Description
Myersiohyla neblinaria is a medium-sized robust treefrog, with males reaching a snout-vent length of 47.7 - 52.3 mm, and females 54.0 - 61.6 mm. It has a large head that is slightly longer than wide, with the head length representing about a third of the total body length. The snout is rounded in dorsal view and truncated in lateral view, with a rounded canthus rostralis and a concave loreal region. The lip is not flared, and the nostrils are slightly protuberant, directed dorsolaterally and located posteriorly to the anterior margin of the lower jaw. The dorsal surface of the head is slightly depressed. The eyes are large, and the distance between the orbits is shorter than the eyelid. The tympanum is rounded, with a diameter corresponding to about 40% of the eye diameter. The supratympanic fold is well-developed, extending from the posterior margin of the eye to the anterior margin of the arm insertion. On the ventral surface of the male head, the vocal sac is single and singular, but indistinct, and glandular tissue is present in the mental area, but the gland is not externally visible. The skin is smooth on the dorsal surfaces and on most of the ventral surfaces, with a finely granular texture on the abdomen. The cloaca opens in a posteroventral direction at the midlevel of the thighs and is surrounded by numerous tubercles on its sides and below (Faivovich et al. 2013).

The arms are well-developed, with a robust forearm possessing a row of low tubercles irregularly spaced along its ventrolateral edge. The fingers are long and slender, with relative lengths of 1 < 2 < 4 < 3 and prominent ovoid apical disks. Webbing is only present at the base of these fingers and restricted to the outer ones, with a formula of II 2⅓–3½ III 3+–3+ IV. On the ventral surface of these fingers, the tubercles are large and predominantly rounded, except for the distal one on finger IV, which has an irregular shape. The tubercles on the palm of the hand are equally large, rounded or irregularly shaped. On the metacarpus, the outer tubercle is small, rounded, and bifid, while the inner one is large and elliptical. A well-developed and semicircular prepollex is present on the finger I. A single glandular nuptial pad covers part of this prepollex and finger I, composed of minute dark epidermal projections (Faivovich et al. 2013).

The legs are well-developed and moderately robust. The tibia measures approximately half the length of the body, while the foot comprises about 40% of the body length. There are no calcar projections or tarsal folds, although the skin in this area is slightly thickened. On the sole of the foot, the inner tubercle is large and elliptical, while the outer one is rounded. The toes are relatively short and have ovoid apical discs, smaller when compared to the finger ones. The relative lengths of these toes are 1 < 2 < 3 ≈ 5 < 4. Extensive webbing is present on the feet, with a formula of I 2–2 II 1½–2½ III 2–3 IV 2½–1½ V. Subarticular tubercles are prominent and rounded, and a series of a few flattened tubercles is present at the base of the toes (Faivovich et al. 2013).

DIAGNOSIS:

Adult Myersiohyla neblinaria can be distinguished from their closest relatives based on their coloration patterns, body proportions, and morphological details on the hand. With a dorsal coloration ranging from uniform, marbled, or reticulated light to dark brown, Myersiohyla neblinaria is quite distinct from Myersiohyla chamaeleo and Myersiohyla liliae, which have a dorsal coloration with a greenish to light tan or brown background, punctuated by stellate melanophores. Among the species that exhibit similar variation in dorsal coloration, Myersiohyla neblinaria can be differentiated from Myersiohyla inparquesi by the absence of sagittal black lines on finger and toe discs (present in Myersiohyla inparquesi); and from Myersiohyla loveridgei, Myersiohyla aromatica, and Nesorohyla kanaima (a former member of the genus Myersiohyla) by being a larger species, with a minimum snout-vent length of 47.7 mm (maximum snout-vent length of 37.8 in Nesorohyla kanaima, 45 mm in Myersiohyla loveridgei, and 46.6 mm in Myersiohyla aromatica). Furthermore, it differs from Myersiohyla aromatica by having a single nuptial pad (double), and from Nesorohyla kanaima by being a more robust species, with more developed prepollex and dark colored nuptial pads (slender body, reduced prepollex and thin, whitish nuptial pad). Among these species, Myersiohyla neblinaria is only known to co-occur with Myersiohyla chamaeleo (Faivovich et al. 2013, Pinheiro et al. 2019).

