Macellicephala patersoni,

Neal, Lenka, Brasier, Madeleine J. & Wiklund, Helena, 2018, Six new species of Macellicephala (Annelida: Polynoidae) from the Southern Ocean and south Atlantic with re-description of type species, Zootaxa 4455 (1), pp. 1-34: 18-19

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Macellicephala patersoni

sp. nov.

Macellicephala patersoni  sp. nov.

( Figures 2FView FIGURE 2 and Figures 9View FIGURE 9, 10View FIGURE 10; Table 2.)

Macellicephala  sp. B in Neal et al. (2017) [record].

Material examined. Holotype, NHMUK.2018.1009, Pine Island Bay , Amundsen Sea, Southern Ocean, cruise JR 179, station BIO4View Materials -EBS-3D, collected on 07/03/2008, epibenthic sledge, epi-net, 74°23'25.836''S, 104°46'4.512''W, 506 m depth.GoogleMaps 

Description (based on holotype). Medium sized species; holotype complete specimen in good condition, 13.5 mm long, 2 mm wide excluding parapodia and 6.55 mm wide including parapodia, 18 segments (segment 1 = tentacular segment); body dorsoventrally flattened, tapering anteriorly and posteriorly; live specimen not observed; dorsum and everted proboscis purple in alcohol ( Fig. 9AView FIGURE 9), remaining body pale yellow ( Fig. 9A, BView FIGURE 9); ceratophore of median antenna and tentacular cirrophores with distinct purple pigmentation ( Fig. 9CView FIGURE 9).

Prostomium bilobed with wide and deep median notch; prostomial lobes slightly pronounced, anteriorly tapering ( Figs. 2FView FIGURE 2 and 8CView FIGURE 8). Frontal filaments distinct, basally slightly inflated, distally slender, extending from tapering prostomial lobes where medially inserted ( Figs. 2FView FIGURE 2 and 9CView FIGURE 9). Eyes absent. Facial tubercle trilobed, composed of three inflated oval lobes, with median lobe larger than lateral lobes ( Figs. 2FView FIGURE 2 and 9CView FIGURE 9). Ceratophore of median antenna massive, bulbous, with purple pigmentation, inserted medially on prostomium (near the base of anterior notch) ( Figs. 2FView FIGURE 2 and 9CView FIGURE 9); style of median antenna very long (longest of all appendages, reaching to beginning of segment 10), smooth and slender. Palps thick, smooth, tapering into slender tips; moderately long (extending to the beginning of segment 6).

Tentaculophores large, cylindrical, equal-sized, with purple pigmentation ( Fig. 9CView FIGURE 9), inserted laterally to prostomium, achaetous; all tentacular styles attached, long slender smooth, similar in form, but shorter in length (about 2/3) than style of median antenna; dorsal tentacular cirrus slightly longer than ventral tentacular cirrus. Pharynx everted, purple, with 9 pairs of equal-sized, triangular papillae distally ( Fig. 9DView FIGURE 9); two pairs of dark ambercoloured jaws, with smooth margins. Second segment with elytrophores, biramous parapodia, chaetae and ventral cirri.

Nine pairs of prominent, bulbous elytrophores, on segments 2, 4, 5, 7, 9, 11, 13, 15 and 17; all elytra missing.

Parapodia biramous. Notopodia reduced to elongate acicular lobe ( Fig. 10AView FIGURE 10), starting on mid-dorsum as two raised ridges, extending into slender elongated acicular lobes, tip of notoacicula not penetrating epidermis; two distinct, narrow, white lines across dorsum of each segment ( Fig. 9AView FIGURE 9), connecting raised ridges; dorsal tubercules not developed. Neuropodia large ( Fig. 10AView FIGURE 10), approaching subtriangular to rectangular shape, with elongate slender acicular lobe, tip of neuroacicula not penetrating epidermis. Cirrigerous segments with prominent, cylindrical cirrophores, inserted basally on notopodia; styles mostly missing, 8 remaining styles very long (much longer than neuropodial acicular lobe), smooth slender, similar in form to styles of median antenna and tentacular cirri. Ventral cirri smooth, slender, tapering; present from segment 2 to last segment; inserted basally on segment 2, where very long, (slightly longer than associated neuropodia lobe); inserted medially on subsequent segments ( Fig. 10AView FIGURE 10), where very short (not reaching distal margin of neuropodial lobe).

Notochaetae about as slender as neurochaetae ( Fig. 10B, CView FIGURE 10); few (<10 observed per ramus); short to very long, straight to slightly convex, with faint serration across convex side ( Fig. 10CView FIGURE 10). Neurochaetae numerous ( Fig. 10A, D –EView FIGURE 10), all translucent, very long and slender; neurochaete of two forms: either flattened subdistally with faint serrations along margins, with bidentate tips (secondary tooth minute) ( Fig. 10HView FIGURE 10), these neurochaetae are few in number and easily overlooked or neurochaete slender with faint serration along margins, with bluntly rounded tips ( Fig. 10D –FView FIGURE 10).

Two distinct white lines running through ventral side of neuropodia and ventrum of each segment (except for tentacular segment). Nephridial papillae on ventrum of segments 10, 11 and 12 small, globular, inconspicuous in other segments, present from segment 5. Reduced parapodia of segment 18 lateral to pygidium, consisting of large notopodia only. Pygidium somewhat truncated, dorsally with two large loops ( Fig. 10EView FIGURE 10). Anal cirri not observed ( Fig. 10E, FView FIGURE 10).

Remarks. Of the Southern Ocean Macellicephala  species, M. patersoni  sp. nov. is most similar to M. brenesorum  sp. nov. It differs from the latter species in having a massive, bulbous and pigmented ceratophore of median antenna, in lacking dorsal tubercules, in possessing two dorsal loops on the pygidium and in having neurochaetae with bidentate tips. For comparison with other known Macellicephala  species, including those described in this publication, see Table 2.

Molecular Information. 16S (434 bp) and 18S (676 bp) were obtained from the holotype. Based on 16S, this species was closest to Macellicephala brenesoru  m sp. nov. with uncorrected 'p' distance 0.156, and distance to M. violacea  was 0.166.

Etymology. Macellicephala patersoni  sp. nov. is named after Dr. Gordon Paterson, who recently retired from the Natural History Museum London after a long and successful career in deep-sea research with the focus on polychaete ecology and systematics.

Distribution. Known only from its type locality, Pine Island Bay, Amundsen Sea, Southern Ocean, depth of 507 m.


Natural History Museum, London