Sabellastarte

Capa, María & Murray, Anna, 2015, A taxonomic guide to the fanworms (Sabellidae, Annelida) of Lizard Island, Great Barrier Reef, Australia, including new species and new records, Zootaxa 4019 (1), pp. 98-167 : 151-152

Sabellastarte sp.

( Fig. 22A–D )

Material examined. Queensland, Lizard Island: AM W.44361, AM W.44362, AM W.44462 (juvenile), AM W.44463, MI QLD 2401.

Other material examined. AM W.9168, Heron Island, 23°26′S, 151°54′E, under coral slab, 8 m, 28 Jul 1976, identified as Sabellastarte pectoralis ( Quatrefages, 1866) by P. Knight-Jones.

Description of material examined. Specimens up to 2.5 mm long, 1.1 mm wide, with eight thoracic and numerous abdominal chaetigers. Live specimens possess orange radiolar crowns with several thin irregular brown transverse bands on rachis and pinnules ( Fig. 22A ). Preserved specimens lose orange pigment and are brownish with darker bands on the radiolar crown. Body with small scattered brown spots, conspicuous interramal eyes on thoracic and abdominal chaetigers and, in some specimens, additional spots on dorsal and ventral edges of parapodia ( Fig. 22C ). Radiolar crown with lobes spiralling with up to one whorl and involuted ventrally. Dorsal basal flanges rounded, ventral basal flanges absent. Basal membrane vestigial, radioles of some specimens interdigitating and giving appearance of two rows ( Fig. 22A ). Radioles with smooth margins, flanges absent. Eight vacuolated cells in cross-section supporting radioles basally. Radiolar eyes absent. Dorsal lips with long radiolar appendages; one pair of pinnular appendages. Ventral lips and parallel lamellae present; ventral sacs inside the crown. Posterior peristomial ring collar with dorsal margins fused to faecal groove, with shallow curved notches and pockets on each side; ventral lappets short and rounded, separated by a midventral incision. Glandular ridge on anterior chaetigers absent. Ventral shields in contact with neuropodial tori; first one with anterior margin Mshaped. Interramal eyespots present in thorax and abdominal segments. Collar chaetae elongate narrowly-hooded, in oblique rows. Following thoracic chaetigers with conical notopodia with superior elongated narrowly-hooded chaetae and inferior spine-like chaetae. Thoracic neuropodial uncini avicular, with about 8 rows of small similarlysized teeth over main fang, covering half its length, well developed breast and short handle. Companion chaetae absent. Abdominal chaetigers with conical neuropodia, with superior elongated narrowly-hooded chaetae and inferior spine-like chaetae, in a C-shaped arrangement. Abdominal notopodial uncini similar to thoracic. Pygidium bilobed with lateral eyespots. Pygidial cirrus absent. Tube with a thick layer of fine sand attached in the exposed anterior end.

Remarks. A recent revision of Sabellastarte aiming to establish species boundaries for members of this genus by combining morphological and molecular data ( Capa et al. 2010), provided evidence that although there is a continuous distribution of Sabellastarte along the coast of Australia, at least three species are present, and only one of them, Sabellastarte australiensis (Haswell, 1884) , has been formally described. Morphological differences between these species are difficult to establish, because intraspecific and interspecific variation overlap. Moreover, that study included no specimens collected from the Great Barrier Reef, so it is uncertain if the Lizard Island specimens belong to the northern lineage, so far reported only from the Northern Territory, or to the New South Wales –southern Queensland lineage (most probably described as Sabellastarte australiensis ) or to a different one altogether. Knight-Jones & Mackie (1998) reported Sabellastarte pectoralis ( Quatrefages, 1866) , a species originally described from Mauritius, from Heron Island (AM W.9168), the only Sabellastarte specimens cited so far from the Great Barrier Reef. Diagnostic features of S. pectoralis , as for other congeners, remain obscure, and assigning the specimens described herein to this species is risky.

Habitat. Under stones and coral rubble on reef crest at shallow depths.

Distribution. Unknown, since the Australian species of Sabellastarte are not well defined.

Figures

FIGURE 22. A – D. Sabellastarte sp. A. Live specimens with radiolar crown exposed outside the tube; B. Dorsal view, showing collar dorsal margins fused to faecal groove forming pockets at either side (white arrow); radiolar lobes with dorsal basal flanges (black arrow); C. Same, lateral view, showing the pigmentation pattern, including the interramal eyespots (white arrow) and the arrangement in a C shape row of inferior abdominal chaetae (black arrows); D. Juvenile showing a different pigmentation pattern to adults; E – F. Sabellomma cupoculata. A. Incomplete specimen, showing pigmentation pattern and rows of ocelli along radiolar margins (arrows); F. Detail of radioles and ocelli (arrows); G – J. Stylomma palmatum, live specimen; G. Anterior end showing the rigid radiolar crown with elongated basal lobes; H. Detail of radiolar tip with unpaired subdistal stalked compound eyes (arrow); I. Anterior abdominal chaetigers, with anterior collar margin incised midventrally and thoracic tori almost in contact with ventral shields; J. Detail of basal lobes, dorsally, showing the flanges joined dorsally with a press stud structure (arrow).