The Sticky Tongue Project

Herpetology, Biodiversity and Conservation.

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Viruses Could be the Key to Healthy Corals

Corals are an invaluable part of the marine ecosystem, fostering biodiversity and protecting coastlines. But they’re also increasingly endangered. Pathogenic bacteria, along with pollution and harmful fishing practices, are one of the biggest threats to the world’s coral populations today.

One of the solutions to the crisis may lie in human medicine. Prof. Eugene Rosenbergof Tel Aviv University's Department of Molecular Microbiology and Biotechnology, working in collaboration withDr. Ilil Atad of his own laboratory and Prof. Yossi Loya of TAU’s Department of Zoology, has developed a treatment for coral infected by Thalassomonas loyana, otherwise known as White Plague disease. This deadly bacterium infects 9 percent of Favia favus corals on the Eilat coral reef in the Red Sea and readily transmits the disease to nearby healthy corals.

Their treatment uses viruses that infect bacteria by injecting genetic material into the bacteria, a therapy originally developed to treat bacterial infections in humans. In this case, the researchers isolated a virus called BA3, one of a category of viruses known as phages. After laboratory experiments showed that BA3 had the ability to kill off White Plague disease, field experiments in the Gulf of Eilat demonstrated that the treatment stopped the progression of the disease in infected corals and prevented the spread of the disease to surrounding healthy corals as well.

These findings were presented at the American Society for Microbiology’s general meeting in June.

From human to marine medicine

Treating bacterial infections in corals is no easy task. Because corals don’t produce antibodies like humans, they can’t be immunized. And pharmaceutical antibiotics are not a viable option because the treatment releases the drugs into the sea, harming the marine environment.

The researchers applied their treatment to two groups of diseased coral, each surrounded by a circle of healthy corals. In the test group, the researchers injected the virus into the area at a concentration of 1000 per milliliter. The control group did not receive the virus.

After 24 hours, the difference in the outcome was highly significant, says Prof. Rosenberg. In the test group, the infection of the diseased coral ceased its progression, and the disease did not spread to the surrounding healthy corals. In the control group, however, the White Plague disease progressed rapidly in the original infected coral and spread to seven out of ten of the surrounding healthy corals.

Amplifying a natural process

One of the most surprising discoveries during the course of their research, says Prof. Rosenberg, was that some corals naturally posses the beneficial virus and are already resistant to infection by the pathogen. When the researchers tested the three corals in the control group that remained uninfected, they discovered that the virus was already present in their biological composition. “We found that this is a natural process that goes on all the time. What we are doing is only shifting the situation in favor of the virus,” he explains.

This method of developing an antidote to specific pathogenic coral bacteria is a crucial breakthrough, Prof. Rosenberg says. Corals in different regions of the world are infected with different pathogens. For each location, it is necessary to isolate the appropriate virus. But microbiologists should be able to develop regionalized treatments based on the methods used by Prof. Rosenberg and his fellow researchers.

The next step is to develop an effective way to spread the viruses over large areas of an infected coral reef. Sufficient amounts of these viruses can be easily manufactured in the laboratory. After that, it’s a question of technology and funding, Prof. Rosenberg adds.

Source: Tel Aviv University

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Amazing Species: Miles’ Robber Frog

Miles’ Robber Frog, Craugastor milesi, is listed as ‘Critically Endangered’ on the IUCN Red  List of Threatened Species TM. This Honduran endemic was once considered ‘Extinct in the Wild’ as it had not been seen since 1983, and surveys between 1992 and 1998 failed to find it. However, the species was rediscovered in 2008 after a single individual was found at Cusuco  National Park, western Honduras.

Once abundant, Miles’ Robber Frog declined dramatically throughout the 1980s. Habitat loss and conversion likely impacted upon the species, but the sudden disappearance of populations in areas of pristine forest may be attributed to chytridiomycosis. This fungus is  known to infect other amphibian species in the region, and the species’ affinity to streamside habitats makes it highly susceptible to infection.

The recent rediscovery of Miles’ Robber Frog gives rise to the hope that a single resistant population remains. However, the species’ status is still extremely precarious, and research is  urgently required to determine the viability of the surviving population.

Source: IUCN Red List

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Frog Friday: Cape Sand Toad

TGIFF!!! Thank Goodness it’s FROG FRIDAY! The species in the spotlight today is the Cape Sand Toad (Vandijkophrynus angusticeps).

This is a medium sized toad and has the typical square, thick-set body which characterizes this genus. The skin is rough and dry with wart-like glandular elevations on the upper side and includes a pair of distinctive parotoid glands on the neck behind the eyes. The legs are longer than the body length and there are no hard ridges on the heel of the hind foot or discs on the toes and fingers. The edges of the toes are fringed with webbing (but two segments of the third toe are free of web). The tarsal fold is distinct and ridged. The upper body surface is light grey to light brown and covered in variable dark patches or blotches. Some of these are arranged in pairs that extend down the length of the back from the snout. There is usually a thin, pale vertebral line extending from the snout to the tip of the urostyle, and the upper surfaces of the feet are generally yellow. The underside is white and has a granular texture except for the throat which has a smoother skin. This species has a relatively soft call, and calling males can be difficult to locate as the calls are widely spaced and the frogs become silent when approached.

The Cape Sand Toad is endemic to the Fynbos Biome and mainly occurs in the winter rainfall region of the Western Cape Province of South Africa, but its habitat also extends eastwards into a winter/summer rainfall transition zone. The Cape Sand Toad is mainly associated with sandy, coastal lowlands but also occurs in some rocky montane areas further inland. It breeds in shallow temporary pools in seasonally flooded land, and this may also include modified habitat such as cultivated lands. Breeding takes place once sufficient rain has fallen for temporary pools to form. This generally happens in the winter period from May to September. During rainy periods in suitable habitat, many of these toads may be seen at night moving across roads to breeding sites (especially early in the breeding season). At the breeding sites, calling males tend to be sparsely distributed and their calls are soft and intermittent. They are known to call from exposed positions at the water’s edge after dark. The eggs, which are 1-2 mm in diameter, are laid in long gelatinous strings of 5-7 mm in width. The eggs develop into free-swimming benthic tadpoles which are relatively small and dark. The tadpoles take about a month or less to metamorphose into tiny toadlets.

The photo shown here is record number 393 from the FrogMAP database. The photo was taken in the Western Cape by Trevor Hardaker and it is the only photographic record of Cape Sand Toad in the database! Please help us to map this cool toad’s 21st century distribution by submitting your photos, along with the location details, to FrogMAP (formerly known as SAFAP) at http://vmus.adu.org.za/

Source: Animal Demography Unit

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