Temperature of the water in a Jonkershoek pond

Temperature is pivotal to the functioning physiology of ectotherms, and for the principally aquatic frog Xenopus laevis the water temperature dictates the temperature of the animals throughout the year. We know that most of the invasive populations of X. laevis were sourced from the South African Cape region in general, and the Jonkershoek hatcheries near Stellenbosch in particular (van Sittert & Measey 2016). 

For the past year, I have had a temperature logger recording the water temperature just above the bottom in a pond in Jonkershoek. 

The same pond has been the source of Xenopus laevis for numerous studies, and likely contains animals that are closely related to those shipped from South Africa all over the world. 

The temperatures between November 2023 and 2024 show that the water reaches maximum temperatures in early February (27.32 C), and a low 6 months later in early August (7.98 C). Despite these extremes, the water temperature varied only 15 C between 10 and 25 C. This is relatively little change compared to the same loggers deployed in Kwa-Zulu Natal (see here). 

Thanks to Martine Jordaan and Andrew Turner who helped with the deployment and collection of this logger. 

A joint meeting of the Herpetological Association of Africa and the African Amphibian Working Group in Wilderness, South Africa: 26 – 29 November 2024

Each of these groups usually meets every two years separately, so it was for the first time in their existance that they met in back-to-back meetings in Wilderness South Africa. First up was the 20th meeting of the AAWG, with plenty of familiar faces from across the globe. 

Next was the 16th meeting of the HAA, which also had great representation and considerably more delegates. 

   

The meeting featured presenters from 9 different African countries: Madagascar, Nigeria, Tanzania, Uganda, Ethiopia, Kenya, Ghana, Namibia and South Africa. This was certainly the best representation of the continent since each of the meetings started. 

The following talks featured MeaseyLab members:

Home and away: the gut microbiome of Xenopus laevis in native and invasive populations

John Measey; Jiankun Yu; Dareen Almojil; Stephane Boissinot; Laurie Araspin; Carla Wagener; Greg Pauly; Reed Ojala-Barbour; Claudio Soto-Azat

The vertebrate gut microbiome is a community largely composed of bacterial, fungal and viral components, whose molecular component equal that of the host. The influence of the microbiome is known to be significant both on an individual basis, and also on population scales in a wide range of host organisms. The gut microbiome is known to be involved with key attributes of animal health, including assimilation of nutrients, immuno-defensive functions and host behaviour. In this study, we used bacterial 16S rRNA amplicon-based sequencing for metataxonomic classification of the gut microbiome of individuals from 12 native populations of Xenopus laevis. These populations were selected to represent the native range of the host species. From the 16S rRNA community profiles, we determine the components of the core microbiome of X. laevis and ask whether deviations from the core are associated with the environmental context in which they live. In addition, we sampled populations from Chile (4) and USA (7) to determine what aspects of the core microbiome are retained by non-native populations. This represents the first time that the microbiome of X. laevis has been assessed across such diverse conditions and provides data that will help understand the role played by the environment within this model organism.

Southern Africa Amphibian Red List Project – updated assessments for the region lead the GAA3

Jeanne Tarrant; Joshua Weeber; Oliver Angus; Adrian J. Armstrong; Ninda L. Baptista; Francois S. Becker; Rebecca M. Brunner; Werner Conradie; Louis H. du Preez; James Harvey; Adriaan Jordaan; Keir Lynch; John Measey; Mohlamatsane Mokhatla; Darren W. Pietersen; Fortunate M. Phaka; Jennifer Swanby; Krystal A. Tolley; Andrew A. Turner; Luke Verburgt

As the most threatened vertebrate class on earth, amphibians are leading the biodiversity extinction crisis. The 2nd Global Amphibian Assessment (GAA2) found that 41.5% of species globally are at risk of extinction, these extraordinary and diverse creatures are experiencing the worst population declines and highest extinction risk of any vertebrate group. South Africa has a good history of updating Red List assessments and has done so consistently since 2004 with the publication of the Atlas and Red Data Book. As some of the first assessments to contribute to GAA3, regional updates are in process for 246 southern African amphibian species. A very high proportion (approximately 74%) are endemic to the region, emphasizing the need to understand their conservation status, and prioritize conservation resources. Over 150,000 records were collated from 16 institutions (including citizen science platforms) and numerous private collections. A team of twenty experts contributed to assessment updates, with the support of the IUCN Amphibian Red List Authority, Amphibian Arc, SANBI and Re:Wild. Applying the IUCN Red List criteria according to IUCN guidelines, the current assessments have resulted in category changes for over 40% of priority species, including assigning a status to all but one Data Deficient species and all Not Evaluated species. Future climate scenarios (2050s) were modelled for South Africa’s threatened frog species and predict a wide range of distributional impacts, which will be exacerbated by ongoing land-use change. 35% of threatened species are likely to be highly impacted by future climate change scenarios. The updated assessments will be published by IUCN in the first half of 2025, and the outcomes of this work will be invaluable in informing an updated conservation and research strategy, the National Biodiversity Assessment, and has already contributed to identifying species in need of urgent recovery in the next decade.

