LAUSR

The pea crab Pinnotheres pisum was described by Linnaeus in 1767 as Cancer pisum and is the type species of the genus Pinnotheres Bosc, 1801, that at present contains 64 species (Palacios-Theil et al., 2016). This species has been so far studied due to its peculiar lifestyle as a symbiont of invertebrates (Orton, 1920; Atkins, 1958; Christiansen, 1959). Schmitt et al. (1973) provided a detailed list of hosts for P. pisum, mainly consisting of bivalves and in addition the ascidians Ascidiella aspersa (Muller, 1776) [as Ascidia aspersa Mueller, 1776], and Ascidia mentula Muller, 1776. However, after their detailed study of the pinnotherids along Europe’s coastal waters, Becker & Turkay (2017) concluded that P. pisum is, like other pinnotherids, not host-specific but still an associate only of bivalves. According to those authors, previous records in ascidians must be misidentifications of P. pisum that must have, on those occasions, been confused with Nepinnotheres pinnotheres (Linnaeus, 1758).