AJCs Virtual Frogroom

Lost a leg? No problem!

noreply@blogger.com (AJC) — Sat, 04 Jul 2009 10:07:00 +0000

Cells keep a memory of their tissue origin during axolotl limb regeneration. Nature 460, 60-65 (2 July 2009)
During limb regeneration adult tissue is converted into a zone of undifferentiated progenitors called the blastema that reforms the diverse tissues of the limb. Previous experiments have led to wide acceptance that limb tissues dedifferentiate to form pluripotent cells. Here we have reexamined this question using an integrated GFP transgene to track the major limb tissues during limb regeneration in the salamander Ambystoma mexicanum (the axolotl). Surprisingly, we find that each tissue produces progenitor cells with restricted potential. Therefore, the blastema is a heterogeneous collection of restricted progenitor cells. On the basis of these findings, we further demonstrate that positional identity is a cell-type-specific property of blastema cells, in which cartilage-derived blastema cells harbour positional identity but Schwann-derived cells do not. Our results show that the complex phenomenon of limb regeneration can be achieved without complete dedifferentiation to a pluripotent state, a conclusion with important implications for regenerative medicine.

Invasive hybrid tiger salamanders impact native amphibians

noreply@blogger.com (AJC) — Thu, 02 Jul 2009 08:12:00 +0000

Although the ecological consequences of species invasions are well studied, the ecological impacts of genetic introgression through hybridization are less understood. This is particularly true of the impacts of hybridization on “third party” community members not genetically involved in hybridization. We also know little about how direct interactions between hybrid and parental individuals influence fitness. Here, we examined the ecological effects of hybridization between the native, threatened California Tiger Salamander (Ambystoma californiense) and the introduced Barred Tiger Salamander (Ambystoma tigrinum mavortium). Native x introduced hybrids are widespread in California, where they are top predators in seasonal ponds. We examined the impacts of early generation hybrids (first two generations of parental crosses) and contemporary hybrids derived from ponds where hybrids have been under selection in the wild for 20 generations. We found that most classes of hybrid tiger salamander larvae dramatically reduced survival of two native community members, the Pacific Chorus Frog (Pseudacris regilla) and the California Newt (Taricha torosa). We also found that native A. californiense larvae were negatively impacted by the presence of hybrid larvae: Native survival and size at metamorphosis were reduced and time to metamorphosis was extended. We also observed a large influence of Mendelian dominance on size, metamorphic timing and predation rate of hybrid tiger salamanders. These results suggest that both genetic and ecological factors are likely to influence the dynamics of admixture, and that tiger salamander hybridization might constitute a threat to additional pond-breeding species of concern in the region.

Invasive hybrid tiger salamander genotypes impact native amphibians. PNAS USA June 29, 2009

The mystery of the legless frogs

noreply@blogger.com (AJC) — Thu, 25 Jun 2009 14:41:00 +0000

Scientists think they have resolved one of the most controversial environmental issues of the past decade: the curious case of the missing frogs legs. Around the world, frogs are found with missing or misshaped limbs, a striking deformity that many researchers believe is caused by chemical pollution. However, tests on frogs and toads have revealed a more natural, benign cause. The deformed frogs are actually victims of the predatory habits of dragonfly nymphs, which eat the legs of tadpoles. In the late 1980s and early 1990s, researchers started getting reports of numerous wild frogs or toads being found with extra legs or arms, or with limbs that were partly formed or missing completely. The cause of these deformities soon became a hotly contested issue. Some researchers believed they might be caused naturally, by predators or parasites. Others thought that was highly unlikely, fearing that chemical pollution, or UV-B radiation caused by the thinning of the ozone layer, was triggering the deformations.

Meanwhile in Ecuador...

noreply@blogger.com (AJC) — Tue, 23 Jun 2009 13:32:00 +0000

More on chytrid

noreply@blogger.com (AJC) — Fri, 05 Jun 2009 08:31:00 +0000

Using itraconazole to clear Batrachochytrium dendrobatidis infection, and subsequent depigmentation of Alytes muletensis tadpoles.
Dis Aquat Organ. 2009 Feb 25;83(3):257-60
Batrachochytrium dendrobatidis (Bd) is a global threat to amphibian biodiversity. Current calls for conservation through captive breeding require that efficient and reliable antifungal treatments be developed for target species. Here we confirm that the antifungal itraconazole is an effective treatment for infection in larval Alytes muletensis (Mallorcan midwife toad). Exceptionally low doses applied as few as 7 times were effective at clearing infection from tadpoles for up to 28 days after treatment. However, we cannot recommend itraconazole as a treatment for this species as depigmentation of tadpoles was observed. Further research is required to determine the putative hepatotoxicity of this treatment.

