Sciency Thoughts: Fanged Frogs

Showing posts with label Fanged Frogs. Show all posts

Tuesday, 4 June 2019

Limnonectes savan: A new species of Fanged Frog from Laos and Thailand.

In a paper published in the journal ZooKeys on 16 May 2019, Somphouthone Phimmachak of the Department of Biology at the National University of Laos, Stephen Richards of the Herpetology Department at the South Australia Museum, Niane Sivongxay, also of the Department of Biology at the National University of Laos, Sengvilay Seateun, agian of the Department of Biology at the National University of Laos, and of the Department of Zoology at Kasetsart University, Yodchaiy Chuaynkern of the Department of Biology at Khon Kaen University, Sunchai Makchai of the National Science Museum, and Hannah Som and Bryan Stuart of the North Carolina Museum of Natural Sciences, describe a new species of Fanged Frog from central and southern Laos and northeastern Thailand.

The new species is named Limnonectes savan, where 'savan' means 'paradise' in Lao, and is a common shortening of Savannakhet Province in Laos, where the species was first discovered, and where it appears to be most numerous. These Frogs have broad, flat heads and stocky bodies that taper towards the groin. The limbs are also robust, though with slender toes. The skin is covered with tubercles, and brown or tan in colour with a grayish white underside; some specimens have a pale vertebral stripe that runs from the tip of the snout to the vent. Females are less robust than the males.

Limnonectes savan in life. (A) Lateral view of male. (B) Lateral view of female. Phimmachak et al. (2019).

The species was found living in Savannakhet, Khammouan, and Champasak provinces in Laos and Ubon Ratchatani Province in Thailand; it may also be present in Amnat Charoen Province in Thailand. It occurs in hill and semi-evergreen forests at altitudes of between 254 and 790 m, Typically being found in or near narrow streams (less than 3 m across) or pools. It breeds in puddles on the forest floor in the rainy season.

Habitat of Limnonectes savan in Savannakhet Province, Vilabouli District, Laos in December 2008 at (A) Houay Khalai Stream, Ban Khalai Village, and (B) Houay Hong Stream, Ban Houay Hong Village. Phimmachak et al. (2019).

Thursday, 15 January 2015

A new species of Fanged Frog from Sulawesi.

Fanged Frogs, Limnonectes spp., are unique among Frogs in that the males are typically larger than the females, and frequently fight for territories, the females then mating with the males perceived as having the best territories in which to lay their eggs, a reproductive strategy common among Fish and Mammals, but otherwise unknown among Amphibians. The males show several adaptations to this lifestyle, notably enlargement of the head, which in extreme cases can comprise half the body-length, and the development of fang-like protrusions on the lower jaw, which give the group its common name. The group are known to have undergone a considerable adaptive radiation on the island of Sulawesi, although the exact number of species present, as many were originally described as populations of species described elsewhere, something which is now realized to be erroneous.

In a paper published in the journal PLoS One on 31 December 2014, Djoko Iskandar of the School of Life Sciences and Technology at Institut Teknologi Bandung, BenEvans of the Center for Environmental Genomics at McMaster University and JimmyMcGuire of the Museum of Vertebrate Zoology, and Department of Integrative Biology at the University of California, Berkeley, describe a new species of Fanged Frog from Sulawesi Utara, Gorontalo, Sulawesi Tengah, and Sulawesi Barat Provinces on Sulawesi, i.e. the entire of the Northern Peninsula and the western part of the Central Core of the island; it may also be present in the highlands of the interior of the Central Core.

The new species is named Limnonectes larvaepartus, meaning ‘to give birth to larvae’ in reference to the unique reproductive strategy of the species. Male adults of the species examined ranged from 39.8 to 44.5 mm, while adult females ranged from 41.2 to 44.3 mm. The Frogs are typically brownish grey, but may be dark brown, reddish brown or golden tan in colour, the underside being yellowish or cream. About 23% of specimens examined had a prominent stripe along the back.

Limnonectes larvaepartus. Male, left, and female, right, collected from Desa Uaemate along the Tasio-Tibo Road, KabupatanMamuju, Provinsi Sulawesi Barat, Sulawesi Island (02.61287S, 119.14238 E, 89 m elev.). Iskander et al. (2014).

Limnonectes larvaepartus is unique in that it apparently combines internal fertilization with the birth of live tadpoles, an otherwise unknown reproductive strategy. A number of Frog species are known to combine internal fertilization with egg laying, and members of the African genera Nectophrynoides and Nimbaphrynoides, as well as the now extinct Puerto Rican Eleutherodactylus jasperi, combine internal fertilization with the birth of small adult Frogs, but the combination of internal fertilization and live birth of tadpoles has not previously been documented.

The birth of live tadpoles was not actually observed in Limnonectes larvaepartus, however several female specimens were found to be pregnant with tadpoles, though none bore Frogs, and several gave birth to viable tadpoles while being handled, and free living tadpoles were also observed. In the direct developing Eleutherodactylus coqui, the eggs of which usually develop directly into Frogs, can hatch as tadpoles if the eggs are disturbed, so potentially Limnonectes larvaepartus could have a similar strategy, giving birth to tadpoles only when stressed, however the presence of live free-living tadpoles in the wild, combined with the absence of any partially metamorphosed Frogs in gravid females, suggests that this is unlikely.

