Prionospio cf. tatura Wilson, 1990

Radashevsky, Vasily I., 2015, Spionidae (Annelida) from Lizard Island, Great Barrier Reef, Australia: the genera Aonides, Dipolydora, Polydorella, Prionospio, Pseudopolydora, Rhynchospio, and Tripolydora, Zootaxa 4019 (1), pp. 635-694 : 673-675

Prionospio cf. tatura Wilson, 1990

( Fig. 25 )

Prionospio tatura Wilson, 1990: 260 –263, figs 48–56.

Material examined. Queensland: AM W.45265, MI QLD 2330 (1); AM W.45266, MI QLD 2440 (1).

Adult morphology. Up to 10 mm long, 0.2 mm wide for 55 chaetigers. Pigmentation in life absent. Prostomium narrow, rounded anteriorly, extending posteriorly to end of chaetiger 1 as a low caruncle ( Fig. 25 A, B). Seven small knobs with short non-motile sensory cilia present on frontal and fronto-lateral edges of prostomium. Occipital antenna absent. Two pairs of small red eyes arranged trapezoidally comprising one pair of median eyes and one pair of lateral eyes situated anteriorly and set wider apart. Nuchal organs U-shaped ciliary bands on lateral sides of caruncle. Posterior dorsal parts of peristomium fused to notopodial lamellae of chaetiger 1 forming small ear-shaped structures. Palps as long as 10–15 chaetigers, with frontal longitudinal groove lined with fine cilia, short transverse bands of cilia regularly arranged on inner surface, and narrow longitudinal band of cilia running on outer fronto-lateral side along frontal groove on distal half of palp; cilia of inner transverse bands beating towards distal end of palp, while cilia of outer longitudinal band beating towards frontal groove.

Chaetiger 1 with short capillaries and small postchaetal lamellae in both rami; notopodial lamellae fused to posterior dorsal parts of peristomium forming small ear-shaped structures. Notopodial lamellae of chaetigers 3 and 4 subtriangular, slightly larger than on other chaetigers; lamellae gradually becoming smaller and rounded on succeeding chaetigers. Neuropodial postchaetal lamellae of chaetiger 2 rounded, not elongated ventrally.

Low single dorsal folds present from chaetigers 10–12 to chaetigers 13–23. Prominent dorsal crests, lateral pouches and ventral flaps absent.

Sabre chaetae in neuropodia from chaetigers 11–12, usually one, occasionally two in a group, very thin on first chaetiger, full-sized from chaetigers 12–13, alimbate, with fine granulation on distal part ( Fig. 25 D).

Hooks in notopodia from chaetigers 25–28, 1– 3 in a tuft among capillaries. Hooks in neuropodia from chaetigers 13–15, up to seven in a series, accompanied by inferior sabre chaetae and 1–4 alternating capillaries throughout. Alternating capillaries up to 2.5 times as long as hooks, in anterior neuropodia with narrow limbation, in posterior neuropodia thin, alimbate ( Fig. 25 E). Hooks multidentate, with 3–4 pairs of very thin upper teeth arranged in two vertical rows above main fang, with inner and outer hoods; shaft slightly bent ( Fig. 25 F).

Up to eight pairs of branchiae on chaetigers 2–9, fewer in small individuals, all apinnate, robust, flattened, with surfaces oriented perpendicular to body axis, longitudinal bands of cilia running along inner and outer edges ( Fig. 25 A). Branchiae full-sized on chaetiger 3, up to two times as long as notopodial lamellae, and then gradually becoming shorter on succeeding chaetigers. Afferent and efferent blood vessels interconnected by numerous radial capillaries giving branchiae annulate appearance.

Nototrochs present on branchiate chaetigers.

Pygidium with long and thin middorsal cirrus and one pair of very short ventral cirri or knobs ( Fig. 25 C).

Oesophagus extending through chaetigers 7–9. Ventral buccal bulb below oesophagus extending to end of chaetiger 1. Gizzard-like structure in digestive tract absent.

Main dorsal blood vessel transformed into gut sinus in anterior part of midgut. Soft heart body up to 20 µm in diameter extending inside main dorsal vessel from level of chaetigers 3–4 to chaetigers 10–11. Blood red, without globules or other elements.

Nephridia in chaetigers 4–6, greenish in life.

Reproduction. The only two individuals collected, in August 2013, were immature.

Remarks. Prionospio with only apinnate branchiae1 from around Australia were referred to P. cirrifera Wirén, 1883 by Blake & Kudenov (1978), Hutchings & Rainer (1979), Hutchings & Murray (1984), and Hartmann- Schröder (1985, 1989, 1990, 1991). Wilson (1990) reassessed all southern Australian records of this species and referred them to three new species, P. tatura , P. wambiri and P. yuriel . He also concluded that additional species might be expected to occur in northern Australia, and P. cirrifera is unlikely to occur in Australian waters.

Prionospio tatura was originally described from estuarine localities in Port Phillip Bay, Victoria, and also recorded from Paynesville, Victoria, and Nornalup, Western Australia, by Wilson (1990). Adults were characterized by the prostomium broadly-rounded anteriorly, two pairs of small red eyes, caruncle extending to end of chaetiger 1, chaetiger 1 with capillaries in both rami, chaetiger 2 with rounded neuropodial lamellae not elongated ventrally, up to 11 pairs of apinnate branchiae from chaetiger 2, branchiae on chaetiger 2 two-three times as long as notopodial lamellae, sabre chaetae in neuropodia from chaetigers 9–12, and hooded hooks with four pairs of upper teeth beginning in notopodia from chaetigers 23–38 and in neuropodia from chaetigers 13–17. Adult P. tatura appear very similar to those of P. wambiri and P. y ur i el and differ from them in the shape of prostomium, length of branchiae and arrangement of sabre chaetae and hooks in neuropodia ( Wilson 1990: Table 2).

Adult Prionospio from Lizard Island with only apinnate branchiae fit the original description of P. tatura . They slightly differ, however, in that worms from Lizard Island have shorter branchiae, up to two times as long as notopodial lamellae, while those from Victoria have branchiae up to three times as long as notopodial lamellae. Moreover, coral reef conditions around Lizard Island differ significantly from estuarine conditions in the type locality of P. tatura . At this point, however, no character was found to distinguish the Lizard material as a separate species. It is therefore herein referred to as P. cf. tatura .

Habitat. In this study, adults of P. cf. tatura were found in coral sand at 14–15 m depth.

Distribution. Australia: Victoria, Western Australia,? Queensland.

Figures

FIGURE 25. Prionospio cf. tatura. A, C, D – F—AM W. 45266; B—AM W. 45265. A, B. Anterior ends, dorsal view; C. Posterior end, dorsal view; D – F. Neurochaetae from median chaetiger; D. Sabre chaeta; E. Alternating capillary; F. Multidentate hooded hook. Scale bars: A – C— 50 µm.