Lack of Evidence for the Drought-linked Chytridiomycosis Hypothesis.
J Wildl Dis. 2009 Apr;45(2):537-41
A significant amount of recent research has focused on the potentially synergistic roles of climate change and disease in causing amphibian declines and extinctions. Herein I discuss the drought-linked chytridiomycosis hypothesis (DLCH), which states that prolonged or intensified dry seasons trigger or exacerbate epidemics of chytridiomycosis, a potentially lethal skin disease of amphibians caused by the chytrid fungus Batrachochytrium dendrobatidis. I demonstrate that the DLCH runs contrary to our knowledge of B. dendrobatidis physiology, biogeography, and host-parasite ecology and conclude that abnormally dry weather should actually favor amphibians by decreasing the prevalence, severity, and spread of chytridiomycosis.

Wild Dendrobate auratus in Costa Rica

noreply@blogger.com (AJC) — Tue, 02 Jun 2009 07:16:00 +0000

Breakfast for the Brazils

noreply@blogger.com (AJC) — Sat, 30 May 2009 10:23:00 +0000

I don't normally bother putting flies in a dish, but occasionally if a lot of crud comes out of the culture and mixes with the files I do in order to avoid too much getting in the viv. Still, it gave them a chance to be sociable :-)

Sobering discovery for Europe’s amphibians

noreply@blogger.com (AJC) — Wed, 20 May 2009 18:01:00 +0000

A new report commissioned by the European Commission and carried out by IUCN highlights alarming declines for a range of frogs, toads, newts, snakes and lizards. The study shows that of Europe’s 85 species of amphibian, 23% now feature on the IUCN’s Red List of Threatened Species:

Overall, nearly a quarter of amphibians are considered threatened in Europe. A further 17% of amphibians are considered Near Threatened. By comparison, 19% of European reptiles, 15% of European mammals and 13% of European birds are threatened. No other groups have yet been comprehensively assessed at the European level. More than half of amphibians (59%) have declining populations. A further 36% are stable, and only 2% are increasing.
The overwhelming majority of threatened and Near Threatened amphibian species are endemic to both Europe and the EU, highlighting the responsibility that European countries have to protect the entire global populations of these species. All species considered threatened (Critically Endangered, Endangered, or Vulnerable) at the European level are endemic to Europe and are found nowhere else in the world.
Amphibian species richness is greatest at intermediate latitudes (France, Germany, Czech Republic) as well as in the south and on islands. Habitat loss, fragmentation and degradation are the most significant threats to amphibians in Europe. Other major threats include pollution (including global climate change caused by greenhouse gas emissions) and invasive alien species.

Tylototriton kweichowensis

noreply@blogger.com (AJC) — Sun, 17 May 2009 14:22:00 +0000

Busy Saturday

noreply@blogger.com (AJC) — Sat, 16 May 2009 11:16:00 +0000

Most weekends, Saturday is my main day in the frogroom, and in addition to the regular maintenance schedule, today seemed to be particularly busy:

Two egg clutches from Dendrobates tinctorius Patricia and Dendrobates leucomelas
Lots of new Mesotriton alpestris apanus larvae
Set up some new rearing boxes for froglets:

But the funniest thing was moving an adult Dendrobates azureus female into a viv with a younger pair who haven't got the hang of the breeding thing yet. I wish I'd taken a video of the ensuing chaos. I had been slight;ly worried about the possibility that the females might fight, but instead, as soon as she clapped eyes on the male, she was after him, chasing him round the viv, stroking and generally behaving in a lustful fashion. He looked terrified!

I think I might be needing those new frog boxes soon :-)

Pacific Tree Frog - Pseudacris regilla

noreply@blogger.com (AJC) — Wed, 13 May 2009 08:00:00 +0000

Pacific Tree Frog via kwout

Vivarium for sale

noreply@blogger.com (AJC) — Sun, 10 May 2009 09:09:00 +0000

90 x 30 x 30cm (30 long x 12 wide x 12 inches), top opening vivarium.
Ventilated escape-proof lid, suitable for amphibians, reptiles, insects, rodents, etc.
£15, buyer collects from Leicester.

