Australasian Science: Australia's authority on science since 1938

Put Away Your Smelly Socks

By Magdeline Lum

Magdeline Lum reports on quirky experiments and research findings.

There may now be a good reason to place smelly socks into the laundry basket rather than leaving them on the floor – the odour may be luring spiders. Fortunately, the spider that is attracted to pungent socks is after a fine dining experience on mosquitoes engorged on human blood. A sweaty sock may be an unfavourable dining place, but for mosquitoes it is the perfect place to set up base camp to gorge on human blood.

This latest finding could lead to new ways to trap mosquito carriers of the deadly malaria parasite and to also lure their predators. All mosquitoes that carry the malaria parasite belong to the genus Anopheles. Research has shown that the species Anopheles gambiae is drawn to the scent of humans.

Researchers at the University of Canterbury in New Zealand have found that the East African jumping spider, Evarcha culicivora, prefers Anopheles mosquitoes as its preferred meal. This comes after finding that this spider can sniff out blood-engorged mosquitoes.

Two New Zealand scientists, Fiona Cross and Robert Jackson, bred a group of adult and juvenile E. culcivora and exposed them to human scent. The scent was sourced from cotton wool socks worn by an anonymous male donor for 12 hours before the trial. The spiders spent significantly more time in chambers scented with smelly sock than in chambers without.

The levels of carbon dioxide, heat, moisture and compounds specific to human odour alert the mosquito An. gambiae to the presence of a human. This odour also entices the E. culicivora in search for a mosquito, rather than a human.

The findings were published in the Royal Society Journal Biology Letters.

Hang Up Your Hat, Indiana Jones
The globetrotting life of Indiana Jones is indelibly imprinted on the minds of people as the archetypal archaeologist. Coupled with this are scenes of hot, dusty locations with an archaeological dig underway.

It is true that archaeologists do go out on trips and get covered in dirt occasionally, but the search for undiscovered sites can now be done by computer. Even more incredible is that the software needed is freely available. You might have heard of it – it’s Google Earth.

Prof David Kennedy, a researcher in Classics and Ancient History at the University of Western Australia, has used Google Earth to identify almost 2000 archaeological remains in Saudi Arabia. It is a country that has a rich archaeological history but it is one of the least explored parts of the Middle East.

“The single most powerful and cost-effective tool for the discovery, location, mapping and initial analysis of archaeological sites is aerial reconnaissance. It transformed the historic human landscape in many parts of Europe,” Kennedy said of Google Earth.

“Even more than most Middle East countries, however, Saudi Arabia seldom makes aerial photographs available to archaeologists, and it is effectively impossible to do any archaeological flying.” Satellite imagery provided by Google Earth offers an alternative solution, especially with high resolution “windows” provided by the software.

Kennedy and Dr Michael Bishop used Google Earth to “interpret” 1240 km2 near Jeddah, a Saudi Arabian city on the coast, and found 1977 probable archaeological sites, of which 1082 are ancient tombs.

“It is readily apparent that the use of Google Earth for the prospection and identification of sites has great potential when dealing with a huge area that is otherwise largely inaccessible on the ground,” he writes in the report.

The findings were published in the Journal of Archaeological Science.

Slimy Farmers
When you think of farming, the first thing that pops to mind is fields or a herd of cattle but certainly not a slime mould. Ants and termites can grow their own food, but now a team from Rice University in Texas has found that Dictyostelium discoideum, a species of amoeba, engage in farming.

Crops that D. discoideum farm are bacteria that they prefer to eat. One-third of spores from a population of the amoeba carry bacteria to “seed” a new habitat for food. This is an advantage when an area has no food or the preferred food is unavailable.

The amoeba “farmers” fared better than non-farming amoeba when transferred to an area with no food readily available. In these conditions, D. discoideum produce a fruiting body containing spores to be carried by the wind to new locations where there may be more food. In the farming population, the fruiting bodies were larger and they produced more spores than the non-farmers.

When the farmers and non-farmers were placed in an area with bacterial abundance, there was no advantage to being a farmer. It proved to be a disadvantage. The farmers in this situation produced less spores than the non-farmers. This could be because farmer D. discoideum populations eat less to save some for harvest.

The findings were published in Nature.