Chaetopterus norvegicus M. Sars 1835

Chaetopterus norvegicus M. Sars, 1835, reinstated

Figs 1, 3A

Chaetopterus norvegicus M. Sars, 1835: 54–58, pl. 11, Fig. 29a–h.

Chaetopterus norvegicus – Ørsted 1844: 78; 1845: 414. — McIntosh 1857: 126. — M. Sars 1860: 86. — Danielssen 1861: 52. — Quatrefages 1866: 214. — Malmgren 1867: 88. — G.O. Sars 1873: 261. — Jensen & Frederiksen 1992: 66.

Tricoelia norvega – Meneghini 1847: 38.

Chaetopterus variopedatus – Joyeux-Laffuie 1890: 345–351. — Lo Bianco 1893: 35. — de Saint- Joseph 1894: 148. — McIntosh 1915: 120. — Fauvel 1927: 77–78.

non Tricoelia variopedata Renier, 1804: 18.

Diagnosis

Small- to medium-bodied, epifaunal Chaetopterus inhabiting a pale cream to brown, laminated, straight or bent tube. Segmental distribution 9A+5B+7–12C. Last segment of region A bearing neuropodia. Parapodia of B1 not posteriorly displaced from segment A-last. Segment B2 short, dorsal surface not fleshy. B1 and B2 neuropodia with four completely unfused, discrete lobes. With 5–10 relatively large light brown cutting notochaetae on segment A4, in a conspicuous ventral fascicle. Uncini tooth distribution as follows: A9 with 6–9 teeth, B1 anterior lobe with 7–9, B1 posterior lobe with 6–8, B3 piston tori with 7–9, B3 ventral lobes and C1 lateral lobes with 6–9, C1 ventral lobes with 8–12 teeth.

Material examined

Lectotype (here designated)

NORWAY • one complete specimen preserved within tube fragment; Bergensfjord; depth 30–60 fathoms [54–110 m]; from original syntype lot NHMO C5877; NHMO C7049.

Paralectotypes (here designated)

NORWAY • 8 fragments and tube fragments; same collection data as for lectotype; from original syntype lot; NHMO C5877.

Other material

NORWAY • 4 fragments; Hardangersfjord, Rute H05-59; depth 30–42 m; 21 Oct 1958; LACM uncataloged specimens Pol2 Z76/58.

Additional known material

The following specimens were examined and identified as Chaetopterus norvegicus by M.E. Petersen; however, their current location was not verified or ascertained. We include them here to contribute additional distributional information for this species:

SWEDEN • 1 spec.; Gullmarfjord, Humlesäcken; depth 30–50 m; 17 Sep. 1984; Claus Nielsen leg., from dredged material housed at the Kristineberg Marine Station • 3 specs; Gullmarfjord, Ös ̂ Holme; depth 37–40 m; 16 Sep. 1969; Claus Nielsen leg.; stones and shells.

DENMARK • 3 specs; Herthas Flak; depth 15–20 m; 19 Jun. 1971.

Description

Based mostly on lectotype and paralectotypes. Uncini data based on LACM specimens, and their tooth counts and measurements are given in Table 1.

GROSS MORPHOLOGY AND PRESEGMENTAL STRUCTURES. Small to medium-sized epibenthic Chaetopterus, 26 mm total body length for 26 chaetigers in lectotype, segmental formula 9A+5B+7–12C. Peristomium ventrally broad, horseshoe-shaped in dorsal view, with broad dorsolateral lobes that sometimes obscure A1 notopodia, sometimes with medium-brown pigment on dorsal surface. Grooved palps short, thin and filiform, inserted at dorsal inner margins of peristomium, 1.5 mm in length (n = 5). Eyes small, faint black spots positioned laterally near the outer base of the palps and obscured by the laterodorsal lobes of the peristomium.

