Harmothoe imbricata ( Linnaeus, 1767 )

Barnich, Ruth & Fiege, Dieter, 2009, Revision of the genus Harmothoe Kinberg, 1856 (Polychaeta: Polynoidae) in the Northeast Atlantic, Zootaxa 2104 (1), pp. 1-76 : 45-48

Harmothoe imbricata ( Linnaeus, 1767)

( Figs. 1 ; 21A–J ; 22A,B )

Aphrodita imbricata Linnaeus, 1767: 1084 .

Harmothoe imbricata: Malmgren (1866) : 66, pl. 9 figs. 8A–8E’; Fauvel (1923): 55, fig. 18f–l; Hartmann-Schröder (1996): 46, fig.12; Chambers & Muir (1997): 104, fig. 26; Barnich & Fiege (2000): 1899 , fig. 5A–D; Barnich & Fiege (2003): 47, fig. 22A–D.

Aphrodita cirrata Müller, 1776: 218 (refers to Müller 1771: “die flache Aphrodite”: 180 pl. 14).

Harmothoe unicolor Baird, 1865: 196

? Polynoe incerta Bobretzky, 1882: 187 , pl. 6: fig. 1A–G.

? Harmothoe imbricata incerta: La Greca, 1949: 156 .

Type material. Harmothoe imbricata : neotype, designated here, SMNH-Type-7728 (selected out of 17 spms., SMNH-79636 ), Iceland, Arnarnäs , 27–46 m, leg. O. Torell.

Harmothoe unicolor : 2 syntypes, BMNH 1860.2 .29.13, Canada, Vancouver Island , Esquimault Harbour, leg. J.K. Lord.

