Genome sequences from two spider species reveal the composition of their silk, and how spider venom exacts its toxic toll.

Mikkel Schierup at Aarhus University in Denmark and his team sequenced the genomes of an African social velvet spider (Stegodyphus mimosarum) and a Brazilian white-knee tarantula (Acanthoscurria geniculata; pictured), and identified proteins that comprise the arachnids' venom and silk. The venom of both species contains numerous protein-cleaving enzymes that probably activate precursors of toxic venom proteins. More than 70% of velvet-spider venom is made up of enzymes that break down fats.

Credit: Davies and Starr/Digital Vision/Getty

The team also found that the velvet spider makes a more diverse array of silk proteins than the tarantula. That is probably because it uses its silk in a greater variety of ways, such as creating complex webs to capture prey, says the team.

Nature Commun. 5, 3765 (2014)