Tanseimaruana, Imajima, Minoru, Reuscher, Michael G. & Fiege, Dieter, 2013

Imajima, Minoru, Reuscher, Michael G. & Fiege, Dieter, 2013, Ampharetidae (Annelida: Polychaeta) from Japan. Part II: Genera with elevated and modified notopodia, Zootaxa 3647 (1), pp. 137-166 : 158

Tanseimaruana gen. nov.

Type species: Amphicteis vestis Hartman, 1965

Diagnosis. Prostomium without incisions or glandular ridges, with nuchal slits. Buccal tentacles smooth. 4 pairs of cirriform branchiae. Segment II with enlarged notochaetae (paleae). 14 thoracic uncinigers. Intermediate uncinigers absent. First abdominal unciniger with 4 dorsal foliose lobes with smooth margin, emerging from transverse dermal fold. Uncini with many teeth in several rows.

Remarks. Tanseimaruana gen. nov. shares the number of thoracic chaetigers, absence of intermediate uncinigers, number of branchiae, and presence of enlarged chaetae (paleae) in segment II with Amphicteis and a number of other genera.

However, because of a number of differences, we think that the description of Tanseimaruana gen. nov. for the two species Tanseimaruana vestis (Hartman, 1965) comb. nov., described as Amphicteis vestis , and T. boninensis sp. nov. is warranted. Tanseimaruana gen. nov. lacks prostomial glandular ridges, possesses 4 foliose lobes that emerge from a dermal fold in the first abdominal unciniger, and its uncini have several rows of teeth, rather than a single row.

Jugamphicteis Fauchald & Hancock, 1981 , another genus that is related to Amphicteis , also has a dorsal lobe structure in the first abdominal unciniger. The dorsal modification of Jugamphicteis is a very high “valve-like” (Fauchald & Hancock 1981) dermal fold with papillated convex margin and a median notch. Despite the same location of the modification, we share the opinion of Fauchald & Hancock (1981) and Holthe (2000), who discussed the status of Tanseimaruana vestis (as Amphicteis vestis ), that the modification of Jugamphicteis is different. Therefore, they are not considered homologous. Furthermore, Jugamphicteis differs from Tanseimaruana gen. nov. by the presence of prostomial glandular ridges.

The modifications in Tanseimaruana vestis comb. nov., in the four species of Jugamphicteis , and in the monotypic genus Ymerana Holthe, 1986 b have been defined as modified notopodial structures by their describers. This terminology was reiterated by subsequent authors (Jirkov 2008, 2011; Reuscher et al. 2009; Parapar et al. 2011). However, a notopodial origin of the dermal fold or lobes seems unlikely. The lobes do not resemble notopodia. They rather seem to be dermal protrusions from a transverse dermal fold across the dorsum. The dermal folds with its accessory structures are likely to be apomorphic structures that might have evolved to help create a current through the mucus-sediment tube (see also Parapar et al. 2011). A notopodial origin seems also unlikely in the light of the phylogeny of the genus. Tanseimaruana gen. nov. and, even more so, Jugamphicteis seem to be genera that are related to Amphicteis . All three genera have 17 pairs of notopodia (paleae of segment II not included). If the modification of Tanseimaruana gen. nov. and Jugamphicteis was of notopodial origin, Amphicteis , the potential ancestral genus, would be expected to have an additional 18th pair of notopodia from which the lobes have been derived. Additionally, the neuropodia of the modified segment are not tori but pinnules, which is a strong indication that the modified segment belongs to the abdomen, rather than to the thorax.

Etymology. The genus is named after the Japanese research vessel R/V Tansei-Maru from which it was collected.