SOLD!

Not this time

noreply@blogger.com (AJC) — Fri, 08 May 2009 14:40:00 +0000

My attempt at breeding Neurergus kaiseri again this year has failed. One difference from previous years was that I overwintered them at a slightly higher temperature, only going down to 10°C, whereas in previous years they were exposed to temperatures close to 0°C. While I'm not convinced that they need to be that cold, it seems that lower temperatures may promote ovulation, since both animals entered the water readily and the male displayed courting behavior, but no eggs were forthcoming.

Fortunately, I have just head of another successful UK spawning of this species. Interestingly, these animals were exposed to temperatures as low as 2°C, which agrees with my theory. In this case however, running water was not used, so maybe temperatures are more important. That makes it approximately 50:50 in the spawnings I have heard about with regard to running water.

My adults are now back in terrestrial accommodation, and of course, I'll try again next year.

Spadefoot toads

noreply@blogger.com (AJC) — Tue, 05 May 2009 14:57:00 +0000

Beautiful slideshow of spadefoot toads in Massachusetts:

Batrachoseps stebbinsi

noreply@blogger.com (AJC) — Thu, 30 Apr 2009 00:56:00 +0000

Los Angeles Times via kwout

The spider that eats frogs

noreply@blogger.com (AJC) — Fri, 24 Apr 2009 10:31:00 +0000

Mountain chickens airlifted to safety

noreply@blogger.com (AJC) — Thu, 23 Apr 2009 08:00:00 +0000

guardian.co.uk via kwout

Demand for Rarity Could Threaten Conservation Efforts

noreply@blogger.com (AJC) — Wed, 22 Apr 2009 07:41:00 +0000

Rare plant and animal species are like rare stamps or coins: they are perceived to be inherently more valuable to people, whatever they look like. Researchers Elena Angulo and Franck Courchamp have found that people are more attracted to species labeled “rare” than those labeled “common” even when they do not know which species are involved. The study shows that this irrational value conferred to unknown items only for the sake of rarity is both an asset and a threat for conservation. It has been recently suggested that the value people place on rarity could lead to the extinction of rare species as we are willing to pay the high costs of exploiting the last individuals.

Many hobbies, such as ecotourism or the keeping of exotic pets, may cause this effect, known as the anthropogenic Allee effect. However, this theory relies on the untested assumption that people do indeed value rarity. To assess whether people really do value rare species more than common ones, Angulo and colleagues set up a website where visitors were told they could view one of two slideshows of images: either one containing images of “rare species” or one containing images of “common species.” No other information about the featured species was provided. When visitors downloaded a slideshow, a progress bar appeared, showing what percentage of the slideshow had been downloaded. The bar filled up after six minutes but the file still appeared to be downloading and did not open. Visitors could cancel the download at any time and were taken to an error page, which would then link them back to the slideshow download page to try again (although the slideshows never opened).

The researchers measured: a) how attractive the rare slideshow was to the visitors (based on the proportion of visitors who downloaded the rare slideshow as their first or only choice), b) how long visitors were prepared to wait to download each slideshow and c) how perseverant visitors were (how many times they tried to download each slideshow before giving up). Even though visitors knew nothing about which species each slideshow contained, more people opted to view the rare species slideshow. Visitors also waited longer for the rare species slideshow to download before giving up than they did for the common species slideshow and after the download failed, they made more attempts to download the rare species slideshow than the common one. Angulo and colleagues concluded that people do value rare species more than common ones and propose that conservationists should be prudent when using rarity to promote conservation. “This is a crucial measure for the conservation of countless plant and animal species, which fall victim to a growing international trade of fuel collections, exotic pet, traditional medicine or luxury markets,” explain the researchers.

Rare Species Are Valued Big Time. 2009 PLoS ONE 4(4): e5215

Think different

noreply@blogger.com (AJC) — Sat, 18 Apr 2009 14:55:00 +0000

Frognet, the venerable dartfrog email list, is a funny beast. It goes dormant for long periods of time, but just when you think it's died, it comes roaring back with top class discussions that really make you think.

