Description
Gastrotheca nebulanastes is a moderately small frog with a head slightly wider than long. Snout vent length (SVL) is about 37.3 mm. The snout appears round from above and nearly truncate in profile. Lips are round and top of head appear flat. Diameter of eye is about equal to its distance from nostril. Arms are slender with moderately large hands that consist of long unwebbed fingers. The discs of the fingertips are moderately large and round. Relative finger lengths (decreasing) are 3,4,2,1. The hind limb is robust with tibia length 54.1% of the SVL. The toes are long and not webbed except for basal webbing between toes 4 and 5. Relative length (decreasing) of toes is 4,5,3,2,1. Skin on dorsal surface, throat, belly, and ventral surfaces appear granular whereas skin on other surfaces is smooth (Duellman et al. 2011).

G. nebulanastes is placed in the genus Gastrotheca because of its unique feature of a closed brood pouch on the dorsum of females. It is similar to G. excubitor but can be distinguished from other closely related members by its longer second finger than first, frequency call range between 1653-1730 Hz, bluntly rounded snout in dorsal view, coarsely granular skin, and absence of stripes (Duellman et al. 2011).

In life, dorsal surfaces present dull green with dark brown to black markings. The flanks are colored like dorsum except with orange-brown suffusion. The hidden surfaces of limbs are orange-brown. Ventral surfaces appear metallic tan (Duellman et al. 2011).

In preservation, dorsal surfaces exhibit pale brown with darker brown markings. The flanks are creamy tan with three large dark brown to black vertical marks. The anterior surfaces of thighs appear tan with dark brown transverse bars extending over dorsal surfaces while the posterior surfaces are dark brown (Duellman et al. 2011).

Males are slightly larger than females. The skin on dorsum is variously granular. The dorsal coloration varies from being beige to dark brown, gray or green with numerous green flecks and a darker pattern of two continuous or interrupted longitudinal marks connected to the interorbital bar. In some individuals the darker pattern is most visible and green flecks are overshadowed by the background dorsal coloration, whereas in other individuals the green flecks are predominant and cover the darker longitudinal marks. The dorsal coloration extends onto the dorsal surfaces of digits and limbs, with transverse bars on thighs barely noticeable in some individuals and presenting a distinct contrast in other individuals. In juveniles the dorsal surface is brown with bronze tones, and green or bluish green flecks are predominant over the darker longitudinal markings; the throat and chest are yellow or cream, whereas the ventral surfaces of abdomen and limbs are vermillion (Duellman et al. 2011).

Distribution and Habitat

Country distribution from AmphibiaWeb's database: Peru

	View distribution map in BerkeleyMapper.
	View Bd and Bsal data (18 records).

G. nebulanastes is known only from elevations of 2000-3300 m in upper Río Kosñipata Valley, Manu National Park, in the Andes of southern Peru. All localities in which this species is found are in cloud forest along the road between Paucartambo and Pilcopata (Duellman et al. 2011).

G. nebulanastes inhabits, the montane scrub, ridges of steep slopes covered with Andean alder, shrubs, and abundance of terrestrial mosses, lycophites, and lichens. It is sympatric with G. antoniiochoai and parapatric with G. excubitor and G. marsupiata (Duellman et al. 2011).

Life History, Abundance, Activity, and Special Behaviors
Males of this species call from grasses, shrubs, trees, terrestrial and arboreal bromeliads, and the ground in the montane scrub or understory of the cloud forest. They can be heard calling on most nights on rock walls bordering the road at elevations between 2700–2800 m. The advertisement call consists of a long note 818.2 ± 70.0 ms (range 689–916 ms) in duration with 41.6 ± 3.2 pulses (range 37–47 pulses), and one or more secondary notes. Secondary notes have duration of 30.9 ± 7.8 ms (range 24–54 ms) at frequencies of 1653–1730 Hz and typically are single-pulsed (Duellman et al. 2011).

Trends and Threats
Severe amphibian population declines in the upper Manu National Park can be attributed to the amphibian pathogenic chytrid fungus Batrachochytrium dendrobatidis from the Kosñipata Valley. Infection with this fungus has been found in G. nebulanastes specimens collected (Catenazzi et al 2011).

Batrachochytrium dendrobatidis causes an infectious disease to amphibians known as chytridiomycosis, which affects the superficial, keratin-containing layers of amphibian skin (Berger et al. 1998). As the infection advances, the skin becomes much thicker and sloughs off (Berger et al. 1998). Consequently, osmoregulation is compromised and electrolyte blood levels drop, leading to death from cardiac arrest (Voyles et al. 2009). Infection intensity appears to be a key factor in facilitating death (Vredenburg et al. 2010). However, in many frog species, even low levels of initial infection can lead to death (Skerratt et al. 2007).

Possible reasons for amphibian decline

Disease
Weakened immune capacity

Comments
G. nebulanastes is derived from the Latin nebula meaning fog and the Greek nastes meaning dweller. The name is applied because the upper Kosñipata Valley inhabited by this species commonly is enshrouded in fog (Duellman et al. 2011).

According to phylogenetic analysis of 16S mitochondrial genes, this species is the sister taxon to G. atympana, a species from farther north in the Cordillera Oriental in Peru (Duellman et al. 2011).

References

Berger, L., Speare, R., Daszak, P., Green, D. E., Cunningham, A. A., Goggin, C. L., Slocombe, R., Ragan, M. A., Hyatt, A. D., McDonald, K. R., Hines, H. B., Lips, K. R., Marantelli, G., and Parkes, H. (1998). "Chytridiomycosis causes amphibian mortality associated with population declines in the rain forests of Australia and Central America." Proceedings of the National Academy of Sciences of the United States of America, 95(15), 9031-9036.

Catenazzi, A., Lehr, E., Rodríguez, L. O., and Vredenburg, V. T. (2011). ''Batrachochytrium dendrobatidis and the collapse of montane anuran communities in the upper Manu National Park, southeastern Peru.'' Conservation Biology, 25, 382-391.

Duellman, W. E., Catenazzi, A., and Blackburn, D. C. (2011). ''A new species of marsupial frog (Anura: Hemiphractidae: Gastrotheca) from the Andes of southern Peru.'' Zootaxa, 3095, 1-14.

Skerratt, L. F., Berger, L., Speare, R., Cashins, S., McDonald, K. R., Phillott, A. D., Hines, H. B., and Kenyon, N. (2007). ''Spread of chytridiomycosis has caused the rapid global decline and extinction of frogs.'' EcoHealth, 4, 125-134.

Voyles, J., Young, S., Berger, L., Campbell, C., Voyles, W. F., Dinudom, A., Cook, D., Webb, R., Alford, R. A., Skerratt, L. F., and Speare, R. (2009). ''Pathogenesis of chytridiomycosis, a cause of catastrophic amphibian declines.'' Science, 326, 582-585.

Vredenburg, V. T., Knapp, R. A., Tunstall, T. S., and Briggs, C. J. (2010). ''Dynamics of an emerging disease drive large-scale amphibian population extinctions.'' Proceedings of the National Academy of Sciences, 107(21), 9689-9694.

Species Account Citation: AmphibiaWeb 2021 Gastrotheca nebulanastes: Kosñipata Marsupial Frog <https://amphibiaweb.org/species/7735> University of California, Berkeley, CA, USA. Accessed Nov 26, 2024.

Citation: AmphibiaWeb. 2024. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 26 Nov 2024.

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