Tag: amphibians

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

Twenty-five frogs added to the amphibian fauna of Mount Oku, Cameroon

While amphibians all over the world are undergoing a continuous decline, their status in certain regions, such as Central Africa, remains unknown due to incomplete information. New paper, published by two scientists in the open access journal ZooKeys, addresses the knowledge gap by providing an updated list of already 50 amphibian species living on Mount Oku, Cameroon.

Scientists Dr Thomas M. Doherty-Bone, Royal Zoological Society of Scotland, and Dr Václav Gvoždík, affiliated with both the Czech Academy of Sciences and the National Museum in Prague, have spent more than 10 years studying the Cameroonian mountain. As a result of their thorough surveys, literature review, and re-examination of museum specimens, there are now 50 species known from the locality, which doubles previous numbers. In their newly published checklist the researchers have listed 49 species of frogs and toads, as well as one caecilian species – a limbless, snake-like amphibian.

However, the number of threatened species seems to increase quite proportionally. Many of the newly recorded frogs, for instance, appear to be extremely endangered, yet they have not been assessed by the International Union for Conservation of Nature (IUCN). Therefore, the authors have used the IUCN criteria to propose conservation assessments for them. If the suggested statuses are approved, together with the updated declines of previously abundant in the area species, the proportion of the threatened would rise to nearly half (48%) of the Mount Oku’s entire amphibian fauna. Meanwhile, it is 42% of amphibians at risk of extinction globally.

In their study, the scientists also review the research and conservation undertaken at the mountain so far, including the work they have initiated themselves. Although Mount Oku’s forest turned out to be the best managed among the rest in the region, threats such as forest loss, encroachment and degradation are still largely present and increasing. Additional threats, including use of agrochemicals, climate change and diseases, have also been identified. However, conservation actions for the amphibians of Mount Oku are on the rise, considering both the population and the ecosystem-level perspectives.

“Our paper provides a foundation for continuously improving amphibian conservation at Mount Oku, as well as other mountains in Cameroon,” conclude the authors.

Original source:

Doherty-Bone TM, Gvoždík V (2017) The Amphibians of Mount Oku, Cameroon: an updated species inventory and conservation review. ZooKeys 643: 19-139. https://doi.org/10.3897/zookeys.643.9422

Scientists identify northeast Mindanao as major ‘bull’s-eye’ of biodiversity

Butuan City, Agusan del Norte. In a scientific report appearing Monday October 17th in the open access journal Zookeys, a team of researchers led by herpetologist Dr. Marites Sanguila of Father Saturnino Urios University announced that they have identified a new “epicenter” of southern Philippine biodiversity in amphibians and reptiles.

The international team of herpetologists (scientists who study frogs, lizards, snakes, turtles, and crocodiles) collaborating on the study is composed of scientists from Father Saturnino Urios University, the University of Kansas, the University of Oklahoma, the National Museum of the Philippines, Silliman University, and the Philippine Department of the Environment and Natural Resources. After an intensive five-year study, the team came to the ground-breaking conclusion that the Caraga Region of northeast Mindanao has the single highest herpetological species count of any similarly sized region in the country known to date.

Following a series of expeditions to four mountains in northern Mindanao, plus analyses of the distributions of species documented in museums around the world, the multi-institution effort culminated today with the announcement that the Caraga region is home total of 126 species of amphibians and reptiles.

According to Dr. Sanguila, this strikingly high diversity includes 40 species of frogs, one kind of caecilian (a secretive eel-like amphibian), 49 types of lizards, 35 varieties of snakes, plus one native freshwater turtle and, of course, one species of crocodile. According to the new study, the key to understanding the Caraga Region’s high biodiversity newly documented distributions of those 126 species, which overlap in northeast Mindanao. At a boundary between mainland Mindanao Island and the eastern Visayas (Samar, Leyte, Bohol, Dinagat, Siargao islands), “the Caraga region is an area where many species’ distributions come together and overlap, making this spot a kind of central hub of biodiversity,” said Dr. Sanguila. The new study brings more good news from the Philippines, a country internationally recognized as global biodiversity conservation hotspot of biodiversity.

“International collaborative biodiversity inventories are a great way to promote student training and faculty research development,” said Dr. Marites Sanguila, “In this research, we followed the example of the life-long collaboration between Dr. Angel Alcala, from the Silliman University, and Dr. Walter Brown, from California Academy of Sciences, and invited our U.S. counterparts to join in the effort to synthesize information on Caraga amphibian and reptile biodiversity. The results have unfolded in ways we could not have predicted, and generated opportunities for students on both sides of the Pacific.”

“Dr. Sanguila’s research tells us in a very special way something we have known intuitively for years, but have been unable to articulate: there is something very special about the unique biodiversity of the Caraga region! At the ‘center of the center’ of southern Philippine biodiversity, our small corner of Mindanao is undoubtedly unique, in need of conservation, and worthy of intensive scientific study,” said Rev. Fr. John Christian Young, president of Father Saturnino Urios University.

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Original Source:

Sanguila MB, Cobb KA, Siler CD, Diesmos AC, Alcala AC, Brown RM (2016) The amphibians and reptiles of Mindanao Island, southern Philippines, II: the herpetofauna of northeast Mindanao and adjacent islands. ZooKeys 624: 1-132. doi: 10.3897/zookeys.624.9814

Greek heroic deity Prometheus now has a namesake in a new tiny rain frog from Ecuador

Prometheus, the mythological Greek heroic deity, has been given a namesake in a new species of tiny rain frog, discovered in southwestern Ecuador. The name was chosen by the international team of scientists, led by Dr Paul Szekely, Ovidius University, Constanta, Romania, in acknowledgement of the Prometeo program, funded by the Ecuadorian government.

The description of this new species (Pristimantis prometeii) is the result of the cooperation between three Romanian Prometeo investigators affiliated with the Universidad Tecnica Particular de Loja and Universidad Nacional de Loja, and two Ecuadorian specialists from Pontificia Universidad Catolica del Ecuador. The full study is available from the open access ZooKeys.

During the day, frogs of the new species were found hiding in flowering plants, while at night — perching on leaves at low heights in well preserved cloud forests. They grow to 2-3 cm with the females being larger than the males.

The newly described species is part of a group of frogs called Terrarana (meaning ‘Land or terrestrial frogs’). This is a lineage of frogs that has evolved directly developing eggs, which are deposited in terrestrial habitats. Unlike other frogs, these ones do not have an aquatic tadpole stage and the embryos develop directly into froglets on land.

The newly described species is only known from Reserva Biologica Buenaventura, southwestern Ecuador, at elevations between 878 and 1082 m. This reserve is privately owned by the Jocotoco Conservation Foundation. The reserve has at least another four endemic species of amphibians, reptiles, and birds.

With more than 470 species, the directly developing rain frogs of the genus Pristimantiscontinue to surprise everyone.

“While new species are described every year, there are over a hundred discovered over the last decade only,” remind the authors.

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Original source:

Szekely P, Cogalniceanu D, Szekely D, Paez N, Ron SR (2016) A new species of Pristimantis from southern Ecuador (Anura, Craugastoridae). ZooKeys 606: 77-97. doi: 10.3897/zookeys.606.9121