Microphthalmus itoi Uchida, 2019

Hiro, Uchida, omi, Lopéz, Eduardo & Sato, Masanori, 2019, New Hesionidae (Annelida) from Japan: Unavailable Names Introduced by Uchida (2004) Revisited, with Reestablishment of their Availability, Species Diversity 24, pp. 69-95 : 87-88

Genus Microphthalmus Mecznikow, 1865 Microphthalmus itoi Uchida , sp. nov.

[New Japanese name: Itô-hina-otohime] ( Fig. 15 )

Microphthalmus itoi Uchida, 2004: 73–76 , fig. 18 (unavailable specific name, without explicit fixation of namebearing types); Westheide 2013: 417 (table 1), 419. Type material. Holotype: (NSMT-Pol H-760), Tsuku- shikoi Beach, Akkeshi, Hokkaido Prefecture (43°0′52″N, 144°50′55″E), intertidal sand layer, coll. T. Itô, July 1971.

Diagnosis. Holotype 7.7 mm long for 61 chaetigers, body dark grey. Median antenna subulate, slightly longer than prostomium; lateral antennae similar, but 2/3 as long; palps similar to lateral antennae ( Fig. 15A ). Proboscis with ten conical marginal papillae ( Fig. 15A ). Parapodia biramous with reduced notopodia ( Fig. 15C, D ). Dorsal cirri in chaetigers 1 and 2 shorter than subsequent ones ( Fig. 15A ); notopodial lobes supported by a single acicula ( Fig. 15G ) and bearing gently sigmoid pectinate chaetae without spur ( Fig. 15F ) and 15–20 acicular simple chaetae ( Fig. 15E ). Neuropodial lobes bearing compound chaetae with blades having coarse basal serration and rounded tips ( Fig. 15H ), or with blades having fine serration and unidentate ( Fig. 15J ) or bidentate ( Fig. 15K ) tips, and simple chaetae with ( Fig. 15L ) or without ( Fig. 15I ) clearly bifid tips. Posterior end with fan-shaped anal membrane fringed with 37 small papillae ( Fig. 15B ).

Etymology. Named in honor of the late Dr. Tatsunori Itô, who collected the holotype during his survey of interstitial fauna in Hokkaido.

Remarks. The detailed description of the type materials was presented in Uchida (2004). Microphthalmus itoi sp. nov. is characterized by having fringed anal membrane, neuropodial simple and compound chaetae combined, pectinate notochaeta, and more than ten simple chaetae in each notopodial lobe. The new species shares these characters with M. fragilis Bobretzky, 1870 , from Europe, and M. urofimbriata Alikunhi, 1943 , from India. However, pectinate notochaetae are gently sigmoid in the new species and in M. fragilis , instead of being bow-shaped as in M. urofimbriata ( Alikunhi 1948) . Furthermore, M. fragilis differs from the new species in having a more complex fringe in anal membrane ( LaGreca 1950; Parapar et al. 2004) and bow-shaped pectinate chaetae without a conspicuous spur. Microphthalmus indefatigatus Westheide, 1974 is the only previously known species with neuropodial compound chaetae having both types of tips, entire and bifid ( Westheide 1974), as M. itoi sp. nov. However, the new species differs from M. indefatigatus in having short notocirri, long pectinate notochaetae, and more notopodial simple chaetae.

Figures

Fig. 15. Microphthalmus itoi sp. nov., holotype (NSMT Pol H-760). A, dorsal view of the anterior body. B, dorsal view of the posterior end. C, posterior view of right parapodium 9. D, anterior view of right parapodium 53. E, notopodial simple chaeta. F, notopodial pectinate chaeta. G, notopodial acicula from chaetiger 9. H, neuropodial superiormost serrated chaeta. I, neuropodial superior simple chaeta. J, long type of neuropodial compound chaeta. K, short type of neuropodial compound chaeta. L, neuropodial inferior simple chaeta. Scale bar: 0.2mm for A; 0.1mm for B–D; 0.02mm for E–L.