Terebellides narribri Hutchings and Peart, 2000

Schüller, Myriam & Hutchings, Pat A., 2010, New insights in the taxonomy of Trichobranchidae (Polychaeta) with description of a new Terebellides species from Australia, Zootaxa 2395, pp. 1-16 : 11-14

Terebellides narribri Hutchings and Peart, 2000

Figures 5–7

Terebellides narribri – Hutchings and Peart 2000: 247 –254, Figs 8c–d, 11, 13c, 15a–f, Table 3

Material examined. Holotype. AM W5048 (1 specimen, gravid, part on SEM stub): Moreton Bay, 4 km S of SW Rocks, Peel Island, Queensland, 2730’ S 15321 ’ E, 1971, 5 m, sand mud and shell.

Additional material examined. AM W24057 (6 specimens, some gravid, part on SEM stub): New South Wales, Towlers Bay North, Pittwater, 3337.30’ S 15117 ' E, Apr 1992; AM W24884 (30 specimens): New South Wales, Port Hacking, 344.6’ S 1516.25’ E, 27 Oct 1994; AM W21652 (1 specimen, gravid): New South Wales, south of airport runway extension, Botany Bay, 3358.7’ S 15111.9’ E, 7 Apr 1992; AM W23840 (2 specimens, gravid): New South Wales, Pittwater, 3333.50’ S 15118.43’ E, 20 Oct 1994; AM W11097 (2 specimens, gravid), AM W12243 (1 specimen): Tasmania, Huon River, 432' S 14617 ' E, 5 Feb 1976.

Description. Holotype ovigerous female with coelomic oocytes ( Figs 5 a, b), complete, 11mm long for 45 segments. Additional specimens 0.4–3.1 mm long, some gravid. Colour pale yellow to reddish brown in preserved specimens.

Prostomium and tentacular membrane compact and slightly expanded. Buccal tentacles of two kinds, uniformly tapered with expanded tips. Upper lip almost completely hidden, lower lip expanded. Second segment smaller than subsequent segments, partially covered by 3rd segment ( Fig. 5 a). Lateral lappets on segments 1–5, best developed on 5th segment ( Fig. 5 a). Ventral glandular bands and glandular areas around parapodia absent. Nephridial papillae inserted dorsally to notopodia of segments 3, 6, and 7 ( Fig. 5 a).

Branchiae arising as single structure dorsally on segments 3 and 4, consisting of 4 distinct lobes, fused to each other for about half their length ( Fig. 5 c). Anterior ones broader and longer than posterior ones. Anterior projecting (5th lobe) present. All lobes composed of tightly packed lamellae, filamentous tips absent ( Fig. 5 c).

Notopodia 18 pairs, present on segments 3–20. First one well developed, only slightly smaller than subsequent ones. Chaetae arranged in 2 tiers (Fig. 6a), narrow - winged, finely pointed capillaries. Shaft consisting of numerous compact filaments with tips slightly splayed so that surface appears plumose (Figs 6a, b). Thoracic neuropodia starting from segment 8 (chaetiger 6), sessile pinnules. First neuropodia with ~ 5 acicular hooks with pointed tips and sharply bent shaft. Subsequent neuropodia with varying number of longhandled uncini (about 13 uncini in holotype), number often increasing from anterior to posterior. Uncini with a dental formula of MF: 3–4:7:~:~, their head strongly crested, teeth very compact and flattened and main fang with surface striations ( Figs 5 d & 6c–e).

Abdomen with more than 20 segments (25 in holotype). Abdominal neuropodia erect pinnules ( Fig. 5 b) with>30 avicular uncini ( Figs 5 e & 6f–h), with a dental formular of MF:4–5:6–7:~~:~~. Abdomen terminating in blunt pygidium without appendages ( Fig. 5 f).

FIGURE 6. Terebellides narribri a–e AM W24057 a—Thoracic notopodia (14th chaetiger) with 2 rows of notochaetae, b—Close up notochaetae, c—Thoracic neuropodial torus from chaetiger 14, d—Lateral view of thoracic neurochaetae, e—Head on view of thoracic neurochaetae, f—Posterior abdominal neuropodial torus, g–h—Head on view of posterior abdominal uncini. Scales: a-20 µm, b-2 µm, c-20 µm, d-3 µm, e-3 µm, f-10 µm, g-1 µm, h-1 µm

The staining with MG results in a compact green coloration of the first 5 segments. The 5th segment is characterized by large oval to “J-shaped whitish glandular regions laterally on both sides of the segment ( Fig. 7 ). From segment 6 on, only the anterior half of the segments is stained resulting in striped pattern which gradually fades posteriorly and vanishing by about segment 12. The ventro-anterior margins of segments 1–6 are pronounced as are the thoracic noto- and neuropodia with this staining.

Remarks. The presented study detected two species among the specimens housed at the Australian Museum in Sydney previously identified as T. narribri . The clarification of characters and separation of the species T. narribri and T. jitu , resulted in additions to the original description of T. narribri by Hutchings and Peart (2000). About half the specimens observed could be designated to T. jitu , without doubt, including two original paratypes of T. narribri (AM W7059 and AM W23828). Treating the morphospecies of the holotype as T. narribri the species is now characterized by well developed first notopodia. Also, the white oval glandular patches in chaetiger 3 (segment 5) stated as a variation in some specimens by Hutchings and Peart (2000) become a key character of T. narribri that clearly separates it from the new species T. jitu . This required a re-assessment of all the material formerly identified as T. narribri and the separation of the new species T. jitu .

Figures

FIGURE 5. Terebellides narribri holotype AM W 5048 a—anterior region, b—abdominal coelomic oocytes, cbranchiae, d—detail head of thoracic uncinus, e—detail head of abdominal uncinus, f—pygidium and posterior segments [* — position of nephridial papillae, arrows—fifth branchial lobe]

FIGURE 7. Methyl green staining of Terebellides narribri holotype AM W 5048, anterior region in lateral view