Parjacti Treefrog
(Hyloscirtus chlorosteus)
The Parjacti treefrog has only been formally collected once in the 1970s, and so very little is known about this species. It was taken at night from a door knob at the agricultural customs inspection station in Parjacti, Bolivia. Other species within the Hyloscirtus genus are closely associated with bromeliads and lay eggs that develop into tadpoles in water. Despite numerous intensive field surveys since 1988, it has not been encountered again. The main threat to this species is the deterioration of its habitat due to agriculture, logging, and infrastructure development for human settlement. Strangely, this species has green bones, which is an unusual feature, even in amphibians!
Urgent Conservation Actions
Protection of the remaining habitat; further survey work to establish whther this species is still extant.
Parjacti, Chapare Province, Bolivia.
The scientific name of the Parjacti tree frog, Hyloscirtus chlorosteus, is from the Greek and is descriptive of the fact that this species has green bones. The common name of the Parjacti tree frog is taken from the locality where it was formally discovered.

There has been some doubt as to the taxonomic validity of this species. Some researchers have suggested that it may not represent a new species, but instead one that has already been described (e.g. Hyloscirtus armatus). However, several independent examinations of the specimen have concluded that this species is unlike any other previously described Andean hylid treefrog.
Evolutionary Distinctiveness
Order: Anura
Family: Hylidae
The Hylidae or “treefrogs” are one of the largest families of frogs, with around 600 member species and nearly 40 composite genera arranged in four subfamilies: Pelodryadinae, Phyllomedusinae, Hemiphractinae, and Hylinae. The treefrogs are usually quite distinctive in appearance, with very large eyes and finger tips expanded into gripping suction pads to enhance climbing ability. They are a diverse and widespread group of frogs, occurring in the Americas, Australasia, tropical Asia, Europe and northern Africa. Among the most bizarre of the hylid treefrogs are certain casque-headed genera, such as Triprion (the “shovel-headed treefrogs”) and Trachycephalus (the “casque-headed treefrogs”), in which the bones of the skull form a solid helmet-shaped head. Some casque-headed species use their bony heads to block the entrances of their burrows and reduce evaporative water loss.

Treefrogs have a fossil record going back to the Palaeocene (65 to 53 million years ago), evidence that the hylid treefrog lineages originated either late in the Cretaceous or early in the Cenozoic, around the time of the extinction of the dinosaurs. Some evoutionary trees indcate that the hylid treefrogs diverged from all other amphibians around 50 million years ago, which in terms of mamal lineages makes them as distinct from their closest relatives as chincillas are from porcupines.

The Parjacti treefrog has only been formally collected once in the 1970s and, despite intensive surveying efforts, has not been seen since. All observations concerning this species are therefore derived from a single subadult male specimen. Even so, this solitary Parjacti treefrog has revealed a couple of highly unusual features about its species. Firstly, it is distinguished from all other Andean hylid treefrogs in having a thick preorbital ridge – a projection the bone above the eyes reminiscent of the skull modifications of the casque-headed treefrogs. Furthermore, this species has green bones, and its scientific name H. chlorosteus is derived from the Greek meaning “green bones” as testament to this remarkable feature. Glass frogs (of the family Centrolenidae), which have transparent undersides that makes their organs clearly visible through their skin, also have green bones.
The Parjacti treefrog is known from only a single individual collected in the 1970s, which was described as a subadult male. This species is a moderate-sized brown frog, measuring around 40 mm in total length. The head of this species is wider than the body and has a prominent “preorbital ridge”, which is a projection of the skull bones over the eyes, which are greenish-gold in colour. The upper arms are slender, with the fore-arms being more robust and covered with more or less parallel rows of low dermal spines. These are probably nuptial spines which help the male to grip the female during mating. The fingers are stout with moderately large discs at their tips and very slight webbing at the base. The hind-limbs are moderately robust and long, with long toes that are partially webbed.

