fig. 4b ) and lasts 0.55– 0.92 s (0.7 ± 0.19, N = 3). All call characteristics are summarized in Table 4 .

Distribution. Amnirana fonensis was described from the Pic de Fon, Simandou Range, and from the Haut Niger National Park, both located in Guinea. Our new records add further localities, including the first records from eastern Sierra Leone, the Nimba Mountains in northern Liberia, and central Ivory Coast. However, we cannot at this point clarify which previous West African records of Amnirana albolabris refer to either A. fonensis or A. parva sp. nov. (but see below).

Life history. The observed and collected individuals were found near forest streams. These forests were less humid than in confirmed A. parva sp. nov. records and comprise semi-deciduous and degraded forest fragments ( Fig. 14d ) surrounded by savanna. Amnirana fonensis males differ from breeding A. parva sp. nov. males, by a bright yellow breeding coloration. Similar yellow breeding color has been reported from many, unrelated frogs across the tropics. In West Africa such color change has been observed in Phrynobatrachus alleni Parker, 1936 ( R̂del 2003; Kanga 2021), Sclerophrys maculata (Hallowell, 1854) (Hillers & R̂del 2007) and S. togoensis (Ahl, 1924) (R̂del & Bangoura 2004). Amnirana fonensis breeds in water bodies of different sizes but seems to prefer stagnant or slow-flowing water.

In a savanna-like habitat (Foma), males called from inundated patches, well concealed between grasses and reeds. In degraded gallery forests at Wataférédou, males called while floating on the water surface ( Fig. 14a ), well concealed between roots of trees and shrubs, or between low vegetation at the water edge. One to two males initiated calling and many other males then joined the chorus. Amnirana fonensis called at night as well as during the day. For instance, between 20:35 GMT and 23:00 GMT, we encountered many calling males (N> 100); the peak of calling activity was between 20:40 GMT and 21:30 GMT. Likewise between 14:45 and 16:00 GMT, we observed numerous calling males (N> 70); the peak of calling activity was at 14:57 GMT.

In Foma, females attached eggs to grasses emerging from flowing water. After a few hours these eggs became submerged. In Wataférédou, the eggs were deposited between roots of trees and shrubs in the forest streams. The dark brown and yellow eggs were deposited in large clumps ( Fig. 14b, c ). We counted 809, 1074, and 2017 eggs in three clutches. The egg diameter ranged from 0.9‒2.4 mm (mean ± sd: 2.1 ± 0.42 mm mm; N= 100). We observed aquatic heteropterans (family Nepidae ) preying on the eggs. It is likely that the tadpoles described by Lamotte (1957) from the Simandou range, can actually be assigned to A. fonensis .

At Wataférédou, where A. fonensis was breeding, the forest stream was regularly polluted by people washing laundry. The edges of this gallery forest were degraded by subsistence farming, and cattle, and cleared for charcoal production and fuelwood.

Figures

FIGURE 4. Advertisement calls of (a) Amnirana ‘albolabris West’ and (b) A. fonensis; shown are oscillogram (top) und spectrogram (bottom; please note different scale of y-axes in a and b).

FIGURE 12. Amnirana fonensis in preservation; (a) the male holotype (SMNS 11788), and (b) an adult female (ZMB 79185), in dorsal and ventral view; scale bars= 10 mm.

FIGURE 13. Amnirana fonensis in life; (a-d) adult males in breeding coloration; (e-f) adult females; (a-b) from near Foma village; (c) from near Moribadou village; (d-f) from a degraded gallery forest near Wataférédou village; all sites in the Simandou Range, Guinea; these individuals were not collected.

FIGURE 14. Calling male (a), clutches (b several hours old; c probably> 1 day old), and (d) breeding habitat of Amnirana fonensis in the Simandou Range, Guinea; (a, c, d), in a degraded gallery forest near Wataférédou village; (b) near Foma village.