Terebrasabella fitzhughi, Murray, Anna & Rouse, Greg W., 2007

Murray, Anna & Rouse, Greg W., 2007, Two new species of Terebrasabella (Annelida: Sabellidae: Sabellinae) from Australia, Zootaxa 1434, pp. 51-68: 57-61

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http://doi.org/ 10.5281/zenodo.175840

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Terebrasabella fitzhughi

sp. nov.

Terebrasabella fitzhughi   sp. nov.

Figures 5–8 View FIGURE 5 View FIGURE 6 View FIGURE 7 View FIGURE 8

Material examined. Type material: Holotype, AM W 29467 View Materials , Tasmania, Eaglehawk Neck, 43 °01'S 147 ° 55 'E, burrows in a clump of spirorbin polychaete tubes attached to intertidal rock. Paratypes, AM W 29468 View Materials (1), AM W 29469 View Materials (2 on SEM stub), Tasmania, Eaglehawk Neck, 43 °01'S 147 ° 55 'E, burrows in a clump of spirorbin polychaete tubes attached to intertidal rock;. All type specimens collected 3 April 1995 by G. W. Rouse.

Non-type material: AM W 29470 View Materials (3 in tubes with larvae), AM W 29471 View Materials (4 specimens, 2 with branchial crowns), AM W 29472 View Materials (5 larvae), AM W 29473 View Materials (2 juveniles on SEM stub), AM W 29474 View Materials (1 juvenile on SEM stub), AM W 29475 View Materials (1 juvenile on SEM stub) Tasmania, Eaglehawk Neck, 43 °01’S 147 ° 55 ’E, all specimens collected from burrows in a clump of spirorbin tubes attached to intertidal rock, 3 April 1995, by G.W. Rouse. AM W 29464 View Materials (1 specimen with branchial crown missing), AM W 29465 View Materials (1 specimen, posterior end only), Queensland, Outer Yonge Reef, Great Barrier Reef, 14 ° 36 'S 145 ° 38 'E, collected from rock and coral rubble with encrusting pink coralline algae, 9m, by P.A. Hutchings & P.B. Weate, 21 Jan 1977, Stn. 77 LIZ 51 – 3; AM W 29466 View Materials (1 specimen with small regrowing branchial radioles and posterior end missing), Queensland, Outer Yonge Reef, Great Barrier Reef, 14 ° 36 'S 145 ° 28 'E, collected from coral rubble from bommie, covered in Lithothamnion   and other algae, 30m, by P.A. Hutchings & P.B. Weate, 25 Jan 1977, Stn. 77 LIZ 57 – 1.

Description. Holotype sexually mature complete specimen (crown detached from body) with eight thoracic and three abdominal chaetigers. Body 2.6 mm long (including crown) ( Fig. 5 View FIGURE 5 A). Anterior chaetigers elongate, slender; abdomen swollen, sac-like with thin body wall. Branchial crown with two pairs of radioles and eight tapering pinnules off each radiole. Radiolar skeleton with two rows of cells, pinnular skeletons with single rows. Branchial lobes mid-dorsally fused, branchial skeleton present as single row of large cells. Radiolar appendages present (sensu Fitzhugh 2003), dorsal lips elongate, distally tapered, but no discernable internal extension of branchial skeleton, nor surrounding sheath ( Figs 5 View FIGURE 5 B–C). Ventral basal flanges present ( Figs. 5 View FIGURE 5 B, 5 C). Ventral lips absent. Palmate membrane, branchial hearts, radiolar flanges, stylodes and radiolar eyespots absent. Anterior peristomial collar dorsally indistinct. Posterior peristomial ring collar incised mid-dorsally; ventrally with elongate, triangular lappets ( Fig. 7 View FIGURE 7 A). Latero-ventral incision present on peristomial ring ( Fig. 7 View FIGURE 7 B). Peristomial segment without eyespots.

