Analysing DNA found in spiders’ guts is helping scientists in Canada understand the role spiders could play in reducing crop pests on farms.
While spiders have been repeatedly proven to suppress agricultural pest populations, because they mostly eat their prey by liquefying it with digestive enzymes scientists have struggled to determine exactly what they eat and when.
However, by using DNA barcoding — a technique that involves sequencing short fragment of DNA from a specific gene to identify a species — researchers at the University of Guelph’s College of Biological Science are getting a more detailed idea of how good arachnids are at crop biocontrol.
Writing in The Conversation Canada, Professor Andrew MacDougall said spider gut content analysis begins by capturing spiders in the field and grinding them into a “DNA soup”.
“This grinding step is important because a spider’s stomach extends into many different parts of the body, and it’s why total body grinding can help find results of the prey’s remains,” he said.
Researchers then use DNA barcoding to discover if a spider is a ‘generalist’ that feeds on a variety of prey, including aphids, or if they are ‘specialists’ that feed on a particular crop pest species.
Armed with this information, they can investigate what spiders eat at different times of year, and determine if they could be used as biocontrol agents.
“We sampled spider communities intensively for four months between May and August, and at different distances from crop fields to study spider movement throughout the crop growing season,” said Prof. MacDougall.
“This knowledge is largely important for managing farm systems to help determine the timing of pesticide applications in crop fields.
“We have been finding a higher abundance of spiders and their insect prey in the semi-natural areas (wetlands, prairies) surrounding the crop fields, and closer to the restored areas,” he added.
“Our preliminary data also shows that June and August are peak times for spider activity on farms, and they move around a lot more than in May and July.”
