What does a spider eat? Look at the DNA in their guts

DNA sequencing found wandering spiders eat at least 96 types of prey, including snakes and lizards

a large brown and yellow spider hanging in its web

Pixabay

Despite not being the favorite animals of many people, spiders are very important land predators that shape the structure of ecological communities and control the populations of their prey species. Some spider species, like the South American “banana spiders” or “wandering spiders” (genus Phoneutria), are also of medical concern due to their potent venom. 

The diet of spiders is mainly inferred by observations in the field and laboratory, which is potentially biased and probably underestimates the number of species ingested. Spiders also pre-digest their prey externally before ingesting, increasing the difficulty in identifying their prey. 

With more advanced molecular technique and ever-growing DNA databases, it is now possible to perform molecular gut content, that is, sequence the DNA present in the gut of the spiders and match them to existing sequences in databases allowing a more precise identification of species. This methodology is called DNA meta-barcoding.

Researchers from the Universidad del Tolima and Universidad de Ibagué in Colombia were the first to use DNA metabarcoding to analyze the diet of a wandering spider, the Phoneutria boliviensis (disclosure: I, the author, worked on this project). We sequenced the guts of 57 spiders and identified 96 species of prey belonging to 10 orders, mainly flies, beetles, butterflies, moths, grasshoppers, locusts, and crickets. We also found the DNA of a species of lizard and snake among the prey species eaten by females. 

In this study, females had a smaller number of preys identified compared to males, even though the opposite was expected since females of this species are generally larger. However, these results indicate that the two sexes have different predatory strategies. The 57 spiders analyzed belong to three different populations in Colombia, and the prey composition of each population also differed, indicating that the three localities have small differences in prey availability. 

This study confirms that wandering spiders feed on a wider variety of species than previously reported, further validating their generalist nature and flexible diet.