Prionospio multicristata Hutchings & Rainer, 1979

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 : 666-669

Prionospio multicristata Hutchings & Rainer, 1979

( Figs 20 , 21 )

Prionospio multicristata Hutchings & Rainer, 1979: 768 –771, fig. 5; Hutchings & Turvey 1984: 11 –12; Hutchings & Murray 1984: 60 –61; Hartmann-Schröder 1982: 86 –87, 1984: 36; Wilson 1990: 256.

Material examined. Queensland: AM W.45251, MI QLD 2391 (1); AM W.45256, MI QLD 2433 (2); MIMB 28127, MI QLD 2433 (1); AM W.45253, MI QLD 2408 (1); MIMB 28128, MI QLD 2408 (1); AM W.45234, MI QLD 2431 (11). Northern Territory: MIMB 28129 (1), Lake Alexander, Darwin, 12.41272°S, 130.83192°E, intertidal, muddy sand, 11 Sep 2013.

Adult morphology. Up to 20 mm long, 0.5 mm wide for 80 chaetigers. Pigmentation in life absent. Prostomium broadly-rounded anteriorly, extending posteriorly to end of chaetiger 3 as a distinct caruncle ( Fig. 20 A), shorter in small individuals. Small knobs with short non-motile sensory cilia present on frontal and frontolateral edges of prostomium. Occipital antenna absent. Two pairs of eyes arranged trapezoidally; lateral eyes small, set anteriorly and wider apart; median eyes each comprising small cup and a large, crescent-shaped spot composed of many spherical pigment globules ( Figs 20 B, 21A); eyes red in life but appearing black in formalin-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 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; cilia of transverse bands beating towards distal end of palp, while compound fronto-lateral cilia beating perpendicular to palp axis towards frontal groove.

Chaetiger 1 with capillaries and small lamellae in both rami; notopodial postchaetal lamellae fused to posterior dorsal parts of peristomium forming ear-shaped structures. Notopodial lamellae of chaetigers 2–5 largest, triangular, gradually becoming smaller and rounded on succeeding chaetigers. Small prechaetal lamellae present in both rami of 10–15 anterior chaetigers. Capillaries thick, with fine granulation in 10–15 anterior chaetigers, becoming thinner and smooth on succeeding chaetigers. Lower part of neuropodial postchaetal lamellae of chaetiger 2 acuminate and elongated ventrally ( Fig. 21 A). Neuropodial lamellae of chaetiger 3 trapezoidal, from chaetiger 4 onwards lamellae rounded, semicircular, diminishing in size on posterior chaetigers.

Moderate dorsal crest present on chaetiger 7; low dorsal crests present from chaetiger 8 to about chaetiger 30 ( Fig. 21 A); gradually diminishing in height posteriorly. Lateral pouches and ventral flaps absent.

Sabre chaetae in neuropodia consistently from chaetiger 10, one, occasionally two in a group, with narrow limbation and fine dense granulation on distal end of shaft. Sabre chaetae large in chaetiger 10, gradually diminishing in size in succeeding chaetigers ( Figs 20 C–F, 21E, F).

Hooks in notopodia from chaetigers 32–44, up to five in a series among capillaries. Hooks in neuropodia from chaetigers 14–16, up to ten in a series, accompanied by inferior sabre chaetae and alternating capillaries throughout ( Fig. 20 D). Alternating capillaries thin, about two times as long as hooks, with narrow limbation in anterior neuropodia, gradually becoming alimbate on posterior chaetigers. Hooks with outer and small inner hoods, multidentate, with 4–6 pairs of small upper teeth arranged in two vertical rows above main fang; shaft slightly bent ( Fig. 21 C, D). Younger hooks situated in lower parts of hook series in anterior neuropodia of small individuals with 2–3 pairs of small upper teeth above main fang.

Four pairs of branchiae on chaetigers 2–5; with those on chaetigers 2 and 5 cylindrical, almost equal in length or on chaetiger 5 slightly longer than on chaetiger 2, each as long as two-three chaetigers; pinnae regularly arranged along lateral and posterior sides leaving 1/4–1/3 distal tip free. Branchiae on chaetigers 3 and 4 apinnate, about 2/3 of length of pinnate branchiae, as long as 1.5–2 chaetigers, robust, flattened, with surfaces oriented perpendicular to body axis. 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 bearing short non-motile sensory cilia ( Fig. 21 B).

