Pinnotherids, or pea crabs, are symbionts of invertebrates used for shelter and as food source. Feeding strategies and morphological adaptations to food uptake are important to understand host relations and how the host specificity is determined. We herein re-examine the host range of pinnotherids based on long-term collections from different localities in European waters. Both species of Pinnotheres are restricted to bivalves. Pinnotheres pisum infests mussels, oysters, the noble pen shell Pinna nobilis and other bivalves. Pinnotheres pectunculi is symbiotic with Glycymeris glycymeris and several other species of venerids. Nepinnotheres pinnotheres infests ascidians and Pinna nobilis . Observations on feeding in Pinnotheres reveal how mucus strings are brushed from the host gills with a setal comb in the chelipeds, which we describe by using scanning electron microscopy. Our observations on feeding structures are discussed in relation to the host specificity of each species and compared to other pinnotherid taxa, taking additional factors of host choice into account.