Holoaden pholeter, Pombal, José P., Siqueira, Carla C., Dorigo, Thiago A., Vrcibradic, Davor & Rocha, Carlos Frederico D., 2008

Pombal, José P., Siqueira, Carla C., Dorigo, Thiago A., Vrcibradic, Davor & Rocha, Carlos Frederico D., 2008, A third species of the rare frog genus Holoaden (Terrarana, Strabomantidae) from a montane rainforest area of southeastern Brazil, Zootaxa 1938, pp. 61-68 : 62-65

Holoaden pholeter sp. nov.

Figs. 1–3

Holotype. MNRJ 51475, adult female, collected on a forested mountain slope (22°22’23” S; 42°33’16” W; ca. 1200 m above sea level) in the district of Theodoro de Oliveira, municipality of Nova Friburgo, Rio de Janeiro State, Brazil, on 17 March 2008 by Thiago A. Dorigo. The area is located within the Parque Estadual dos Três Picos, a recently created Conservation Unit that encompasses much of the Serra dos Órgãos mountain range.

Paratypes. MNRJ 53482 (male) and MNRJ 53483 (female), both collected at the same locality of the holotype, on a nearby mountain slope (22°21’59” S; 42°33’31” W; ca. 1400 m a.s.l.), on 14 August 2008 by Carla C. Siqueira.

Diagnosis. Dorsum densely glandular, toes free of webbing, fingers and toes with rounded tips not expanded into disks, large and relatively wide head, absence of a tympanum, big forward-directed eyes, and rhomboid or round (when dilated) pupils. Holoaden pholeter is a comparatively large Holoaden species with a large head, glandular texture on dorsum, limbs long and slender, overall dorsal coloration deeply dark, and ventral body surface dark with a light abdominal blotch of variable size.

Comparisons with the other species. The new species differs from Holoaden bradei in its larger body size (maximum 37 mm SVL in H. bradei ; Lutz 1958), longer limbs, wider head, palmar and plantar tubercles and tips of digits leaden gray in life (yellow in H. bradei ; Lutz 1958), and dorsal coloration uniformly dark purplish-brown (upper surfaces olive brown with irregular soot-black suffusions in H. bradei ; Lutz, 1958; see color picture in Haddad et al. 2008, page 80). Holoaden pholeter is morphologically more similar to H. luederwaldti , but is distinguished from the latter by its moderately bulging dorsal glands (dorsal glands markedly bulging and more conspicuous in H. luederwaldti ; see figures 1-2 in Caramaschi & Pombal 2006 and figure 98 in Hedges et al. 2008), darker dorsal coloration (dorsal surfaces brown to reddish brown in H. luederwaldti ; see figure 98 in Hedges et al. 2008), and ventral surfaces dark (slightly lighter than dorsum) with a light blotch on abdomen (ventral surfaces uniformly cream, distinctly lighter than dorsum in H. luederwaldti ).

Description of holotype. Body robust; head large, wider than long, and wider than body; snout nearly semicircular in dorsal view and slightly protruding in lateral view; eyes large, protuberant, directed slightly forward; pupil round; nostrils protuberant, directed dorsolaterally; canthus rostralis not well marked and slightly concave; loreal region concave; tympanum absent; a glandular supratympanic fold extending from corner of eye to insertion of front limb; tongue large; vomerine teeth in two short series behind and between choanae; choanae circular; a single small toothlike process in front of lower jaw with a small single socket between premaxillae; numerous teeth on maxilla and premaxillae. Arms slender; forearms and fingers long and slender; finger lengths II<IV<I<III; finger tips rounded, without expanded discs; fingers not webbed nor fringed; subarticular tubercles single, slightly elliptical or rounded; inner metatarsal tubercle large, ovoid; outer metatarsal tubercle large, slightly rounded; few supranumerary tubercles. Legs short, slender; toes long, slender; toe lengths I~II<III~V<IV; toes tips rounded, without expanded discs; toes not webbed or fringed; subarticular tubercles slightly elliptical; inner metatarsal tubercle large, ovoid; outer metatarsal tubercle medium-sized, slightly rounded. Head and dorsum glandular; loreal region, fore limbs and hind limbs smooth; undersurfaces smooth.

