Tag: toad

Exceptional reproductive biology in extremely restricted critically endangered Nimba toad

The critically endangered Nimba toad is long known for its exceptional reproductive biology. The females of this unique species give live birth to fully developed juveniles, having for nine months continuously provided nutrition to the foetuses in the womb (matrotrophy). While live birth (viviparity) among frogs and toads is rather an exception than a common characteristic, matrotrophy, in place of alternatives such as the foetus being fed with yolk, unfertilized eggs, or smaller siblings, is what makes the Nimba toad one of a kind.

However, more than 40 years of research had not been comprehensively, accessibly and completely summarised. The gap has recently been filled with a new paper, published in the open access journal Zoosystematics and Evolution by German scientists Drs. Laura Sandberger-Loua and Mark-Oliver Rödel, both affiliated with Museum für Naturkunde, Berlin, and Dr. Hendrik Müller, Friedrich-Schiller-Universität Jena.

Studying the phenomenon, the scientists went through the literature published over four decades to gather the scattered details. They have also discussed the relationship between the toad’s reproductive biology and its specific habitat of merely 4 km² of high altitude grasslands located at a minimum of 1,200 m in the Nimba mountains, West Africa.

The climate of the area is characterised by a rainy season lasting from April to October and a dry season from November to February/March. These seasons are found to determine the activity of the Nimba toads. The amphibians are only active during the rainy season, when they give birth to their young, mate, and then find shelter underground, where they stay dormant during the dry season.

Visibly females can be distinguished from male Nimba toads by their differing cloaca and often larger size, compared to the males. Also, males show darker backs and, during most of their adult life, nuptial pads on their thumbs, which look like spiky swellings. This secondary sex characteristic, in its seasonal change linked to spermatogenesis, is used by the males to grasp tightly the female while mating.

In this species mating occurs without a copulatory organ. Instead, the sperm is transferred through connection of the cloacae, where the male’s swells and encloses the female’s cloaca. Furthermore, Nimba toads have a unique behavioural repertoire. Males crouch on their front legs and as soon as the female moves, follow her and grab her tightly in the groin. Due to the spiky nuptial pads, the males often injure their partner.

Giving birth in Nimba toads may take over two days, depending on the number of offspring, which can be up to 12 in older females – far fewer than the hundreds of eggs in most toad species. While giving birth, a female assumes a unique “birthing posture” to compensate for the lack of enough muscle power to expel juveniles. By the time the juveniles are ready to be born, they have already taken up nearly all the space in their mother’s body. The scientists conclude that the offspring play an active role in the process, as a juvenile toad’s death midway in the oviduct leads to the mother dying of sepsis.

Living exclusively in the Nimba mountains, and being listed as Critically Endangered, according to the IUCN, the studied toad is only one of the species restricted to the high altitude grasslands, which led to the declaration of the Nimba mountains as a World Heritage Site by UNESCO. Separated from other mountains, its inhabitants are isolated from external contacts, thus presumably leading to their evolutionary separation from related species. Furthermore, the toad’s unique reproductive biology is probably the result of this isolation, argue the authors.

In conclusion, the authors suggest that “it is likely that the harsh unpredictable environment and scarcity of open water promoted viviparity in Nimba toads, or supported the survival of this unique reproductive mode in these special and isolated conditions. Considering their complex life cycle, in which reproductive and seasonal cycles are tightly linked, understanding and protecting the Nimba toad’s threatened environment is of utmost importance.”

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Original source:

Sandberger-Loua L, Müller H, Rödel M-O (2017) A review of the reproductive biology of the only known matrotrophic viviparous anuran, the West African Nimba toad, Nimbaphrynoides occidentalis. Zoosystematics and Evolution 93(1): 105-133. https://doi.org/10.3897/zse.93.10489

Emerald and gold: Two new jewel-eyed endemic tree frog species from Taiwan

Two endemic tree frog species, not recognised by science until now, have been identified in broadleaf forests in the island country of Taiwan. Unlike their siblings from mainland China and Southern Asia, they demonstrate reproductive behaviour, characterised with egg-eating (oophagous) tadpole embryos feeding on eggs, while still inside the mother’s womb. What told them apart initially, however, were their jewel-coloured eyes. The research team, led by Dr. Shu-Ping Wu, University of Taipei, have their study published in the open-access journal ZooKeys.

