''Microhyla borneensis'' ( junior synonym ''Microhyla nepenthicola''), also known as the Matang narrow-mouthed frog, is a species of microhylid

frog A frog is any member of a diverse and largely carnivorous group of short-bodied, tailless amphibians composing the order Anura (ανοὐρά, literally ''without tail'' in Ancient Greek). The oldest fossil "proto-frog" ''Triadobatrachus'' is ...

found in the Matang Range in

Sarawak Sarawak (; ) is a state of Malaysia. The largest among the 13 states, with an area almost equal to that of Peninsular Malaysia, Sarawak is located in northwest Borneo Island, and is bordered by the Malaysian state of Sabah to the northeast, ...

Borneo Borneo (; id, Kalimantan) is the third-largest island in the world and the largest in Asia. At the geographic centre of Maritime Southeast Asia, in relation to major Indonesian islands, it is located north of Java, west of Sulawesi, and ea ...

. It was once the smallest known frog from the Old World (the current record holder is ''

Paedophryne amauensis ''Paedophryne amauensis'' is a species of microhylid frog endemic to eastern Papua New Guinea. At in snout-to-vent length, it is considered the world's smallest known vertebrate. (See also Ecological guild.) The species was listed in the '' ...

'' from New Guinea). Adult males of this species have a snout-

vent Vent or vents may refer to: Science and technology Biology *Vent, the cloaca region of an animal * Vent DNA polymerase, a thermostable DNA polymerase Geology *Hydrothermal vent, a fissure in a planet's surface from which geothermally heated wate ...

length (SVL) of , but adult males can reach a maximum of ,and adult females of this species have a snout-

length of ,

Tadpole A tadpole is the larval stage in the biological life cycle of an amphibian. Most tadpoles are fully aquatic, though some species of amphibians have tadpoles that are terrestrial. Tadpoles have some fish-like features that may not be found ...

s measure just 3 mm.

Discovery

''Microhyla borneensis'' was first described by

Hampton Wildman Parker Hampton Wildman Parker (5 July 1897 – 2 September 1968) was an English zoologist. Parker was Keeper of Zoology at the Natural History Museum from 1947 to 1957. He is the author of several works on snakes and frogs: Parker discovered a new speci ...

in 1928. Frogs of the species that was eventually described as ''Microhyla nepenthicola'' had been known for at least 100 years prior to its description in 2010. However, scientists had always assumed that the frogs were juveniles of another species. Researchers and Alexander Haas recognized that they were actually adults when they heard the frogs calling in Kubah National Park, since only adult frogs make calls. Adult males call from the pitcher plants at dusk. However, in 2011 it was shown that ''Microhyla borneensis'' and ''Microhyla nepenthicola'' are the same species. What was until that point commonly known as ''Microhyla borneensis'' was another species, newly described as '' Microhyla malang''. The smallest known Old World frog species prior to the description of ''Microhyla nepenthicola'' were '' Stumpffia pygmaea'' and '' Stumpffia tridactyla'', ''Stumpffia pygmaea'' with a snout-vent length of 10–12.5 mm, ''Stumpffia tridactyla'' with a snout-vent length of 8.6–12 mm.About Stumpffia tridactyl PDF.page66-67(page336-337)
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Description

''Microhyla borneensis'' is a very small species with a snout to vent length of about for females and around two thirds of this for males. It has a broadly triangular body that is flattened dorso-ventrally. The snout is obtusely pointed, the eyes are small and have round pupils and there are no visible

tympani Timpani (; ) or kettledrums (also informally called timps) are musical instruments in the percussion family. A type of drum categorised as a hemispherical drum, they consist of a membrane called a head stretched over a large bowl traditionally ...

. The skin on the dorsal surface may be smooth or bear tubercles and that of the ventral surface is always smooth. The limbs are short. The hands are unwebbed and the outer digits are spatulate. The digits of the feet are partially webbed. The dorsal surface of this frog is reddish-brown, the throat is mottled brown and the ventral surface is pale.

Distribution and habitat

''Microhyla borneensis'' is known from the Matang Range in

, but it is presumably widespread in suitable habitats in the lowlands of northern Borneo. ''M. borneensis'' is found near

Mount Serapi Mount is often used as part of the name of specific mountains, e.g. Mount Everest. Mount or Mounts may also refer to: Places * Mount, Cornwall, a village in Warleggan parish, England * Mount, Perranzabuloe, a hamlet in Perranzabuloe parish, C ...

in Kubah National Park,

. It spends much of its life cycle in the traps of the

pitcher plant Pitcher plants are several different carnivorous plants which have modified leaves known as pitfall traps—a prey-trapping mechanism featuring a deep cavity filled with digestive liquid. The traps of what are considered to be "true" pitcher p ...

Nepenthes ampullaria ''Nepenthes ampullaria'' (; Latin ''ampulla'' meaning "flask") is a very distinctive and widespread species of tropical pitcher plant, present in Borneo, the Maluku Islands, New Guinea, Peninsular Malaysia, Singapore, Sumatra, and Thailand.McPh ...

'', after which it is named. It is therefore considered a

nepenthebiont ''Nepenthes'' infauna are the organisms that inhabit the pitchers of ''Nepenthes'' plants. These include fly and midge larvae, spiders, mites, ants, and even a species of crab, ''Geosesarma malayanum''. The most common and conspicuous p ...

. This is not particularly unusual; in fact, it shares this environment with a species of crab spider, '' Misumenops nepenthicola'', which is also commonly found in '' Nepenthes'' pitchers, and is similarly named for this reason. ''Microhyla nepenthicola'' has less webbing on its feet than most frogs, which may be beneficial when trying to climb the sides of the pitcher plants, which can be slippery.

Biology

''Microhyla borneensis'' breeds in the water-filled pitchers of ''

'', a pitcher plant that is a feature of the floor of the Borneo rainforest. Multiple clutches may be laid in the same pitcher which may contain tadpoles of different ages. Metamorphosis takes place about a fortnight after the eggs are laid.

Status

This frog is seldom seen, perhaps because of its small size and inconspicuous appearance. Its numbers are thought to be in slow decline but the

International Union for Conservation of Nature The International Union for Conservation of Nature (IUCN; officially International Union for Conservation of Nature and Natural Resources) is an international organization working in the field of nature conservation and sustainable use of nat ...

(IUCN) rates it as being of "

Least Concern A least-concern species is a species that has been categorized by the International Union for Conservation of Nature (IUCN) as evaluated as not being a focus of species conservation because the specific species is still plentiful in the wild. T ...

" as it considers that the rate of decline is insufficient to justify listing it in a more threatened category. No particular threats to this species have been identified.

References

{{Taxonbar, from=Q1936018 borneensis Amphibians described in 1928 Taxa named by Hampton Wildman Parker Nepenthes infauna Endemic fauna of Borneo Endemic fauna of Malaysia Amphibians of Malaysia Taxonomy articles created by Polbot Amphibians of Borneo