Allobates ripicolus, Fouquet & Ferrão & Jairam, 2023

Fouquet, Antoine, Ferrão, Miquéias & Jairam, Rawien, 2023, Two new species of Allobates of the trilineatus clade (Anura: Aromobatidae) from the Eastern Guiana Shield, Zootaxa 5297 (4), pp. 533-561 : 547-549

Allobates ripicolus sp. nov.

Colostethus aff. marchesianus Vences et al. 2003

Allobates granti Fouquet et al. 2007

Allobates spumaponens Avila-Pires et al. 2010

Allobates sp. Saul Fouquet et al. 2012

Allobates sp. gr. trilineatus Fouquet et al. 2015a

Allobates aff. tapajos 4 Vacher et al. 2020

Allobates aff. tapajos 2 Réjaud et al. 2020

Allobates aff. tapajos Moraes and Lima 2021

Allobates tapajos Clade D Ferr„o et al. 2022

Holotype. MNHN-RA-2022.0095 (field n° APA-973-1-AF2828), an adult male from Mitaraka , French Guiana (2.23577 N 54.44928 W, 300 m asl), collected by A. Fouquet and M. Dewynter on 01/03/2015 ( Fig. 7 ).

Paratopotypes. Two adults: MNHN-RA-2022.0094 and 0096 (field n° APA-973-1-AF2789 and APA-973-1- AF2855), two females collected with the holotype.

Paratypes. Sixteen adults: MNHN-RA-2022.0081 (field n° AF1048), a male from Gros Arbres, Saul, French Guiana (3.62573 N 53.28052 W, 220 m asl), collected by A. Fouquet, K. Pineau, E. Courtois, B. Villette and C. Bedeau on 16/03/2013 ; MNHN-RA-2022.0083–84 (field n° AF1658; AF1686), two males from Crique Limonade , Saul, French Guiana (3.56311 N 53.19083 W, 280 m asl), collected by A. Fouquet, E. Courtois and J.P. Vacher on 23/02/2014 ; MNHN-RA-2022.0085 (field n° AF1905), a male, and MNHN-RA-2022.0086 (field n° AF1907), a female from Flat de la Waki , French Guiana (3.0835 N 53.41257 W, 180 m asl), collected by J.P. Vacher on 05/04/2014 ; MNHN-RA-2022.0092–93; 0088–89 (field n° AF2072–3; AF2216; AF2218), four males and MNHN-RA-2022.0087; 0090–91 (field n° AF1962; AF2276; AF2290), three females from Sipaliwini, Suriname (2.03253 N 56.11449 W, 280 m asl), collected by A. Fouquet and J.P. Vacher on 25/04/2014 ; MNHN-RA-2022.0097 (field n° AF3221), a male from Mitan , French Guiana (2.62840 N 52.55404 W, 100 m asl) collected by A. Fouquet and P. Nunes on 26/03/2015 ; MNHN-RA-2022.0098 (field n° AF3587), a male from Itoupé , French Guiana (3.02647 N 53.07983 W, 800 m asl), collected by A. Fouquet, E. Courtois, B. Villette and M. Dewynter on 07/01/2016 ; MNHN-RA-2022.0100 (field n° AF5397), a male from Camp Saut Richard , French Guiana (3.47363 N 53.20857 W, 200 m asl), collected by E. Courtois and M. Dewynter on 03/05/2019 ; MNHN-RA-2022.0099 (field n° AF5476), a male from Trois-Saut , French Guiana (2.19689 N 52.90168 W, 180 m asl), collected by E. Courtois and M. Dewynter on 28/04/2019 .

Etymology. The specific epithet “ripicolus” is derived from a Latin word which means river banks, referring to the ecology of the species that is generally found nearby mid-sized rivers, on the ground of the frequently flooded major bed.

Generic placement. The new species is assigned unambiguously to the genus Allobates because the tip of finger IV does not reach the distal subarticular tubercle of finger III, toe IV with basal webbing and lateral fringe on its preaxial side, pale paracloacal marks (characters 5, 43 and 50 of Grant et al. 2017), respectively) and its phylogenetic relationship as assessed by molecular data.

