Dipolydora armata Langerhans 1880

Dipolydora armata (Langerhans, 1880)

(Fig. 5)

Polydora armata Langerhans, 1880: 93 –94, pl. 4, fig. 5a–c; Blake & Kudenov 1978: 255 –258, fig. 43a–e. Dipolydora armata.— Blake 1996 (Part.): 196–198, fig. 4.36; Bick 2001: 178 –186, figs. 1–7; Williams 2001: 438 –442, figs 5,

6; Radashevsky & Nogueira 2003: 377–381, figs 1–7; Sato-Okoshi et al. 2008: 495–496, fig. 4. Dipolydora cf. armata.— Radashevsky & Fauchald 2000: fig. 6F.

Material examined. Queensland: AM W.45506, MI QLD 2447 (20); MIMB 28114, MI QLD 2447 (7).

Adult morphology. Up to 2.5 mm long, 0.3 mm wide for 30 chaetigers. Body and palp pigmentation absent. Prostomium incised anteriorly, extending posteriorly to end of chaetiger 2 as a low caruncle. Occipital antenna and eyes absent.

Chaetiger 1 with capillaries and small postchaetal lamellae in both rami. Winged notopodial capillaries gradually becoming longer, thinner and less numerous along midbody chaetigers. Notopodia from chaetigers 18– 24 onwards with up to three thin alimbate capillaries and 15 awl-like spines in a bundle (Fig. 5 E, F).

Chaetiger 5 with up to three dorsal superior winged capillaries, two heavy falcate spines, and four ventral winged capillaries (Fig. 5 A, B). Falcate spines with central main fang, large lateral tooth and apical structure appearing as wide cowling or third tooth on convex side of main fang; numerous fine bristles present on basis of teeth (Fig. 5 B).

Hooks in neuropodia from chaetiger 7, up to three in a series, accompanied by 1–2 inferior capillaries throughout body and 1–3 alternating capillaries in 5–10 posterior chaetigers (Fig. 5 C, D). Hooks bidentate; shaft slightly curved, without constriction (Fig. 5 C, D).

Branchiae from chaetiger 7 to chaetiger 11, fewer in small individuals, flattened, with surfaces oriented parallel to body axis, basally fused to notopodial postchaetal lamellae.

Pygidium small, cup-shaped, with only narrow dorsal gap or bilobed, divided by dorsal gap and ventral incision into two rounded lateral lobes.

Remarks. Dipolydora armata was originally described from Madeira Island by Langerhans (1880) as a borer of calcareous algae and has since been reported world-wide. In Australia, D. armata was reported from Western Australia (Augener 1914; Hartmann-Schröder 1979; Sato-Okoshi et al. 2008), Victoria and South Australia (Blake & Kudenov 1978; Hartmann-Schröder 1987; McDiarmid et al. 2004). Worms from Lizard Island appear identical to D. armata described from California (Hartman 1941; Blake 1996), the Marshall Islands (Woodwick 1964), Mediterranean (Bick 2001), Philippines (Williams 2001), Brazil and other localities (Radashevsky & Nogueira 2003, type material re-examined).

Dipolydora armata has been considered cosmopolitan, widespread in tropical and subtropical waters, and rare in boreal and temperate waters. Such a wide distribution of the same species seems, however, suspicious taking into account small size of adults (usually 3–4 mm long for 30–35 chaetigers), low fecundity (up to 100 eggs per brood), adelphophagy (larvae feeding on the nurse eggs inside egg capsule), low larval production, and very short time that larvae swim in the water (see Lewis 1998 for details of larval development in the species). Molecular investigation is certainly needed to confirm the conspecificity of the remote populations.

Habitat. In this study, adult D. armata were found boring into the shell of a gastropod Turbo sp. at about 14 m depth.

Distribution. Widespread in tropical and subtropical waters. Intertidal to 100 m. The species is herein reported for the first time from Queensland and the Great Barrier Reef.