Pelagobia longicirrata Greeff, 1879

(Figs 1, 9)

Pelagobia longicirrata Greeff, 1879: 247, Pl. XIV, Figs. 23–25 [original description, Tenerife Bay, Canary Islands].– Viguier 1886: 377, Pl. XXI, Figs. 1–13 [description, Bay of Alger].– Reibisch 1895: 21, Pl. II, Figs. 1–9 [description, Gulfstream, East- and West-Greenland, Labrador and Florida curents, the Sargasso Sea, Bermudans].– Southern 1909: 2, Pl. I, Fig. 1 [description, Irish Sea, Dublin Bay].– Bergström 1914, 186, Fig. 70 [brief description, North and Central Atlantic, Indian Ocean].– Fauvel 1916: 61, Pl. I, Figs. 6, 7 [description, Central Atlantic].– Fauvel 1923: 192, Fig. 72 a–c [description, Central Atlantic].– Nolte 1938: 274, Figs. 217–223 [description, North Atlantic].– Støp-Bowitz 1948: 21 [brief description, North Atlantic].– Fauvel, 1953: 131, Fig. 63 a–d [description, Indian Ocean].– Ushakov 1955: 105, Fig. 11 [description, North Pacific].–Dales 1955: 435 [brief description].–1957: 107, Figs. 11–13 [brief description].– Tebble, 1960: 419. Fig. 22 [brief description, South Atlantic].– Ushakov 1972: 187–188, Pl. XXI, Fig. 1–4 [brief description, East Pacific].– Böggemann 2009: 338–340, Figs. 71–72 [description, Central Atlantic].– Sarda et al. 2009: 11–15, Fig. 6 [description, Mediterranean].– Isaychev et al. 2013: Figs. 1–3 [description of specimens from the Drake Passage and comparison with literature data], Isaychev 2015: Figs. 1–6 [morphological comparison of specimens from different parts of the world]; Rozbaczylo et al. 2020: 150–151, Fig. 4 [brief description, North Pacific].

Pelagobia erinensis Nolte, 1938: 278, Figs. 224, 225 [original description, Atlantic Ocean, North-Equatorial, Guinea and South-Equatorial currents, Azores].

Material examined. Three specimens: ZMMU WS20993 (FA, Et), ZMMU WS20994 (FA), ZMMU WS20995 (FA, Et) .

Description (based on all our material). Body length 5 mm, 12 segments and also range of chaetigers in the material examined. Live worms transparent, with pale-yellow nuchal organs; intestine yellow. Proboscis muscular, with pair of small terminal jaws. Prostomium pentagonal-elongated, with terminal depression, as long as wide. Two pairs of thin filiform appendages (pair of antennae and pair of palps) reach half of prostomium length. Pair of red eyes with lenses, well visible both in live and preserved specimens. Pair of nuchal organs forming distinct conicalrounded lappets on lateral sides of head. Tentacular segment with fascicle of 3 or 4 minute compound chaetae and two pairs of large tentacular cirri of subequal length, reaching 3 rd segment. Acicular structures in tentacular cirri absent. Parapodia of 2 nd segment without dorsal cirri, parapodia of following segments with dorsal and ventral cirri. Dorsal cirri as long as podial lobes; ventral cirri slightly shorter. Each parapodium with tuft of 12 to 16 chaetae and one thick acicula; all chaetae compound spinigers, with long smooth heterogomph shaft and serrated blade. Additional chaetae mentioned by Tebble (1960) and Böggeman (2009) absent. Pygidium short, bifurcated.

Distribution. The type locality of P. longicirrata is the Tenerife Bay, Canarian Islands (Greeff 1879). Later records of P. longicirrata include North, South, tropical and subtropical Atlantic, Mediterranean Sea, North Pacific, Indo-Pacific; South Indian Ocean; Central Red Sea (this study). We do not include here the numerous records of P. longicirrata from the Arctic and Antarctic waters because we believe that these may be Pelagobia viguieri Gravier 1911 (Kolbasova et al. 2023).

Remarks. Pelagobia longicirrata from the Red Sea conforms well to the P. longicirrata specimens from the Central Atlantic both morphologically and according to the 18S marker (Fig. 9). They are notably small, and gametes were not found within the body cavity, but the original description of P. longicirrata also gave a body length of only 3 mm and 15 chaetigers (Greeff 1879), while P. longicirrata specimens from the Azores and Ireland were reported to have 14–19 segments with a body length of 7–8 mm (Støp-Bowitz 1948). Larger specimens from circumpolar regions with 25 chaetigers and the body length of 8–12 mm (Ushakov 1972; Isaychev et al. 2013; Kolbasova et al. 2020, 2023) must be P. viguieri (Gravier, 1911) .