*4.1. Animals*

Adult *E. viridis* (ca. 5–10 cm length) were collected by hand in Parede Beach, an intertidal rocky beach in Western Portugal (38◦41-42" N; 09◦21-36" W), during the low tide. Organisms were then transported to the laboratory and kept in a mesocosm recreating their natural habitat consisting of dark-walled aquaria, equipped with a system providing constant aeration and water recirculation, to which natural rocks were added, with barnacles and mussels collected from the same area to provide shelter and feed to the worms, as developed by Rodrigo et al. [18]. Salinity, water temperature and photoperiod were maintained restrained at about 30, 18 ◦C and 16:8 h light-dark, respectively. Animals were thus acclimatized for 7–14 days until pigment extraction.

Mussels (*Mytilus* sp.) were also collected as models for the ex vivo assay. Laboratory cultures of wild-type *Daphnia pulex* were maintained in an aquarium with filtered pond water, replicating optimal environmental conditions for their reproduction (temperature: 20 ± 2 ◦C; pH: 7.5; photoperiod: 16 h light:8 h dark). *Daphnia* were fed with a mixture of *Arthrospira platensis* and *Saccharomyces cerevisiae*, following Pellegri et al. [30] and Santos et al. [31].
