Trophoniella hephaistos, Jimi, Naoto & Fujiwara, Yoshihiro, 2016

Jimi, Naoto & Fujiwara, Yoshihiro, 2016, New species of Trophoniella from Shimoda, Japan (Annelida, Flabelligeridae), ZooKeys 614, pp. 1-13 : 3-6

Taxon classification Animalia Terebellida Flabelligeridae

Trophoniella hephaistos sp. n. Figs 2, 3, 4, 5

Material examined.

Holotype. No. NSMT-Pol-H-601 Incomplete, posterior end absent. Unknown sex, non-reproductive adult, body length 9.0 cm, body width 0.3 cm, 103 chaetigers, 24 September 2015, collected by N. Jimi, tank of the SMRC, sandy mud.

Paratypes. No. NSMT-Pol-P-602. Complete, two specimens. Unknown sex, non-reproductive adult, body length 10.2-11.2 cm, body width 0.4-0.5 cm, 129-141 chaetigers, 24 September 2015, collected by N. Jimi, tank of the SMRC, sandy mud. No. NSMT-Pol-P-603. Incomplete, posterior body absent, nine specimens. Unknown sex, non-reproductive adult, body width 0.4-0.5 cm, 24 September 2015, collected by N. Jimi, tank of the SMRC, sandy mud. No. NSMT-Pol-P-604. Incomplete, posterior body absent, one specimen. Unknown sex, body width 0.3 cm, 26 November 2014, collected by N. Jimi, tank of the SMRC, sandy mud.

Diagnosis.

Body covered by large sediment grains dorsally, ventrally, and laterally, without posterior region. Sediment grains not immersed in the tunic. Papillae arise in four rows ventrally and two rows dorsally from first chaetiger to posterior end, longitudinal rows. Tongue-shaped branchial plate. Paired black eyes on center of prostomium. Anchylosed bidentate neurohooks start from chaetiger 17-20, accessory tooth length same as fang.

Description.

Body length 10.2-11.2 cm (complete specimens), width 0.3-0.7 cm, 129-141 chaetiger (complete specimens). Body white in ethanol, cylindrical anteriorly and tapering posteriorly (Fig. 2). Tunic thick, papillated, with large sediment grains dorsally, ventrally, and laterally (Figs 2A, B, 3A, B), without posterior end region. Sediment grains with long axes of 70-1000 µm, contain sand and shell fragments, not immersed in the tunic. Papillae capitate, sparse, arise in four rows ventrally and two rows dorsally from first chaetiger to posterior end, longitudinal rows. Dorsal 1-6 and ventral 1-3 chaetiger’s papillae are large. Cephalic cage chaetae approx. 1.5 times longer than body width. Chaetiger 1-5 involved in cephalic cage, chaetiger 1 dorsolateral, and chaetiger 2-3 lateral. Chaetal transition from cephalic cage to body chaetae gradual. Chaetiger 1 has about 9 notochaetae and 7 neurochaetae. Anterior dorsal margin of first chaetiger arise multifid lobe (Fig. 3C). Cephalic hood margin papillated, thin, transparent. Caruncle well developed, reaching the end of the tongue-shape branchial plate. Branchia arise from tongue-shaped branchial plate (Fig. 3E), thin, long (0.5-2 mm), green in live, white in ethanol, over 100 filaments arise from two groups (Fig. 3B, D). One pair palps, green in alive, white in ethanol, cylindrical, grooved, long (2 mm in length) (Fig. 3B, D). Prostomium low-cone, paired black eyes on center. Notochaeta all multiarticulated capillaries with articles, bidentate (Fig. 4A, B). Multiarticulated capil lary neurochaeta in chaetiger 1, chaetiger 2-16 bidentate neurohooks (Fig. 5A, B). Anchylosed bidentate neurohooks start from chaetiger 17-20 (Fig. 5C, D), yellow, bidentate. Accessory tooth thin, length same as fang. Parapodia poorly developed, chaetae arise from body wall. Noto- and neuropodia have two prechaetal papillae and three postchaetal papillae. Gonopodial lobe absent. Pygidium simple, no anal cirri.

Etymology.

The worm is coated with sediment particles, resembling armor. Hephaistos (Ἥφαιστος) was the name of the ancient Greek god of blacksmiths who forged the armor worn by Achilleus. Hephaistos is also spelled Hephaestus. The Japanese name is derived from the type locality (Shimoda), Japanese armor (Yoroi), and flabelligerids in Japanese (Habouki).

Distribution.

This new species is currently only known from the tank of the type locality. The seawater in the tank was drawn only from Nabeta Bay from a depth of 3 m directly facing the SMRC. The natural habitat of this species remains unknown. Due to the location of the head gate, Trophoniella hephaistos could be a shallow-water species. However, several sublittoral (~50-60 m) invertebrates were collected from this tank (Dr. Hiroaki Nakano, pers. comm.). Additional sampling efforts in Nabeta Bay will clarify the natural habitat of this species.

Phylogenetic analysis.

The final lengths of the aligned sequences were 669 bp (COXI), 485 bp (16S), 1893 bp (18S), and 910 bp (28S). The bootstrap value of 98% in ML analysis strongly supported the monophyly of Flabelligeridae , but internal relationships of Flabelligeridae were not resolved (Fig. 6). The sister group of Trophoniella was Piromis . The bootstrap value in ML analysis (100%) demonstrated the monophyly of this clade (Fig. 6).

Remarks.

Trophoniella hephaistos sp. n. resembles Trophoniella enigmatica Salazar-Vallejo, 2012 and Trophoniella indica (Fauvel, 1928) in having dorsal tubercles at the anterior chaetigers, a tunic covered with large sediment grains dorsally and ventrally, and anchylosed neurohooks starting from chaetiger 14 or posterior. However, Trophoniella hephaistos is discriminated by the presence of anchylosed neurohooks starting from chaetigers 17-20, whereas those of Trophoniella enigmatica start from chaetiger 40, and of Trophoniella indica from chaetiger 14. Additionally, Trophoniella enigmatica does not have a tongue-shaped branchial plate and Trophoniella indica does not have eyes. Chaetiger number of Trophoniella hephaistos was more than twice as many as that of Trophoniella indica . Trophoniella hephaistos has dorsal body papillae in two longitudinal rows, whereas Trophoniella enigmatica in three and Trophoniella indica in five.

Trophoniella hephaistos also resembles Trophoniella avicularia Caullery, 1944 and Trophoniella harrisae Salazar-Vallejo, 2012 in having anchylosed neurohooks starting from chaetigers 18-20. Trophoniella hephaistos also has dorsal tubercles in the anterior chaetigers, while Trophoniella avicularia does not. Trophoniella harrisae has sediment particles only on its dorsal area, whereas Trophoniella hephaistos has particles on both its dorsal and ventral areas.

The phylogenetic analysis showed Trophoniella to be the closest relative of Piromis in Flabelligeridae supported by a high bootstrap value (See Fig. 6). Our findings are consistent with previous morphological studies that indicated a close relationship between Trophoniella and Piromis based on their shared characters such as tongue-shaped lobe, multiarticulated notochaeta, and thick tunic ( Salazar-Vallejo 2011b; Salazar-Vallejo et al. 2008).