That's exactly what's happened in the last week with an interesting discussion about vivarium design and substrates (the latter being a perpetual topic on Frognet). The part I was interested in concerned flow-through vivarium designs which water drains continuously from the viv rather than collecting in the substrate. This rapidly gathered the strapline "Your frog is a sponge", the idea being that flow-through substrates remain "cleaner", which is beneficial to frogs.

As ever, the sides in this debate involved more emotion and intuition than scientific evidence, but the thought that cleaner substrates and lack of stagnant water mean healthier frogs is an attractive argument. My vivaria are not set up for flow through, and ripping my frogroom apart to install drains just isn't going to happen, especially since it's clearly not essential (as my frogs have told me over many years). But that doesn't mean that I haven't taken something from the debate. Although I periodically used to flush and siphon out my substrates, I've resolved to do this more frequently, at least once a month.

I'm a huge fan of using your nose to diagnose the condition of a vivarium or aquarium (aiming for an "earthy" smell rather than something you would describe as excessively stale or "smelly"). Interestingly, the water I siphoned out of different vivaria smelt quite differently, better in some cases than others, but because I'm sure this will do no harm, this has now become a more regular part of my maintenance regime.

In another part of the Frognet thread, one of my frogkeeping gurus, Brent Brock, put forward one of his favourite theories - diversity is good. In this case, Brent was advocating that vivarium "health" is supported by having the biggest diversity of plant species possible. In addition to fast growing, nutrient hungry species, slower growing plants also play an important role by potentially absorbing different compounds. Although Brent admits that it's easier to do this in bigger vivs (and Brent's vivs are pretty big) than smaller ones, it's still influenced my thinking, and I've moved a few cuttings around this morning.

Change for change's sake is generally a bad thing, but sometimes, it pays to think different.

Cyclorana platycephala, the water holding frog

noreply@blogger.com (AJC) — Fri, 17 Apr 2009 10:33:00 +0000

Your Easter Treat: The Thin Green Line

noreply@blogger.com (AJC) — Fri, 10 Apr 2009 07:54:00 +0000

It is the greatest mass extinction since the dinosaurs. Population by population, species by species, amphibians are vanishing off the face of the Earth. Despite international alarm and a decade and a half of scientists scrambling for answers, the steady hemorrhaging of amphibians continues like a leaky faucet that cannot be fixed or a wound that will not heal. Large scale die-offs of frogs around the world have prompted scientists to take desperate measures to try to save those frogs they can, even bathing frogs in Clorox solutions and keeping them in Tupperware boxes under carefully controlled conditions to prevent the spread of a deadly fungus. Will it ever be safe to return the frogs back to the ecosystem from which they were taken? Video:

Froglife is metamorphosing

noreply@blogger.com (AJC) — Tue, 07 Apr 2009 11:08:00 +0000

Froglife and The Herpetological Conservation Trust (The HCT) have announced their intention to merge, forming a single conservation organization. The new organisation will be called the Amphibian and Reptile Conservation Trust and will continue the range of activities currently undertaken by Froglife and the HCT, while providing a stronger basis for conserving amphibians and reptiles in the future.

"Both Froglife and the HCT have worked closely on key issues in recent years, including the Government’s Biodiversity Action Plans, on issues like amphibian disease and on advice and guidance for the public and land-managers. Throughout this time it has become increasingly clear that the two organisations could be many times more effective in their mutual aim of conserving amphibians and reptiles, if united as a single organisation."

Pretty Worms

noreply@blogger.com (AJC) — Sun, 05 Apr 2009 08:49:00 +0000

If you live your life underground, why would you want to be brightly coloured? In the case of caecilians, amphibians with earthworm-like bodies that spend most of their lives underground, some of the colouration may have been retained from distant ancestors which lived above ground. However, many caecilians are dark-coloured on top and ligherter underneath, which could protect them from predators if they are accidentally exposed at the surface or if they temporarily emerge at night. Some of the brightly-coloured caecilians could also be toxic, although the colours might just be a bluff! We know so little about this group of animals that it is very difficult to be sure.

