Tag: Amphibians

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Xenopus Enrichment

Smooth frogs and fake plants
embracing in the water.
Happiness is here.

The African Clawed Frog, Xenopus laevis, is a common laboratory model species of amphibian, used in research primarily for their embryos and eggs. Yet despite their popularity little attention has been given to the housing and husbandry – what is the best way to keep the African Clawed Frog?

Recently, however, things have begun to change as more attention is being given to the welfare of ‘lower’ vertebrates and invertebrates. Indeed, in 2016 we published research demonstrating that a darker tank background resulted in lower levels of corticosterone (a stress hormone), lower instances of stereotypical behaviour and less change in body mass (Holmes et al, 2016). The results suggest that darker backgrounds are better for African Clawed frog welfare in captivity (check out the sciku ‘Clawed frogs indicate‘ for more information about the study and the likely reasons behind the preference).

Now in 2021 new research has been published by Ramos and Ortiz-Díez that examines X. laevis preferences for types of physical enrichment within their tanks. The researchers provided tanks of frogs with artificial plants and opaque PVC tunnels and checked on the frogs three times a day for 6 weeks to see where in the tanks they were spending their time – with the plants, tunnels or in the open areas of the tanks. The results indicate that the frogs preferred the plants 40% more than the tunnels, although both were preferred over the areas of open space in the tank.

As research into the welfare of amphibians gains momentum it’s good to see more work focussing on this common laboratory animal and how it’s kept in captivity. Particularly warming is that in the experimental methods the researchers specifically state that tanks with dark sides and bases were used to reduce visual stress, referencing our earlier work.

Original research: https://doi.org/10.1177%2F00236772211011290

A note about the sciku: The phrase ‘smooth frogs’ that starts the poem is a reference to the meaning of the name laevis – smooth (the word Xenopus means ‘strange foot’).

Interested in African clawed frogs? Check out these other Xenopus sciku: ‘Clawed frogs indicate‘, ‘Have frog, will travel‘, ‘Fungal culprit‘ and ‘Reservoir or predator‘.

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Indigenous Engagement

The benefits of
indigenous engagement:
Ethics and Science.

Local knowledge and an awareness of local context can be integral to conducting a variety of research. However, one thing that’s less often considered is the impact of the diversity of the research team itself.

Conservation research by Ward-Fear et al (2019) into the impact of cane toads on yellow-spotted monitor lizards in Australia has unintentionally produced evidence of the scientific benefits of collaborating with local indigenous people.

Large cane toads are spreading through tropical Australia but are fatally toxic if eaten by yellow-spotted monitor lizards. Ward-Fear et al (2016) trained lizards with smaller, non-lethal cane toads and then compared the survival rates of trained and non-trained lizards in the wild over an 18 month period. They found that trained lizards had a greater survival rate than non-trained lizards, suggesting that the training helped the lizards to avoid eating the larger toxic cane toads.

Yet their study also revealed the importance of researcher diversity. In monitoring the population of lizards over 18 months, the research team included western scientists (professional, nonindigenous ecologists) and indigenous rangers (Australian-Aboriginal Traditional Owners of the region).

The indigenous rangers saw lizards from a greater distance, in more dense vegetation, under poorer light levels, and more frequently when the lizard was stationary. Additionally, when assessing the behavioural traits of the lizards, those that were spotted by the indigenous rangers were found to be more shy. What’s more, the ranger caught lizards appeared to benefit more from the training against the toxic cane toads.

All this highlights the importance of cultural diversity within research teams and in particular shows that indigenous collaboration can be utterly crucial for conservation efforts.

Original research:

Training of predatory lizards reduces their vulnerability to invasive toxic prey: https://doi.org/10.1098/rsbl.2015.0863

Collaboration with indigenous peoples can alter the outcomes of conservation research: https://doi.org/10.1111/conl.12643

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Giant becomes five

Giant becomes five

endangered salamanders.

Hidden extinction?

 

The Chinese Giant salamander is the world’s largest amphibian, adults can be 2 meters long and weigh up to 50 kg. It’s critically endangered in the wild due to habitat destruction, fungal infection and because the species is used as a luxury food source in China. It is kept in far greater numbers in captivity as a result of it being farmed for food. Two studies published in Current Biology add additional concerns for the future of this species in the wild.

In what is thought to be the largest wildlife survey conducted in China, Turvey et al (2018) found that giant salamander populations were either critically depleted or had been eradicated, as well as finding plenty of evidence for illegal poaching. The researchers were unable to confirm the survival of wild Chinese giant salamanders at any of their survey sites, raising the question of whether this species is all but extinct in the wild.

In a companion piece of research, Yan et al (2018) performed a genetic analysis on Chinese giant salamanders and found that the species actually consists of at least five species-level lineages, potentially up to eight. This suggests that some of these distinct lineages (effectively separate species) may well have already gone extinct in the wild – a phenomenon known as cryptic or hidden extinction. This has crucial importance for conservation efforts, particularly with regards to re-releases from captive populations where the five lineages have been mixed and the resulting offspring are effectively hybrids.

Original research:

Turvey et al (2018): https://doi.org/10.1016/j.cub.2018.04.005

Yan et al (2018): https://doi.org/10.1016/j.cub.2018.04.004

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Have frog, will travel

Have frog, will travel,

yet what impact on welfare?

Best to avoid moss.

