The evolution of silk production in Crustacea

Abstract

Spun silk is found only in arthropods, where it plays critical roles in feeding, protection, and reproduction. It has evolved repeatedly within the arthropods, providing an opportunity for comparative analyses to reveal the mechanisms driving convergent evolution within this taxon. Silk in crustaceans has received much less attention than silk in arachnids and insects but may have unique and useful properties. We combine data on the morphology of silk and silk systems with ancestral state reconstruction and find that silk has likely evolved convergently at least six times within Crustacea. We also break down the components of crustacean silk as a composite trait by discussing the silk properties, the silk production systems, and the silk genes. We find that amphipod and tanaid silks are similar to silkworm and spider silks but have their own unique silk system morphology. Much remains unknown about the origins and diversification of silk in crustaceans; we propose that the molecular investigation of silk genes and systems will provide a path forward. By investigating the evolution of silk production in crustaceans, we may discover insights into predispositions for silk production in arthropods and valuable substrates for biomaterial research.