Chaunus tacana, Padial, José M., Reichle, Steffen, Roy & Riva, Ignacio De La, 2006

Padial, José M., Reichle, Steffen, Roy & Riva, Ignacio De La, 2006, A new species of arboreal toad (Anura: Bufonidae: Chaunus) from Madidi National Park, Bolivia, Zootaxa 1278, pp. 57-68 : 59-63

Chaunus tacana sp. nov.

Fig 1 , 3–4

Holotype

MNK­A 7188, an adult female from Huairuro (14º19'28.2'' S, 68º05'36.1'' W), path from San José de Uchupiamonas to Apolo, Serranía Eslabón, Madidi National Park, Province Franz Tamayo, Department La Paz, Bolivia ( Fig. 2 ), collected the night of 16–17 December 2003 by José M. Padial (field number JMP 556).

Paratypes

MNK­A 7187 (field number JMP 555), an adult male ( Fig. 3 ) and MNCN 42072 (field number JMP­558), an immature female, both collected with the holotype; an adult male MNCN 42073 (field number JMP­574) and a juvenile MNK­A­7194 (JMP575) collected at Arroyo Huacataya (14º20'12.1" S, 68º5'57.3" W), path from San José de Uchupiamonas to Apolo, Serranía Eslabón, Madidi National Park, Department La Paz, Province Franz Tamayo, Bolivia, collected the night of 17–18 December 2003 by José M. Padial, Pere Comas and Pedro Macuapa.

Etymology

The specific name is a substantive in apposition that refers to the Bolivian indigenous group Tacana , who inhabit the lowlands and foothills of the Madidi National Park. The Tacana people have successfully demonstrated (through management of the Chalalán Ecolodge) that community development is compatible with conservation of their cultural and natural heritage.

Diagnosis

A small species of Chaunus with long and slender extremities, tentatively assigned to the C. veraguensis group sensu Duellman and Schulte (1992) based on external characters. The new species is distinguished from other putatively related species by the following combination of characters: (1) canthus rostralis sharp, orbitotympanic and postorbital crest weak; (2) tympanum distinct, oval; (3) parotoid glands large, round, not contacting the tympanic membrane; (4) numerous scattered small, round warts on dorsal surfaces of body; (5) extremities moderately long and slender; (6) a dorsolateral row of round, enlarged, and elevated warts; (7) tarsal fold absent; (8) webbing on hands and feet fleshy ( Figure 3 ); (9) first finger shorter than second (figure 3); (10) males with vocal slits; (11) small keratinous spines on dorsal surfaces of thumb; (12) iris green in life.

The most similar species is one that is being described by J. A. Chaparro, J. Pramuk and A. Gluesenkamp from Department Cusco, Peru. We examined specimens of this undescribed taxon and compared them with C. tacana . Both species are similar in habitus, both are arboreal and inhabit cloud forests and humid montane forests. Nevertheless, C. tacana differs from the species from Cusco as follows (characteristics of the latter in parentheses): fingers thin and long (thick and short); webbing of hands and feet less developed, almost absent between Finger I and II (well developed between finger I and II); tarsal fold absent (present); parotoid glands proportionally smaller; parotoid glands and tympanic membrane not in contact (in contact); vocal slits present in males (absent); dorsal coloration in life dorsally pale greenish­brown to brownish­green with brown stripes or spots and red warts (homogeneously black); ventral coloration whitish­cream with light brown reticulation (red with dark blotches); iris green (reddish­orange).

Chaunus tacana can be distinguished from another similar and arboreal species, C. arborescandens , mainly by the visible tympanic membrane (absent in the latter), and the concave internarial area (flat). Chaunus tacana has visible tympanic membrane while C. amboroensis , C. justinianoi , C. quechua , and C. veraguensis lack visible tympanic membrane. C. fissipes may have a visible tympanum although barely evident. Nevertheless, C. fissipes is larger [mean adult females SVL= 68.1 (range= 65.8–71.9, n=8); see Köhler (2000)] and has two prominent dorsolateral rows of tubercles. Moreover, C. fissipes has the first finger longer than second, the parotoid glands are slightly elevated and not protruding laterally, and it presents serrate foot webbing. The new species can be distinguished from C. multiverrucosus and C. chavin by the nuptial spines on the first finger in breeding males, and by the lack of enlarged glands on dorsum and extremities. Chaunus tacana differs from C. inca by having the first finger shorter than second. The new species differs from C. nesiotes by having pronounced parotoid glands (low and diffuse in C. nesiotes ) and a row of enlarged dorsolateral warts (absent). C. tacana differs from C. rumbolli by the long and slender extremities, inconspicuous cranial crests and first finger longer than second (shorter in C. rumbolli ).

