Chiasmocleis magnova, Moravec, Ji Ř Í & Köhler, Jörn, 2007

Moravec, Ji Ř Í & Köhler, Jörn, 2007, A new species of Chiasmocleis (Anura: Microhylidae) from the Iquitos region, Amazonian Peru, with possible direct development, Zootaxa 1605, pp. 59-67 : 60-64

Chiasmocleis magnova sp. nov.

Figs. 1–4

Holotype. MHNSM 19993, adult female, from the area at 31 km on the road from Iquitos to Nauta (04°00’ S, 73°26’ W), ca. 120 m a.s.l., ca. 40 km straight SW of Iquitos, Departamento Loreto, Peru; collected by J. Moravec on 22 March 2002.

Paratype. NMP 6 V 71196, adult female, from the vicinity of Puerto Almendras (03°50’ S, 73°22’ W), ca. 120 m a.s.l., ca. 17 km straight SW of Iquitos, Departamento Loreto, Peru; collected by J. Moravec on 9 March 2001.

Diagnosis. A small species of Chiasmocleis distinguished from all other members in the genus by the following combination of characters: (1) small size, SVL 17.2–18.3 mm in females, body ovoid; (2) snout round in dorsal and lateral views; (3) canthus rostralis indistinct, rounded in cross-section; loreal region posterior to nostril slightly concave; (4) skin on dorsal surfaces slightly shagreen (smooth in alcohol), with tiny tubercles and scattered miniature light dermal spines dorsolaterally; outer margin of tarsus and toe V with scattered minisized light spines; (5) fingers I and IV reduced, finger IV shorter than finger II; fingers basally webbed, slightly fringed, lacking discs; finger tips depressed, pointed asymmetrically; (6) toe I reduced; toes free, distinctly fringed, toes II–V having flat asymmetrically pointed discs, disc not grooved; (7) subarticular tubercles absent; inner metatarsal tubercle small, ovoid; (8) large unpigmented eggs; (9) in life, dorsal surfaces dark brown with minute white spots irregularly scattered on flanks and hind limbs; a whitish stripe extending from tip of snout along the canthal region reaching the posterior end of upper eyelid margin; fore limbs reddish brown; (10) in life, ventral surfaces brown with irregularly scattered white flecks, belly becoming translucent in posterior part; (11) iris dark brown in life.

Comparisons. Chiasmocleis magnova can be distinguished from other species of Chiasmocleis by its distinctly reduced fingers I and IV. Additionally, in comparison to the Amazonian species of Chiasmocleis , the new species differs from C. anatipes by free toes, and by colouration ( C. anatatipes has a white belly and ventral surfaces of legs with brown-black marks, fully webbed feet) ( Walker & Duellman 1974, Rodríguez & Duellman 1994); from C. bassleri by fringes on toes and by colouration ( C. bassleri has black inguinal spots, white belly with large black spots, pale dorsal surfaces of arms, lacks fringes on toes) ( Dunn 1949, Rodríguez & Duellman 1994); from C. hudsoni by absence of grooved terminal discs and by colouration ( C. hudsoni has white ventral surfaces with brown stippling on gular region and a brown reticulum on the limbs, and black plantar surfaces) ( Parker 1940); from C. jimi by smaller size, tips of fingers III an IV not swollen, and by colouration ( C. jimi has a cream heavily greyish spotted venter and lacks a light canthal stripe) ( Caramaschi & Cruz 2001); from C. shudikarensis by smaller size, free toes and by colouration ( C. shudikarensis has a light middorsal line, black inguinal spots, light median line on the throat, and cream ventral side with black spotting or mottling) ( Dunn 1949); and from C. ventrimaculata by smaller size, free toes and by colouration ( C. ventrimaculata has yellowish white ventral surfaces with large brown spots) ( Andersson 1945).