The skin on chest, belly, and undersurfaces of the thighs is coarsely granular, and the throat is minutely granular. The skin of the back and the upper surfaces of the hind- and fore-limbs is scattered with low lying warts. This colour of the dorsal (or upper) surfaces is brown patterned with darker brown. The thighs and sides of the body have yellowish markings. The ventral (or lower) surfaces are opalescent gold to cream in colour, with a pinkish tinge towards the rear, and the chin is also opalescent gold.
This species is an arboreal (tree-dwelling) forest species, reported in the Yungas Forest. There is no information on breeding, though it is likely that its tadpoles develop in water, as is the case for the other species in the Parjacti treefrog’s genus. Other species in the Hyloscirtus genus are known to inhabit bromeliads, a group of plants in the Neotropics that possess overlapping leaves that may trap water and organic debris, providing a habitat for numerous species of invertebrate, amphibian and other creatures. They often occur growing on trees, attaching by structural roots to branches or bark. These bromeliads are referred to as “epiphytic”, from the Greek “epi” meaning upon and “phyton” meaning plant. The larger tank-forming bromeliads contain a number of substantial pools of water (or small aquaria) between their leaves, and therefore constitute a particularly humid micro-environment and, potentially, breeding pools for these treefrogs.

The only individual of this species that has ever been collected by scientists was taken at night from a door knob at the agricultural customs inspection station in Parjacti, Bolivia. This limited information may indicate that the species is nocturnal (or night-active).
This species was found in high altitude tropical moist montane forest (or Andean cloud forest) on the oriental slopes of the Andes, at over 2,000 metres above sea level. It is also thought to be associated with permanent freshwater streams and creeks, which are likely to represent breeding habitat for the Parjacti treefrog.
This species occurs on the oriental slope of the Andes, and is known only from the locality where it was formally discovered: Parjacti, 83.2 km by road northeast of Cochabamba, on the road to Villa Tunari, Chapare Province, Department of Cochabamba, Bolivia, at an elevation of approximately 2,044 metres above sea level. The areas surrounding this locality have been well-surveyed in recent years, but the species has not been recorded again since its original collection in the 1970s.
Population Estimate
The Parjacti treefrog was described from a single subadult male specimen collected from Parjacti in the Provincia Chapare, Bolivia in the 1970s. Despite intensive searches since 1988, no other individuals have been seen and the population status of this species is therefore unknown. Given the declining quality of its habitat, it may already be extinct.
Population Trend
The Parjacti treefrog is thought to be in decline by the IUCN Red List of Threatened Species.
The Parjacti treefrog is listed as Critically Endangered in the IUCN Red List of Threatened Species because its extent of occurrence is less than 100 km sq. and its area of occupancy is less than 10 km sq., all individuals are in a single location, and there is continuing decline in the extent and quality of its habitat in the Bolivian Andes.
The main threat to this species is the deterioration of the quality of its habitat, which is continuing due to agriculture, logging, and infrastructure development for human settlement.
Conservation Underway
The Parjacti treefrog is not known from any protected areas, and there are currently no conservation measures underway fro this species.
Conservation Proposed
The priority action for this species is urgent survey work in order to determine whether it still survives in the wild. If further individuals are found, a Conservation Action Plan should be developed for this species to formally detail the distribution of this species and the threats to it survival so that appropriate conservation strategies can be developed.

In addition to conserving native habitat for this species, the IUCN Technical Guidelines for the Management of Ex situ Populations, part of the IUCN Red List of Threatened Species, recommend that all Critically Endangered species should have an ex situ population managed to guard against the extinction of the species. An ex situ population is ideally a breeding colony of a species maintained outside of its natural habitat, giving rise to individuals from that species that are sheltered from problems associated with their situation in the wild. This can be located within the species’ range or in a foreign country that has the facilities to support a captive breeding programme for that species. Since the Parjacti treefrog is categorised as Critically Endangered, the possibility of a captive breeding programme for this species should be investigated if it is still extant.
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