Terebellides mira, Schüller, Myriam & Hutchings, Pat, 2013

Schüller, Myriam & Hutchings, Pat, 2013, New species of Terebellides (Polychaeta: Trichobranchidae) from the deep Southern Ocean, with a key to all described species, Zootaxa 3619, pp. 1-45 : 16-19

Terebellides mira sp.n.

Figs 9 , 10 , 11

Holotype: ANDEEP II, St. 133-5, GKG [drawing, MG photo] (ZMH-26009)

Paratype: ANDEEP II, St. 133-5, GKG [MG photo, SEM, stub MI539 & MI540] (AM W38719) Description: (Based on both holotype and paratype)

Holotype 15 mm in length, 1 mm in width, complete with 28 abdominal chaetigers ( Fig. 9 ).

Head region: Tentacular membrane largely expanded, horseshoe shaped. Lower lip rectangular, expanded, but not distinctly folded upwards. Tentacles only short and simple on the outer margins of the tentacular membrane, minute papillae apparent on tentacular membrane with MG staining.

Branchiae: Branchial lobes free from each other, lamellae broad, loose, only few present, with filamentous tips. Posterior branchial lobes missing. Fifth branchial lobe absent. Annulation of branchial stem present, stem very long, longer than actual branchial lobe ( Figs 9 , 10 A, B, D, 11).

Anterior chaetigers: Notopodia from segments 3–20, 18 pairs, all notopodia of similar size ( Fig. 10 A). Notochaetae, capillaries, graded lengths within fascicle with slightly inflated thecae ( Fig. 10 E, F). First neuropodia on thoracic segment 8 (chaetiger 6) with geniculate hooks, about 7 per side, strongly protruding, declining in size within a torus from dorsal to ventral ( Fig. 10 G), curved with inflated bases and short pointed tips, base of curve with minute teeth. Subsequent neurochaetae long handled hooks with multiple teeth above a main fang in thoracic segments, and abdominal uncini numerous within a torus and with elongate hooks, main fang completely covered by numerous elongate accessory teeth ( Fig. 10 H).

Lateral lappets: Present from TC-1–7, with TC-1=3>2=4>5=6=7 or TC-1=2<3=4>5<6=7.

Ventral pads: Ventrum glandular to chaetiger 11, distinct raised ridges extend across the ventrum with elevated anterior margins.

Nephridial papillae: Present on segments 3, 4, 6, 7, elongate papillae posterior dorsal to notopodia.

MG staining pattern 9 ( Figs 2 , 11 ): Anterior solidly stained with thin white “glandular” region lateral in segment 5 (TC-3), TC-4 more solidly stained than all others, striped from TC-5 on, TC-12–16 only with very fine stripe. White bands may be present in TC-9–11, anterior margins not pronounced. Neuropodia not stained, notopodia can stain initially and fade quicker than remaining body.

Pygidium: 2 blunt lateral papillae ( Fig. 9 B).

Remarks: Terebellides mira sp.n., is characterised by having branchial lobes completely free of each other, all notopodia of similar size and lateral lappets on chaetiger 1–7 and a large number of geniculate hooks on chaetiger 6. Terebellides mira sp.n., belongs to a group of Terebellides which have the first thoracic chaetiger only slightly smaller than subsequent chaetigers but with distinct notopodial lobe present and branchial lamellae few in number and loosely packed ( Terebellides lobatus Hartman & Fauchald, 1971 , Terebellides diva Schüller & Hutchings, 2012 and Terebellides gingko Schüller & Hutchings, 2012 ), but can be distinguished from these species by having filamentous tips to the branchial lobes and lateral lappets to thoracic chaetiger 7. For more details see the key.

Habitat: Western Weddell Sea upper continental slope in 1166 m. Known only from type locality.

Etymology: The specific name mira refers to the first variable star ever discovered in the constellation Cetus which represents the Sea Monster and was discovered in 1596 by David Fabricius.

Figures

FIGURE 2. MG staining patterns of observed species, adapted and extended from Schüller & Hutchings (2010).

FIGURE 9. Terebellides mira sp. n. (ZMH- 26009), A—anterior thorax, B—pygidium.

FIGURE 10. Terebellides mira sp. n. (AM W 38719), A—anterior thorax, lateral, B—branchiae, C—branchial lamellae, detail, D—anterior thorax, ventral, E—median thoracic notopodium, F—thoracic notochaetae, detail, G—geniculate neuropodial hooks on TC- 6, H—abdominal uncini of median neuropodium.

FIGURE 11. Terebellides mira sp. n. MG-staining, A—thorax, dorsal, B—thorax, lateral, C—anterior thorax, ventral, D—thorax, ventral (ZMH- 26009), E—anterior chaetigers, lateral, F—anterior thorax, dorso-lateral, G—anterior thorax, ventro-lateral (AM W 38719).