http://www.digitaljournal.com/science/new-techniques-can-identify-spiders-from-their-webs/article/454715

New techniques can identify spiders from their webs

Posted Jan 13, 2016 by Tim Sandle
Advancements in genetic techniques have led to researchers being able to identify black widow spiders from their webs. The method allows researchers not only to identify the spider, but also its prey.
A spider in a web  from an English garden.
A spider in a web, from an English garden.
By analysing web samples, from black widow spiders fed with crickets, scientists can now take DNA samples and identify the spider and the species of its recent prey.
The spiders of interest are the North American black widows (Latrodectus mactans, L. hesperus, and L. variolus.) The venomous bite of these spiders is considered particularly dangerous because of the neurotoxin latrotoxin.
The research was initiated by a doctoral student called Charles Cong Yang Xu. After various experiments, Xu developed a new non-invasive source of spider and insect DNA through. This was through extracting DNA from spider webs. By taking the DNA, he was able to use sophisticated molecular biology methods to amplify and sequence the sampled mitochondrial DNA. This proved remarkably accurate at identifying the spider and the species inset recently consumed by the spider.
Further studies showed the extracted DNA to remain detectable for a minimum of 88 days after it was sampled. Part of this longevity came down to the structure of the web and it innate stickiness. A further application can extend to other insects that blow into the web and are capture, but not necessarily eaten by a spider.
The research group, along with Xu, who are based at the University of Notre Dame, hope that the findings will help with conservation research and allow biologists to track and account for rare or endangered species. Other applications include pest management and biogeography.
Black-widow female spider. Hungry females are more likely to attack and eat the male before or after...
Black-widow female spider. Hungry females are more likely to attack and eat the male before or after mating.
Steve Ryan
This is a relatively new field of research called biomonitoring. The key advantage is that the organism of interest is not damaged or harmed in any way.
The research has been published in the journal PLOS One. The research paper is headed “Spider Web DNA: A New Spin on Noninvasive Genetics of Predator and Prey.”