Prionospio (Aquilaspio) sexoculata Augener, 1918

Dagli, