Cirrophorus brevicirratus Strelzov 1973

Cirrophorus brevicirratus Strelzov, 1973

(Fig. 3)

Cirrophorus brevicirratus Strelzov, 1973: 124, fig. 53A–J.

Material examined. 4020 Askøy 2007 KL1–4; 10.07.2007; 60.4068°N–5.2286°E; 14 m; one specimen. 6244 Veslefrikk VFR 03; 60.7760°N–2.9100°E; 170 m; 27.05.2013; five specimens.

Additional material. BENTART–AP21, Antarctic Peninsula; 64.9000°S–63.0185°W; 107 m; 23.02.2003; three specimens.

Description. All specimens incomplete, largest one 10 mm long, 0.1 mm wide for 80 chaetigers. Body slender, dorsoventrally flattened in pre- and branchial regions, cylindrical in postbranchial region. Prostomium triangular, slightly wider than long (Fig. 3A); minute median antenna in largest specimens only (Strelzov 1973), lacking in the examined specimens from Norway; apical sensory organ absent; pair of nuchal organs as slightly oblique nuchal slits (Fig. 3A). Notopodial postchaetal lobes of chaetiger 1 as short, rounded tubercles (Fig. 3A); slightly longer and piriform on remaining prebranchial chaetigers and in branchial region; short and digitiform in postbranchial region (Fig. 3C). Branchiae from chaetiger 4, 9 pairs, bearing ciliation on their inner edge, digitiform and distally rounded, up to four times as long as wide (Fig. 3A, B). Noto- and neurochaetae as geniculate bilimbated capillaries in prebranchial and branchial regions (Fig. 3A, B); in postbranchial region as thin, straight capillaries, clearly less numerous (Fig. 3C); from chaetiger 4–8 bearing 1–2 forked notopodial chaetae with tines similar in thickness but differing in length, with inner edges bearing short spinulation (Fig. 3D); modified neurochaetae absent.

Remarks. Our specimens can be accurately referred to C. brevicirratus by having forked modified notochaetae, up to 15 pairs of branchiae and very short notopodial postchaetal lobes in the branchial region. Although typical of genus Cirrophorus, in this species the median antenna is very small and only appreciable in largest individuals, which are 0.4 mm wide and possess more than 90 chaetigers (Strelzov 1973); this size is much larger than that of the examined specimens from Norway. The other two species within the genus that bear forked modified notochaetae, namely C. americanus Strelzov, 1973 and C. furcatus (Hartman, 1957), have more branchiae (up to 33 pairs in C. furcatus and 46 in C. americanus) and bear digitiform notopodial postchaetal lobes in the branchial region. In addition, the antenna of C. brevicirratus is much smaller when present than those of the other two species (Strelzov 1973). This species was described based on material from Southern Ocean, where it has been recorded several times (Hartmann-Schröder & Rosenfeldt 1988; Sicinski 2004; Parapar et al. 2011). Strelzov (1973) also included some material from western North Atlantic in the description, but the species was never again recorded outside of Antarctica or its vicinity. Thus, this record and its comparison with material collected from Antarctica confirms the Arctic-Antarctic distribution of the taxon.

Distribution. New England (Strelzov 1973). South Orkney (Strelzov 1973) and South Shetland Islands (Sicinski 2004); Antarctic (Hartmann-Schröder & Rosenfeldt 1988; Parapar et al. 2011). First record for Norway and adjacent waters.