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

Terebrasabella fitzhughi sp. nov.

Figures 5–8

Material examined. Type material: Holotype, AM W29467, Tasmania, Eaglehawk Neck, 43°01'S 147°55'E, burrows in a clump of spirorbin polychaete tubes attached to intertidal rock. Paratypes, AM W29468 (1), AM W29469 (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 W29470 (3 in tubes with larvae), AM W29471 (4 specimens, 2 with branchial crowns), AM W29472 (5 larvae), AM W29473 (2 juveniles on SEM stub), AM W29474 (1 juvenile on SEM stub), AM W29475 (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 W29464 (1 specimen with branchial crown missing), AM W29465 (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 W29466 (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 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 B–C). Ventral basal flanges present ( Figs. 5 B, 5C). 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 A). Latero-ventral incision present on peristomial ring ( Fig. 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 A–B, 7B). 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 C). Neurochaetae absent from chaetiger 1. Chaetigers 2–6 with 2–4 acicular homodont crested uncini ( Figs 6 F, 7D–E) and 1–2 companion chaetae with broad blade twisting at junction of, and perpendicular to, handle ( Figs 6 E, 7E–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 G). Chaetiger 7 with 20–24 uncini per row; chaetiger 8 with ~11 per row ( Fig. 8 A). Chaetigers 9–11 with 2–3 short narrowly-hooded neurochaetae per fascicle ( Figs 6 D, 8B). 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 H, 8C). Faecal groove indistinct on chaetigers 11–9, appearing to ascend to dorsal side from 8th chaetiger; ‘grooved rings’ leading from dorsal to ventral on each of chaetigers 7–11. Faecal groove lined with elongate cilia along sides ( Fig. 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 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 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 C); the shorter broadly-hooded capillary notochaetae in the inferior position of the thoracic fascicles ( Fig. 7 C) and the long, narrowly-hooded capillary chaetae present in abdominal fascicles ( Fig. 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 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.

Figures

FIGURE 5. Terebrasabella fitzhughi sp. nov., Paratype AM W 29468. A. Whole specimen, lateral view. B. Medial view of right side of branchial crown, with indication of branchial and radiolar skeletons. C. Medial view of left side of branchial crown. DOR = dorsal side, VEN = ventral side, vbf = ventral basal flange, dl = dorsal lip. Scales: A = 0.5 mm; B & C = 0.1 mm.

FIGURE 6. Terebrasabella fitzhughi sp. nov., chaetae (specimen destroyed for chaetal drawings). A. Thoracic superior notochaeta, chaetiger 1. B. Thoracic inferior notochaeta, chaetiger 1. C. Thoracic notochaeta, chaetiger 7. D. Abdominal neurochaeta. E. Companion chaeta, chaetiger 3. F. Neurochaetal uncinus, thoracic chaetiger 3. G. Thoracic neurochaetal uncinus, chaetiger 7. H. Abdominal notochaetal uncinus, chaetiger 10. Scales: A – H = 0.01 mm.

FIGURE 7. Terebrasabella fitzhughi sp. nov., S. E. M. photographs, AM W 29469. A. Anterior end, ventral view. B. Anterior end, lateral view. C. Notochaetal fascicle, chaetiger 2. D. thoracic neurochaetal uncini, chaetiger 3. E. Neurochaetal fascicle, 2 companion chaetae and 4 uncini, chaetiger 3. F. Thoracic neurochaetal uncini and companion chaeta, chaetiger 4.

FIGURE 8. Terebrasabella fitzhughi sp. nov., S. E. M. photographs, AM W 29469 A. Row of rasp-shaped uncini from (thoracic) chaetiger 7. B. Abdominal capillary neurochaetae and notochaetal uncini, chaetiger 11. C. Three abdominal notochaetal uncini, chaetiger 11. D. Ciliated faecal groove. AM W 29473 E. Anterior end, juvenile. AM W 29474 F. Abdominal chaetigers, juvenile specimen. AM W 29469 G. Chaetiger 8, notochaetal fascicle, showing capillary chaetae, and newly-emerging chaetae.