Color of holotype. In life, upper surfaces and flanks dark purplish-brown; eyes slightly lighter than dorsum ( Fig. 1 ); throat and ventral surfaces slightly lighter than dorsum, with a whitish patch on abdomen; palmar and plantar tubercles and tips of digits leaden gray; in close-up view, dorsal surfaces and eyes have a pattern of numerous very small light dots on a dark brown background. In preservative, upper surfaces and flanks dark purplish-gray, almost black.

Measurements of holotype. Snout-vent length 44.6; head length 15.2; head width 16.3; eye diameter 5.4; interorbital distance 5.9; eye-nostril distance 4.6; internasal distance 3.6; forearm length 12.9; hand length 11.2; femur length 19.9; tibia length 19.0; foot length 17.7.

Variation. Measurements for the male and female paratypes are, respectively: snout-vent length 41.6, 47.7; head length 14.7, 18.4; head width 16.4, 19.3; eye diameter 4.7, 6.6; interorbital distance 4.2, 6.2; eyenostril distance 3.7, 4.4; internasal distance 3.1, 3.4; forearm length 11.9, 12.8; hand length 11.0, 12.0; femur length 17.7, 20.6; tibia length 18.0, 19.3; foot length 17.7, 19.5. The forearm in the male paratype is slightly more robust and longer than in the two females. The light abdominal blotch is variable in size, being smallest in the male paratype and largest in the female paratype.

Etymology. The specific epithet “ pholeter ” is a Greek word, herein used in apposition, which means “one who lurks in a hole”, in allusion to the cryptic habits of the species (see below).

Distribution. Holoaden pholeter is known only from the type locality, at 1200-1400 m a.s.l., on the eastern portion of the Serra dos Órgãos (a subdivision of the Serra do Mar mountain range), within the Atlantic Forest domain (fig. 4).

Natural history. All three specimens of Holoaden pholeter were collected at night. The holotype was found when it emerged from the leaf litter that was accumulated among tree roots after the site was disturbed by one of us (TAD). Paratype MNRJ 53483 was collected on the leaf litter, whereas MNRJ 53482 was found shortly afterwards, hidden inside a hole at the base of a tree, ca. 1 m from where the female was found. The hole where it was found (ca. 10 cm high, 10 cm deep, and 5 cm wide) was adjacent to a second hole, quite similar in dimensions and structure, which may have been used by the female. The floor of these holes consisted of bare soil with a shallow depression (on which the male was nested). Although there was abundant leaf litter on the forest floor surrounding this double den, its interior was clean of litter, as was the small area within 10 cm of its entrance. Judging by these observations, it is possible that this shelter was “cleaned up” by its occupant(s). We cannot assure that Holoaden pholeter (and maybe other congeners) actually “prepare” such dens, but if they do, this would represent a unique behavior among terraranan frogs. Nevertheless, our observations, along with those of Lutz (1958), suggest that Holoaden spp. are reclusive animals, frequently hiding in various types of shelters.

Upon capture, MNRJ 53483 released a copious amount of a colorless and very sticky secretion. It is likely that the numerous, conspicuous dorsal glands of Holoaden are responsible for secreting that substance, possibly as a defense, though there is currently no information on other species of the genus regarding such behavior nor the chemical nature of such secretions.

The holotype and paratype MNRJ 53483 contained large unpigmented eggs, as is believed to occur in all Terrarana, a clade of direct-developing frogs ( Hedges et al. 2008). Similar eggs were reported for H. bradei by Lutz (1958) who observed parental care and direct development in that species.

Figures

FIGURE 1. Holoaden pholeter sp. nov., holotype (MNRJ 51475, adult female, SVL 44.6 mm), in life.

FIGURE 2. Holoaden pholeter sp. nov., holotype (MNRJ 51475, adult female, SVL 44.6 mm), dorsal and ventral views.

FIGURE 3. Holoaden pholeter sp. nov., holotype (MNRJ 51475). Dorsal and lateral views of head; ventral views of hand and foot; scale bars represent 5 mm.