Roura, Á., González, Á. F., Pascual, S., and Guerra, Á. 2010. A molecular approach to identifying the prey of cephalopod paralarvae. – ICES Journal of Marine Science, 67: 1408–1412. A molecular method was developed to detect Artemia franciscana within Octopus vulgaris paralarvae, as a first step towards understanding the diet of octopus during this life stage. Wild eggs were collected from a spawning female in the Ría de Vigo (northwestern Spain) in late summer, and brought to the laboratory. After hatching, paralarvae were reared in 30 l rectangular tanks with an open seawater filtered system. Paralarvae were fed Artemia, then immediately fixed in 80% ethanol and preserved at −20°C. Primers specific to A. franciscana were designed for the gene cytochrome c oxidase subunit I. A nested polymerase chain reaction was necessary to detect A. franciscana within octopus paralarvae. This molecular method provides a new framework for resolving the diet of cephalopod paralarvae in the wild, essential for ecological understanding and increasing survival rates in aquaculture.