Physalaemus pustulosus, the mud puddle frog

noreply@blogger.com (AJC) — Fri, 03 Apr 2009 10:37:00 +0000

Questioning the chytrid hypothesis

noreply@blogger.com (AJC) — Sun, 29 Mar 2009 08:00:00 +0000

I had an interesting discussion with someone this week about chytrid, to the effect that the story is much more complicated that it's often made out to be. Part of this was stimulated by three scientific papers published recently.

The first suggests that the disease may have been around unrecognized for much longer than most people think:

Batrachochytrium dendrobatidis, a novel pathogen approaching endemism in central California. Dis Aquat Organ. 2009 83: 1-9
The recent emergence of amphibian chytridiomycosis has precipitated competing hypotheses regarding the endemic versus novel nature of the causative agent, Batrachochytrium dendrobatidis (Bd). We conducted a retrospective survey of the California Academy of Sciences' (San Francisco, California, USA) amphibian collection, testing for presence of Bd in 4 amphibian species collected from central California between 1897 and 2005. The earliest detection of Bd was found in 2 Rana catesbeiana in 1961, and the data support the hypothesis that Bd was a novel pathogen introduced into central California prior to 1961 that spread out geographically and taxonomically from at least one central location and is now endemic throughout most of central California. The taxonomic pattern of infection prevalence and the ecological constraints of the 4 species we tested suggest that, although Bd was initially detected in R. catesbeiana, the more efficient and most likely local vector for Bd in central California is actually Pseudacris regilla.

The next paper points at one possible reason why that might be:

Addition of antifungal skin bacteria to salamanders ameliorates the effects of chytridiomycosis. Dis Aquat Organ. 2009 83: 11-6
Chytridiomycosis, caused by the skin fungus Batrachochytrium dendrobatidis (Bd), has caused population declines of many amphibians in remote protected habitats. Progress has been made in understanding the pathogen's life cycle, documenting its devastating effects on individual amphibians and on populations, and understanding how and why disease outbreaks occur. No research has directly addressed the critical question of how to prevent declines and extinctions caused by outbreaks of the disease. We have identified a number of bacterial species of amphibian skin that inhibit Bd in vitro. Here, we demonstrate that a species of anti-Bd skin bacteria can be successfully added to skins of salamanders Plethodon cinereus, and that addition of this bacterium reduced the severity of a disease symptom in experimentally infected individuals. This is the first demonstration that manipulating the natural skin microbiota of an amphibian species can alter the pathogen's negative effects on infected amphibians and appears to be the first demonstration that an epibiotic manipulation of any wildlife species can lessen the effects of an emerging infectious disease. It suggests that probiotic or bio-augmentation manipulations of cutaneous microbiota could have the potential to reduce susceptibility of amphibians to the disease in nature. This is the first approach suggested that could slow or halt epidemic outbreaks and allow successful reintroductions of amphibian species that have become locally or globally extinct in the wild. Our results also suggest a mechanism for the association of climate change and the likelihood of chytridiomycosis outbreaks via the effects of the former on antifungal bacterial communities.

The third paper also supports the idea of the interaction between the pathogen and the environment:

Skin microbes on frogs prevent morbidity and mortality caused by a lethal skin fungus. ISME J. Mar 26 2009
Emerging infectious diseases threaten human and wildlife populations. Altered ecological interactions between mutualistic microbes and hosts can result in disease, but an understanding of interactions between host, microbes and disease-causing organisms may lead to management strategies to affect disease outcomes. Many amphibian species in relatively pristine habitats are experiencing dramatic population declines and extinctions due to the skin disease chytridiomycosis, which is caused by the chytrid fungus Batrachochytrium dendrobatidis. Using a randomized, replicated experiment, we show that adding an antifungal bacterial species, Janthinobacterium lividum, found on several species of amphibians to the skins of the frog Rana muscosa prevented morbidity and mortality caused by the pathogen. The bacterial species produces the anti-chytrid metabolite violacein, which was found in much higher concentrations on frog skins in the treatments where J. lividum was added. Our results show that cutaneous microbes are a part of amphibians' innate immune system, the microbial community structure on frog skins is a determinant of disease outcome and altering microbial interactions on frog skins can prevent a lethal disease outcome. A bioaugmentation strategy may be an effective management tool to control chytridiomycosis in amphibian survival assurance colonies and in nature.

There's a long way to go before there is any hope of practical intervention in the chytrid pandemic, but it is certain that we will need some new thinking if there is any hope of averting complete disaster.