Studying Mosquitofish from the South of France is Not as Glamorous as It Sounds, Part 3

The fish have been collected, the experimental plans organised, and now ... it's time to watch and swim and measure fish.

 

Robbie and Frank split up the work associated with their experiment - Robbie observed the females' behaviour and Frank measured metabolic rates.  

Here's the behavioural set-up:

And the metabolic set-up:

 

Frank swam fish in a little glass jar to ramp up their metabolic rates, so he and Robbie could calculate the metabolic scope.

That's all we can say for now, as the data haven't been analysed and the paper has yet to be written. But we wanted to give you some insight into what an eco-physiological experiment entails. It may not be as glamorous as it sounds, but the excitement of discovery and exploring new ideas is what keeps scientists going. The development of an experiment like this one was a lot of fun!

Studying Mosquitofish from the South of France is Not as Glamourous As It Sounds, Part 2

We now return to our story of mosquitofish from murky waters in southern France ... gallantly collected and brought back to the lab, where they were used to address a very important question:

How expensive is pregnancy?

Now, having been pregnant once before, I was willing to share my own experiences with expense in pregnancy: the financial costs associated with becoming addicted to eBay; the social costs of inexplicable moodiness; the energetic costs of lumbering to and from the bathroom; the mental costs manifested in an inability to concentrate/find keys/remember things.

But, apparently fish are different.

Mosquitofish, in fact, are live-bearers that can produce 20 to 70 young in a pregnancy - young that altogether can weigh up to 30-40% of the female's own body weight.

This extra mass and the energy required to produce all these baby fish can substantially increase a female's metabolism - even when she's resting. A higher resting (or basal) metabolism would be expected to limit a female's metabolic scope.

What's metabolic scope? It's the difference between resting and maximum metabolic rates - or the amount by which the body can increase metabolism to deal with high levels of physical activity or stresses. Because maximum metabolic rates are limited by the body's capacity to uptake oxygen and eliminate cell waste, they don't change much. So we expect the metabolic scope of a pregnant mosquitofish to diminish as her resting metabolic rate increases.

But.

That's not all.

Temperature also increases the resting metabolic rate of fish: higher temperatures mean higher resting metabolic rates.

So that's what Robbie and Frank and their French collaborators were keen to look at - how temperature affects the metabolic scope of pregnant mosquitofish.

(to be continued ...)

Studying Mosquitofish from the South of France is Not as Glamourous As It Sounds, Part 1

Recently, Robbie was invited to collaborate with scientists at France's prolific CNRS (Centre National de la Resherche Scientifique). These researchers included Head of the CNRS's Ariege unit, Prof Jean Clobert; and Marie Curie Fellow, Dr Camille Bonneaud. Robbie joined his long-time Australian collaborator and friend - A/Prof Frank Seebacher - in the idyllic location of Moulis* to study the behaviour, physiology, and performance of the invasive mosquitofish (Gambusia holbrooki) relative to their state of pregnancy.

*Let me assure you, that for all the un-glamourousness of the fish- and data-collection, the research station was spectacularly situated.

Imagine working in a well-funded research program in a quaint French village, in a building that adjoins a rushing brook amidst the green-capped mountains of the Pyrenees.
Mag. nif. ique.

But, alas, mosquitofish don't like pristine, bubbling streams. They prefer dank, stagnant places. So when Robbie and Frank took a drive toward the Mediterranean coast, it was looking for swamps. And though there are no pictures to document the collection of the fish, it allegedly involved:

1) wading through reeking swamp mud
2) numerous biting insects
3) a decomposing, floating, probable-mammal the size of a beaver
4) a swift change of clothes before returning to the hire car

And a pink net.

Some hearty beef stew and a few beers upon returning home didn't hurt, either.

Then it was off to the lab to set up the experiments ... (to be continued) ...

Biodiversity Research with Anindilyakwa Rangers

Our team has headed back up to Groote Eylandt (and I'm still here ... sigh ... ), so I thought I might take this opportunity to talk more about our collaboration with the Anindilyakwa people of the island. We have much to learn from each other - but more than that, collaboration between scientists and Indigenous peoples can be a rewarding and effective means of conserving the environment.

Aboriginal Australians have a powerful cultural connection to their environment. It sustains them, physically and spiritually. Conservation of biodiversity is innate, and information about the environment - the organisms that inhabit it, the seasonality of events - have been passed down via narratives and stories for thousands of years. Though this knowledge is more qualitative than quantitative, it represents a long-term picture of the environment that few, if any, scientific studies would provide.

Besides, the ability of Aboriginal trackers and rangers to navigate the bush is incomparable - which facilitates conservation-based studies of wildlife, including the northern quoll. On our trips to Groote Eylandt, our team trains the Indigenous Rangers in scientific methods of capturing, tagging, and 'processing' animals. We talk through research ideas, hypotheses, protocols, and analyses with them. And we absorb their beautiful culture.

We'll be sharing more about our current trip shortly, including photos of some very non-quoll-related fish, and a story about why Billy is currently sitting poolside at the resort, rather than working. (Ahem)

How to Catch and Process a Quoll*

*and no ... we're not making sausages out of them ...