One of the new species, whose scientific name, K. berylliniris, translates from Latin to ‘green-coloured iris’, has been found to dwell among the leaves of moist forests in eastern Taiwan. It is a slender-bodied amphibian with the females slightly bigger than the males, measuring an average length of 41 mm versus 35 mm, respectively. Matching its emerald eyes is its body, which can be either dark green in colour, or deep tan. It is only the belly and the throat that, in contrast, are white and sometimes faintly speckled. On the other hand, its tadpoles vary from heavily dark brown to black.

The second new tree frog, called Kurixalus wangi after pioneer herpetologist Mr. Ching-Shong Wang, can be distinguished with its golden-yellow eyes and extraordinarily small body. Compared to its related species, this one measures an average of 30 mm for males and 34 for female individuals. Its upper-side body is brownish-green with deep brown and black spots, while its belly and throat – whitish.

Both new frog species have been seen to lay their eggs in tree holes, but at different time of the year. The couple, described in the present paper, are also the first representatives of their genus found in the East-Asian country, although the scientists believe it is unlikely for them to be the only ones.

“The actual amphibian species diversity on the island of Taiwan is likely higher than currently thought, given the diverse habitats and the dynamic history of geographic events,” they argue. “Although Taiwan is a highly developed island with significant alterations to the natural landscape and destruction of critical habitats for amphibians, it is noteworthy that during the last fifty years, six of the seven newly described frog species in Taiwan were tree frogs inhabiting forested areas.”

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Original source:

Wu S-P, Huang C-C, Tsai C-L, Lin T-E, Jhang J-J, Wu S-H (2016) Systematic revision of the Taiwanese genus Kurixalus members with a description of two new endemic species (Anura, Rhacophoridae). ZooKeys 557: 121-153. doi: 10.3897/zookeys.557.6131

New tiny arboreal toad species from India is just small enough for its own genus

Found on a herb bush, a toad of only 24 mm average length, measured from its snout tip to its cloaca, was quick to make its discoverers consider its status as a new species. After identifying its unique morphological and skeletal characters, and conducting a molecular phylogenetic analysis, not only did Dr. Aggarwal, Centre for Cellular & Molecular Biology, Dr. Vaudevan, Wildlife Institute of India and Laboratory for Conservation of Endangered Species along with their team, introduce a new species, but also added a new genus. The new ‘Andaman bush toad’, as its proposed common name is, is described in a paper published in the open-access journal ZooKeys.

With its significantly smaller size when compared to its relatives, the new toad species seems to have had its name predetermined by nature. After naming its genus after the initiator of herpetological studies in the Andaman and Nicobar Islands and the first Curator of the Asiatic Society of Bengal, Edward Blyth, the species name was derived from the local epithet ‘beryet’, referring to ‘small frog’ in Andamanese. As a result, the toad was named Blythophryne beryet.

“We believe that the Great Andamanese knew of the existence of this small arboreal anuran,” the scientists explained their choice. “We hope the nomen we coin here will also raise awareness about the dwindling, indigenous tribal populations in the Andamans, their culture and extinction of their tribal languages.”

The herein described toad species occupies mostly evergreen forests across five of the Andaman Islands in the Bay of Bengal, India. Although highly abundant, this is probably because of its narrow range of distribution.

Being active at night, the little amphibian can be regularly seen all year round, rested on the leaf surface of herb bushes. During daytime, it tends to hide under leaf litter on the forest floor. It is also characterised by reddish brown colouration, complete with two feeble dark brown inverted ‘V’-shaped markings.

Because of its severely fragmented population, restricted to no more than 10 locations, its conservation status is regarded as ‘Endangered’ based on the IUCN. Additional threats to the so far monotypic genus and its habitat are also posed by human activity and invasive fauna.

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Original source:

Chandramouli SR, Vasudevan K, Harikrishnan S, Dutta SK, Janani SJ, Sharma R, Das I, Aggarwal RK (2016) A new genus and species of arboreal toad with phytotelmonous larvae, from the Andaman Islands, India (Lissamphibia, Anura, Bufonidae). ZooKeys 555: 57-90. doi: 10.3897/zookeys.555.6522