Prionospio kulin 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 : 660-663

Prionospio kulin Wilson, 1990

( Figs 16 , 17 )

Prionospio kulin Wilson, 1990: 253 –256, figs 24–33.

Material examined. Queensland: AM W.45248, MI QLD 2330b (2); AM W.45249, MI QLD 2360; MIMB 28120, MI QLD 2360 (1); AM W.47865, MI QLD 2373 (12); MIMB 28121, MI QLD 2373 (7); AM W.45250, MI QLD 2374 (2); AM W.45254, MI QLD 2410 (2); MIMB 28122, MI QLD 2410 (2); AM W.45255, MI QLD 2410 (4); MIMB 28123, MI QLD 2410 (4); AM W.47461, MI QLD 2391 (1); AM W.45233, MI QLD 2405 (1); AM W.45257, MI QLD 2439 (1); AM W.45258, MI QLD 2440 (1); MIMB 28124, MI QLD 2440 (1); AM W.45507, MI QLD 2447 (2); AM W.45511, MI QLD 2447 (1); AM W.45252, MI QLD 2382 (1). Northern Territory: AM W.47462 (4), MIMB 28125 (3), Bullocky Point, Fannie Bay, Darwin, 12.4356°S, 130.8323°E, muddy sand intertidal, 3 Sep 2013; MIMB 28126 (1), same locality, 5 Sep 2013.

Adult morphology. Up to 32 mm long, 0.5 mm wide for 100 chaetigers. Pigmentation in life absent. Prostomium bell-shaped, wide anteriorly, extending posteriorly to end of chaetiger 2 as a distinct caruncle ( Fig. 16 A). Seven small knobs with short non-motile sensory cilia present on frontal and fronto-lateral edges of prostomium. Occipital antenna absent. Two pairs of eyes arranged trapezoidally; lateral eyes small, situated anteriorly and set wider apart; median eyes small in individuals up to 0.2 mm wide, large, crescent-shaped in larger worms ( Fig. 16 B–D); eyes red in living and fixed specimens. Nuchal organs U-shaped ciliary bands on lateral sides of caruncle. Posterior dorsal parts of peristomium fused to notopodial lamellae of chaetiger 1 forming moderate 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 short compound motile cilia on fronto-lateral surfaces along frontal groove ( Fig. 17 A, B); cilia of transverse bands beating towards distal end of palp, while compound fronto-lateral cilia beating perpendicular palp axis towards frontal groove. Longitudinal band of cilia not observed on outer fronto-lateral side along frontal groove.

Chaetiger 1 with short capillaries and small postchaetal lamellae in both rami; notopodial lamellae fused to posterior dorsal parts of peristomium forming moderate ear-shaped structures. Notopodial lamellae of chaetigers 3–5 largest, triangular, gradually becoming smaller and rounded on succeeding chaetigers. Capillaries thick, with fine granulation in 10–15 anterior chaetigers, becoming thinner and smooth in succeeding chaetigers. Lower part of neuropodial postchaetal lamellae of chaetiger 2 acuminate and elongated ventrally. Neuropodial lamellae of chaetiger 3 trapezoidal, from chaetiger 4 onwards rounded, semicircular, diminishing in size on posterior chaetigers.

Moderate dorsal crest present on chaetiger 7 and low crests present from chaetiger 8 to chaetigers 15–24, gradually diminishing in height on posterior chaetigers ( Fig. 17 F). Lateral pouches and ventral flaps absent.

Sabre chaetae in neuropodia from chaetiger 10, usually one, occasionally two in a group in first two-three chaetigers; large in chaetiger 10, gradually diminishing in size in succeeding chaetigers. Sabre chaetae with narrow limbation and fine dense granulation on distal end of shaft ( Fig. 17 G).

Hooks in notopodia from chaetigers 24–51, up to six in a series among capillaries. Hooks in neuropodia from chaetigers 11–18, up to 11 in a series, accompanied by inferior sabre chaetae and alternating capillaries throughout. Alternating capillaries thin, with narrow wing in anterior neuropodia, gradually becoming alimbate in posterior chaetigers, 2–3 times as long as hooks. Hooks with outer and small inner hoods, multidentate, with 2–6 pairs of small upper teeth situated in two vertical rows above main fang; shaft slightly bent ( Fig. 17 H). Hooks in anterior neuropodia of small individuals with 2–3 pairs of small upper teeth above main fang; hooks in large individuals with 4–6 pairs of upper teeth.

Four pairs of branchiae on chaetigers 2–5; those on chaetigers 2 and 5 cylindrical, with numerous long digitiform pinnae regularly arranged on lateral and posterior sides; those on chaetigers 3 and 4 apinnate, stout flattened triangles, with surfaces oriented perpendicular to body axis, similar in length to notopodial lamellae. Branchiae on chaetiger 2 up to two times as long as those on chaetigers 3 and 4, with pinnae arranged all along stem or leaving 1/5–1/6 distal tip free ( Fig. 16 E). Branchiae on chaetiger 5 longest, up to three times as long as those on chaetigers 3 and 4, in large individuals extending posteriorly to end of chaetiger 9, with 1/3–1/4 distal tip free from pinnae. Longitudinal bands of cilia running on inner and outer edges on each branchia; ciliation heavier on branchiae on chaetigers 3 and 4. Afferent and efferent branchial blood vessels interconnected by numerous radial capillaries which forming loops inside pinnae.