So how do you catch a feisty little marsupial, that's nocturnal and ground-dwelling and generally doesn't like to be caught?
Ecologists typically use baited traps, but of a sort that aren't likely to harm the captured animal - like this Elliott Trap, which has a door that springs shut when the animal steps inside.

Just before dark, our intrepid quoll-catchers set out the traps (with goodies inside) and then return to camp to give the quolls a chance to find - and take - the bait.

When a quoll's been captured, we take it back to the lab to 'process' it. Which sounds really suss but actually just means that we measure them and add tracking and identification devices to them. This is so we can obtain information about the health and size of the quolls, and keep track of particular individuals over time.

After we've taken all the important measurements, it's time to 'mark' the animals. In this study, we mark with ear tags, pit tags (like microchips), and collars - which may seem like overkill, but actually allows us to collect different kinds of data.

Ear tags are like earrings that have a specific number on them, unique to the animal. This means that if we catch this quoll again, we can easily and quickly determine its identity. Ear tags, toe tags, and leg or flipper bands (depending on the animal of focus) are commonly-used by ecologists for this purpose.

Pit tags are the second line of identification ... they're inserted under the skin, and hold all the relevant information about the animal - just like the microchip that you can get for your dog or cat. The coolest thing about pit tags? You read them with a scanner.

(as in, "clean up on aisle 3 ... ")

And collars - they're for the purpose of tracking the animal, using either radio frequencies or GPS (depending on the type of collar). By tracking individuals, ecologists can learn more about how the animals interact with each other, how large their range is, and how much they move around. If you want to know more, we talked about tracking koalas here and here.

After all this, the quoll is released back into the wild ... where it is no longer the anonymous little carnivore it once was.

So now you know how to catch and process a quoll. (Or, for that matter, any animal of ecological interest). Please use your wisdom for good, not evil.

Thanks Gavin, Sean, Robbie, Billy and Bill for the great photos!

Run Gecko Run (Don't Ever Look Back)

How do scientists study running performance? Well, with humans we'd take subjects out onto a track and measure how fast they could sprint between two points.

With geckoes?

It's pretty much the same. Except we have
to design a track that encourages the gecko to move as quickly as it can in a straight line. (Because geckoes aren't as good at taking verbal directions as humans are ... )

Skye's current experiment is based around this running track. She puts a gecko into the near end (as shown in the top photo) and then chases it down the track with a foam paddle. Don't worry, the gecko's fine - the paddle is just to prevent it from stopping or turning around or anything that might disrupt measurements.

As the gecko runs down the track (away from us, in this picture), it passes the 4 light sensors that help Skye to accurately record the gecko's speed. Skye repeats the run 3 times more, so that she can get the gecko's fastest performance (best of 12 time splits - 3 trials x 4 sensors).

After measuring running performance, Skye takes the weight of the gecko to account for its body size in her calculations. This is because larger geckoes will be able to run faster independently of temperature.

Then, the gecko returns to its home in the lab.

Each gecko completes 8 running trials at temperatures between 15 and 38 degrees Celcius. Some populations won't ever have seen some of these temperature extremes in the wild (and others will have). 

Skye is predicting that where a gecko comes from will affect how it performs at these different temperatures. For example, at low temperatures geckoes from tropical North Queensland should perform more poorly than geckoes from Brisbane - because, in nature, Brisbane geckoes experience low temperatures every year (and tropical geckoes don't). 

Skye's still working hard measuring gecko running speeds ... so we can't tell you any results yet. But watch this space!

Why Temperature Matters to Geckoes

At the moment, Skye's doing a really cool experiment looking at how Asian house geckoes from different environments handle changes in temperature.

Why is this important? Well,
climates are changing. And scientists want to know how species will handle climate change - will they go extinct? will they do even better?

To answer these questions, we have to know more about how species perform across their natural range. Because animals that are already living close to their thermal limits might be at greater risk if things heat up, or even cool down. And because some animals have a greater capacity to rapidly adjust to temperature change (or acclimate) than others. And because most of the animals on the planet are what we call ectotherms, which (unlike humans) can't warm themselves up internally: their digestion, brainpower, muscle activity - everything - is dependent on the temperature in their environment.

So what's Skye doing? She's collected Asian house geckoes from across their latitudinal range in Australia - from Brisbane all the way up to Cape York. (ahem - more traveling??). Geckoes from all these different populations have grown up in quite different environments - but in general, temperatures get hotter and less variable as you head north from Brisbane.

Which leads us to some fundamental questions in thermal ecology: do animals in these different environments become 'experts' at performing under just those conditions? Or can they perform over a wide range of temperatures - just not very well? Is the pattern changeable (suggesting acclimation) or unchangeable (suggesting adaptation)?

Skye is testing these questions by looking at the running performance of geckoes from different populations  - across a range of temperatures. If you've ever watched a gecko on your window at night, you'll see why running is so important to them - it's how they catch prey, but also how they escape from predators and is a key factor in determining dominance of individuals.

So looking at running performance is a great way to assess how temperature affects the geckoes' ability to survive and make babies.

This is just a teaser, really. Letting you know why *some* people spend hours tending to and running geckoes in all sorts of temperatures. In the next post, I'll talk a bit more about the specifics of Skye's study - including her amazing experimental set-up!