Description
Hyalinobatrachium yaku is a species of glass frogs with small, middorsal, dark green spots on the head and dorsum, and a transparent pericardium. It was described from four males, one female, and two juveniles. The snout-vent length in adult males is 20.8 – 22.3 mm and about 21.1 mm for the adult female. The head is just wider than body. The snout is truncate in the lateral view. The nostrils are slightly bulging and oval. Enameled glands are absent from sides of head in this species. The area between the eye and the nostrils are slightly concave. When it comes to forelimbs, there is basal webbing between Fingers 1 and 2, and moderate webbing between external fingers. There is also a small pad on Finger 1. The hind limbs are slender with a tibia length about 59% of snout-vent length and moderate foot webbing. (Guayasamin et al. 2017)

DIAGNOSIS:

Hyalinobatrachium yaku is closely related to H. pellucidum but is distinguished by a longer call and small, dark green spots on its head. Hyalinobatrachium yaku can be also distinguished by a completely exposed heart and presence of middorsal dark green spots on the anterior half of the body. Only H. talamancae and H. vireovittatum share these traits, however, they are not phylogenetically related and can be differentiated by the dark green dorsal spots in H. yaku. Hyalinobatrachium munozorum and H. ruedai can be found in sympatry with H. yaku, but these species have a white or mostly white pericardium vs the transparent pericardium in H. yaku, dorsal pigment cells of different sizes, which in contrast are uniform-sized in H. yaku. Additionally, the snout is rounded in lateral view in both H. munozorum and H. ruedai, which in contrast is truncate in H. yaku. Lastly, they lack the row of dark green middorsal spots of H. yaku, which also differentiates the focal species from H. anachoretus. Additionally, the call of H. anachoretus has a lower dominant frequency, 4670 – 4800 Hz versus 5219.3 – 5329.6 in H. yaku (Guayasamin et al. 2017).

COLORATION:

The dorsal surfaces of this species are apple green to yellowish green with small yellow spots and tiny gray to black pigment cells. Along the midline from the posterior head to the anterior half of the body there are a few small, well-defined dark green spots, with the largest spots located in the anterior region. The red heart is fully visible along with red ventral veins and white bones through the transparent parietal peritoneum, pericardium, kidneys and urinary bladder are transparent. Iris coloration in life is silver to yellow, with small dark spots that are concentrated around the pupil, giving the impression of a ring (Guayasamin et al. 2017).

When put in preservatives, the dorsal surfaces are pale white with tiny lavender to black pigment cells. There is no trace of the characteristic dark green middorsal spots in preservative specimens. The ventrum becomes white. The iris turns white with lavender pigment cells growing more numerous towards the pupil (Guayasamin et al. 2017).

VARIATION:

The other male from the same locality as the holotype (a stream near the Kallana river, near the Kichwa community of Kallana, province of Pastaza, Ecuador) has more foot webbing than the holotype (Guayasamin et al. 2017). There may be sexual dimorphism, with the female being smaller than the males. The eye diameter in males is 2.4 - 2.5 mm and 1.6 mm in the female specimen. The limbs and bones are also smaller in the female when compared to males. There is no color difference recorded between sexes (Guayasamin et al. 2017).

Distribution and Habitat

Country distribution from AmphibiaWeb's database: Ecuador

View distribution map in BerkeleyMapper.

Hyalinobatrachium yaku is found in three localities in the Amazonian lowlands of Ecuador in tributaries of the Kallana River at elevations between 300 - 360 meters: Timburi-Cocha Research Station, near San José de Payamino in the province of Orellana, near Ahuano in the province of Napo, the Kichwa community of Kallana in the province of Pastaza. Given the distance between the sites, it is likely that the species distribution extends into Peru (Guayasamin et al. 2017).

Life History, Abundance, Activity, and Special Behaviors
Hyalinobatrachium yaku is nocturnal, rare, and found in streams affluent of the Kallana river in the province of Pastaza, Ecuador (Guayasamin et al. 2017).