Transporting animals for research, agricultural, conservation or leisure reasons can involve a range of potential stressors. It’s therefore important to be aware of the impact of transportation on animals so as to minimise any negative effects.

African clawed frogs are a common laboratory animal, used for a range of developmental studies. Holmes et al (2018) investigated the impact of transportation between research facilities. They found that transportation and re-housing had a negative impact across a short- and longer-term, with corticosterone (a ‘stress hormone’) remaining high for 1 week and body mass remaining low for 5 weeks after transportation. Investigating further the researchers found evidence that being transported in moss might be the least preferable transport medium, with water or sponge appearing to be more suitable.

Original research: https://doi.org/10.1016/j.ygcen.2018.03.015

Interested in African clawed frogs? Check out these other Xenopus sciku: ‘Clawed frogs indicate‘, ‘Xenopus enrichment‘, ‘Fungal culprit‘ and ‘Reservoir or predator‘.

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Reservoir or predator

African clawed frog –

reservoir or predator

of the fungal blight?

Amphibian populations worldwide are being devastated by a fungal infection (known as chytrid or Bd). As an invasive species and carrier of the fungal infection African clawed frogs are often blamed for the spread of chytrid and the current conservation crisis.

Research by Wilson et al (2018) suggests the story is more complicated than it at first seems though. Field studies in California suggest a 10% level of Bd infection in the frogs, with infected individuals having very low levels of infection. Additionally, larval clawed frogs appear to eat the Bd zoospores and may therefore actually be helping to reduce the negative impact and spread of the fungus. Unfortunately the study also suggests that the frog larvae also eat Daphnia, which are another predator of the Bd zoospores.

This latest research adds to growing evidence suggesting that African clawed frogs may not be as guilty as they seemed at first.

Original research: https://doi.org/10.1371/journal.pone.0191537

Interested in African clawed frogs? Check out these other Xenopus sciku: ‘Clawed frogs indicate‘, ‘Have frog, will travel‘, ‘Fungal culprit‘ and ‘Xenopus enrichment‘.

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Exploiting blind spots

Tropical clawed frogs –

what you can’t see can’t hurt you.

Exploiting blind spots.

 

Providing sufficient shelter for animals in captivity is frequently an important method to improve welfare, however cover may limit the ability to observe animals for health checks. Western clawed frogs (or tropical clawed frogs) are a common model organism, kept in high numbers in laboratories around the world, but there is comparatively little empirical evidence for how best to adequately house this species in captivity.

Cooke (2017) found that a black overhead cover was the optimal method of providing refuge for this species. In a second experiment exploiting the frog’s inability to see certain wavelengths the black cover was swapped for a red translucent cover which was found to be just as effective.

Red translucent covers could therefore be an effective method of providing refuge for the animals whilst simultaneously allowing carers to observe and conduct health checks.

Original research: https://doi.org/10.1177/0023677217737798

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Fungal culprit

Fungal culprit of

amphibian genocide –

Innocent scapegoat?

Amphibian populations are in the midst of a pandemic, the spread of chytrid fungus devastating species around the world. Conservationists have pointed a finger of blame at African clawed frogs: they are hosts of the fungus, have a degree of immunity and have spread around the world due to their use in research laboratories and hospitals.

The circumstantial evidence seems damming but research by Tinsley et al (2015) into long-standing UK populations suggests otherwise. Native amphibian species present alongside populations of African clawed frogs were not infected with chytrid fungus, despite the African clawed frogs themselves carrying it. What’s more, the African clawed frog populations have been present for decades yet surveys revealed continued high native species abundance. If fungal transmission from African clawed frogs were an issue then such levels of native amphibians would be unlikely.

It seems then that African clawed frogs may be scapegoats after all.

Interested in African clawed frogs? Check out these other Xenopus sciku: ‘Clawed frogs indicate‘, ‘Have frog, will travel‘, ‘Xenopus enrichment‘ and ‘Reservoir or predator‘.

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Clawed frogs indicate

Clawed frogs indicate

by action and reaction

a choice between shades.

 

Ensuring the welfare of animals used for research is vital both from an ethical stand point and for the quality of the research produced – animals in poor condition do not produce accurate or reliable results. The African clawed frog is a common research species found in laboratories around the world but little work has investigated how to optimally house it in captivity.

Holmes et al (2016) found that a black tank background produced lower levels of ‘stress’ hormone (corticosterone), lower amounts of stereotypical behaviour and a smaller loss in body mass than a white tank background.

As African clawed frogs are naturally dark green/brown in colour and use camouflage to avoid predation, a light background might be more stressful for the frogs as they may appear more exposed. Providing dark tank backgrounds could therefore be an easy method for improving the welfare of thousands of African clawed frogs housed in captivity around the world.

Interested in African clawed frogs? Check out these other Xenopus sciku: ‘Fungal culprit‘, ‘Have frog, will travel‘, ‘Xenopus enrichment‘ and ‘Reservoir or predator‘.

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Perfect storm

Spreading fungal scourge

salamanders succumbing

perfect storm draws near.

 

Many of the world’s amphibians are under threat from a chytrid fungus (Bd), particularly in the tropics where it is driving many amphibian species towards extinction. More recently a sister species (Bs) has been observed in Western-European salamanders. Observations of a salamander population across two years following initial detection of Bs suggest a rapid population collapse with little recovery. Bs also has an increased transmission strategy over Bd and may behave as a “perfect storm” as it spreads through European populations of salamanders. Stegen et al, 2017.