Flabelligena hakuhoae Jimi, 2020

Jimi, Naoto, Ogawa, Akito, Hiruta, Shimpei F, Ikehara, Minoru & Imura, Satoshi, 2020, A new deep-sea species of Flabelligena from off the South Orkney Islands, the Southern Ocean, Biodiversity Data Journal 8, pp. 53312-53312 : 53312

Flabelligena hakuhoae Jimi sp. n.

Materials

Type status: Holotype. Taxon: phylum: Annelida; family: Acrocirridae; genus: Flabelligena; Location: higherGeography: Southern Ocean; off the South Orkney Islands; waterBody: Southern Ocean; locality: off the South Orkney Islands ; verbatimDepth: 2036-2479 m; Identification: identifiedBy: Naoto Jimi; Event: samplingProtocol: rock dredge; eventDate: 02-01-2020; year: 2020; month: 1; day: 2; habitat: rocks and sands; Record Level: language: en; ownerInstitutionCode: NSMT Type status: Paratype. Taxon: phylum: Annelida; family: Acrocirridae; genus: Flabelligena; Location: higherGeography: Southern Ocean; off the South Orkney Islands; waterBody: Southern Ocean; locality: off the South Orkney Islands ; verbatimDepth: 2036-2479 m; Identification: identifiedBy: Naoto Jimi; Event: samplingProtocol: rock dredge; eventDate: 02-01-2020; year: 2020; month: 1; day: 2; habitat: rocks and sands; Record Level: language: en; ownerInstitutionCode: ICHUM

Description

Holotype (NSMT-Pol H-813) 1.8 cm long, 1 mm wide (without chaetae, at widest chaetiger) for 27 chaetigers (incomplete). Body cylindrical (Fig. 2 ), rounded in anterior and posterior end, yellowish in life and after fixation, with darker pigmentation around the anterior end, without ventral centre line, surface papillated, slightly inflated laterally in chaetigers 5-11, subannulations absent. Body papillae presented on several areas. Papillae of body surface oval, each papilla about 15 μm long and 10 μm wide (n = 10), not arranged in transverse rows, scattered. Papillae around branchial scars (Fig. 3 ) cylindrical, each papilla about 35 μm long and 10 μm wide (n = 10), 5-6 papillae present around branchial scars. Papillae on prostomium (Fig. 3 A), cylindrical, each papilla about 35 μm long and 20 μm wide (n = 10), scattered. Papillae between noto- and neurochaetae (Fig. 5 A and D), circular, each papilla about 30 μm long and 30 μm wide (n = 10), one papilla between chaetae (Fig. 5 D). Paired ventral large papillae present ventral side of parapodium in chaetiger 6 (Fig. 2 B and D), short (72 μm long and 55 μm wide), conical, one pair.

Prostomium subtriangular, eyes absent, nuchal organs absent. Peristomium distinct. Palp scars on anterior margin of prostomium, one pair (Figs 3 , 4 ), palps cirrigerous shape, with numerous cirri on ventral side. Branchial scars three pairs (Figs 3 , 4 ), branchiae globular shape (Figs 2 , 4 ). Nephridial lobe consists of nephriodiopore papillae and globular base (Fig. 3 B), two nephriodiopore papillae per globular base (Fig. 3 B). Notochaetae spinulose capillary (Fig. 5 B), 1-2 per fascicle throughout the body. Neurochaetae compound (Fig. 5 C): blades sickle-shaped, bidentate (one over another), inner edge of blade smooth; blade length 6/5 of shaft in chaetigers 1-17, as long as shaft in chaetigers 18-27; 1-2 per fascicle in chaetigers 1-17, 3-4 per fascicle in chaetigers 18-27. Pygidium lost.

Paratype (ICHUM-6113, used in SEM observation) 1.2 cm in length, 0.9 mm in width (without chaetae, at widest chaetiger), 23 chaetigers. Pygidium rounded (Fig. 3 F), with many body papillae (about 15 μm long and 8 μm wide, n = 10), without pygidial cirrus. Other characters the same as holotype.

Etymology

The species is named after the R/V Hakuho-maru, a gear of the ship which collected the type specimens from the Southern Ocean. The specific name is a noun in the genitive case.

Distribution

The new species is only known from the type locality, off the South Orkney Islands, the Southern Ocean (60°33.54'S, 35°24.43'W - 60°34.07'S, 35°23.40'W), 2036 - 2479 m in depth.

Taxon discussion

Flabelligena hakuhoae sp. nov. belongs to Flabelligena because it has the following features: retractile anterior region, absence of distinct body region, presence of various pairs of branchiae, composite falcigerous neurochaetae, simple spinulose or serrated notochaetae ( Aguirrezabalaga and Ceberio 2006). This species is different from the other known species by having the following features (see Table 1 ): i) paired ventral large papillae present on the ventral side of parapodium in chaetiger 6; ii) three pairs of branchiae; iii) short body papillae between noto- and neurochaetae. Flabelligena erratica (Orensanz, 1974) and F. gascognensis Aguirrezabalaga and Ceberio, 2006 have paired ventral papillae between chaetigers 6-7, but do not have them at the ventral side of a parapodium in chaetiger 6 ( Orensanz 1974, Aguirrezabalaga and Ceberio 2006). Additionally, F. gascognensis has long (as long as neurochaetae) papillae around the parapodium, while the new species does not have them (1/6 of neurochaetae). Two species, F. amoureuxi Gillet, 2001 and F. erratica , have been found in the vicinity of the Southern Ocean as well as this new one. The new species can be distinguished from the other two species by having three pairs of branchiae, paired ventral large papillae near the parapodium of chaetiger 6 and absence of eyes. Flabelligena amoureuxi has a pair of branchiae and does not have paired ventral large papillae and eyes. Flabelligena erratica has a pair of branchiae, paired ventral large papillae between chaetigers 6-7 and eyes (see Table 1 ).

Figures

Figure 2. Flabelligena hakuhoae sp. nov., holotype (NSMT-Pol H- 813). A. Anterior end, dorsal view; B. anterior end, ventral view, arrows indicate ventral papillae; C. anterior end, dorsal enlarged view, an arrow head indicates a branchia; D. ventral large papilla, enlarged view. Scale bars: A-B, 500 μm; C, 125 μm; D, 50 μm.

Figure 3. Flabelligena hakuhoae sp. nov., paratype (ICHUM- 6113), scanning electron micrographs. A. Anterior end, frontal view, proboscis is not everted; B. Anterior end, dorsal side, frontal view; C. Anterior end, ventral side, frontal view; D. Anterior end, lateral view; E. branchial scars and nephridial lobe, enlarged view; F. pygidium, dorsal view. Asterisks indicate branchial scars. Arrow heads indicate papillae around branchial scars. Abbreviations: nl, nephridial lobe; p, palp; ps, palp scar. Scale bars: A, 300 μm; B-D, 200 μm; E 100 μm; F, 200 μm.

Figure 4. Flabelligena hakuhoae sp. nov., holotype (NSMT-Pol H- 813), anterior end, frontal view. Proboscis is everted. Abbreviation: b, branchia; nl, nephridial lobe; prob, proboscis; pros, prostomium. Asterisks indicate branchial scars. Arrow heads indicate palp scars. Scale bar = 500 μm.

Figure 5. Flabelligena hakuhoae sp. nov., paratype (ICHUM- 6113), scanning electron micrographs. A. Notochaetae and neurochaetae, posterior region; B. Notochaetae; C. Neurochaetae; D. Body papilla under the notochaetae. Scale bars: A, 200 μm; B, 10 μm; C, 100 μm; D, 50 μm.