Nototrochs present between branchial bases on chaetigers 3 and 4. Short transverse curved band of short cilia present between chaetigers 3 and 4. Dorso-lateral longitudinal ciliation present on chaetigers 3–6 as short bands of dense cilia extending between successive notopodia.

Pygidium with one long middorsal cirrus and a pair of short ventral cirri; all cirri bearing non-motile sensory cilia ( Fig. 16 F).

Oesophagus extending through 6–10 anterior chaetigers. 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 22 µm in diameter extending inside main dorsal vessel from level of chaetigers 3–4 to chaetigers 9–13 ( Fig. 17 C–E). Blood red, without globules or other elements.

Nephridia in chaetigers 4–6, greenish in life ( Fig. 16 A).

Reproduction. Prionospio kulin is gonochoristic. Both in female and males gametes develop from chaetiger 12 to chaetigers 41–72. Oogenesis is intraovarian. Vitellogenic oocytes develop in ovaries attached to segmental blood vessels. One female (AM W.45249) had intraovarian oocytes up to 100 µm in diameter, with germinal vesicle about 50 µm and single nucleolus 30 µm in diameter ( Fig. 17 I). Oocyte envelope is 2–3 µm thick, with rugose external surface and about 10 depressions (vesicles) arranged in a circle; each vesicle is about 10 µm in diameter and 8–9 µm deep, with external opening about 5 µm in diameter. Spermatogonia proliferate in testes; spermatogenesis occurs in the coelomic cavity. Spermatids are joined in tetrads. Spermatozoa are ect-aquasperm with small acrosome, spherical nucleus 2–3 µm in diameter, spherical mitochondria probably four in number, and a long flagellum.

Remarks. Prionospio kulin was originally described from Eastern Bass Strait by Wilson (1990). Worms were numerous and widespread in Bass Strait on a variety of sediments at 16–137 m depth, and a single record was off North Head, Sydney at 32 m. The species has not been reported since. The species was characterized by the caruncle extending back to end of chaetiger 2, large red median eyes, chaetiger 1 with capillaries in both rami, chaetiger 2 with prominent acuminate neuropodial lamellae elongated ventrally, pinnate branchiae on chaetigers 2 and 5, smooth branchiae on chaetigers 3 and 4, prominent dorsal crest on chaetiger 7 and low crests from chaetiger 8 to chaetigers 17–21, sabre chaetae in neuropodia from chaetiger 10, and hooded hooks with 4–5 pairs of upper teeth in notopodia from chaetigers 21–39 and in neuropodia from chaetigers 13–21.

Prionospio from around Lizard Island and Darwin appear similar to P. kulin and are herein referred to this species. Change of the dentition of hooks in ontogenesis, and oocytes with rugose vesiculate envelope are reported for the first time for Prionospio .

Habitat. In this study, adult P. kulin were found in fine coral sand and rubbles from intertidal to 21 m depth.

Distribution. Australia: Bass Strait, New South Wales, Queensland, Northern Territory. This is the first report of P. k ul i n from Queensland and Northern Territory.

Figures

FIGURE 16. Prionospio kulin. A, B—AM W. 45248; C—AM W. 45250; D – F—MIMB 28125. A – D. Anterior ends, dorsal view, showing various shapes of prostomium and eyes; E. Branchia of chaetiger 2; F. Posterior end with pygidium, dorsal view. Abbreviations: la—lateral eyes, me—median eyes, ne—nephridia. Scale bars: A – C— 100 Μm; D – F— 50 µm.

FIGURE 17. Prionospio kulin. A, B, D – F—MIMB 28125; C—AM W. 45255; G – I—AM W. 45249. A. Left palp, inner side, with short transverse ciliary bands; B. Same, frontal side, showing longitudinal ciliated groove; C. Chaetigers 6 – 9, dorsal view, showing soft heart body inside main dorsal blood vessel; D, E. Heart body inside main dorsal blood vessel; D. Main dorsal blood vessel partly contracted; E. Main dorsal blood vessel open; F. Chaetigers 7 – 14, dorsal view, showing prominent transverse crest on chaetiger 7 and lower crests on succeeding chaetigers; G. Inferior sabre chaeta from a median neuropodium; H. Multidentate hooded hooks from a posterior neuropodium; I. Developed coelomic oocyte with soft envelope. Abbreviations: cb—ciliary bands, dc—dorsal crests, dv—main dorsal blood vessel, gv—germinal vesicle, hb—heart body, nl—nucleolus, ve—vesicles, depressions in oocyte envelope. Scale bars: A, F— 200 Μm; B – E— 50 µm; G – I— 20 µm.