The BioSoundSCape project: Automating frog detection for ecological monitoring in the Cape Floristic Region

Andrew A. Turner; John Measey; Oliver Angus; Colleen Seymour; Alan Lee; Rose Snyder; Festus Adebgola; Leo Salas; Matt Clarke

Monitoring frogs has the potential to provide useful insights into measuring ecosystem health and the management of these ecosystems. Yet currently this monitoring is highly restricted, in space and time consuming. Data acquired from automated sound recording devices can extend the reach of ecological monitoring. The BioSCape project is a large, multi-party collaboration with NASA that aims to relate biodiversity patterns on the ground with remotely sensed, cutting edge spectral imaging that provides very high spectral resolution across the electromagnetic spectrum. One of the novel ways to measure biodiversity is to measure bioacoustic diversity. The BioSoundSCape project deployed a large number of automated sound recorders (AudioMoths) across the Cape Floristic Region and recorded nearly 1 million sound recordings. These recordings are freely available on NASA’s Distributed Active Archive Center. The project set up pattern matching algorithms to detect frog calls of 13 frog species, ran statistical pattern matching, validated results and used the resultant validated sound sonographic signatures for training input to a machine learning (computational neural network) system as implemented by RFCx in Arbimon. From this we calculated diversity indices and present examples of these outputs. Once the entire data collection, processing and analysis can be automated, it can realise the ability for large-scale, frog and ecosystem monitoring.

Management Measures and Costs note (MMC) for the EU on Xenopus laevis released

As Xenopus laevis is now on the list of concern for invasions in the European Union, a guide of measures how to mitigate and potential costs incurred was required. The production of this note required an online workshop (which took place in May 2024), with participants from around the world. The expertise of all those who have engaged with control and mitigation of Xenopus  invasions was sought and distilled into an MMC which was released today (see here). 

The final MMC is nearly 40 pages long and contains lots of really useful information on Xenopus laevis invasions. Many thanks to all those who participated, especially Ana Nunes and Grace Bond from IUCN.

Measey, J. (2024). The management of invasive alien Xenopus laevis. Information on measures and associated costs for species on the Union list. Technical note prepared by IUCN for the European Commission

A talk for the University of Portsmouth

Readers of the blog will be familiar with my repeated visits to the University of Portsmouth and in particular the European Xenopus Resource Centre (EXRC). In January 2024 (see here) I became a Visiting Researcher, School of Biological Sciences, University of Portsmouth, and so during a brief visit to Portsmouth this week, I was asked to give a talk to the School.

The EXRC is a special place for anyone working on Xenopus as they hold breeding stock for anyone in Europe working on Xenopus frogs. Recently, we were able to supply them with some gametes from the progeny of wild caught animals from South Africa. I hope to report more on that project here on the blog in future.

Matt Guille leads the EXRC and received a flashing Xenopus neon sign for the EXRC lab.

Measey, J. (2024) What can biological invasions teach us about rapid evolutionary change? 1 November 2024 School of Biological Sciences at University of Portsmouth

The 10th World Congress of Herpetology in Kuching, Sarawak, Malaysia

It was a great pleasure to attend the 10th World Congress of Herpetology in Kuching this month. The congress was a great opportunity to catch up with herpetologists from across the planet, including many that I have known for many years as well as many many new faces. 

I presented my work on the gut microbiome of Xenopus laevis, and was pleased to see many former members of the MeaseyLab presenting their own work.

Burrowing in Snakes: a Comparative Study on the Performance and Mechanics of Snake Burrowing
Anthony Herrel, David J. Gower, James C. O’Reilly, Nathan J. Kley, Philippe Gaucher, Ilian Grima, John Measey and Marion Segall

Snakes are an incredibly diverse lineage of squamates that have radiated into a great diversity of habitats from a possibly fossorial ancestor. Fossoriality imposes strong constraints on obligatory head-first burrowers and this has been suggested to have impacted the morphological evolution of both head and cranial shape. The strength of constraints on head shape likely depend on the taxon and burrowing style but quantitative data on the forces exerted during burrowing or the kinematics of burrowing remain scarce. Preliminary data suggested that typhlopid snakes were capable of generating higher forces than other snakes for a given size and body diameter but taxon sampling was limited. Here, we present data on the three-dimensional burrowing forces for 26 species of snakes distributed across most major lineages. We further present the first X-ray data on the kinematics of locomotion through tunnels and soil for a subset of species including sand swimmers (Eryx) and true burrowers (Anilius, Xenopeltis, Cylindrophis, Homalopsis and Aspidelaps). Our data show significant differences in maximal resultant forces and force orientation in different species. Moreover, our kinematic data show that sand swimmers are unique in showing kinematics of subsurface locomotion similar to those observed in snakes swimming in water. Finally, we show that some snakes such as Anilius are capable of performing internal concertina locomotion documented previously only for caecilians. Overall our data shed new light on the diversity of burrowing performance and kinematics in snakes and help understand the evolution of this lifestyle and its constraints on form and function.

