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Tadpole anti-predator strategies

10 July 2019

What do tadpoles do when they sniff a predator?

Natasha Kruger asked this question of populations of the invasive African Clawed Frog in a study conducted with Jean Secondi in France. Clawed frogs have been invasive there for ~30 years, but a number of studies are suggesting that they have already started to adapt to the local conditions (see here). 

As an invasive frog, once you’ve been moved to the new environment, not only do you have to cope with new conditions, but your tadpoles do too. This means that tadpoles should be able to respond to new predators, as well as ones that they already know. This was the basis for the work that Natasha conducted on tadpoles of the invasive African clawed frog, Xenopus laevis, in France.

Natasha tested to see how tadpoles reacted to known and unknown predators. For example, she tried cues from aquatic snails and another invasive species in France, the red swamp crayfish, Procambarus clarkii.

Tadpoles were placed into fresh water in a cup with a cross drawn across the bottom. The cue was then dropped from above and their reaction filmed. She was particularly interested in the number of times that the tadpoles crossed the lines in the cup – showing a response to the cue.

Like other tadpoles, African clawed frogs were found to decrease their activity in the presence of a predator. That is they crossed the line less often when cues were given, compared to novel cues.

The early version of the manuscript is now up online and you can enjoy reading it here:

Kruger, N., Measey, J., Herrel, A., & Secondi, J. (in press) Anti-predator strategies of the invasive African clawed frog, Xenopus laevis, to native and invasive predators in western France. Aquatic Invasions

  Frogs  Lab  Xenopus

Off to France again

03 May 2019

Natasha is back in France

Yes, it's time again for Natasha to move from Summer in the southern hemisphere to summer in France. One of the plus sides to doing a PhD is that you get to travel, and Natasha has certainly done that. 

John sends Natasha off to Paris

It wasn't an easy start to the French season. Natasha was off walking those oh so hard streets of Paris all day Friday hoping that the French admin would provide a password for her to pick up her stipend. Finally the code came through and she was able to pick up her bursary from Campus France - not an easy task on a Friday afternoon and it did take a 20 minute international call to underline the importance of students needing money to survive the weekend.

So what will Natasha be doing in France? 

Apart from the odd visit to a museum (actually the MNHN to spend a week with Anthony Herrel), Natasha will be analysing and writing up all of the data that she's collected over the past 2.5 years. It's a big task, so we're all eagerly waiting to hear what she's managed to find out about Xenopus laevis tadpoles.

Interested in doing a PhD? See some advice on this subject from this YouTuber:

  Lab  Xenopus

Paper on Chinese Xenopus published

03 May 2019

African Clawed Frogs in China

Some of you may remember that I visited China in June last year (if not, see the blog post here). Today the resulting paper with my Chinese collaborator, Supen Wang, was published in BioInvasions Records.

There are a couple of interesting points about this new invasion:

1. It's the first reported for mainland China. Not surprising perhaps as China is the source of most of the pet Xenopus laevis that are pumped around the world at the moment (that was the subject of another paper - see here). 

2. This is the first report of an albino invasive population. All of the others around the globe feature the 'wild-type' African clawed frogs that most of you will be familiar with. However, in the pet trade, it is albinos that dominate.

Here's a piece I wrote for the CIB website


A new population of African clawed frogs (Xenopus laevis) has become established on mainland China, according to a new publication by C·I·B Core Team Member, John Measey. Working with colleagues from the Chinese Academy of Sciences, Measey trapped a site near the city of Kunming, Yunnan Province. The African clawed frogs they found were all albinos, the most common form in the pet trade. Previous work by Measey had shown that the vast majority of African clawed frogs moving around the world in the pet trade originate from China.

Invasive populations of African clawed frogs are known from Europe, North and South America and were previously only known from Japan in Asia. This discovery now places an invasive population on continental Asia with the potential for a much larger invasion in this area. These frogs are known to heavily impact local amphibian and invertebrate populations.

Trade in the African clawed frog started in the 1930s following their use as the first pregnancy test. The species was so easy to keep that it then became the standard laboratory amphibian all over the world, a status it continues to enjoy today. Breeding in laboratories has become so successful that animals are no longer exported from South Africa. Since the 1980s, however, this species has become very popular in the pet trade. Now hundreds of thousands of animals are shipped around the globe destined to become aquarium pets.

The researchers used molecular methods to check whether members of the invasive population carried the fungal chytrid pathogen, known for decimating amphibian populations globally. All frogs caught tested negative. However, the site is known for having a population of American bull frogs, which the team heard calling as they set out the traps. It is unknown how these two globally invasive frogs interact.

The site is on the edge of Lake Kunming, possibly allowing these frogs access to a large are in southern China”, said Measey. “We were surprised to find an established population as this area fell outside the global climate model predicting suitable areas.

Read the full article here:

Wang, S., Hong, Y. and Measey, J. 2019. An established population of African clawed frogs, Xenopus laevis(Daudin, 1802), in mainland China. BioInvasions Records (2019) Volume 8, Issue 2: 457-464. DOI 10.3391/bir.2019.8.2.29.

  Frogs  Lab  Xenopus

Cape platanna time with OTS

21 March 2019

A Whole Lotta Froggin' in Frog Week

To celebrate Frog Week, I spent the week with the OTS students in the Cape of Good Hope section of Table Mountain National Park monitoring the Cape platanna (Xenopus gilli). Another great crew from the Organisation for Tropical Studies (OTS). I was last with OTS in October (see here), and before that in October and see blog entry here, hereherehere and here.

Celebrating Frog Week was top on the list of things to do...

Getting up to all the usual tricks. The Cape of Good Hope didn't let us down; we saw rain, we saw sun, and pretty much everything in between. And the frog FFP crew were magnificent, presiding over a catch of >600 animals, this rivals any previous haul from this event.

Of course, no good OTS trip would be complete without the annual Suur Dam running event. It was super special this year as most of the OTS crew took part, and Caitlin broke the 30 second barrier - previously thought to be impossible. 

  Frogs  Lab  Xenopus

Why have a pet amphibian?

04 March 2019

Why do people want pet amphibians?

We know that the trade in amphibians increases year on year, but what is driving the demand? This might be a no-brainer for many of you reading this blog. Why wouldn't anyone want to have a pet amphibian? In a first attempt to dig into this intriguing question, we reasoned that people who upload their videos to YouTube might be sharing what they consider to be the most important qualities of their pets. After all, why else would you upload a video of your pet amphibian?

We were about to find out!

So the truth is that people upload videos of their amphibians for all sorts of reasons. That was our conclusion after watching more than 1000 videos. Who would have thought that 'unboxing' would be such a popular category? We found videos of people driving toads in lego cars, tying them to helium baloons and watching them float away, as well as preparing a Chinese giant salamander for the pot. But we also saw plenty of much loved amphibians in people's homes, and we were able to look at the behaviour that was being filmed to give us some insights to answer our question

To read more about what we found, why not read our paper? It's free to read online.

Measey, J., Basson, A., Rebelo, A., Nunes, A., Vimercati, G., Louw, M., & Mohanty, N.P. (2019) Why have a pet amphibian? Insights from YouTube. Frontiers in Ecology And Evolution  7: 52 doi:10.3389/fevo.2019.00052

  Frogs  Lab  Xenopus
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