Cochranella oyampiensis

Cochranella oyampiensis
Conservation status
Least Concern (IUCN 3.1)
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Subphylum:	Vertebrata
Class:	Amphibia
Subclass:	Lissamphibia
Order:	Anura
Suborder:	Neobatrachia
Family:	Centrolenidae
Genus:	Cochranella
Species:	C. oyampiensis
Binomial name
Cochranella oyampiensis (Lescure, 1975)
Synonyms
Centrolenella ametarsia Flores, 1987 Centrolenella oyampiensis Lescure, 1975 Cochranella ametarsia (Flores, 1987) [1]

Cochranella oyampiensis is a South American frog species in the glassfrog family (Centrolenidae). It was first found in a restricted region of Brazil north of the lower Amazon River and in the Guyanas. Its range is bordered northeastwards by the Atlantic and in the west essentially ends at the tepui region of the Guyana Shield, barely into Venezuela where it has only been recorded once, from the Gran Sabana.^[2]

Formerly, it was believed to occur further westwards deep into Venezuela, but this population is now known to be a distinct species (Helena's Glass Frog, C. helenae). But its range might extend further upstream the Amazon River, as the species also seems to occur in lowland Colombia and Ecuador. When this population was first discovered, it was compared with frogs subsequently recognized as C. helenae and thus mistakenly described as a new species C. ametarsia. Its local name in French is cochranelle des Oyampis ("Wayampi Glass Frog").^[3]

Description

C. oyampiensis is a tiny glassfrog that lacks humeral spines in males and has a lobed liver, placing it in the genus Cochranella. Adult males measure 17–21 mm from the snout to the vent, while the females are a bit larger at about 19.5-24.5 mm snout-vent length. Its snout tip is neatly rounded. The translucent eardrum is visible but not large, measuring about one-fourth to one-third of the eye's diameter; the tympanic annulus is not hidden except for the dorsal margin which is covered by the supratympanic fold.^[4]

Their color looks pale green above, but in fact this is much due to their green skeleton being visible through the weakly pigmented skin. This species has many clear and fine blackish spots decorating its upperside, which may appear as if they were suspended a bit above the greenish background in very weakly pigmented specimens. Helena's Glass Frog (C. helenae) on the other hand has a more heavily pigmented yellowish-green upperside (but also the characteristic spots, which led to them being confused). The back has a smooth shagreen-like texture, while the entirely transparent belly skin has a grainy surface. The forward quarter to half of the parietal (outer) peritoneum is white, while the rest is transparent, allowing to see the frog's interior. The pericardium and the inner peritoneum covering the gastrointestinal tract are white, while the inner peritoneum protecting the brown lobes of the liver is also transparent except for the anterior tip (where some iridophores may be present). The iris is greyish white with a network of thin dark grey lines; in Helena's Glass Frog it is bright yellow. Melanophores are abundant on the dorsal surface of the two outer but absent on the two inner fingers. Preserved specimens are lavender above, with the dark spotting remaining unchanged; the white iridophores of the viscera can dissolve in preserved specimens.^[4]

The dentigerous process of the vomer carries one tooth at most; it can be entirely toothless. The males have a type-I nuptial pad; the prepollex stands out at the base of the first finger. The toes and the outer two fingers of C. oyampiensis are webbed; the first two fingers (of which the first is a bit longer) are completely free. The webbing formula for the outer fingers is III (2^--2^1/3) – (1⁺-2^-) IV; for the toes, it is I 1 – (2^--2) II (1-1⁺) – (2-2^1/4) III (1⁺-1^1/2) – 2⁺ IV (2-2^1/3) – 1 V.^[4]

The disc at the tip of the third finger is mid-sized, larger than the eardrum but less than half the diameter of the eye. This species has tubercles on the thighs below the vent, but only low folds with no iridophores on the ulna and inner tarsus.^[4]

Ecology

Its natural habitats are tropical moist lowland forests and rivers; it is usually found in riparian vegetation. Occurring at elevations below 1,000 m ASL; it is apparently also absent from the coastlands up to some dozen meters above sea level.^[2]

The calls of this species have supposedly been described at least twice, but it is not clear whether they are actually of C. oyampiensis; one description appears to be of C. midas calls instead. The other notes that the males call sitting on the upperside of leaves, usually giving very brief (0.10–0.15 seconds) calls that are loudest around 4640–5160 Hz singly or doubly, but apparently never three in a row – Helena's Glass Frog (C. helenae) gives double or triple but apparently never single calls. It is unknown if and how the males physically fight for females. The clutches are deposited on either side of leaves above small streams; after hatching the tadpoles drop into the water. Other aspects of its reporoduction, as well as its tadpoles, remain undescribed as of 2008.^[3]

Though tiny and inconspicuous, it is not considered a particularly rare species. With a considerable range including several protected areas and apparently able to live in secondary forest and tolerate some amount of human use of its habitat, it is not considered threatened by the IUCN. ^[2]

Systematics and taxonomy

C. oyampiensis was for some time alled with Helena's Glass Frog (C. helenae) and Cochranella castroviejoi, and these three were called the "oyampiensis group". But actually, it seems to be a closer relative to the group of species around Cochranella spinosa, and thus the "oyampiensis group" has been abolished. The spinosa group is rather well-established and although not yet tested by cladistic analysis is more likely to by and large represent a clade than some other groups of Cochranella.^[5]

This frog was initially described in the genus Centrolenella, which is nowadays included in Centrolene. With the reassignment of Centrolenidae to reorganize known paraphyletic taxa, it was moved into its present genus due to the traits noted above. In 2008, it was found to include that the frogs that had been described as Centrolenella ametarsia are indistinguishable from the present species.^[4]

The holotype of this species is specimen MNHNP 1973.1673, that of C. ametarsia is specimen MCZ A96522.^[4]

Footnotes

1. ^ Guayasamin et al. (2008)
2. ^ ^{a b c} La Marca & Reynolds (2008)
3. ^ ^{a b} Guayasamin et al. (2008), Kok & Castroviejo-Fisher (2008), La Marca & Reynolds (2008)
4. ^ ^{a b c d e f} Guayasamin et al. (2008), Kok & Castroviejo-Fisher (2008)
5. ^ Kok & Castroviejo-Fisher (2008)

References

• Guayasamin, Juan M.; Cisneros-Heredia, D.F. & Castroviejo-Fisher, Santiago (2008): Taxonomic identity of Cochranella petersi Goin, 1961 and Centrolenella ametarsia Flores, 1987. Zootaxa 1815: 25–34 [English with Spanish abstract]. PDF fulltext
• Kok, Philippe J.R. & Castroviejo-Fisher, Santiago (2008): Glassfrogs (Anura: Centrolenidae) of Kaieteur National Park, Guyana, with notes on the distribution and taxonomy of some species of the family in the Guiana Shield. Zootaxa 1680: 25-53 [English with Spanish and French abstract]. PDF English and Spanish abstracts
• La Marca, Enrique & Reynolds, Robert (2008). Cochranella oyampiensis. In: IUCN 2008. IUCN Red List of Threatened Species. Downloaded on 07 April 2009.