Other species of Chiasmocleis from non-Amazonian regions are distinguished from C. magnova as follows: C. capixaba Cruz, Caramaschi and Izecksohn , C. cordeiroi Caramaschi and Pimenta , C. crucis Caramaschi and Pimenta , and C. leucosticta (Boulenger) all exhibit well-developed webbing on feet (Cruz et al. 1997, Caramaschi & Pimenta 2003). C. centralis Bokermann is larger (SVL 24.4 mm in female), has broader lateral fringes on toes. C. albopunctata (Boettger) is larger (SVL 28.2–38.0 mm in females) and, together with C. mehelyi Caramaschi and Cruz has less reduced fingers, broader white canthal stripes and numerous small spines on dorsum (Caramaschi & Cruz 1997). C. schubarti Bokermann is larger (SVL 20.4–34.5 mm in females), exhibits light longitudinal lines at posterior surfaces of thighs and a cream coloured venter marbled with dark brown blotches. C. atlantica Cruz, Caramaschi and Izecksohn is larger (SVL 30.0– 31.8 mm in females) and has a cream coloured venter with dark marbling. C. carvalhoi Cruz, Caramaschi and Izecksohn has less reduced fingers, smooth dorsal skin and a whitish venter (Cruz et al. 1997). C. alagoanus Cruz, Caramaschi and Freire is larger (SVL 25.5–27.8 mm in females), has a more stubby body shape, a truncate snout in dorsal view, and a light longitudinal line at posterior side of thighs ( Cruz et al. 1999). C. gnoma Canedo, Dixo and Pombal has less reduced fingers, weaker fringes on toes, posterior surface of thighs with cream longitudinal line, and belly boldly marbled in brown and pale cream ( Canedo et al. 2004). C. panamensis Dunn, Trapido and Evans has less reduced fingers, a white venter with brown flecks and a light brown dorsum with irregular dark brown stripe ( Dunn et al. 1948).

The new species is somehow similar to an unnamed microhylid frog mentioned by Duellman & Mendelson (1995) as " Microhylidae incerta sedis " by sharing similar size, reduction of fingers I and IV and toe I, brown dorsum with minute cream spots, light canthal stripe, and grey venter with white flecks. However, C. magnova clearly differs from this taxon by the absence of an external tympanum, less reduced fingers and toes and a dark brown iris in life. The tympanum of C. magnova (diameter 0.8 mm) is embedded under the skin and covered by muscles posterodorsally. Similar tympanum condition was found also in C. bassleri (tympanum completely hidden under muscles) and C. ventrimaculata (tympanum hidden posteriorly).

Description of holotype. Body ovoid; head nearly triangular, wider than long; snout slightly rounded in dorsal view, protruding and rounded in lateral view; upper jaw projecting beyond lower; lower jaw with trilobed anterior margin; nostrils near tip of snout, directed laterally; distance from nostril to eye shorter than diameter of eye; internostril distance smaller than eye diameter and slightly larger than eye-nostril distance; canthus rostralis indistinct; loreal region posterior to nostril slightly concave; interorbital area flat, ELW 45.5% of IOD; eye small, slightly protruding, its diameter about three times depth of lip below eye; external tympanum absent; supratympanic fold absent; occipital fold absent. Arms slender, ulnar folds and tubercles absent; fingers I and IV reduced, relative length of fingers I<IV<II<III; fingers basally webbed, slightly fringed, lacking discs; finger tips depressed, pointed asymmetrically; subarticular and supernumerary tubercles absent; palmar tubercle large, flat, rounded; prepollical tubercle well developed, ovoid. Legs short, moderately robust; tarsal fold and tarsal tubercles absent; toe I reduced; relative length of toes I<II<V<III<IV; toes free, distinctly fringed, toes II–V having flat asymmetrically pointed not grooved discs; subarticular and supernumerary tubercles absent; inner metatarsal tubercle small, ovoid; outer metatarsal tubercle absent. In life, skin on dorsum, head, and dorsal surfaces of limbs slightly shagreen (smooth in alcohol) with tiny tubercles and scattered miniature light dermal spines dorsolaterally; skin on venter, throat and lower surfaces of thighs smooth; outer margin of tarsus and toe V with scattered minute light spines. Cloacal opening directed posteriorly at upper level of thighs. Tongue ovoid to elongate, not notched posteriorly; tongue attached anteriorly, posterior parts and lateral margins extensively free; choanae small, nearly rounded, widely separated; premaxillary, maxillary, and vomerine teeth absent; two palatal ridges present. Oviducts contain at least six and four (left/right) unpigmented eggs each app. 2.5 mm in diameter.