Definition. A small species of cryptically-colored Allobates . (1) Mean SVL of males 15.8 mm (range 15.0– 16.4 mm); mean SVL of females 16.4 mm (range 15.5–16.8 mm); (2) In life, dorsal surface of snout light brown, same color extending posteriorly until eye level; dorsum light brown laterally, with diffuse dark brown blotches scattered from interorbital region to urostyle region; background color of dorsal surfaces of legs light brown to gray; conspicuous diffuse transverse bands or blotches of a darker brown color present across dorsal surfaces of thigh (on its proximal region), shank (at mid-level) and foot (at mid-level); posterior surface of thigh and groin dark brown; (3) skin texture of dorsum granular, with larger granules on the posterior half of dorsum and legs; (4) lateral dark brown band with diffuse upper and lower edges particularly on posterior parts; (5) pale ill-defined dorsolateral stripe only reaching midbody; (6) oblique lateral stripe inconspicuous reaching midbody, reduced to a paler inguinal region within the lateral dark brown band; (7) cream ventrolateral stripe present, extending from the inguinal region to the snout, at times interrupted; (8) pale paracloacal mark present; (9) throat and chest of males white in preserved specimens, yellow in life, with melanophores concentrated on the posterior half of the throat; (10) abdominal surfaces white centrally, yellow towards the flanks in live males; (11) throat translucent without any melanophores, chest and abdomen uniformly white in preserved and live females; (12) dark throat collar absent; (13) iris is metallic gold, without a pupil ring; (14) median lingual process absent; (15) vocal sac distinct, subgular; (16) maxillary teeth present; (17) third phalanx of Finger III slightly swollen preaxially in males; (18) distal tubercle absent on Finger IV; (19) tip of Finger IV not reaching the distal subarticular tubercle of Finger III; (20) tip of Finger II reaching the base of distal subarticular tubercle of Finger III; (21) terminal discs clearly expanded; (22) basal webbing present between Toes III and IV; (23) weak lateral fringes preaxially on Toe II and III; (24) Toe I very short, its tip not reaching the base of the subarticular tubercle on Toe II; (25) mature oocytes pigmented; (26) diurnal habits, males calling in daytime; (27) advertisement calls characterized by the continuous emission of single notes; notes with ascending frequency modulation and dominant frequencies between 5,519 –6,072 Hz, split by regular silent intervals of approximately 391 to 686 ms between calls.

Morphological comparisons with other Allobates . The character states of compared species are shown in parenthesis. Allobates ripicolus differs from A. granti and A. vicinus , the two other co-occurring species of cryptically colored Allobates in the eastern Guiana Shield by (1) its dark brown lateral band with diffuse edges and not as wide as the eye (lateral band as wide as the eye with sharp edges, black in A. granti and dark brown in A. vicinus ); (2) its longer feet but small arms FL/FAL= 44–45% (46–49% in A. granti and A. vicinus ); (3) the presence of melanophores concentrated on the posterior half of throat in males and yellow throat in life, females with white ventral surface (from chin to mid-belly and translucent throat, females ventral surface yellow); (4) its single-note call (two-notes call).

Allobates ripicolus differs from the closely related A. tapajos occurring south of the Amazon River by (1) the absence of basal webbing between Toes II and III (present); (2) the presence of melanophores concentrated on the posterior half of throat (no melanophores); (3) its cream ventrolateral stripe continuous or interrupted (absent); (4) its call composed exclusively by a single note (usually composed of two notes [73% of calls], less frequently of one note [23% of calls] and rarely three notes [4% of calls]; Lima et al. (2005)) ( Fig. 4 ).

Allobates ripicolus differs from the closely related A. kamilae by (1) its throat entirely translucent without melanophores in femals (yellowish anteriorly with melanophores) (Fig. 7,8); (2) its Finger III slightly swollen preaxially in males (Finger III not swollen); (3) its call composed exclusively of a single note (frequently 2–5 notes and rarely 6–17 notes per call) ( Fig. 4 ).

Allobates ripicolus differs from A. sumtuosus by (1) the presence of diffuse irregular dark brown blotches scattered on dorsum from eye level to urostyle region (dorsum uniformly brown); (2) its throat and chest yellow with melanophores concentrated on the posterior half of throat in males (white translucent uniformly covered with melanophores only in the throat margins); (3) its single note call with dominant frequency 5,519 –6,072 Hz (call consisting of a trill of 23–35 notes and dominant frequency 6,172 –6,480 Hz). Allobates ripicolus differs from A. amissibilis by (1) the presence of diffuse irregular dark brown blotches scattered on dorsum from eye level to urostyle region (dorsum uniformly brown); (2) its throat and chest yellow with melanophores concentrated on the posterior half of throat in males (white translucent uniformly covered with melanophores); (3) its single note call (call consisting of a trill of 1–19 notes).