Does Plasticity or Genetic Adaptation Induce Variation in Thermal Sensitivity of an Invasive Frog (Xenopus laevis)? A Population Level Study, from Tadpoles to Adults
Laurie Araspin, John Measey and Anthony Herrel

Life history traits of organisms are modulated by the selective pressures of the environment, generating variation in phenotypes. This phenotypic diversity can be observed at the interspecific level but also at the intraspecific level in populations living in different environments. Temperature is a characteristic of an animal’s habitat and one of the dimensions of the ecological niche. It is a critical factor impacting all aspects of the biology of organisms, especially in ectotherms. Xenopus laevis is an aquatic frog that is invasive on four continents, with invasive populations inhabiting a diversity of environments. The objective of this study was to investigate the thermal adaptation ability of this species that is successfully established in dramatically different thermal environments. The use of thermal performance curves allowed to assess the relationship between temperature and locomotor performance and basal metabolic rate in individuals from two generations. Phenotypes from a F1 generation of the studied populations raised in a common garden environment were compared to the F0 phenotypes. This allowed to understand whether the observed differences among populations
are plastic or genetically based. This study demonstrated that populations exhibit a different thermal dependence of their performance, and that genetic and plastic processes are involved in the thermal adaptation, highlighted by a significant genotype by environment interaction. Variation in performance depending on temperature provides an insight into how this invasive species can survive and cope with different thermal environments, especially in the context of climate change.

Of Toads and Toxins: Shrinking Toxin Glands but Stable Toxin Composition Indicate Directions and Constraints of Adaptation in Invasive Populations of an African Toad
Max Mühlenhaupt, Cláudia Baider, James Baxter-Gilbert, André J. de Villiers, Nhlanhla S. Dludla, F. B. Vincent Florens, Buyisile G. Makhubo, Xavier Porcel, Julia L. Riley, Willem A. L. van Otterlo and John Measey

Many amphibian species use chemical defenses to avoid predation, yet, how these defenses vary between populations, or change as populations colonize novel habitats is not well understood. The Guttural Toad (Sclerophrys gutturalis) has established three invasive populations, located in Mauritius, Réunion, and Cape Town. All of these populations originated from a clade located at the port city of Durban in eastern South Africa, providing an excellent study system to examine how biological invasions drive phenotypic change. To investigate how toad chemical defenses may have shifted along their invasion path, we compared the relative size of the parotoid glands (as a correlate of toxin quantity) and the composition of the toxic secretions that exude from these glands (as an indicator of toxin potency) between native and invasive populations. While the two oldest invasive populations, Mauritius and Réunion, showed pronounced convergent decreases in gland size, the toxin composition remained stable between all populations. These results indicate that the invasive populations of this chemically defended toad may have experienced reduced predation pressure in their novel habitats, which resulted in reduced selection pressure for defense. Furthermore, within the native populations, gland size may also be a more variable trait than toxin composition. Integrating both quantitative as well as qualitative information will help us better understand the evolution of chemical defenses in animals and could aid in predicting if and how chemically defended invasive species colonize novel environments.

Home and Away: The Core Gut Microbiome of Xenopus laevis is Modified by its Environment
Measey, J., Ren, Q., Guille, M., Almojil, D., Araspin, L., Wagener, C., Boissinot, S., Watts, J. and Robson, S.

The vertebrate gut microbiome is a community largely composed of bacterial, fungal and viral components, whose molecular component equal that of the host. The influence of the microbiome is known to be significant both on an individual basis, and also on population scales in a wide range of host organisms. The gut microbiome is known to be involved with key attributes of animal health, including assimilation of nutrients, immuno-defensive functions and host behavior. In this study, we used bacterial 16S rRNA amplicon-based sequencing for metataxonomic classification of the gut microbiome of individuals from eight populations of Xenopus laevis. These populations were selected to represent an altitudinal gradient in the native range of the host species (0 to 3,000 m asl). From the 16S rRNA community profiles, we determine the components of the core microbiome of X. laevis , and ask whether deviations from the core are associated with the environmental context in which they live. In addition, we sampled four European invasive populations and a laboratory population from the European Xenopus Resource Centre (EXRC) in the UK, to determine what aspects of the core microbiome are retained by non-native populations. This represents the first time that the microbiome of X. laevis has been assessed across such diverse conditions, and provides data that will help understand the role played by the environment and inform monitoring of health within this model organism.

ROUNDTABLE "TAKING THE INVASIVE TOAD TOOLKIT GLOBAL"

John Measey, Georgia Ward-Fear & Angelica Crottini

Invasive toads are a global problem, and yet many solutions and mitigations are available –
particularly as a result of a large investment into cane toad invasions in Australia. But how
much of the “invasive toad toolkit” can be exported to other invasions? This round-table event
is aimed at stakeholders with an interest in toads and toad invasions to precise what parts of
the toad toolkit can be used in toad invasions worldwide.