REGION A. Anterior region with 9 segments (Fig. 1A); 4.9 mm mean length (range 4.5–6 mm, n = 6) and 4.5 mm mean width (range 3–6 mm, n = 6), slightly longer than wide or as wide as long; ventral surface of A with broad, rectangular glandular shield (Figs 1B, 3A). Region A notopodia shortest at A1 or A4, increasing from A4 to a maximum at A6 and decreasing in length again to segment A9; A4 notopodia shorter than neighboring notopodia. Small swellings not visible at dorsal base of A notopodia. Segment A4 notopodia bearing 5–10 relatively large apically blunt, light brown, cutting chaetae, with a distinct ventral tooth, on the ventral side of the notopodia (Fig. 1A). Other notopodia and the distal side of A4 notopodia bear lanceolate and simple chaetae. Region A chaetigers uniramous except the last, A9, also with fan-shaped neuropodia in 4 of 5 specimens; mean width 1.3 mm (range 1–1.5 mm, n = 4) and furnished with uncini on posterior margin (Figs 1B, 3A). A9 uncini asymmetrically pyriform to D-shaped, apically blunt and pointed at base, widest at middle or slightly below, with a curved proximal margin (Fig. 1D).

REGION B. Middle body region 10 mm in length in complete specimen. B1 with long aliform notopodia, 6 mm mean length (range 5–7 mm, n = 6), reaching anteriorly to the peristomium (Fig. 1 A–B). B1 and B2 neuropodia bilobed, with four completely unfused, discrete lobes, with uncini on distal lobe margins (Figs 1B, 3A). Anterior pair of neuropodial lobes in B1 narrow and situated medially (Figs 1B, 3A); uncini ovate to D-shaped, sometimes slightly pyriform, apically blunt and pointed or rounded at base, widest at middle or slightly below (Fig. 1E). Posterior neuropodial lobes of B1 broader than anterior and situated laterally (Figs 1B, 3A); uncini asymmetrically pyriform to ovate, apically blunt and pointed or rounded at base, widest at middle or slightly below, with a curved proximal margin (Fig. 1F). Segment B2 relatively short, 5 mm in length in one posterior fragment specimen; neuropodia bilobed with four completely unfused, discrete lobes; anterior pair of neuropodial lobes situated more laterally than posterior pair. Neuropodia of B3–B5 with a single pair of short, medially fused and ridge-like lobes, bearing uncini on posterior margins. B3 uncini of piston tori ovate to D-shaped, apically blunt and pointed at base, widest at middle, with straight proximal margin (Fig. 1G). B3 ventral lobe uncini asymmetrically pyriform to D-shaped, apically blunt and pointed at base, widest at middle or slightly below, with straight proximal margin (Fig. 1H).

REGION C. Posterior body region mean length 6 mm (range 2–10 mm, n = 4), with 7–12 chaetigers. Region C notopodia long and thin, tapering evenly to apex; C1 notopodia mean length 3.3 mm (range 2.5–4.5 mm, n = 4). Neuropodia bilobed, ventral lobes medially unfused, C1 ventral neuropodial lobes broader than those in succeeding segments; lateral lobes of C neuropodia lacking dorsal and ventral cirri, one specimen with small dorsal inflations on dorsal margin of lateral lobes. Both neuropodial lobes bear a row of uncini on distal margin. C1 lateral lobe uncini asymmetrically pyriform to D-shaped, apically blunt and pointed at base, widest at middle or slightly below, with straight or curved proximal margin (Fig. 1I). C1 ventral lobe uncini long D-shaped, apically blunt and pointed or rounded at base, widest at middle, sometimes with marked curvature toward proximal side (Fig. 1J).

TUBE. Tube straight or irregularly bent, pale cream-white and paper-like, very thin and delicate, composed of laminated proteinaceous material, without externally affixed sediment (Fig. 1C).

COI barcode sequence

GenBank ID DQ209254 (Osborn et al. 2007),as Chaetopterus sarsi M. Sars, 1860, from Trondheimsfjord, Norway, SAM E3557. Included in BOLD Barcode Index Number BOLD: AAW6559, identified from photographs.

Ecology and distribution

Chaetopterus norvegicus is an epifaunal species found on rocky substrates, sometimes among the branches of the coral Desmophyllum pertusum (Linnaeus, 1758) (Malmgren 1867, as Lophelia prolifera; Ørsted 1845, as Oculina prolifera; Jensen & Frederiksen 1992, as Lophelia pertusa), from depths of 30– 550 m. Chaetopterus norvegicus was recorded as a prey item of haddock, Melanogrammus aeglefinus (Linnaeus, 1758) by McIntosh (1857). Little else is known about its ecology.