Additional material. NE Atlantic: 4 spms., SMF 17329, "Johan Ruud" St. 728, 69°38.72’N, 18°52.06’E, N Norway, V/ Grindøya, 07 October 2002, epibenthic sledge, 16 m, leg. & ded. C. d’Udekem d’Acoz. 7 spms., SMF 17330, "Johan Ruud" St. 729, 69°38.16’N, 18°52.76’E, N Norway, V/ Grindøya, 07 October 2002, epibenthic sledge, 24 m, leg. & ded. C. d’Udekem d’Acoz. 56 spms., SMF 17331–17333, "Johan Ruud" St. 730, 69°38.23’N, 18°52.81’E, N Norway, V/ Grindøya, 07 October 2002, epibenthic sledge, 22 m, leg. & ded. C. d’Udekem d’Acoz. 16 spm., SMF 17334, "Johan Ruud" St. 731, 69°40.69’N, 18°48.30’E, N Norway, Haakøy Nordbotn, 07 October 2002, epibenthic sledge, 32 m, leg. & ded. C. d’Udekem d’Acoz. 21 spms. (juv.), SMF 17335, "Johan Ruud" St. 807, 69°39.53’N, 18°45.75’E, N Norway, Haakøy Sørbotn, 28 October 2002, epibenthic sledge, 29 m, leg. & ded. C. d’Udekem d’Acoz. 4 spms. (juv.), SMF 17336, "Johan Ruud" St. 808, 69°38.53’N, 18°45.89’E, N Norway, Haakøy Sørbotn, 28 October 2002, epibenthic sledge, 25 m, leg. & ded. C. d’Udekem d’Acoz. 1 spm., SMF 17337, "Johan Ruud" St. 810, 69°38.23’N, 18°45.05’E, N Norway, Haakøy Sørbotn, 28 October 2002, epibenthic sledge, 20 m, leg. & ded. C. d’Udekem d’Acoz. 1 spm., SMF 17338, "Johan Ruud" St. 811, 69°38.91’N, 18°45.28’E, N Norway, Haakøy Sørbotn, 28 October 2002, epibenthic sledge, 18 m, leg. & ded. C. d’Udekem d’Acoz. 12 spms., SMF 17339, "Johan Ruud" St. 813, 69°40.16’N, 18°45.95’E, N Norway, Haakøy Nordbotn, 28 October 2002, epibenthic sledge, 47 m, leg. & ded. C. d’Udekem d’Acoz. 1 spm., SMF 17340, "Johan Ruud" St. 816, 69°40.91’N, 18°50.96’E, N Norway, Sandnessundet Sandnes, 28 October 2002, epibenthic sledge, 21 m, leg. & ded. C. d’Udekem d’Acoz. 1 spm., SMF 17349, N Norway, Tromsø area, Kvaløya, Grøtfjord, western side, 30 June 2002, lower shore, below stones, leg. & ded. C. d’Udekem d’Acoz. 2 spms., SMF 17341, N Norway, Tromsø area, some km E of Hansnes, 26 April 2002, exposed shore, below stones, leg. & ded. C. d’Udekem d’Acoz. 2 spms., SMF 17363–17364, N Norway, Tromsø area, Håkøy, NE coast, 30 April 2006, lower shore, below stone on mud, leg. & ded. C. d’Udekem d’Acoz. 5 spms., SMF 17350–17354, N Norway, Tromsø area, Kroken, 27 February 2005, shore, leg. & ded. C. d’Udekem d’Acoz. 9 spms., SMF 17357–17362, N Norway, Tromsø area, Kroken, 12/ 13 March 2005, shore, leg. & ded. C. d’Udekem d’Acoz. 7 spms., SMF 17355, N Norway, Tromsø area, Kroken, 01 April 2002, lower shore, leg. & ded. C. d’Udekem d’Acoz. 1 spm. (juv.), SMF 17356, N Norway, Tromsø area, Kroken, 25 April 2002, lower shore, 0.5 m, leg. & ded. C. d’Udekem d’Acoz. 10 spms., SMF 17342–17344, N Norway, Tromsø area, Sommarøy, eastern islet, N coast, 27 April 2002, lower shore, below stones, leg. & ded. C. d’Udekem d’Acoz. 1 spm., SMF 17346–17348, N Norway, Tromsø area, Sommarøy, 25 May 2002, lower shore, leg. & ded. C. d’Udekem d’Acoz. 1 spm., SMF 17345, N Norway, Tromsø area, Sommarøy, 69°38’N 18°02’E, 04 July 2002, lower shore, below stones, leg. & ded. C. d’Udekem d’Acoz. 18 spms., SMF 11842, 1 spm., 16581, 2 spms., 16582, Denmark, Flensburg fjord, near Brunsnaes, marina, 22 July 1999, between mussels, 0.5 m, leg. T. Wehe. 4 spms., SMNH- 79634, Iceland, Berufjord, 55 m, leg. O. Torell.11 spms., SMNH- 79635, Iceland, Seglefjord, 22 m, leg. O. Torell. 16 spms., SMNH- 79636, Iceland, Arnarnäs, 27–46 m, leg. O. Torell. 6 spms., SMNH- 79637, Iceland, Berufjord, 55 m, leg. O. Torell. 10 spms., SMNH- 79638, Iceland, Seglefjord, 22 m, leg. O. Torell. 6 spms., SMNH- 79639, Iceland, Reykjavik, stones, leg. O. Torell. 8 spms., SMNH- 79640, Iceland, Arnarnäs, 46 m, leg. O. Torell. 1 spm., SMNH- 79641, Iceland, Hofsås, leg. O. Torell. 15 spms., SMNH- 79766, Sweden, Bohuslän Koster area, N of Styrsholmen, Pomatoceros reef, 30 August 1986, leg. F. Pleijel.

Diagnosis. Anterior pair of eyes anteroventral beneath cephalic peaks. Elytral margin with short fringing papillae; surface covered by conical microtubercles and few scattered papillae, with or without row of conical to drop-like macrotubercles near posterior margin.

Description (based on neotype of H. imbricata ).

Body with 38 segments. At anterior end ( Fig. 21A ), prostomium bilobed, with distinct cephalic peaks; ceratophore of median antenna in anterior notch, lateral antennae inserted ventrally, styles of antennae papillate, slightly inflated subdistally, then abruptly tapering to filiform tip; anterior pair of eyes situated anteroventrally beneath cephalic peaks, posterior pair dorsally near hind margin of prostomium; palps papillate, tapering.

Tentaculophores inserted laterally to prostomium, each with a notochaeta and a dorsal and ventral tentacular cirrus, styles of cirri papillate, slightly inflated subdistally, then abruptly tapering to filiform tip. Second segment with first pair of elytra, biramous parapodia, and long buccal cirri. Following segments with tapering, short ventral cirri.

Fifteen pairs of elytra, covering dorsum, on segments 2, 4, 5, 7, then on every second segment to 23, 26, 29, 32; last six segments cirrigerous; elytral margin and surface with few, scattered, short papillae; conical microtubercles covering surface; few, conical, rather indistinct macrotubercles present in a row near posterior margin; elytral surface with mottled pigmentation. ( Fig. 21B,C ). Cirrigerous segments with distinct dorsal tubercles; dorsal cirri with cylindrical cirrophore, style papillate, slightly inflated subdistally, then abruptly tapering to filiform tip.