Newborn tadpoles of Limnonectes larvaepartus. Iskander et al. (2014).

Thursday, 27 November 2014

A new species of Fanged Frog from Sarawak.

Fanged Frogs of the genus Limnonectes get their name from fang-like protrusions on the jaws of the male Frogs. They are unusual for Frogs in that the males are larger than the females (the reverse is usually the case), and apparently defend territories through physical contests with other males, with females mating with the males with the best territories. The males also often have greatly enlarged heads, sometimes forming as much as half the body, apparently also an adaptation to this lifestyle.

In a paper published in the Raffles Bulletin of Zoology on19 September 2014, Masafumi Matsui and Kanto Nishikawa of the Graduate School of Humanand Environmental Studies at Kyoto University and Koshiro Eto of the Kyoto University Museum describe a new species of Fanged Frog from Samarahan Division in the state of Sarawak in East Malaysia (Borneo).

The new species is named Limnonectes cintalubang, meaning ‘hole-lover’ in Malay, due to its being found dwelling in burrows. The species is described from nine specimens, one male, two females and seven juveniles. The male was 45 mm in length, the females 32.0 mm and 43.1 mm. The Frogs are a dark chocolate brown colour, with pale undersides and small blue-white spots. They did not appear to dig their own burrows, instead occupying what appeared to be abandoned Rat burrows – although no Rats could be found living in the area. The skin of Limnonectes cintalubang is exceptionally fragile, which Matsui et al. suggest may be a defence mechanism, the Frog losing part of its skin to an attacker to evade capture.

Limnonectes cintalubang, male. Matsui et al. (2014).

Thursday, 13 November 2014

Breeding behaviour in a Fanged Frog from Vietnam.

Fanged Frogs of the genus Limnonectes are found across southern China and Japan, as well as the Philippines, Southeast Asia and much of Indonesia. They are unusual in that the males are considerably larger than the females (the reverse of the situation found in most Frogs), with greatly enlarged heads and powerful jaws. The name of the group comes from the fang-like odontoid processes on the lower jaws of both sexes. Mating behaviour seems to vary considerably within the group, with some species giving birth to live young, while others lay eggs, sometimes in nests, and sometimes provide parental care to nestlings. The males often lack vocal sacs and in many species have been seen to fight over territory.

In a paper published in the journal Zootaxa on 4 November 2014, JodiRowley of the Australian Museum Research Institute, Doung Thi Thuy Li and Huy Doc Huang of the Faculty of Biology at the University of Science-Ho Chi Minh City and Ronald Altig of the Department of Biological Sciences at Mississippi StateUniversity, describe the mating behaviour of the Fanged Frog Limnonectes dabanus for the first time.

Males of Limnonectes dabanus show the most extreme enlargement of the head of any species of Fanged Frog, with a head that comprises almost half the body length. The species is found on the Langbian Plateau in Lam Dong Province, Vietnam, and around tributaries of the Mekong and Krong No rivers in Cambodia and southern Vietnam. The species lives in forested areas, and its biology is not well understood.

Adult male Limnonectes dabanus. Rowley et al. (2014).

Rowley et al. observed the Frogs at the Nui Ong Nature Reserve in Binh Thuan Province, Vietnam, where they were able to observe the mating, and collect specimens of the eggs and tadpoles. Males of Limnonectes dabanus were observed calling from beside a rivulet beneath a rock overhang, from a drainage line in mixed forest, and at the base of a Pandanus plant in a large but shallow temporary pond. Despite lacking vocal sacs they were able to produce a short monotonal chirp, which sounded to human listeners like a drip falling into water; Rowley et al. suggest that if other species of Fanged Frogs make similar noises then this might have been overlooked by herpetologists. One male was observed with two females in close attendance while none of the calling males had another male nearby, suggesting that the males secure and defend territories, mating with any female that comes to its territory (though combat between males was not observed).

Adult female Limnonectes dabanus. Rowley et al. (2014).

Eggs within the rock overhang territory were found on the underside of the overhang (about 40 cm above the water surface), on the adjacent rockface and in the water beneath the overhang (which was mostly only a few millimetres deep). This distribution is difficult to understand, as it appears the female Frogs were relatively unconcerned as to where their eggs were deposited. Rowley et al. suggest that the female Frogs may be exhibiting behaviour similar to that seen in Frogs of the genus Mixophyes, who lay eggs they kick them onto a nearby moist surface, with some eggs subsequently falling to the floor.

Adult male, M, and female, F, in seep area beneath an overhanging boulder with eggs on the ceiling (yellow up arrow) and floor (yellow down arrow). Rowley et al. (2014).

Tadpoles were collected from a muddy, leaf-litter filled pool on the forest floor. The largest was 21.2 mm in length, with coarsely placed teeth and an upper jaw sheath with fine serrations, and a v-shaped lower sheath. The tail fin was clear with speckles.

Limnonectes dabanus (A) eggs grouped for photography, (B) tadpole in lateral view 21.2 mm, tail tip damaged). (C) Oral apparatus of same tadpole (stained with crystal violet to reveal translucent structures) and (D) dorsal view of same tadpole. Rowley et al. (2014).