Description of the holotype. An adult male 16.2 mm SVL ( Fig. 7 ; Table 1 ) in good condition, with a few superficial scars on dorsum and snout and a large incision in the abdomen for tissue sample; body slender; head slightly longer than wide (HL/HW=1.05); head length 33.0 % of SVL; snout broadly rounded in dorsal view, acutely rounded in lateral view, extending past lower jaw. Nares located laterally, opening posterolaterally; canthus rostralis concave, loreal region slightly concave, flaring slightly at upper lip; internarial distance 41.2 % of head width (IN/HW); eye-naris distance distance 28.2 % of head length (EN/HL); 79.5 % of eye length (EN/ED). Tympanum sub circular, directed posterolaterally, 54.2 % of eye length (TD/ED); supratympanic fold absent, supratympanic area slightly concave; tympanic annulus visible anteroventrally, posterodorsal aspect of tympanum barely visible. Tongue attached anteriorly, broadly rounded posteriorly, longer than wide, median lingual process absent. Choanae very small, sub circular, lateral. Vocal slits long, lateral. Very small teeth present on maxillary and premaxillary, dentigerous process of vomers absent. Cloacal tubercles absent; vent at level of upper thighs, a small anal flap above it.Skin granular on dorsum, granules weakest on head, with scattered larger granules becoming denser posteriorly, more easily visible in life; one distinctly enlarged tubercle on each eyelid; belly smooth.

Forelimb slender, skin smooth; metacarpal ridge absent; ulnar fold absent; hand length 23.3 % of SVL; Finger I as long as II when fingers adpressed; fingers unwebbed, proximal edge of Finger III conspicuously swollen; tip of Finger IV not reaching distal subarticular tubercle on Finger III when fingers adpressed; terminal discs clearly expanded, discs of Fingers III and IV widest; width of disc on Finger III 0.44 mm; discs with distinct dorsal scutes. Relative lengths of adpressed fingers III>I =II> IV; palmar tubercle large, ovoid, 0.67 mm in its largest diameter, 17.7 % of hand length, periphery pigmented; thenar tubercle conspicuous but not protuberant, ovoid, periphery pigmented, about a third the size of the palmar tubercle and largely separated from it. One subarticular tubercle on Fingers I, II, and IV; two subarticular tubercles on Finger III; subarticular tubercles on Finger I largest, distal tubercle on Finger III smallest ( Fig. 7 ).

Hindlimb robust, skin granular; thigh length 44.8 % of SVL; tibia length 48.9 % of SVL; heels overlapping when hindlimbs are flexed at right angles to sagittal plane of body; foot length 46.0 % of SVL; relative length of adpressed toes IV> III> V> II> I; Toe I very short, its tip not reaching the base of the subarticular tubercle on Toe II when toes are adpressed; discs on Toes II, III, IV, and V larger than width of distal phalanges; disc on Toe I equal to width of distal phalanx. Width of disc on Toe IV 0.55 mm; basal webbing present only between Toes III–IV, posteriorly pigmented; weak lateral fringes preaxially on Toe III and IV. Inner metatarsal tubercle oval, 0.40 mm in length, periphery pigmented, outer metatarsal tubercle round, projecting, 0.33 mm in diameter. Two subarticular tubercles present on Toes III, IV and V, and one on Toes I and II, basal tubercle of Toe IV barely visible on the right toe and very small (about 0.05 mm) and located postaxially on the left one. Subarticular tubercles on Toe I largest; distal subarticular tubercle on Toe IV smallest. Metatarsal fold absent. Tarsal keel well-defined, short, tubercle-like, directed transversely across tarsus, located 0.62 mm from proximal edge of inner metatarsal tubercle, not extending from it ( Fig. 7 ).