Parapodia biramous; notopodia with elongate acicular lobe; neuropodia with elongate prechaetal acicular lobe with short, digitiform supra-acicular process; neuropodial postchaetal lobe shorter than prechaetal lobe, rounded; tips of noto- and neuroacicula penetrating epidermis ( Fig. 21D ). Notochaetae stouter than neurochaetae; with distinct rows of spines and blunt tip ( Fig. 21E,F ); neurochaetae with distinct rows of spines, mostly with bidentate tip with stout, distinctly set off secondary tooth, some lowermost neurochaetae unidentate ( Fig. 21G–J ).

Measurements. Neotype of H. imbricata , SMNH-Type-7728 ( Fig. 21A–J ): L 24 mm, W 7 mm for 38 segments. Additional specimens, SMF 16582: L 24 mm, W 7 mm for 37 segments ( Fig. 22A ); L 14 mm, W 4 mm for 36 segments ( Fig. 22B ).

Remarks. Harmothoe imbricata is one of the most frequently identified and most problematic scaleworm species from northern European coasts. The description given by Linnaeus (1776) is insufficient and it is not clear at all which species the author had at the time. Our search for the type specimens in Swedish and other museums was not successful and now we consider the type material lost. The current concept of the distinguishing characters of this species is due to Malmgren’s (1866) redescription and, since H. imbricata is a well established name, we decided to preserve it and provide a redescription based on a well preserved neotype. The selected neotype originates from Iceland, where J. G. König sampled Linnaeus’ specimens (see also Malmgren 1866: 69).

Among the Northeast Atlantic species with anterior eyes anteroventral beneath the cephalic peaks (see Fig. 1 ), H. imbricata is recognised by its elytra with short fringing papillae and conical micro- and macrotubercles. In the neotype few macrotubercles are present in a row near the posterior margin and the elytral surface shows a mottled pigmentation. The presence of macrotubercles and the pigmentation of the elytra are rather variable (see also Fig. 22A,B and Pettibone 1963: 36). In some specimens from the same population, macrotubercles might even be missing, which makes differentiation from H. spinifera ( Ehlers, 1864) less obvious. It is still possible to separate the species, since the elytral margin is papillate in H. imbricata and smooth in H. spinifera .

Differentiation of H. imbricata specimens without macrotubercles from those of H. grisea Ehrenberg & Grube in Grube, 1869, however is problematic. The latter species was recently redescribed by Wehe (2006) in his study of polynoids from the Red Sea and the Arabian Gulf. So far, our investigation of polynoids from the Pacific showed that H. grisea is widely distributed in the Indian and Pacific Oceans and that it is to be considered a senior synonym of H. praeclara ( Haswell, 1883) . Since detailed description and synonymy of H. grisea and its possible differentiation from H. imbricata is well beyond the scope of this revision, this has to be discussed in a forthcoming paper.

Distribution. Arctic, North Pacific, North Atlantic, North Sea, Skagerrak to the eastern Baltic Sea, and Mediterranean Sea.

Habitat. On various substrates, either free-living or commensal with tubicolous polychaetes or pagurids; from the intertidal down to 300 m.

Figures

FIGURE 1. Identification characters of Harmothoe anoculata, H. ingolfiana, H. areolata, H. spinifera, H. antilopes, and H. imbricata.

FIGURE 21. Harmothoe imbricata (neotype, SMNH-type-7728). (A) anterior end; left palp bent downwards; (B) left 2nd elytron from segment 4; (C) detail of lateral margin of same; (D) left elytragerous parapodium from segment 15, posterior view; (E) distal half of long notochaeta; (F) tip of same; (G) distal part of middle neurochaeta; (H) tip of same; (I) tip of upper neurochaeta, secondary tooth abraded; (J) tip of lowermost neurochaeta. (Scales: A, B = 2 mm; C, E, G = 250 µm; D = 1 mm; F, H–J = 100 µm).

FIGURE 22. Harmothoe imbricata (additional specimens, SMF 16582). (A) left elytron from segment 5 of large specimen; (B) right elytron from segment 9 of smaller specimen. (Scales: A = 2 mm; B = 1 mm).