Description of the holotype

A small Chaunus with long and robust body (for measurements see table 1); head small, slightly broader than long, its width 30% of SVL, length 30% of SVL; snout short, subacuminate in dorsal view, acute in profile, with a vertical keel on the tip; cranial crests absent; skin of head not coosified with underlying cranial bones; internarial area concave; narines not protuberant, very small, oriented laterally; canhus rostralis sharp, concave in dorsal view; lips flat; eye­nostril distance equal to eye length; tympanic membrane visible, conspicuous, oval, surrounded by granules, 70% of eye length; tympanic annulus thin, overlapped with surrounding granules. Forelimb long and slender; hand broad, with short fingers; relative length of fingers I<II<IV<III; basal webbing fleshy, extending as a fringe on lateral edges of fingers; webbing formula I1­ 2 II basal III basal IV; tips of digits round, not expanded; ulnar region granular with a row of enlarged tubercles; palmar tubercle round and low; prepollical tubercle irregular to ovoid, diffuse; subarticular tubercles ovoid to round, low, diffuse, inconspicuous; supernumerary tubercles round, diffuse, smaller than subarticular. Hind limbs and feet long; tibia length 40% of SVL; foot length 40% of SVL; no tarsal fold; outer metatarsal tubercle ovate, prominent, 1/3 the size of inner; inner metatarsal tubercle large, prominent, ovate; relative length of toes 1<2=5<3<4; webbing fleshy, almost complete, but last phalange free, only basal between toes 4 and 5; webbing formula I1 /2­ 1II 1/2­ 1III 1/2­ 3 IV3­ 2V; tip of toes rounded; subarticular tubercles low, round to ovate, diffuse, larger than supernumerary tubercles; supernumerary tubercles abundant, small, irregular or rounded.

Skin on dorsum of head, body, and limbs bearing abundant small, flat granules of irregular size and low rounded warts, larger than granules; enlarged granules forming an irregular row that resembles a dorsolateral fold; parotoid gland round, large, more displaced to side of the head than to dorsum, almost in contact with tympanic membrane, and in contact with small, short orbitotympanic and postorbital crests composed of granules; enlarged glands absent on limbs. Skin on throat and other ventral surfaces granular. Anal opening slightly protuberant, directed posteroventrally at upper level of thighs.

One choanae small and round, placed anterolaterally, while the other is concealed by the palatal shelf of the maxillary arch; vomerine odontophores absent; tongue cordiform, free behind for about one­third its length.

Color in preservative: Dorsum dark grey, with enlarged light brown warts; interocular, scapular, and central areas of dorsum with a bold black irregular x­shaped stripe; granules forming a dorsolateral row cream; flanks scarcely lighter than dorsum; tympanic membrane dark greyish­brown; head dark greyish­brown, lighter in lower parts; forelegs barred and hind legs greyish­brown with dark brown, almost black, transverse bars; toes barred with dark brown; ventral regions irregularly mottled with brown and cream, lighter at the level of groin; plantar surfaces cream with some brown spots.

Color in life: dorsal coloration pale brown to greenish­brown; scapular and central areas of dorsum with a dark brown black irregular x­shaped stripe with greenish­brown tonalities; granules forming the dorsolateral rows brown or red; tympanic membrane brown; head brown with some red granules and small greenish­brown spots on interorbital region; extremities brown, barred with dark brown to greenish­brown; toes barred with dark brown; ventral coloration whitish­cream with light brown reticulation; iris green, pupil black.

Variation

Little variation is observed. There is little sexual dimorphism in size. Males present nuptial excrescences in form of a single group of black (in life) or white (in alcohol) keratinized spines on the dorsal surface of each thumb. Male specimens present vocal slits lateral to tongue. Males seem to have shorter snout relative to eye length (80%) than females (100%), and also narrower snout (EN 160% of EE distance in females versus 130% in males). In one male ( MNCN 42073) both choanae are visible, they are anterolateral and are separated by a distance equal to six times the diameter of a choanae. Most spicules and granules can be concentrated on neck and head, while the flanks have larger granules and warts but density of granules is lower. In MNCN 42073 the parotoid gland is slightly ovate, displaced to the lateral part of the head, where it reaches the level of the lower margin of the tympanic membrane. In MNCN 42073 the foot webbing formula differs slightly from that of the holotype: I1 /2­1/ 2II 1/2­1/ 2III 1­ 3 IV3­ 3V. Juveniles are identical to adults in general appearance. Dorsal pattern varies slightly in the intensity and form of the stripes. Some individuals have more red warts. SVL of two juveniles: 25.3 ( MNCN 42072, female) and 21.8 (NKA­A7194, unsexed). NKA­A 7187 lack dorsal pattern and is darker than any other specimen in alcohol ( Fig. 3 ).

Distribution and natural history

This species is known only from two close localities in Serrania Eslabón ( Fig. 2 ), at about 1500 m a.s.l. The habitat is composed by primary humid montane forest with high abundance of arboreal ferns, bromeliads and other epiphytes. Potentially flooded flat surfaces are almost inexistent but there are some small streams. C. tacana is a nocturnal species that can be found active on leaves of bushes or on the trunk of trees from 1–4 m height. It climbs graciously vertical trunks covered by moss. As C. tacana , C. veraguensis may also show greenish dorsal coloration and has been reported to climb in trees ( Köhler 2000). This mimetic coloration could be related to their arboreal habits. The adult female presented convoluted oviducts and small white ova. The call, tadpole and reproductive mode are unknown. Other anuran species that occur in the area are Atelopus tricolor , Epipedobates bolivianus , Hyalinobatrachium bergeri , Hyloscirtus armatus , Hypsiboas balzani , Eleutherodactylus danae and E. madidi .

Figures

FIGURE 1. Adult female holotype of Chaunus tacana sp. nov. from Serranía Eslabón, Madidi National Park, Bolivia (MNK­A 7188)

FIGURE 2. Map of Bolivia with a bold square indicating the type locality of Chaunus tacana sp. nov.

FIGURE 3. Dorsal and ventral view of an adult male of Chaunus tacana sp. nov. from Serranía Eslabón, Madidi National Park, Bolivia (MNK­A 7187).

FIGURE 4. Dorsal view of and adult female of Chaunus sp. (left) from Department Cusco, Peru and the holotype (adult female) of Chaunus tacana sp. nov (MNK­A 7188).