Walking on the Seabed, Miniature Steam engines and Cool Mosquitoes

We explore how African lungfish are providing insight into the evolution of walking, the design of the world's smallest steam engine, how birds tweet at a higher pitch to be...

18 December 2011

Interview with

Heather King, University of Chicago; Clemens Bechinger, University of Stuttgart; Emily Mockford, University of Aberystwyth; Claudio Lazzari, University of Tours

Part of the show What Colour is a Dead Chameleon?

20100507-pano4_small.jpg

Credit:

Heather King, University of Chicago

Play Download

Walking Lungfish

The African lungfish uses its fins to walk rather than swim underwater. Publishing in the journal PNAS, Heather King from the University of Chicago monitored the movements of lungfish in tanks of water and found them using their pelvic fins as hind legs to walk along the bottom of the tank. The finding suggests that walking may have evolved underwater rather than on land.

Heather - This is evidence to support the idea that perhaps walking evolved before feet evolved or digits or terrestriality in this lineage, lobed-fin fishes to which tetrapods belong, and of course, we are tetrapods, every land animal with a backbone and forelimbs is a tetrapod. So that's why lungfish are important to look at because they're one of the last closest relatives of the tetrapods that still alive.

The World's Smallest Steam Engine

The smallest steam engine in the world has been developed by scientists at the University of Stuttgart. Using a single colloidal particle called melamine, thousandths of millimetre in size, submerged in an equally small chamber of water, Clemens Bechinger used a laser to trap the particle and varied the laser's intensity to either restrict or free the particle, resembling the compression and expansion seen in a large scale steam engine. A second laser was used to heat and cool the water bath.

Clemens - If we change the intensity of the heating and compression expansion laser beams in the right way, we can then make this engine to work and a surprising result is that if you tune the parameters correctly, then the efficiency of such a small steam engine, although it stutters, and it doesn't run as smoothly as its microscopic counterpart, can be as large as that of a macroscope steam engine.

Urban Birds Tweeting High

Birds living in cities produce higher pitch sounds that those living in more rural environments. It's long been known that urban birds produce a different song to those in the countryside but the reasons why had been subject to speculation. But now, recording and monitoring the songs of great tits in and around the city of Sheffield, Emily Mockford from the University of Aberystwyth found that birds within the city produce sounds of a much higher pitch, enabling the sounds to travel further and echo less off surrounding buildings.

Emily - The architecture of a city is in fact changing, the way that sound travels to the environment and it will affect how birdsong travels through the environment as well. We need to think about the way we build our cities and the way that wildlife has to adapt around us. It's not actually the noise that we're making, but it's actually the physical sound scapes that we're creating as well that they have to adapt around. It is the larger cities that will have this problem because it's the massive reflective surfaces and urban canyons and open spaces that are changing the way that sound travels.

Cool Mosquitoes

Mosquitoes release droplets of fluid to keep themselves cool whilst feeding. Scientists have often wondered how cold blooded insects such as mosquitoes prevent themselves overheating when consuming hot blood from a human. Using thermal cameras to monitor mosquitoes during a meal, Claudio Lazarri's team from the University of Tours in France noticed that as they feed, the insects exude droplets of fluid to cool their bodies down to ambient temperatures.

Claudio - We have seen that at the beginning, the mosquito warms up and very soon during the feeding process, they start emitting a droplet of fluid that they keep attached to their body and at that moment, the temperature of the mosquitoes' body start to decrease because of the evaporation of this fluid. So, the evaporation produces a loss of heat in the mosquitoes' body.

The work could be used to control mosquito populations in the future and is published this week in the journal Current Biology.