Prionospio (Aquilaspio) krusadensis Fauvel 1929

Figures 6–7

Prionospio krusadensis Fauvel, 1929:182 –184, fig. 2; Okuda 1937:244 –246, fig. 21. Prionospio (Aquilaspio) krusadensis: Imajima 1990b:5 –8, fig. 3.

Material examined. ESFM –POL/05–3206, 1 specimen, 9 September 2005, Iskenderun Bay, G1, 36º35΄37΄΄N, 36º11΄0 9΄΄E, 8 m, mud; ESFM –POL/05–3207, 1 specimen, 10 September 2005, Iskenderun Bay, D13, 36º33΄22΄΄N, 35º34΄17΄΄E, 10 m, muddy sand; ESFM –POL/05–3201, 161 specimens, 14 September 2005, Iskenderun Bay, K9, 36º54΄22΄΄N, 35º58΄0 5΄΄E, 1 m, sand; ESFM –POL/05–3204, 12 specimens, 14 September 2005, Iskenderun Bay, K8, 36º45΄40΄΄N, 36º11΄58΄΄E, 5 m, sand; ESFM –POL/05–3203, 2 specimens, 15 September 2005, Iskenderun Bay, K11, 36º33΄20΄΄N, 35º22΄44΄΄E, 1 m, sand; ESFM –POL/05–3202, 28 specimens, 17 September 2005, Mersin Bay, G11, 36º45΄47΄΄N, 34º51΄54΄΄E, 5 m, sandy mud; ESFM –POL/ 05–1355, 11 specimens, 18 September 2005, Mersin Bay, K 14, 1 m, sand; ESFM –POL/05–1260, 223 specimens, 19 September 2005, Mersin Bay, K17, 36º28΄42΄΄N, 34º10΄21΄΄E, 4 m, sand; ESFM –POL/05–3205, 1 specimen, 22 September 2005, Anamur, K27, 36º01΄17΄΄N, 32º48΄14΄΄E, 0.1– 5 m, sand.

Description. Largest specimen complete, 0.32 mm wide, 14.9 mm long, with 79 chaetigers. Body slender, stouter in anterior part and gradually decreasing in width towards posterior end. Color in alcohol generally pale yellow.

Prostomium bottle-shaped, bluntly rounded anteriorly, lateral margin somewhat convex, posterior part forming long narrow caruncle, extending to posterior margin of chaetiger 1 (Fig. 6 B). Two pairs of eyes arranged in rectangle, anterior pairs larger than posterior ones (Fig. 6 A, B). Peristomium dorsally fused to chaetiger 1, forming moderate wings. Palps elongate, extending back to chaetiger 7 (to 11 in some specimens), with distinct ciliated groove; densely ciliated on frontal side; basal part of palps thickened, gradually tapering towards end of tip.

Three pairs of pinnate branchiae on chaetigers 2–4; first pairs long, extending to chaetiger 5, with digitiform pinnules on posterior side; tips without pinnules. Second pair of branchiae shorter than first pair, with digitiform pinnules. Third pair shortest, slender, with small sparse pinnules (Fig. 6 A).

Parapodia of chaetiger 1 smaller than subsequent parapodia, with foliaceous notopodial lamellae, without chaetae (Fig. 6 B); neuropodial postsetal lamellae small, rounded, with chaetae. Parapodia of chaetiger 2 with ear-like notopodial lamellae and subrectangular neuropodial lamellae, ventrally pointed. Notopodial postsetal lamellae largest on chaetiger 4, triangular, with dorsally pointed tip; subsequent lamellae gradually becoming smaller and rounded. Neuropodial lamellae of chaetigers 3–5 small, subrectangular; lamellae on remaining chaetigers low, elliptical, becoming rather inconspicuous on posterior chaetigers (Fig. 6 A). No membranous dorsal crests between parapodia.

Anterior noto- and neuropodial lobes with only capillary chaetae, with thin sheath; all capillaries moderately granulated (Fig. 6 E). Ventral sabre chaetae usually from chaetiger 11, sometimes from chaetiger 10, numbering one per fascicle; short, stout, curved, lightly granulated, with a short distal filament (Figs. 6 D, 7C). Neuropodial hooded hooks present from chaetiger 19–20, numbering up to 7–8 per fascicle, accompanied by capillaries throughout. Notopodial hooded hooks long, slender, usually from chaetigers 34– 35, numbering up to 4–5 per fascicle. Hooks with three tiers of two teeth and one apical tooth above main fang (Figs. 6 C; 7 A–B).

Pygidium with one long medial and two short dorsolateral cirri (Fig. 6 F).

Remarks. Prionospio (Aquilaspio) krusadensis was first described from the Gulf of Manner (Indian Ocean) by Fauvel (1929) and subsequently from the coast of Japan by Imajima (1990b). Although the main morphological features of the Mediterranean specimens of P. (A.) krusadensis are similar to those of the original and subsequent descriptions, some slight differences were observed. These differences are: (1) the length and width of the Mediterranean specimens (length: 14.9 mm, width: 0.32 mm) are smaller than those of the Japanese specimens (length: 26 mm, width: 0.6 mm); (2) notopodial hooded hooks in the Japanese specimens are present from chaetigers 27–31, whereas those in the Mediterranean specimens are present from chaetigers 34–35; and (3) hooks in the Japanese specimens have 5–6 small teeth above the main fang, whereas those in the Mediterranean specimens have 7 small teeth above the main fang (Fig. 7 A–B).

Wu & Chen (1964) synonymized P. (A.) krusadensis with P. (A.) sexoculata, without giving any reasons. Foster (1971) later synonymized P. (A.) krusadensis with P. (A.) aucklandica Augener, 1923 and Blake & Kudenov (1978) and Maciolek (1985) followed this synonymy. However, Imajima (1990b) did not accept this synonymy and considered these two species as distinct. We also agree with Imajima’s view as there are important differences between these species. For example, P. (A.) krusadensis has three pinnate branchiae (vs. two pinnate branchiae in P. (A.) sexoculata); a spindle-shaped, anteriorly rounded prostomium (vs. a rectangular prostomium with median peaks in P. (A.) sexoculata); and lanceolate notopodial lamellae on chaetiger 1 (vs. chaetiger 1 reduced in P. (A.) sexoculata).

Ecology. The highest population density (5575 individuals.m -2) of this species was found on sandy substratum at 4 m depth at station K17 (Mersin Bay).

Distribution. Western Pacific Ocean and Indian Ocean (Imajima, 1990b); intertidal to 33 m. This species could have been introduced to the area by ballast waters of ships.