Spider web formed only once in evolution?
In the course of evolution, the orb web of spiders only arose once and not several times independently in several groups. Jessica Grab and her colleagues draw this conclusion from a genetic analysis that found the same hereditary factors for silk proteins in different representatives [1].
The scientists examined the genome of Deinopis spinosa and Uloborus diversus. These two representatives of the cribellata equip their net with cribellum wool: the finest wool threads that are loosely brushed onto the main thread with a kind of comb. These fine threads bind the prey with adhesive forces.
In return, the Ecribellata, which also includes the garden spider, wet their fangs with sticky droplets. Until now, these different approaches have led researchers to assume that the highly developed orb network converged at least twice. According to genetic analysis, however, a common ancestor and inventor of the orb network may have lived at least 136 million years ago.
An amber find from Spain demonstrates how long spiders have been successfully hunting insects. A research team led by David Grimaldi from the American Museum of Natural History discovered a parasitic wasp, a mite and a beetle trapped in the remains of sticky spider silk in a 110-million-year-old piece [2]. They complement the find of the oldest orb-web spider fossil to date in a 115-million-year-old piece of amber, also in Spain, which was published on Wednesday.
