Osedax braziliensis, Fujiwara, Yoshihiro, Jimi, Naoto, Sumida, Paulo Y. G., Kawato, Masaru & Hiroshi Kitazato,, 2019

Fujiwara, Yoshihiro, Jimi, Naoto, Sumida, Paulo Y. G., Kawato, Masaru & Hiroshi Kitazato,, 2019, New species of bone-eating worm Osedax from the abyssal South Atlantic Ocean (Annelida, Siboglinidae), ZooKeys 814, pp. 53-69 : 58-62

Osedax braziliensis sp. n. Figures 3, 4 New Japanese name: Burajiru-honekuihanamushi

Osedax sp. nov.: Sumida et al. 2016: 1-6, figs 3-4, Table 1. Osedax : Alfaro-Lucas et al. 2017: 1-9, fig. 2B.

Type material.

Holotype: NMST-Pol H-685, trunk 14 mm long, 2 mm wide, female, 4,203 m depth, 26 April 2013, collected by YF, DDBJ No. LC381421, LC 381422, LC381424. Paratypes (14 specimens): NSMT-Pol P-686-690 and JAMSTEC-1130038806, 1130039105, 1130039113, 1130039116, 1130039146, 1130039163, 11 specimens, female, 24 and 26 April 2013, collected by YF, DDBJ No. LC381777, LC381766, LC381767, LC381768, LC381769, LC381771; JAMSTEC-1130057454, 1130057457, 1130057458, 3 specimens, male, 26 April 2013, collected by YF.

Type locality.

São Paulo Ridge, Brazil, 4,204 m depth.

Diagnosis.

Trunk length long. Gelatinous hemispherical tube encases trunk and base of palps. Yellow bump or patch present (absent in some specimens). Pinnules on inner margin of palps. Root lobulated without branching.

Description.

Genetic data (COI, 16S, and 18S) deposited in DDBJ (LC106303, LC381421, LC381422, LC381424, and LC381765-LC381787). Trunk length up to 22 mm, width at collar 0.5 mm, reddish purple while alive and whitish after fixation (Fig. 3 A–C); gelatinous hemispherical tube encases trunk and base of palps, 1-2 mm thick, contains eggs and dwarf males (Fig. 3A, C). Prostomium whitish while alive, present at top of trunk. Yellow bump or patch present behind prostomium: this yellow bump or patch size varies among individuals, biggest bump reaches top of trunk, and is absent in some specimens (Fig. 3 D–F). Crown consists of four palps; palps about 1.5 mm length, red colour while alive with two whitish stripes on the inner side, fused for about 30% of length; pinnules on inner margin of palps, about 50-250 µm, 7-8 pinnules in transverse rows (Figs 3A, C, 4B, C). Oviduct free to base, adjoined to the trunk at opposite side of prostomium region, reaching up to 20-30% of palp length (Fig. 4C). Ovisac whitish; trunk–ovisac junction about 15% of trunk length, light green while alive (Fig. 3B). Root lobulated without branching, yellow greenish while alive and whitish after fixation; intracellular symbiotic bacteria in root tissue (Fig. 3B). Eggs about 150 µm diameter (n = 20), whitish while alive (Fig. 3B).

Dwarf male about 250 µm in length (n = 20), fusiform, whitish while alive, prostomium and pygidium rounded, no appendage organs; posterior hooks present, two pairs (5-7 hooks per bundle) arranged in three rows (Figs 3C, 4D).

Etymology.

This species is named after the type locality, Brazil. This name is an adjective used as a substantive in the genitive case.

Distribution.

Only known from a whale carcass of the type locality. São Paulo Ridge, off Brazilian coast, 4,204 m depth.

Phylogenetic analysis.

The final lengths of the aligned sequences were 1,004 bp (COI), 486 bp (16S), and 1,604 bp (18S). The phylogenetic position of O. braziliensis sp. n. determined from our ML analysis recovered, with total support, a distinct species from that of all other Osedax species reported (Fig. 5). The six Osedax clades proposed by Rouse et al. (2018) were recovered. The phylogenetic analysis showed that O. braziliensis sp. n. falls into Clade IV, and is a sister species of O. frankpressi known from Monterey Bay at depths between 1,820 m and 2,898 m (Fig. 5).

Remarks.

This species resembles Osedax frankpressi in the pinnules distributed only at the inner margin of palps, lobulated root structure without branching, gelatinous hemispherical tube, and dwarf males ( Rouse et al. 2004). However, it can be discriminated from O. frankpressi by the presence of the yellow bump or patch behind the prostomium, trunk length, and genetic data. In O. braziliensis sp. n., the yellow bump or patch was present in some specimens including holotype, and the trunk length is long (6-22 mm), whereas in O. frankpressi , the bump or patch is absent in all specimens, and the trunk length is shorter (4.5 mm). COI genetic distances between O. braziliensis sp. n. and O. frankpressi are 0.111-0.117, which are greater than intraspecific values in O. braziliensis sp. n. (0.001-0.006). Genetic distances between O. braziliensis and the rest of the Osedax taxa for the COI ranged from 0.117 to 0.236 (Table 3).