As evident from the radiographs, there are eight presacral vertebrae in the holotype. The basal transverse processes on the urostyle are missing.

In ethanol, dorsal surfaces of head, body, and limbs light brown with scattered inconspicuous minute light dots; head with a arrow whitish stripe extending from tip of snout along the canthal region till the posterior end of upper eyelid margin. Throat light brown with few scattered small light dots; belly whitish, becoming translucent posteriorly; ventral surfaces of limbs light brown.

In life, all dorsal and lateral surfaces except of forelegs dark brown with scattered small white to whitishblue dots; forelegs reddish-brown to dark brown; canthal stripe cream; groin slightly translucent. Throat dark brown with few scattered small white dots; belly brown with small white dots in pectoral area, becoming translucent posteriorly; ventral surfaces of limbs dark brown with irregular minute white dots. Iris dark brown with lighter upper part of inner margin.

Measurements of the holotype: SVL 18.3; HL 4.2; HW 5.6; EN 1.2; ED 1.6; ELW 1.0; IOD 2.2; TL 7.9; FL 13.0; 4TD 0.6.

Variation. Measurements of paratype are as follows: SVL 17.2; HL 3.9; HW 5.3; EN 1.0; ED 1.6; ELW 0.9; IOD 2.0; TL 7.6; FL 12.0; 4TD. General colouration of paratype does not differ from that of the holotype.

As obvious from pectoral girdle dissection, clavicles and procoracoid cartilages are present but reduced and clavicles are not in contact with coracoids. Observed phalangeal formulae of paratype hand and foot are 1–2– 3–2 and 2–2–3–4–3, respectively.

Distribution and ecology. Chiasmocleis magnova is known only from the surroundings of Iquitos, Departamento Loreto, Peru ( Fig. 5 ). The holotype was collected in disturbed unflooded Amazonian lowland forest with sandy substrates. It represents a gravid female, found at daytime sitting on top of a 115 cm high stub of a young cut tree. The paratype was collected by day from leaf litter in disturbed terra firme forest at the alluvial zone of the Rio Nanay. Both specimens have small ants in their stomachs. The presence of large unpigmented eggs in the holotype strongly argues for a mode of terrestrial reproduction, a condition so far unknown in other members of the genus (see Discussion). Other microhylids found in sympatry with C. magnova were Chiasmocleis bassleri and Hamptophryne boliviana (Parker) . Males and larvae of C. magnova are unknown. According to the threat criteria used by the Global Amphibian Assessment (www.globalamphibians.org), we classify C. magnova as 'data deficient'.

Etymology. The specific name is an adjective derived from the Latin magnus meaning large and the Latin ovum meaning egg. The name refers to the unusually large unpigmented eggs, which are characteristic for the new species.

Figures

FIGURE 1. Adult female holotype of Chiasmocleis magnova sp. nov. (MHNSM 19993) in life. Photograph by J. Moravec.

FIGURE 2. Ventral view of adult female holotype of Chiasmocleis magnova sp. nov. (MHNSM 19993) in life. Photograph by J. Moravec.

FIGURE 3. Holotype of Chiasmocleis magnova sp. nov. (MHNSM 19993). (A) Lateral, and (B) dorsal views of head. Scale bar equals 2 mm. Original by J. Moravec.

FIGURE 4. Holotype of Chiasmocleis magnova sp. nov. (MHNSM 19993). (A) Palmar, and (B) plantar view of right hand and foot. Scale bar equals 2 mm. Original by J. Moravec.

FIGURE 5. Schematic map showing the known distribution (indicated by a black dot) of Chiasmocleis magnova sp. nov.