Clutch size in this species is unknown, but males provide parental care by attending to egg clutches located on the underside of leaves overhanging streams (Guayasamin et al. 2017).

The reproductive biology of H. yaku is still undescribed. The species authority reported that they rely on water, however, it was only true for two out of three populations identified. The third population was found in shrubs, grasses and ferns, more than 30 meters away from the closest stream (Guayasamin et al. 2017).

Although there is little information on the breeding biology of this species, for a closely related species, Hyalinobatrachium cappellei, reproduction occurred during the wet season and was considered prolonged breeding. Reproductive behavior in H. cappellei is as follows: a female approaches the calling male, which initiates the vocalization of courtship call. The female begins touching the male and the male ‘turns’ its body around the female to initiate amplexus. The couple traverses both the upper and lower face of the leaf to find an oviposition site. The female leaves the clutch while male remains. The male remains on clutch while the female abandons the reproductive site (Noronha and Rodrigues 2018). Noronha, J. D. C. D., & Rodrigues, D. D. J. (2018). “Reproductive behaviour of the glass frog Hyalinobatrachium cappellei (Anura: Centrolenidae) in the Southern Amazon.” Journal of Natural History, 52(3-4), 207-224.

The advertisement call consists of a single tonal note, which they make calls from the underside of leaves. The call consists of a frequency of 5219.3 – 5329.6 Hz, a pulse rate of 44.1 kHz/second and duration of 0.27 - 0.4 seconds. No aggressive behavior was observed among conspecific males or between males and predators (Guayasamin et al. 2017).

Trends and Threats
The species authority recommend that H. yaku be given a threat status of “Data Deficient.” However, water pollution, mainly through oil and mining activities, represents one of the biggest threats for Amazonian amphibians, as well as for numerous other water-dependent species. Extraction of natural resources increases the level of regional road development, which could threaten populations of H. yaku due to habitat degradation and isolation. Additionally, at one site, some of the specimens were found calling from the underside of leaves of riverine vegetation in pristine forests suggesting that this species needs more undisturbed habitats to reproduce. The authors also predict that climate change may also negatively impact their habitat in the future (Guayasamin et al. 2017).

Possible reasons for amphibian decline

General habitat alteration and loss
Habitat modification from deforestation, or logging related activities
Mining
Habitat fragmentation
Local pesticides, fertilizers, and pollutants
Climate change, increased UVB or increased sensitivity to it, etc.

Comments

PHYLOGENETIC RELATIONSHIPS:

The species was placed in the genus Hyalinobatrachium on the basis of morphological and molecular data. The main diagnostic phenotypic traits of Hyalinobatrachium are: (1) the ventral parietal peritoneum is completely transparent; (2) the digestive tract and bulbous liver are covered by iridophores; (3) humeral spines absent; (4) the bones are white in life; and (5) males call from the undersides of leaves. Additionally, Maximum Likelihood analysis of 12S, 16S, ND1 mitochondrial sequences has confirmed that this species belongs to the genus Hyalinobatrachium and is sister to H. pellucidum (Guayasamin et al. 2017).

ETYMOLOGY:

The specific epithet “yaku” is the Kichwa word for “water”. Kichwa is the language of indegious people of Ecuador. Water is fundamental for the reproductive biology of all glass frogs although the water resources for this frog may already be threatened due to water pollution with oil and mining (Guayasamin et al. 2017).

References

Guayasamin, J.M., Cisneros-Heredia, D.F., Maynard, R.J., Lynch, R.L., Culebras, J., Hamilton P.S. (2017) “A marvelous new glassfrog (Centrolenidae, Hyalinobatrachium) from Amazonian Ecuador.” ZooKeys, 673, 1–20. [link]

Species Account Citation: AmphibiaWeb 2021 Hyalinobatrachium yaku: Yaku Glassfrog <https://amphibiaweb.org/species/8622> University of California, Berkeley, CA, USA. Accessed Nov 21, 2024.

Citation: AmphibiaWeb. 2024. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 21 Nov 2024.

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