Terebellides stroemii Sars, 1835

Parapar, Julio, Mikac, Barbara & Fiege, Dieter, 2013, Diversity of the genus Terebellides (Polychaeta: Trichobranchidae) in the Adriatic Sea with the description of a new species, Zootaxa 3691 (3), pp. 333-350 : 342-344

Terebellides stroemii Sars, 1835

( Figures 9–11 , 12 c, 13)

Terebellides stroemii Sars, 1835: 48 –50, Pl. 12 (labelled 13), Fig. 31a–e.

Terebellides stroemii —Garraffoni et al. 2005: 14. Garraffoni & Lana 2003: 356. Garraffoni & Lana 2004: 973, Tables 1–2, Figs 5–6 . Jirkov 2001: 529, Figs 1–5 . Parapar et al. (2011): 14, Figs 11 , 12 , 13 d.

Terebellides stroemi —Williams 1984: 119, Figs 1 a–c, 3, 6. Imajima & Williams 1985: 11. Holthe 1986a: 170. Solís-Weiss et al. 1991: 147. Bremec & Elías 1999: 177.

non Terebellides stroemii —Hutchings & Peart 2000: 254, Figs. 13 f, 16, Tab. 3.

Material examined. A total of 51 specimens were examined (60.7% of the total Terebellides specimens collected) in all four stations studied.

Station SJ 0 0 5: 28.05.2003 (PMR-14563, 1 spec.; PMR-14564, 1 spec.); 0 7.06.0 4 (PMR-14565, 1 spec.); 0 2.12.2004 (PMR-14566, 1 spec.; PMR-14567, 2 specs.). Station SJ 0 0 7: 27.02.2003 (4 specs.) (coll. BM); 28.05.2003 (PMR-14568, 4 specs.); 12.08.2003 (MNCN 16.01/14717, 2 specs.; MNCN 16.01/14718, 1 spec.); 29.01.0 4 (PMR-14569, 2 specs.); 30.08.0 4 (PMR-14570, 1 spec.). Station LIM K2: 0 7.07.2010 (PMR-14571, 10 specs.); 0 7.07.2010 (10 specs.) (coll. BM). Station LIM K5: 0 7.07.2010 (PMR-14572, 9 specs.; PMR-14573, 2 specs. on one SEM stub).

Description of Adriatic Sea specimens. Complete specimens ranging from 25 to 34 mm in length and 3.0 to 2.0 mm in width; specimens from LIM stations much larger than ones from SJ stations; body tapering posteriorly with segments becoming increasingly shorter and compact towards pygidium. Prostomium compact; tentacular membrane surrounding mouth and provided with buccal tentacles with expanded tips. First segment forming an expanded structure below tentacular membrane. Lateral lappets on SGIII–IX ( CH 1–7) ( Fig. 9 a, b). Some specimens with more or less conspicuous dorsal rounded projection in CH 4 – 6. An oval-shaped glandular region could be seen in lateral part of thoracic CH 3 ( Fig. 9 a, b).

Branchiae arising as single structure from segment 3 consisting of a single stalked structure located middorsally made up of two pairs of posterior lobes fused along most of their length; lower pair of same length but thinner than upper pair ( Fig. 9 b). Pointed projection of posterior region of lobes present in both lobes. Anterior branchial projection (fifth lobe) present. Branchiae provided with papillar projections pointing over the edge of the branchial lamellae, the latter also provided with several parallel bent rows of cilia on both sides ( Fig. 9 c–d).

Eighteen pairs of thoracic notopodia (SGIII −XX). Notopodia and notochaetae of CH 1 shorter in size to subsequent notopodia. Neuropodia present as sessile pinnules from CH 6 (SGVIII) to pygidium and provided with uncini in single rows throughout. First thoracic neuropodia ( CH 6) with 4−5 sharply bent, acute tipped, geniculate acicular hooks ( Fig. 10 a). Minute teeth forming a capitium on geniculate chaetae not observed ( Fig. 10 b). Second and all subsequent thoracic neuropodia with up to 10–16 uncini per torus. Uncini provided with long shafted denticulate hooks with 2−4 teeth above main fang surmounted by about 3 shorter teeth and an upper crest of several smaller denticles ( Fig. 10 c, d), dental formula MF:2–4:3:∞. Between 30–32 abdominal neuropodia as erect pinnules provided with about 23 uncini per torus; uncini with 4 teeth above main fang surmounted by an upper crest of 3−5 shorter teeth and a variable number of smaller teeth ( Fig. 11 a), dental formula MF:4:3–5:∞.

One large, button-hole like nephridial opening on each notopodium of CH 4–5 ( Fig. 11 b). Low ciliated papillae located dorsally to all thoracic notopodia from second chaetiger ( Fig. 11 c, d).

Pygidium blunt, funnel-like depression.

MG staining pattern 5 ( Fig. 12 c; 13a): compact green colouration in CH 1–3, after turning into striped pattern in CH 4–12 and fading in following segments. Oval-shaped glandular region of CH 3 also stained but differently to others. Colour in alcohol pale brown ( Fig. 13 b), oval region of CH 3 slightly lighter.

Remarks. General characteristics of Adriatic specimens agree with those of Icelandic specimens identified as T. stroemii sensu Holthe (1986a) by Parapar et al. (2011), and therefore differ from those characters referred to this species by Hutchings and Peart (2000) from the study of some Norwegian specimens: presence and degree of development of the anterior lateral lappets, position of nephridial openings and shape of geniculate chaetae.

