Black Widow Spider Webs Reveal Genetic Secrets Of Spiders And Their Prey
Those spiderwebs often easily cleared away from one’s home may hold crucial information on the eight-legged creature's genetics as well as of its prey.
New research published Nov. 25 in the journal PLOS One featured the first collection of genetic material from spider silk – a noninvasive technique for extracting, amplifying and sequencing DNA from spiderwebs spun by three black widow spiders that were fed house crickets.
The team, led by Charles Xu from the University of Notre Dame, successfully extracted spider and cricket DNA from the spiderwebs. Since genetic material can remain on a spiderweb for an extended period, they were able to extract the DNA even after 88 days following the death of one of the spiders.
"Sticky spiderwebs are natural DNA samplers, trapping nearby insects and other things blowing in the wind,” explained Xu, who pointed out the potential of this research for many practical applications such as management, conservation and biogeography and biodiversity studies.
“[S]piders build webs in so many places,” he added, citing its use in broad environmental monitoring.
Xu said that there are many different techniques to study spiders, including collecting specimens via beating – that is, beating on a tree until the spiders fall from it – or aspiration, where one sucks an insect into a glass vial through a rubber tube.
Genetic sequencing, however, is becoming more affordable and accessible, allowing for new methods to collect information about spiders and their prey without having to capture or kill them.
To study the DNA, Xu said they first had to make a lot of it. The researchers used primers, or single-stranded fragments of DNA targeting particular DNA regions, for probing. The primers caused the DNA to create millions of copies of itself.
The team then amplified the cytochrome oxidase 1 gene, typically used for DNA barcoding or a process used for identifying an organism the way a bar code identifies a grocery item. DNA barcoding has been previously used to identify new creatures such as bats and fungi.
A database of these DNA bar codes are being actively built around the world since 2007, but barcoding spiderweb DNA was first attempted by Xu’s team.
Xu highlighted the greater sensitivity of these genetic techniques from traditional sampling tools. "They could allow earlier detection of [endangered or invasive] species,” he added.
Xu’s team aims to do further research in the woods and collect webs to identify other members of the spider and insect community that left their DNA there.
Photo: Matt Maves | Flickr