Color of holotype in life. Color in life of the holotype is shown in Fig. 7 . Dorsal coloration medium brown with dark brown scapular region and diffuse dark brown blotches on dorsum; dorsum light brown laterally from eye level to midbody forming an ill-defined dorsolateral band; laterally a wide dark-brown band from tip of snout around the body to the groin with ill-defined boundaries posterodorsally. The oblique lateral stripe embedded in the black band consists of a diffuse lighter area extending from the groin to about two-third of the distance to the arm insertion. Flanks are creamish white below the lateral dark brown band forming an interrupted ventrolateral stripe extending ventrally along flanks. Upper lip is creamish white. Throat is yellow with scattered tiny melanophores particularly concentrated on the posterior half. Belly is immaculate creamish with scattered tiny melanophores. Upper surfaces of thighs and shanks are brown with ill-defined dark brown transverse bands or blotches. A pale paracloacal mark is present. Forelimbs are reddish anterodorsally and dark gray on the posterior surface of forearms from elbow to wrist. A gray blotch is present on the wrists. Digits are dark gray with a few white dots. The upper surface of tympanum is black, the lower surface white. The iris is copper.

Color of holotype in preservative. After seven years in 70 % ethanol, colors of the specimen have faded, the dorsum is light brown; the lateral band is dark brown and the diffuse oblique lateral stripe is barely distinguishable. Flanks, belly, and upper lips are immaculate white. Throat is white; the melanophores are visible. Upper surface of thighs and shanks are brown with dark brown blotches and dark brown bands. The pale paracloacal mark is still visible. Forelimbs are white. Fingers and digits are light brown. ( Fig. 7 ).

Variation in the type series. Apart from sexual dimorphism and dichromatism (males are slightly smaller than females and throat of females is translucent white and without melanophores), there is considerable variation in size, conspicuousness and distribution of dark brown blotches on dorsum and legs ( Fig 8 ). The dorsal surface of legs varies in coloration from dark gray to light brown with more or less conspicuous dark brown bands and blotches. The ventrolateral stripe is continuous (MNHN-RA-2022.0081) or interrupted in some individuals (MNHN-RA-2022.0086; Fig 8 ). Ventral surface is immaculate white to yellowish.

Advertisement call. The call consists of a single high pitched note emitted regularly every 550 ms (391–686 ms) and lasting 37 ms (26–45 ms). These notes have an upward frequency modulation, with a dominant frequency about 5,770 Hz (5,519 –6,072 Hz), and a minimum starting frequency of about 5,250 Hz (4,914 –5,745 Hz) and as maximum ending frequency of about 6,090 Hz (5,875 –6,465 Hz), which represents a 463 Hz (352–613 Hz) difference (MxF1-MiF1) ( Fig 4a ).

Natural history and distribution. Allobates ripicolus is generally associated with the temporary flooded banks of medium-sized rivers where males form patches of two to three individuals. But it is also found on bauxite plateaus such as Itoupé, where individuals were found around a temporary pond at 800 m. Males are territorial and call mainly in the morning and late afternoon. Two egg clutches were found in Sipaliwini ( Suriname). They were deposited within folded dead leaves of Cecropia spp. One was very recent and contained 18 eggs ( Fig 7 ). The male was calling 40 cm from it. The second one was cloudy and contained 37 well developed embryos, possibly in fact corresponding to two different clutches. The tadpoles are probably carried to a nearby water body by the male.

Allobates ripicolus occupies the southern half of French Guiana (Saul, upper Oyapock, Itoupé, Mitaraka) and is absent from the northern half. It also occurs in the west of Amapá ( Brazil), the south of Suriname and the north of Pará ( Brazil). It is therefore an endemic species of the eastern part of the Guiana region. Its distribution is similar to that of Rhinella aff. magnussoni which also has its sister species south of the Amazon River, Brazil ( Vacher et al. 2020).

Figures

FIGURE 4. Examples of sonograms of Allobates aff. tapajos, A. tapajos and A. kamilae: (A) depicting a series of calls (a single call in A. tapajos and A. kamilae) on a 1s window and (B) focusing on a single note on a 0.2 s window; (C) PCA plot of the first two PCs and the correlation circle representing variable contributions, and (D) excluding A. kamilae. Only the range of the number of notes per call (NC) do not overlap across the three species.

FIGURE 7. Dorsal, ventral, left palmar and left plantar views of preserved holotype of Allobates ripicolus sp. nov. and lateral view of the holotype in life. Additional uncollected specimen of a calling male from Sipaliwini, Suriname and a clutch found nearby.

FIGURE 8. Additional specimens in life illustrating the variation of coloration within Allobates ripicolus sp. nov., A. tapajos (photos L.J.C.L. Moraes and A.P. Lima) and A. kamilae (photos A.P. Lima).