Prionospio aucklandica Augener 1923

Prionospio aucklandica Augener, 1923

(Fig. 11)

Prionospio aucklandica Augener, 1923: 69 –70, fig. 24; 1926: 158–159, fig. 1; Wilson 1990: 247. Prionospio (Aquilaspio) aucklandica.— Blake & Kudenov 1978: 221 –222, fig. 25 b–g.

Aquilaspio aucklandica.— Foster 1971 (Part.): 106; Hutchings & Turvey 1984: 8 –9.

Material examined. Queensland: AM W.45236, MI QLD 2330a (1); MIMB 28117, MI QLD 2330a (1); AM W.47866, MI QLD 2373 (6); MIMB 28118, MI QLD 2373 (4); AM W.45237, MI QLD 2410 (1); AM W.45238, MI QLD 2431 (1); AM W.45509, MI QLD 2435 (1); AM W.47867, MI QLD 2447 (1).

Adult morphology. Up to 16 mm long, 0.4 mm wide for 100 chaetigers. Pigmentation in life absent. Prostomium narrow, rounded anteriorly, extending posteriorly to end of chaetiger 1 as a prominent caruncle (Fig. 11 A); posterior part of caruncle pressed into anterior part of chaetiger 2 towards level of nototroch, thus caruncle appearing as extending until middle of chaetiger 2. Small knobs with short non-motile cilia present on frontal and fronto-lateral edges of prostomium. Occipital antenna absent. Two pairs of small red eyes arranged trapezoidally; lateral eyes situated anteriorly and set wider apart, slightly larger than median eyes. Nuchal organs U-shaped ciliary bands on lateral sides of caruncle. Posterior dorsal parts of peristomium fused to notopodial lamellae of chaetiger 1 forming prominent 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 with narrow longitudinal band of cilia running on outer fronto-lateral side along frontal groove on distal half; 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 in neuropodia and postchaetal lamellae in both rami; notopodial postchaetal lamellae fused to posterior dorsal parts of peristomium forming ear-shaped structures; notochaetae absent. Notopodial lamellae of chaetigers 2–4 triangular, small on chaetiger 2, largest on chaetiger 4; lamellae smaller and rounded on succeeding chaetigers. Lower part of neuropodial postchaetal lamellae of chaetiger 2 rounded to pointed and elongated ventrally. Dorsal crests, lateral pouches and ventral flaps absent.

Sabre chaetae in neuropodia from chaetiger 10, 1– 2 in a tuft, with narrow wing and fine granulation on distal half of shaft.

Hooks in notopodia from chaetigers 23–38, 1– 2 in a group among capillaries. Hooks in neuropodia from chaetigers 16–21, up to five in a series, accompanied by alternating capillaries and inferior sabre chaetae throughout. Hooks with three pairs of small upper teeth arranged in two vertical rows above main fang, with inner and outer hoods; shaft slightly curved.

Three pairs of pinnate branchiae on chaetigers 2–4 in adults; branchiae of chaetiger 2 up to three times longer than those of chaetiger 3; branchiae of chaetigers 4 1.5 times shorter than those on chaetiger 3; small individuals with two pairs of pinnate branchiae on chaetigers 2 and 3; median-sized individuals with three pairs of branchiae of which first and second pairs pinnate and third pair smooth, apinnate (Fig. 11 B–D). All branchiae cylindrical, with longitudinal bands of cilia along inner and outer sides; flattened digitiform pinnae regularly arranged along lateral and posterior sides in 2–5 rows (Fig. 11 A). Afferent and efferent branchial blood vessels interconnected by circular capillaries which forming loops inside branchial pinnae.

Nototrochs with short cilia present between branchial bases on chaetigers 2 and 3. No other ciliation on chaetigers.

Pygidium with thin, long middorsal cirrus and one pair of short and thick ventral cirri; all cirri bearing long non-motile sensory cilia.

Oesophagus extending through 6–8 anterior chaetigers. Ventral buccal bulb below oesophagus extending to end of chaetiger 1. Gizzard-like structure in digestive tract absent.

Heart body up to 20 µm in diameter extending inside main dorsal vessel from level of chaetigers 3–4 through chaetigers 11–14. Blood red, without globules or other elements.

Nephridia in chaetigers 4–6, greenish in life.

Reproduction. All individuals of P. aucklandica collected around Lizard Island Group in August 2013 were immature.

Remarks. Prionospio aucklandica was originally described from Port Ross, Auckland Island, New Zealand by Augener (1923, 1926). The only two types of the species have never been re-described and were apparently lost. The most characteristic features of the species reported by Augener (1923, 1926) included three pairs of pinnate branchiae on chaetigers 2–4, sabre chaetae from chaetiger 10 and hooded hooks in neuropodia from chaetiger 19. Foster (1971) noticed that similar features were also present in P. krusadensis described from Krusadai Island, India by Fauvel (1929) and considered the latter species to be a junior synonym of Aquilaspio aucklandica 1.

Blake & Kudenov (1978) identified Prionospio (Aquilaspio) aucklandica for the first time from Australia: New South Wales and Victoria. They reported that worms had notochaetae on chaetiger 1 and dorsal crest on chaetiger 7. Hutchings & Turvey (1984) reported Aquilaspio aucklandica from South Australia and noticed ventrally acuminate neuropodial lamellae of chaetiger 2, and absence of notochaetae on chaetiger 1 and dorsal crest on chaetiger 7. Wilson (1990) reported Prionospio aucklandica from Western Australia and noticed that his material agreed closely with the description by Hutchings & Turvey (1984). He also re-examined Blake & Kudenov’s material and confirmed the absence of dorsal crests in those specimens.

1. Foster (1971) established a new genus Aquilaspio to encompass Prionospio members with two to four pairs of only pinnate branchiae beginning from chaetiger 2. The taxon was treated as genus or a subgenus by following authors but Wilson (1990) and Sigvaldadóttir (1998) placed those species back into Prionospio sensu lato (see above Remarks to the Prionospio sensu lato section). In the absence of a phylogenetic hypothesis about relationships of the Prionospio members and support of monophyly of Aquilaspio, it would be however practical to recognize non-taxonomic groups of species based on shared simple diagnostic characters. One of those groups may include Prionospio members with three pairs of only pinnate branchiae beginning from chaetiger 2 and be referred to as the Prionospio aucklandica group of species.

Prionospio with three pairs of pinnate branchiae from Lizard Island fit the descriptions of P. aucklandica by Hutchings & Turvey (1984) and Wilson (1990) and are referred to this species. They are characterized by two pairs of small eyes, three pairs of pinnate branchiae on chaetigers 2–4, sabre chaetae consistently starting from chaetiger 10, and by the absence of dorsal crests, folds and lateral pouches. Conspecificity of worms with three pairs of only pinnate branchiae from Auckland Island, New Zealand, Australia and Krusadai Island, India, should be verified in a future study.

Habitat. In this study, adult P. aucklandica were found in coral sand and rubble at 6–16 m depth. Distribution. Auckland Island, New Zealand; possibly all around Australia. This is the first report of P. aucklandica from Queensland.