COLORATION:

Adult individuals of Myersiohyla neblinaria exhibit considerable variation in their dorsal color. In life, its dorsum are uniform, marbled, reticulated, or blotched by different shades of brown and tan. In most of the individuals, a dark brown middorsal line is present. The limbs have contrasting darker brown transversal bars. The dark brown flanks and thighs are mottled or have lighter blotches of variable size. The iris is golden to coppery yellow with fine black reticulation. Hand and toe discs are almost black dorsally, without sagittal black lines. Ventrally, individuals are colored in variable shades of purplish brown, with tan markings across the chest (Faivovich et al. 2013). In preserved individuals, the contrasting shades of brown and tan on the dorsal surfaces of the body and limbs are maintained, as well as the darker middorsal line. The apical discs become dark gray dorsally. The ventral surface acquires a brown hue, and the lighter markings persist in the chest (Faivovich et al. 2013).

VARIATION:

Apart from the most notable variation in coloration patterns and sexual dimorphism in body size stated above, the forearm is proportionally more robust in males. Web extension on the feet can vary according to the formula I (2–2½)–(2–2½) II (1+–2-)–(2½–3) III (1½–2)–(2–3) IV (2½–3)–(1+–2-) V (Faivovich et al. 2013).

Distribution and Habitat

Country distribution from AmphibiaWeb's database: Venezuela

View distribution map in BerkeleyMapper.

Myersiohyla neblinaria is only known from the highlands of the Neblina mountain range, on the border between southern Venezuela (Amazonas state) and northwestern Brazil (Amazonas state). Although it has been formally reported only to the Venezuelan side of this mountain range, its occurrence on the Brazilian side is expected. It inhabits the mosaic of typical montane environments, including open seasonally flooded savannas, rocky outcrops, and forestal formations. Individuals have been recorded from 1450 to 2100 m above sea level (Faivovich et al. 2013).

Life History, Abundance, Activity, and Special Behaviors
Given the limited sightings of Myersiohyla neblinaria due to its remote habitat, our understanding of the species' biology remains scarce. The available information derived from a few expeditions indicate that it is a nocturnal species, which can be found active on the margins of streams, perched on vegetation, rocks, or on mossy and grassy ground. During the day, the species rests in the axils of rosette-forming plants, such as large bromeliads(Faivovich et al. 2013).

Males have been heard calling at night in February, and an individual was recorded calling from beneath a cascade in a stream with large stones. The species' call is a long train of well-spaced notes lasting 0.3 - 0.4 seconds, emitted at a rate of approximately 23 notes per minute. These individual notes are pulsated and consist of 7 - 9 pulses. The call is frequency modulated, with the fundamental frequency ranging from around 1500 Hz at the beginning to approximately 1600 Hz at the end. Some gravid females were collected in November and February, and all males collected during these months had well-developed nuptial pads, suggesting that breeding activity occurs during this period (Faivovich et al. 2013).

When disturbed, a gravid female produced a considerable amount of a milky white exudate on its dorsum (Faivovich et al. 2013).

Larva
Tadpoles of Myersiohyla neblinaria at Gosner stage 25 exhibit a wide variation in total body length (22 to 76 mm), suggesting that they are long-living larvae. The anterior portion of their body is dorsoventrally flattened, while the posterior portion is ovoid. The eyes are small and located dorsolaterally. The snout is truncated dorsally and sloping laterally, with small nostrils that have fleshy rims and two triangular projections. The spiracle is positioned laterally on the left side of the body, fused to it in its distal portion, and with a dorsally-oriented opening. The vent tube is on the right of the body, longer than wide, and fused to the lower fin. The fin originates before the tail dorsally and at the body-tail junction ventrally, tapering posteriorly and culminating in a pointed tip at the tail's end (Faivovich et al. 2013).

The oral disc is positioned ventrally and relatively large. It is surrounded by a single row of low marginal papillae and a few scattered submarginal papillae in the distal area. Many teeth rows are present, with a formula ranging from 9/10 to 16/21. There are small gaps between them, which have approximately the same length. Near the mouth, the teeth are wider, resulting in the distal rows having more teeth. The sheaths are pigmented, with the upper jaw sheath being slender with small serrations, and the lower jaw sheath being V-shaped with low rounded serrations (Faivovich et al. 2013).