Other characters also in agreement with Parapar et al. (2011) are the MG coloration pattern and the distribution of branchial ciliature.

Habitat. The species was reported in a wide range of depths and temperatures in all world oceans, nevertheless, it is impossible to establish with confidence any habitat preferences given that today, it is considered a complex of species. Terebellides stroemii was frequently reported in all parts of the Adriatic Sea on soft bottoms up to a depth of 1,150 m and was considered a species of wide ecological distribution. In this research the species was found in the northern Adriatic Sea on offshore stations on silty sand bottom at 31 m depth and on coastal stations on muddy bottom at 28–29 m depth.

Distribution. Boreo-Arctic waters (Hutchings & Peart 2000). Our record in the Adriatic Sea confirms the presence of T. stroemii in Mediterranean waters.

Figures

FIGURE 1. Map of the study area showing collecting stations.

FIGURE 2. SEM micrographs of Terebellides gracilis (Malm, 1874) from the Adriatic Sea (station SJ 007) (a) anterior end, latero-ventral view; (b) edge of branchial lamellae; (c) detail of branchial ciliation; (d) detail of first three thoracic chaetigers. Scales: (a) 450 µm, (b) 45 µm, (c) 10 µm, (d) 200 µm. CH 1 = chaetiger 1, CT = cilia tufts.

FIGURE 3. SEM micrographs of Terebellides gracilis (Malm, 1874) from the Adriatic Sea (station SJ 007) (a) anterior end, latero-dorsal view; (b) edge and inner side of branchial lamellae; (c) geniculate chaetae of chaetiger 6 (broken at distal end); (d) detail of nephridial opening of thoracic chaetiger 5. Scales: (a) 300 µm, (b) 50 µm, (c) 15 µm, (d) 25 µm. CT = cilia tufts; CR = cilia rows.

FIGURE 4. SEM micrographs of Terebellides gracilis (Malm, 1874) from the Adriatic Sea (station SJ 007) (a) thoracic unciniger; (b) thoracic uncini; (c) abdominal unciniger; (d) abdominal uncini. Scales: (a) 25 µm, (b) 10 µm, (c) 30 µm, (d) 5 µm.

FIGURE 5. SEM micrographs of Terebellides mediterranea spec. nov., from the Adriatic Sea (station SJ 007) (a) anterior end, lateral view; (b) branchiae, latero-ventral view; (c) anterior end, latero-dorsal view (prostomial lobe and branchiae distorted); (d) detail of first thoracic chaetiger. Scales: (a) 1 mm, (b) 350 µm, (c) 1 mm, (d) 300 µm. LB = branchial lobe, CH = chaetiger, NP = nephridial pore.

FIGURE 6. SEM micrographs of Terebellides mediterranea spec. nov., from the Adriatic Sea (station SJ 007) (a) branchial lamellae; (b) detail of branchial ciliation; (c) detail of scales covering notochaetae; (d) geniculate chaetae of chaetiger 6. Scales: (a) 45 µm, (b) 15 µm, (c) 5 µm, (d) 35 µm. CR = cilia rows; CT = cilia tufts.

FIGURE 9. SEM micrographs of Terebellides stroemii Sars, 1835 from the Adriatic Sea (station LIM K 5) (a, b) anterior end, latero-ventral view, of two specimens; (c) papillar projections on edge of branchial lamellae; (d) ciliation of branchial lamellae. Scales: (a, b) 1 mm, (c) 100 µm, (d) 50 µm. CR = cilia rows; PP = papillar projection; star marking position of glandular region of fifth chaetiger.

FIGURE 10. SEM micrographs of Terebellides stroemii Sars, 1835 from the Adriatic Sea (station LIM K 5) (a) geniculate chaetae of chaetiger 6; (b) detail of geniculate chaeta capitium; (c) thoracic uncini; (d) detail of rostral teeth of thoracic uncini. Scales: (a) 50 µm, (b) 5 µm, (c) 10 µm, (d) 3 µm.

FIGURE 11. SEM micrographs of Terebellides stroemii Sars, 1835 from the Adriatic Sea (station LIM K 5) (a) detail of rostral teeth of thoracic uncini; (b) detail of nephridial opening of thoracic chaetiger 5; (c) ciliation of sensory button dorsal to thoracic notopodia; (d) detail of ciliation. Scales: (a) 5 µm, (b) 30 µm, (c) 10 µm, (d) 2.5 µm.

FIGURE 12. Methyl green staining of three Terebellides species found in the Adriatic Sea. LM pictures of anterior region in ventral (a – c) and lateral view (d – e). (a, d – e) T. mediterranea spec. nov., (b) T. gracilis, (c) T. stroemii.

FIGURE 13. Diagrammatic representation of several diagnostic body characters in three Adriatic Terebellides species. (a) Body staining patterns—following Schüller & Hutchings (2010) — in ventral view; chaetigers indicated in Arabic numbers, (b) Branchial and chaetiger characters in lateral view; segments indicated in Roman numbers. LBL = lower branchial lobes; UBL = upper branchial lobes; TM = tentacular membrane; LL = lower lobe; UL = upper lobe. Ventral (a) and lateral (b) lappets marked by bold lines.