Shedding light on caecilians - the world’s most unusual and mysterious underground amphibians

November 09, 2018
  • Shedding light on caecilians - the world’s most unusual and mysterious underground amphibians

On the 11th of October 2018, Dilmah Conservation hosted a public lecture on one of the most elusive and least understood amphibians on the planet – caecilians. The lecture was conducted by one of the world’s leading experts on caecilian evolution and conservation - Dr. David Gower (Head of Vertebrates Division of the Natural History Museum of London). The lecture is part of Dilmah Conservation’s initiative to share knowledge on lesser-known organisms and encourage young environmentalists in Sri Lanka to take an interest in exploring uncharted areas in natural science and conservation.

Why are they important?

Caecilians are likely to be an indicator species that can give scientists an indication of the health of ecosystems and the extent of pollution and climate change. Like other amphibians, their skin secretions may also contain valuable bioactive compounds with potentially revolutionary biomedical applications. What’s most interesting about them, however, is there unique evolutionary history – their ancient independent lineage coupled with their unique adaptations provide comparative biologists with an opportunity to test evolutionary theories. For example, caecilian mothers use a unique mechanism to feed their young – they grow a layer of fatty nutritious skin that the young scrape off and feed on using their cusped teeth. Scientists believe that this adaptation, coupled with the fact that some caecilians give birth to live young, hints at the evolutionary origins of lactation.

What are caecilians?

Caecilians are famous amongst vertebrate biologists for being the least understood group of the generally poorly understood class of amphibians. They are a group of burrowing limbless amphibians with an evolutionary history that spans over 300 million years. They have sturdy bullet-shaped heads with needle-sharp teeth and an extremely smooth snake-like body that’s well adapted to burrowing. Their eyes, which are of little use underground, have reduced greatly in size and are covered by a protective layer of skin and sometimes even bone. Their tear ducts have evolved into unique sensory tentacles that help them locate prey without having to rely on vision. Caecilian species can grow anywhere between 12 cm - 2 m in length and are generally land-dwelling (although some water-dwelling species also exist). They can be found in loose moist soils in forests and agricultural areas in the tropics.

What’s the present status of caecilian conservation and research?

Amphibians because they breathe through their moist delicate skin, are extremely sensitive to pollution and other perturbances in ecosystems. It has been noticed since the 1980’s that amphibians are declining worldwide at an abnormally high rate. It is estimated that greater than 70% of the world’s amphibians are in decline; a harbinger of the human-induced 6th mass extinction on Earth. The conservation status for a majority of the currently know caecilians cannot be established because a large proportion of species remain data deficient. As a result, we may be greatly underestimating the decline of these unique species.

Three species of caecilians are known to exist in Sri Lanka. All three species are from the Ichthyophis genus and endemic to the island. They are considered threated because their ranges are limited to narrow shrinking forest habitats in the wet zone of the country. The last caecilian species identification in Sri Lanka took place over 50 years ago in 1965. In 2005, Dr. Gower and his team conducted DNA studies that indicated the existence of a fourth cryptic species in Sri Lanka. However further studies to prove the exitance of more caecilian species in the island is yet to be completed. Therefore, caecilian research in Sri Lanka presents a unique opportunity to uncover novel species and contribute to the protection of a valuable and fascinating threatened group of organisms.

Over recent years, there has been a multitude of new caecilian discoveries in India thanks to an increased enthusiasm for caecilian research in the country. In 2012 an entirely new ancient lineage and radiation of caecilians were discovered in a threatened and underexplored habitat in north-eastern India. The caecilians which were found on this land, which was previously considered too dry for caecilian habitation, is now accepted to be an entirely novel family of amphibians. This finding has led scientists to believe that there could be at least double the number of caecilian species worldwide than currently recognised.

Dilmah Conservation’s Involvement in Species Conservation

The Dilmah Conservation Novel Species Program was initiated to drive research and awareness on Sri Lanka’s less charismatic but no less important threatened species. The program fuels research on vulnerable species lacking scientific data and undertakes awareness-raising campaigns in Sri Lanka to promote appreciation for the more obscure species on the island. Currently, the project is working towards protecting Sri Lanka’s rich lichen, snake and amphibian populations in partnership with the Herpetological Foundation of Sri Lanka and an internationally acclaimed lichenologist Dr. Gothamie Weerakoon from the Natural History Museum in London. To read more about Dilmah Conservation’s efforts in driving research on Sri Lanka’s underappreciated and lesser-known species, click here.

Dilmah Conservation is the environmental arm of the MJF group and was founded in 2007 as an extension of Dilmah’s commitment to ensuring that all its operations are bound by a respectful and sustainable interaction with the natural environment.