According to the limited field notes available, these tadpoles are greenish colored in life, with darker pigmentation scattered along the head, body, and tail. Patches of iridophores are also visible above the eyes. They are active both during the day and night, and can be found swimming in crevices of rocks in stream sections with reduced water flow (Faivovich et al. 2013).

They differ from the known tadpoles of closely related species by having a longer fin and a single row of marginal papillae with scattered submarginal papillae around the oral disc (the fin starting posteriorly to the base of the tail, three rows of marginal papillae, and no submarginal papillae in Myersiohyla inparquesi); a dorsoventrally flattened body (globular in Myersiohyla aromatica and Myersiohyla chamaeleo); and more rows of teeth, with a minimum formula of 9/10 (maximum of 6/11 for Myersiohyla chamaeleo and 2/4 for Nesorohyla kanaima) (Faivovich et al. 2013).

Trends and Threats
Despite limited data on population sizes and temporal trends of Myersiohyla neblinaria, and the species being highly constrained to a single montane region (Faivovich et al. 2013), its occurrence in a remote and inaccessible area currently encompassed by protected areas on both the Venezuelan and Brazilian sides limits many of the direct threats to its survival and viability. The increasing impacts of climate change on species typical of colder montane environments, along with the emergence of globally impactful pathogens, are considered current threats to the species (Señaris and Rojas-Runjaic 2022).

Possible reasons for amphibian decline

Subtle changes to necessary specialized habitat
Disease
Climate change, increased UVB or increased sensitivity to it, etc.

Comments

PHYLOGENETIC RELATIONSHIPS:

Maximum Parsimony, Bayesian Inference, and Maximum Likelihood analyses based on the information of mitochondrial and nuclear DNA have consistently shown the genus Myersiohyla as one of the earliest diverging lineages within the treefrog Cophomantini tribe radiation, and the sister taxa of the monotypic genus Nesorohyla. Within the genus, Myersiohyla neblinaria is found to be sister taxa of a clade composed by Myersiohyla liliae and Myersiohyla chamaeleo. However, as of 2023. only three of the six known species of Myersiohyla have ever been included in such phylogenetic inferences, which greatly hinders our resolution on the species' relationships within this genus (Faivovich et al. 2013, Pinheiro et al. 2019).

ETYMOLOGY:

Myersiohyla neblinaria was named in reference to its locality of occurrence, the Neblina mountain range, in the southeasternmost Venezuela. The species epithet 'neblinaria' means 'related to Neblina’ (Faivovich et al. 2013).

OTHER INTERESTING INFORMATION:

The number of labial tooth rows in the oral discs of Myersiohyla neblinaria tadpoles (up to 16/21) is the highest known among all living anuran larvae. However, we still have limited knowledge about the biological significance of such a high number of tooth rows, and whether it is an ancestral characteristic throughout the tribe radiation or secondarily developed. Furthermore, further research is needed to understand a putative ontogenetic increase in such a number of labial tooth rows (Faivovich et al. 2013)

Specimens of Myersiohyla neblinaria were initially collected from its remote habitat during 1984-1985. However, it took several years of investigation and analysis from various data sources before the species was formally described in 2013 (Faivovich et al. 2013). This significant time lapse highlights the value and relevance of information sheltered within scientific collections over time.

References
Faivovich J, McDiarmid RW, and Myers CW. (2013). Two new species of Myersiohyla (Anura: Hylidae) from Cerro de la Neblina, Venezuela, with comments on other species of the genus. American Museum Novitates 3792, 1–63 [link].

Pinheiro PD, Kok PJR, Noonan BP, Means B, Haddad CFB, and Faivovich J. (2019). A new genus of Cophomantini, with comments on the taxonomic status of Boana liliae (Anura: Hylidae). Zoological Journal of the Linnean Society 185, 226–245 [link].

Señaris JC and Rojas-Runjaic FJM. 2022. Myersiohyla neblinaria (amended version of 2020 assessment). The IUCN Red List of Threatened Species 2022: e.T87735921A198667433. https://dx.doi.org/10.2305/IUCN.UK.2022-1.RLTS.T87735921A198667433.en. Accessed in June 2023

Species Account Citation: AmphibiaWeb 2023 Myersiohyla neblinaria <https://amphibiaweb.org/species/8110> University of California, Berkeley, CA, USA. Accessed Apr 18, 2024.

Citation: AmphibiaWeb. 2024. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 18 Apr 2024.

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