Reported from the North Sea and Arctic waters, west to the Faroe Islands (Jensen & Frederiksen 1992), with the northernmost reports from Karlŝ, near Tromsø in northern Norway; widespread in coastal Norway, including areas near Bergen, Oslo, and Trondheim; Koster, Väder̂arma and Gullmann in western Sweden, south to Kattegat (Malmgren 1867); not known from the Baltic Sea.

Remarks

The lectotype is delicate and in fair condition, and represents the sole complete specimen within the original syntype lot. The paralectotypes consist of the remaining original syntypes and are in a similar condition. To avoid destructive sampling of the original type material, we examined uncini from a Norwegian specimen in the collections of the LACM. The external morphological features of this specimen agree with those of the lectotype and paralectotypes. Three additional specimens of Chaetopterus norvegicus from Denmark and western Sweden were examined and figured in detail by the late M.E. Petersen (see Additional known material, above). The present location of these specimens is unknown, but the notes and drawings agree well with the features present in the type material.

Chaetopterus norvegicus M. Sars, 1835 was the second species described within the genus Chaetopterus. The original description of Chaetopterus norvegicus is detailed and includes illustrations; however, Sars mistook the dorsal side for the ventral, and included segment B 1 in the anterior body region, as first remarked by Quatrefages (1866). Sars noted the apparent absence of eyes in C. norvegicus in his description; however, lateral eyespots appear in his later, unpublished figures of C. norvegicus (M. Sars ca 1870) and are faintly visible in the type specimens.

Prior to this study, eight nominal species of Chaetopterus had been described from the North Atlantic, including the Caribbean, Mediterranean, and North Seas: C. variopedatus (Renier 1804), C. pergamentaceus Cuvier, 1830, C. norvegicus M. Sars, 1835, C. sarsii Boeck in Sars, 1860, C. insignis Baird, 1864, C. valencinii Quatrefages, 1866, C. quatrefagesi Jourdain, 1868, and C. brevis Lespés, 1872. Chaetopterus norvegicus is readily distinguishable from other North Atlantic species by its unfused neuropodia in segments B1 and B2, a character clearly shown in Sars’ figures (M. Sars 1835, ca 1870). All other species of Chaetopterus previously described from the North Atlantic possess fused, sucker-like neuropodia in segments B1 and B2 (but see below).

The most recent phylogenetic analysis of the family recovered C. norvegicus in a clade including C. pugaporcinus Osborn, Rouse, Goffredi & Robison, 2007 and C. antarcticus Kinberg, 1866 (Moore et al. 2017; C. norvegicus is misidentified there as C. sarsii). This clade is sister to all other species of

Chaetopterus, including C. variopedatus. Thus, genetic evidence does not support the long-standing synonymy of C. norvegicus with C. variopedatus.

Additionally, several morphological features distinguish between these species. While the original description of C. variopedatus is brief and without figures (Renier 1804), the examination of six specimens of C. variopedatus from the Mediterranean and Adriatic Seas (USNM 5102, UF 4254 to UF 4258) revealed several characters clearly distinguishing these species. Chaetopterus variopedatus has a body size of 7–14 cm, medially fused, bilobed, sucker-like neuropodia in segments B1 and B2, and over 20 segments in tagma C. Furthermore, C. variopedatus secretes a large (~ 30 cm), infaunal tube of heavily laminated, flexible, brown parchment-like material covered externally in coarse sediment. Chaetopterus norvegicus, in contrast, has a body size of approximately 2–3 cm, distinctive unfused bilobed neuropodia in segments B1 and B2, 7–12 chaetigers in tagma C, and inhabits a relatively small, stiff, delicate and somewhat translucent white tube, and is epifaunal on hard substrates. The unusual unfused neuropodia of B 1 in C. norvegicus contrast with the sucker-like, fused neuropodia found in C. variopedatus and other species of Chaetopterus (Fig. 3). These strong genetic, morphological and ecological differences warrant the resurrection of C. norvegicus as a valid species.