Nichomache Malmgren, 1865
Nichomache cf. lumbricalis (Fabricius, 1780) sensu Hartman, 1967
Voucher. SEALION: station 80MFC.
Diagnosis. Complete specimen; small to medium sized, slender species; 20mm long and 0.4mm wide for 22 chaetigers and two pre-anal achaetous segments; colour in alcohol light pink, with redish brown pigments anteriorly on ventrum of chaetigers 1-5 (most pronounced on chaetigers 2 and 3). Chaetigers 1 – 6 short (about twice as long as wide), chaetigers 7 – 12 long; from around chaetiger 13 getting progressively shorter again, with the last 2 chaetigers and 2 pre-anal segments very short.
Prostomium fused to peristomium; without cephalic plaque; rounded, forming hood-like projection overhanging mouth with greatly arched cephalic keel; nuchal grooves as parallel slightly pigmented slits.
Notopodia of chaetigers 1–22 with fascicles of long and narrow capillary chaetae of two types; long, very thin and sparsely hirsute along most of its shaft (about 2 per fascicle) and smooth, stout, narrowly limbate chaetae (about 5 per fascicle). Additionally, from chaetiger 5 a single, very long, thin and often spiralled chaeta present; its posterior distribution uncertain. Neuropodia of chaetigers 1–3 with a single large, stout, dark yellow, pointed acicular spine. Posterior to chaetiger 4, neuropodia with a row of rostrate uncini. Each uncinus with a main fang and 4 small teeth; with long, and up to 4 thin fibrils (barbels) below main fang; number of rostrate uncini variable, with up to 6 observed.
Two very short, equal, pre-anal achaetous segments present. Anal funnel symmetrical, cup-shaped, with relatively shallow-rim bearing 17 short, sub-triangular, equal-sized anal cirri. Anus terminal, located in center of funnel.
Remarks. Comparative table of all known Nichomache species was recently given by De Assiz et al. (2007). So far two Nichomache species are known from the region of interest here. N. lumbricalis , is an assumed cosmopolitan species, but it seems doubtful that Southern Ocean records belong to the Northern European species. The drawing and description in Hartman (1966) shows a smooth anal plaque, without any cirri while comparative table of all Nichomache species provided by de Assis et al. (2007) states anal plaque as cup shaped bordered by 17-31 asymmetrical cirri. Another report of N. lumbricalis by Hartman (1967) includes a record (denoted by “?”) from Falklands Is. in 646-845m. This record is accompanied by very brief description of posterior end only, which states that:” …(anal) plaque surrounded by a circlet of 17-21 fringes; all are about equally short. The last setigerous segment is followed by two segments without chaetae”. This is consistent with the form of anal plaque in FI specimens found here. Further work would be necessary to establish if this really represents a new species different form Northern European Nichomache cf. lumbricalis, therefore the FI specimens are assigned to Nichomache lumbricalis (Fabricius, 1780) sensu Hartman, 1967.
N. monroi was described from Bismarck Strait in 93-315m by Hartman (1967) but it differs from the current species because it possesses about 30 papillae bordering the anal plaque preceded by 2 achaetous segments and up to 2 spines in first three neuropodia.