Ophelina abranchiata

Ophelina abranchiata (Støp-Bowitz, 1948)

Figure 10 (D–E)

Ophelia abranchiata Støp-Bowitz, 1948: 22.

Ophelina abranchiata: Eliason 1962: 73; Hartman 1965: 186; Parapar & Moreira 2008: 121; Parapar et al. 2011: 88 –89, fig. 4; Blake & Maciolek 2016a: fig. 7.20.1.6C.

Ophelina farallonensis Blake, 2000: 159 –160, fig. 7.6.

Material examined. Oahu, Hawaii: Mamala Bay, Jun/1995, Sta. 15.1.B, 21°14'53.88" N, 157°58'44.94" W, 417 m (1 spm); Sta. 13.2.A, 21°14'55.80" N, 157°57'45.66" W, 426 m (2); Sta. 16.1.B, 21°14'54.12" N, 157°59'31.98" W, 397 m (1); Sta. 11.2.B, 21°13'00.66" N, 157°56'59.82" W, 507 m (1); Sta. 17.2.A, 21°14'23.94" N, 157°53'00.59" W, 502 m (1); Sta. 14.2.A, 21°14'55.14" N, 157°58'14.34" W, 426 m (3, BPBM-R3890); Sta. 6.1.B, 21°13'19.68" N, 157°57'05.70" W, 498 m (1); Sta. 12.2.B, 21°13'50.21" N, 157°57'00.18" W, 481 m (1); Sta. 1.1.B, 21°15'08.61" N, 157°56'51.07" W, 428 m (1).

Diagnosis. Branchiae absent. Anal tube long, narrow, roughly 1/5 of total body length, with 25–40 transversal markings; unpaired anal cirrus long, convoluted and slender, arising from near posterior border.

Description. Specimens complete, ranging from 2.5–5.5 mm long and 0.2 mm wide, with 15–19 chaetigers. Body cylindrical and glossy tapering towards posterior end (Fig. 10D). Prostomium elongate with terminal clavate palpode, not conspicuous. Nuchal organs oval and postero-lateral. Eyespots not observed. Pharynx not everted in any specimen. Preserved specimens pale yellow to transparent, lacking any distinct body pigmentation. Branchiae absent.

Parapodia biramous, chaetae emerging from discrete parapodial lobes throughout. Chaetiger 1 emerging from a distance from anterior end and a number of achaetous segments may be present. Simple capillary chaetae in two bundles; 2–4 capillaries in each noto- and neuropodia anteriorly reducing to 1–3 posteriorly; notochaetae 1.5x longer than neurochaetae.

Anal tube long, narrow, roughly 1/5 of total length of specimens, with 25–40 transversal markings, without ventral groove (Fig. 10E). Unpaired anal cirrus long, convoluted and slender, arising from near posterior border (Fig. 10E).

Remarks. Several authors considered Ophelina farallonensis as a synonym of O. abranchiata Støp-Bowitz, 1948, mostly based on the absence of branchiae in both species (Parapar et al. 2011; Barroso & Paiva 2013). Blake (2000) raised O. farallonensis for Ophelina abranchiata specimens from the Pacific Ocean having a long anal tube (1/5 of the worm’s body length) and lacking distinct lobes. The original description of O. abranchiata was based on specimens lacking an anal tube and this has led to further comparative confusions. The anal tube of specimens identified as O. abranchiata from the Atlantic Ocean has been described and illustrated as being long and easily detachable (Parapar et al. 2011; Barroso & Paiva 2013) but more details on the number of transversal markings and presence and number of lobes are lacking. The material from Hawaii is herein identified as O. abranchiata although it fully agrees with the description proposed by Blake (2000). All ten specimens from Hawaii collected in 1995 were preserved with intact anal tube.

Distribution. This species was originally described from cold water of the Atlantic North where it has been reported at multiple locations (see Parapar et al. 2011). Pacific records of O. abranchiata include those from off California in slope depths of 1,020–3,060 m (Blake 2000) and Peru (Borowski & Thiel 1998; Borowski 2001). This is a new record for this species in the western Pacific Ocean, and material from Hawaii was collected from depths of 397– 507 m.