Brachyura, Høeg & Noever & Rees & Crandall & Glenner, 2020

Høeg, Jens T., Noever, Christoph, Rees, David J., Crandall, Keith A. & Glenner, Henrik, 2020, A new molecular phylogeny-based taxonomy of parasitic barnacles (Crustacea: Cirripedia: Rhizocephala), Zoological Journal of the Linnean Society 190, pp. 632-653 : 643

Hosts: Brachyura and Gebiidea.

Genera: Parasacculina , gen. nov. (five spp.) and Polyascus Glenner, Lützen & Takahashi, 2003 (three spp.)

Remarks: The family comprises the taxa that originate at node 9 in Figure 3 and is well defined by the molecular analysis. External morphology is similar to that seen in Sacculinidae , but a possible apomorphy for Polyascidae is the tendency to form multiple externae ( Glenner et al., 2003), which has become obligatory in Polyascus . Multiple externae at a frequency higher than by chance are extremely rare in Sacculinidae . The family consists of Polyascus (three spp.) and the new genus Parasacculina (five spp., see p. 13). All these species were formerly placed in Sacculinidae . In Figure 3, the genus Polyascus is monophyletic and united by the apomorphy of having colonial externae that are replaced in successive generations. Compared with all earlier uses, the species names of Polyascus polygenea (Lützen & Takahashi, 1997) , Polyascus gregaria (Okada & Miyashita, 1935) and Polyascus plana ( Boschma, 1933) have been altered here and in WoRMS (2019) to comply with the masculine gender of the genus name. About 160 ‘ Sacculina ’ species remain to be analysed by molecular data. The species concerned will, in all likelihood, be allocated to both Sacculinidae and Polyascidae , and this will undoubtedly also require additionalgenericlevelchangesinbothfamilies. Glenner et al. (2003) listed a number of Sacculina species, where multiple externae seem to occur more frequently than by chance, although not obligatorily, but no formal taxonomic steps were taken. A future analysis is needed to decide whether these species should be transferred to Polyascidae , perhaps as members of Parasacculina .