Anomura, 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 : 640-641

Hosts: Anomura , Galatheoidea.

Genera: Triangulus (four spp.). The two species of Triangulus included here ( Triangulus munidae and ‘ Triangulus ’ galatheae ) do not form a monophyletic group. ‘ Triangulus ’ galatheae is positioned within our redefined Peltogastridae , and we therefore (see p. 10) transfer it to a new genus. The type species, Triangulus munidae , is placed with high support as sister to all other Rhizocephala. Owing to its basal position, Triangulus munidae and other assured members (see below) of this new family will be crucial for tracing character evolution within all Rhizocephala. The World Register of Marine Species (WoRMS, 2019) lists four additional species of Triangulus . Of these, Tortugaster boschmai (Brinkmann, 1936) was already transferred from Triangulus to that genus in Peltogastridae (in its old definition) by Høeg & Lützen (1985); this view was seconded by Øksnebjerg (2000) and is upheld here. The remaining three species are Triangulus bilobatus (Boschma, 1925) , Triangulus cornutus (Boschma, 1935) and Triangulus papilio (Kossman, 1872) , which were transferred from Lernaeodiscus to Triangulus by Van Baal (1937). They are here by default left in Triangulus in Triangulidae , but with confirmation of this position subject to a future analysis. A new record of Triangulus cf. munidae recently sampled from New Zealand might well prove to represent a new species in the family.

Remarks: The new family is based principally on molecular evidence. The morphological diagnosis is amended from that given for the genus Triangulus by Øksnebjerg (2000). A future analysis should search for a more robust diagnosis based on morphological apomorphies.

FAMILY PELTOGASTRIDAE LILLJEBORG, 1861 , AMENDED

Type genus: Peltogaster Rathke, 1842 .

Type species: Peltogaster paguri Rathke, 1842 .

Diagnosis: By the molecular data. Externae never colonial; externa shape variable, elongated and sometimes tortuous, spherical to ovoid or more or less compressed dorsoventrally. Stalk issuing from between middle of dorsal side to near posterior extremity. Mantle opening at other end in elongate forms; in compressed forms, situated either in the midline or distinctly displaced to the left or right side. Visceral mass normally fused broadly with mantle. Colleteric glands normally simple, sometimes subdivided tubes. Paired receptacles with straight or tortuous ducts. Disposition of colleteric glands and receptacles either bilaterally symmetrical or asymmetrical.

Hosts: Anomura , Galatheoidea and Paguroidea; Gebiidea; Caridea.

Genera: Briarosaccus Boschma, 1930 (four spp.), Dipterosaccus Van Kampen & Boschma, 1925 (two spp.), Galatheascus Boschma, 1929 (two spp.), Lernaeodiscus Müller, 1862 (eight spp.), Ommatogaster Yoshida & Osawa, 2011 (one sp.), Paratriangulus gen. nov. (one sp.), Peltogaster (16 spp.), Pterogaster Van Baal, 1937 (two spp.), Septodiscus Van Baal, 1937 (one sp.), Septosaccus Duboscq, 1912 (four spp.), Temnascus Boschma, 1951 (one sp.), Tortugaster Reinhard, 1948 (three spp.), Triangulopsis Guerin-Ganivèt, 1911 (one sp.) and Trachelosaccus Boschma, 1928 (one sp.).

Remarks: The family comprises the taxa that originate at Figure 3, node 5. The diagnosis is adapted from Øksnebjerg (2000) to accommodate also former members of Lernaeodiscidae now included in the redefined family. Monophyly of Peltogastridae as here conceived is supported by the molecular analysis, but it is clearly the morphologically most variable taxon in Rhizocephala. Lilljeborg, who erected the family, published his taxonomic papers on rhizocephalans in identical form in several journals and languages, including private reprints (see, e.g. Høeg 1982). The citations used here are the most recently updated ones from the WoRMS (2019) database, as recommended by C. Boyko. The redefined family includes all former peltogastrids and lernaeodiscids, except for those transferred to the new families Triangulidae and Peltogasterellidae . These are parasitic on Anomura and Caridea (only Trachelosaccus ), but never on Brachyura . Although not included in our analysis ( Fig. 1), Yoshida et al. (2011) used molecular methods to show that Ommatogaster and Dipterosaccus are sister groups, and this clade is, in turn, sister to a species of Peltogaster . This indicates that both genera belong in Peltogastridae as presently defined. Pterogaster , Septodiscus , Temnascus and Triangulopsis have not yet been subjected to a molecularly based phylogenetic analysis but are retained in the redefined family pending future analysis. These genera are morphologically rather “close” to the peltogastrid forms included in the present analysis. The monotypic Trachelosaccus is also retained in the family, although this little-known form has a somewhat unusual morphology and differs, like Mycetomorphidae , in parasitizing Caridea ( Høeg & Lützen, 1985).

Peltogasterella and Cyphosaccus are positioned higher in the tree and are therefore transferred to a new family (defined on p. 11). The monotypic genus Angulosaccus , formerly in Peltogastridae , is also transferred to this new family. Except for Triangulus munidae , species of the former Lernaeodiscidae as listed by Boyko & Harvey (2000) are included in our redefined Peltogastridae (viz. Tortugaster , Lernaeodiscus , Paratriangulus syn. Triangulus , Triangulopsis and Septodiscus . It seems clear that the diagnostic characters for the former Lernaeodiscidae (see Boyko & Harvey, 2000; Øksnebjerg, 2000) arose by convergence. A forthcoming phylogenetic analysis by molecular methods will include many members of the large genus Peltogaster and also the king crab ( Lithodidae )-infesting genus Briarosaccus . This will entail changes at both species and generic levels, but the family as here defined will remain monophyletic (C. Noever, in preparation).

GENUS PARATRIANGULUS HØEG & GLENNER GEN.