Asteroporpa (Astrohelix) Döderlein, 1930

Okanishi, Masanori, 2017, A taxonomic review of the genus Astrohelix Döderlein, 1930 including the synonymy of the subgenus Asteroporpa (Astromoana) Baker, 1980 to Astrohelix, Zootaxa 4227 (4), pp. 543-553 : 544

Asteroporpa (Astrohelix) Döderlein, 1930

Asteroporpa (Astromoana) Baker, 1980: 36 –38; McKnight, 2000: 57; Okanishi & Fujita, 2011: 27. Type species: Astrotoma bellator Koehler, 1904 .

Diagnosis. No concentric ridges or furrows exist on aboral disc. The hooklet-bearing plates occur on the aboral periphery of the disc. Each hooklet bears one to three secondary teeth. Except for the hooklet-bearing plates, body is entirely covered by round granule-shaped epidermal ossicles, round or polygonal plate-shaped epidermal ossicles, and cone-shaped epidermal ossicles with one to five terminal projections. Teeth are acute, spiniform. Three to six arm spines are adjacent to each tentacle pore in middle portion of the arms.

Remarks. The genus Astrohelix is morphologically similar to the subgenus Asteroporpa (Astromoana) in having no conspicuous ridges on the aboral disc; epidermal ossicles with terminal projections on disc and basal arms; five arm spines in basal portion of arms; hooklets with one or two inner teeth; and small genital slits ( Koehler, 1904; Döderlein, 1930; Mortensen, 1933). However, the presence of hooklet-bearing plates on the aboral disc, which is a clear and distinctive diagnostic character of the genus Asteroporpa (Astromoana) Baker, 1980 , have not been previously described in Astrohelix bellator paucidens ( Mortensen, 1933) . Döderlein (1930) redescribed holotype of Astrotoma bellator (= Astrohelix bellator bellator ) and noted the presence of the hookletbearing plates on disc, but he did not include it as a diagnostic character of his erected genus Astrohelix . My examination of all known specimens of Astrohelix revealed that they certainly possess hooklet-bearing plates on the aboral periphery of the disc ( Figs 1 A, E; 3C, E). Therefore, there are no morphological differences between Astrohelix Döderlein, 1930 and Asteroporpa (Astromoana) Baker, 1980 , and I here propose the synonymy of these two taxa. On the molecular tree in Okanishi & Fujita (2013), Asteroporpa (Asteroporpa) australiensis sitting between A. (Astromoana) reticulata (or Astrohelix reticulata ) and A. (Astromoana) muricatopatella (or Astrohelix muricatopatella ). Hence, Asteroporpa (Astromoana) (or Astrohelix ) is not monophyletic. However, I here refrain from synonymising Astrohelix with Asteropotpa at the genus level because I did not take into account all species of Asteroporpa in this study. Therefore, I here simply combine Astrohelix as Asteroporpa (Astrohelix) Döderlein, 1930 . Molecular analysis with all species of Asteroporpa and Astrohelix are required for the taxonomic review of these (sub) genera.

Asteroporpa (Astrohelix) bellator comprises two subspecies, A. (Astrohelix) bellator bellator ( Koehler, 1904) and A. (Astrohelix) bellator paucidens Mortensen, 1933 . Okanishi & Fujita (2011) provided a diagnostic character key of Asteroporpa (Astromoana) (= Asteroporpa ( Astrohelix )) and the holotypes of two subspecies can be distinguished from each other by the combination of these characters (see Discussion below). Therefore, I here propose that the two subspecies should be elevated to species-level as Asteroporpa (Astrohelix) bellator ( Koehler, 1904) and A. (Astrohelix) paucidens ( Mortensen, 1933) .

In addition to Asteroporpa (Astrohelix) bellator ( Koehler, 1904) from the southern Philippines , 275 m and A. (Astrohelix) paucidens ( Mortensen, 1933) from western Japan, 190 m, this subgenus currently comprises the following species: A. (Astrohelix) indicus Baker, 1980 from northwestern Australia to Fiji, 141 m ; A. (Astrohelix) reticulata Baker, 1980 from northwestern New Zealand to southern New Caleconia , 71–301 m ; A. (Astrohelix) muricatopatella Okanishi & Fujita, 2011 from southwestern Japan, 140–410 m ; and A. (Astrohelix) koyoae Okanishi & Fujita, 2011 from southern Japan, 743.1 m ( Baker, 1980; Okanishi & Fujita, 2011; T. D. O’Hara, pers. comm.). A tabular key to the six species is given in Table 1 .

Figures

FIGURE 1. Holotype (ZMA E 2044) of Astrotoma bellator Koehler, 1904 (= Asteroporpa (Astrohelix) bellator (Koehler, 1904 )). A, aboral disc; B, oral disc and basal portion of the arm; C, aboral central part of the disc; D, cone-shaped epidermal ossicles on aboral center part of the disc; E, aboral periphery of the disc; F, aboral basal portion of the arm; G, jaws; H, oral peripheral part of the disc. Arrow heads indicate hooklets (E), transverse rows of hooklet-bearing plates (F) and cone-shaped epidermal ossicles (G, H). Abbreviations: AS, arm spine; GS, genital slit.