Spiders have long been known to travel great distances by using strands of their web silk to glide through the air, but scientists have yet to fully understand how these arachnids can survive their journey across bodies of water.
This is what inspired a team of researchers from the University of Nottingham and the Natural History Museum to find out how some species of spiders are able sail over water.
In a study featured in the open access journal BMC Evolutionary Biology, Morito Hayashi of the Natural History Museum led the team in studying 21 common spider species endemic to small islands in the United Kingdom.
The scientists gathered 325 adult spiders from several nature reserves around Nottinghamshire and placed them on water trays to observe how they would react to air generated through a pump. They then compared their observations to the spiders' behavior on dry surfaces.
Hayashi and his colleagues discovered that the majority of the arachnids adopted intricate postures, including lifting up their legs, to glide through the wind current while they were on the water. This move allowed the spiders to sail in different water conditions such as still and turbulent as well as salt and fresh water.
The spiders also used their web silk as anchors to stop or slow down their movement on water. This proves that the silk serves as some form of dragline that helps the spiders hang onto objects floating on the water or to reach the shore.
The findings also show the adaptability of the creatures during encounters with different aquatic environments. This is important especially for spiders that travel by air through ballooning as it allows them to survive even if they fall to the water.
"Being able to cope with water effectively 'joins the dots' as far as the spider is concerned," Sara Goodacre, a co-author of the study from Nottingham, explained. "It can move from one land mass to another, and potentially across huge spatial scales through the air. If landing on water poses no problem then in a week or two they could be a long way away from where they started."
The researchers also noted how being able to sail can also help spiders who cannot balloon to increase their chance of survival during rainfall and flooding events.