First chaetiger with broadly-hooded capillary notochaetae only, 2–3 in superior row, and 1–2 shorter ones in inferior row ( Figs 6 View FIGURE 6 A–B, 7 B). Chaetigers 2–6 with same types and numbers of notochaetae per fascicle as chaetiger 1. Notochaetae of last two thoracic segments, chaetigers 7–8, with 3–4 broadly-hooded chaetae ( Fig. 6 View FIGURE 6 C). Neurochaetae absent from chaetiger 1. Chaetigers 2–6 with 2–4 acicular homodont crested uncini ( Figs 6 View FIGURE 6 F, 7 D–E) and 1–2 companion chaetae with broad blade twisting at junction of, and perpendicular to, handle ( Figs 6 View FIGURE 6 E, 7 E–F) per neuropodial fascicle. Neurochaetae of chaetigers 7–8 single row of rasp-shaped avicular uncini. Uncini with five or more rows of small teeth above distal tooth, prominent breast and handle as long as dentate region ( Fig. 6 View FIGURE 6 G). Chaetiger 7 with 20–24 uncini per row; chaetiger 8 with ~ 11 per row ( Fig. 8 View FIGURE 8 A). Chaetigers 9–11 with 2–3 short narrowly-hooded neurochaetae per fascicle ( Figs 6 View FIGURE 6 D, 8 B). Abdominal notochaetae acicular uncini, with many rows of small teeth lying above main fang; teeth smaller, more numerous than those of thoracic acicular uncini, of equal size, and lie closely adpressed to main fang (= homodont-crested) ( Figs 6 View FIGURE 6 H, 8 C). Faecal groove indistinct on chaetigers 11 – 9, appearing to ascend to dorsal side from 8 th chaetiger; ‘grooved rings’ leading from dorsal to ventral on each of chaetigers 7–11. Faecal groove lined with elongate cilia along sides ( Fig. 8 View FIGURE 8 D). The anus opens dorsally, subterminally.

Variations/Remarks. There were different degrees of longitudinal body contraction and torsion exhibited in the range of specimens examined. Size range examined: 0.3 to 2.8 mm in length, including two juveniles of 0.3 mm and 0.57 mm long (no branchial crowns). Juveniles up to an eight-chaetiger stage had no crown developed and are ~ 0.3 mm in length ( Fig. 8 View FIGURE 8 E). Companion chaetae are absent, chaetigers 2–5 have a single acicular homodont-crested thoracic-type neurochaetal uncinus on some (not all) segments, chaetigers 6–7 have a few rasp-toothed avicular uncini as neurochaetae, and chaetiger 8 has 2–3 acicular homodont-crested abdominal-type uncini (with smaller teeth) dorsally. Another juvenile specimen of approximately 0.5 mm length has 11 chaetigers, but again, no branchial crown, one anterior achaetigerous segment, and two posterior achaetigerous segments. The rasp-toothed avicular uncini are absent from this specimen and all neurochaetal uncini on chaetigers 2–7 are of the acicular crested thoracic-type, whereas the uncini on chaetigers 8–11 are of the acicular homodont-crested abdominal-type, with a reversal from ventral to dorsal position from chaetigers 9 to 10. There also appears to be a greater number of these abdominal uncini embedded deeply into these last 2 chaetigers of the abdomen ( Fig. 8 View FIGURE 8 F). There is some variation in the numbers of the different types of chaetae.

Neuropodial companion chaetae vary in number (1–2) on thorax, and there does not appear to be any consistency in their number on any one chaetiger, even with size, although examination of more specimens may find some correlation of number with size. The number of rasp-shaped uncini on chaetiger 7 varies from ~ 12– 24 per row. On chaetiger 8 the number varies from 5–14 per row. SEM examination showed that there are basically three types of capillary chaetae: the broadly-hooded capillary chaetae present in the superior position of the thoracic notopodia ( Fig. 7 View FIGURE 7 C); the shorter broadly-hooded capillary notochaetae in the inferior position of the thoracic fascicles ( Fig. 7 View FIGURE 7 C) and the long, narrowly-hooded capillary chaetae present in abdominal fascicles ( Fig. 8 View FIGURE 8 B). However, some specimens also possess in the thoracic fascicle on chaetiger 8, a smaller “whiptail” capillary chaeta and a minute “setule” in a superior position ( Fig. 8 View FIGURE 8 G), both of which may be newlyemerging notochaetae.

While we could discern no difference between the specimens of T. fitzhughi   sp. nov., from Tasmania and those from the northern Great Barrier Reef, the great distance separating them and the fact that Terebrasabella   brood larvae ( Fitzhugh & Rouse 1999) suggests they may represent more than one species. Further collections and analysis of molecular sequence data may resolve this issue.

Distribution. Recorded from Eaglehawk Neck, Tasmania, and also from Outer Yonge Reef on the Great Barrier Reef, Queensland, Australia.

Etymology. Terebrasabella fitzhughi   sp. nov., is named after Dr Kirk Fitzhugh, in recognition of his continuing and invaluable contribution to sabellid taxonomy and systematics.