A new invasion of Xenopus laevis in Chiba City

Before my visit to Japan I was looking for information about current invasions in the country when I came across a citizen conservation group in Chiba City, who had recorded Xenopus laevis  in a river flowing through a conservation area in their city. I made arrangements to visit the site with Takaki Kurita from the Chiba Prefecture Natural History Museum, and was greeted by a band of entthusiastic conservationists who were all happy to jump into the river with us to capture some Xenopus.

It wasn't long before the first shout went up, and then another and another. In the 34 C heat, we were pulling lots of animals out of the river, including an array of native and invasive fish and American crayfish. 

It was great to work with such enthusiastic conservationists in Chiba Prefecture. 

Xenopus from the Tanabe peninsula

The invasive population of Xenopus on the Tanabe peninsula has been one that I have wanted to visit for many years. I was alterted to its presence through a paper by Kento Takata from the Wakayama Prefecture Natural History Museum (Takata et al. 2023).

I was really pleased to take this opportunity to visit the Tanabe Peninsula and meet up with Kento and Hiroshi Doei who has been working for 16 years to eliminate Xenopus laevis from the Tanabe Peninsula. Unfortunately for me, Doei has done such a good job that despite setting over 100 traps the night before I arrived, we did not capture a single individual. In fact, they had not seen any individuals in 2024, and only a handful in 2023, with the last tadpoles seen in 2022. 

If this invasive species really has been eliminated from the Tanabe peninsula, this would be a remarkable feat. I take my hat off to Hiroshi Doei who had come up with some truely inventive  ways to set traps and capture animals in more than 30 ponds on the peninsula. It was a great visit, even if I was not able to sample any Xenopus!

One of the key innovations that Hiroshi Doei made was to place traps on a pulley across the pond. This enabled him to set 30 or more traps at a single site with minimal effort..

To get an idea of just how bad the Xenopus population was on the Tanabe peninsula, take a look at this video.

Sampling the invasive population of Xenopus on Awaji Island

Japan has several invasive populations of Xenopus laevis and among them is the one on Awaji Island, South of Kobe City. Prof Takeshi Igawa kindly accompanied me to the site, making the trip possible. We were joined there by the amazing Nobuyuki Higashiguchi who has been catching Xenopus from this population for over 6 years. 

The island has a lot of rice paddys and small resevoirs that are needed to flood them. These present a myriad of habitats for Xenopus as they are all interconnected. 

We spent several days trapping in various different ponds and amassed a large number of animals. We were also treated to the mastery of a throw net as Nobuyi showed us how to catch tadpoles from one of the reservoirs. 

Collecting Xenopus from WuHu, Anhui Province

My friend and collaboratory Prof. Supen Wang had mentioned to me that he had captured Xenopus leavis  near his laboratory in WuHu, Anhui Province, China. So, In mid-June Qen Qen and I flew up to WuHu to see what we could collect. 

It was great to meet up with Profs. Wang and Zhao again. I had been capturing Xenopus with Prof Wang in 2019 in Kunming, but I hadn't seen Prof Zhao since Beijing in 2016. Qen Qen and I were accompanied by their students, Zhirong He and Yuting Wang, to the field sites where we set some bucket traps.

Walking out with our bucket traps

Setting traps at the site of an established population of Xenopus laevis  outside WuHu.

We were successful in capturing some Xenopus laevis (albino) alongside Ambystoma mexicanum (axolotl) in the same trap! Both species are widely available in the pet trade in China.

Many of the animals we captured were very small metamorphs, making dissection challenging!

Sirkelsvlei - there's more than meets the eye

For many years, the MeaseyLab conducted monitoring of Xenopus gilli in Cape Point. We also conducted a lot of research during that period and, thanks to the excellent work of Andre de Villiers, learned a lot about the biology of this species.

Now, Sue Matthews, has written up some of this information in a feature article for the magazine Water Wheel.  In the article Sue tells the story of this special vlei that occurs in Cape Point. She also takes the opportunity to tell her readers a lot more about the story of Xenopus gilli  conservation. It's well worth a read!

Further Reading:

Matthews, S. (2024) Sirkelsvlei - Taking a stroll through Cape Point’s largest permanent waterbody. Water Wheel.  pdf