Oesophagus extending through 6–11 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 20 µm in diameter extending inside main dorsal vessel from level of chaetigers 3–4 to chaetigers 9–12 ( Fig. 20 G). Blood red, without globules or other elements.

Nephridia in chaetigers 4–6, greenish in life.

Reproduction. Prionospio multicristata is gonochoristic. Both in females and males from around Lizard Island the gametes develop from chaetiger 12 to chaetigers 50–62. Oogenesis is intraovarian. Vitellogenic oocytes develop in ovaries attached to segmental blood vessels. Intraovarian oocytes were up to 110 µm in diameter, with germinal vesicle about 60 µm and single nucleolus 20 µm in diameter. Oocyte envelope is 2–3 µm thick, with rugose external surface. One mature female off Darwin ( MIMB 28129) has all morphological features same as specimens from Lizard Island but oocytes from chaetiger 15 onwards; the oocyte envelope has single semispherical depression 25–30 µm in diameter and 15–20 µm deep ( Fig. 20 H–J). 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 multicristata belongs to the P. steenstrupi group (see above Remarks for P. anneae n. sp.). It was originally described from Careel Bay, New South Wales, Australia by Hutchings & Rainer (1979). The species was characterized by the prostomium broadly-rounded anteriorly, black eyes in fixed specimens, with median eyes large, comma-shaped, caruncle extending to end of chaetiger 3, chaetiger 1 with capillaries in both rami, chaetiger 2 with prominent acuminate neuropodial lamellae elongated ventrally, moderate dorsal crest on chaetiger 7 and lower crests from chaetiger 8 to chaetigers 25–30, sabre chaetae in neuropodia from chaetiger 10, and hooded hooks with 5–6 pairs of upper teeth in notopodia from chaetigers 40–50 and in neuropodia from chaetiger 17. Hutchings & Turvey (1984) reported the species from South Australia. They did not describe the color of eyes but mentioned that the only specimen had caruncle to end of chaetiger 4. This caruncle appears longer than originally described in specimens from Careel Bay and also observed in specimens from Queensland. The record from South Australia should be verified.

Prionospio with black eyes from Lizard Island and Darwin appear identical to the original description of P. multicristata and are herein referred to this species. These worms also appear very similar to P. ku l i n in the shape of branchiae and neuropodial postchaetal lamellae on anterior chaetigers (with elongated acuminate lower part in chaetiger 2, trapezoidal in chaetiger 3, and rounded, semicircular from chaetiger 4 onwards), moderate dorsal crest on chaetiger 7 and lower crests on a series of succeeding chaetigers, arrangement of sabre chaetae and hooks, hook dentition and gametes starting from chaetiger 12. The two species occur together in some localities. Fixed adults of these species can be distinguished by the color of eyes, black in P. multicristata and red in P. kulin , and length of the caruncle, to the end of chaetiger 3 in P. multicristata and to the end of chaetiger 2 in P. k ul i n. Living small individuals of the two species have red eyes and short caruncles and appear similar to each other.

Habitat. In this study, adults of P. multicristata were found in fine coral sand from intertidal to 16 m depth.

Distribution. Australia: New South Wales, Queensland, Northern Territory.

Figures

FIGURE 20. Prionospio multicristata. A, C – G—AM W. 45256; B—AM W. 45251; H – J—MIMB 28129. A, B. Anterior end, dorsal view; C. Neuropodia of chaetigers 11 and 12, left lateral view; D. Neuropodium of chaetiger 21, left lateral view; E. Sabre chaeta from neuropodium of chaetiger 10; F. Sabre chaeta from neuropodium of chaetiger 15; G. Chaetigers 8 – 10 in dorsal view, showing soft heart body inside main dorsal blood vessel; H – J. Developed coelomic oocytes with soft envelope. Abbreviations: al—hair-like alimbate capillaries alternating with hooded hooks, dv—main dorsal blood vessel, gv—germinal vesicle, hb—heart body, la—lateral eye, me—median eye, nl—nucleolus, sa—sabre chaetae, ve—vesicles, depressions in oocyte envelope. Scale bars: A, B, G— 100 Μm; C, D— 50 µm; E, F— 20 Μm; H – J— 30 µm.

FIGURE 21. Prionospio multicristata. A – F—AM W. 45256. A. Anterior end, left lateral view; B. Posterior end, dorsal view; C. Hooded hook from neuropodium of chaetiger 20, frontal view; D. Same, lateral view; E. Sabre chaeta from neuropodium of chaetiger 10; F. Sabre chaeta from neuropodium of chaetiger 15.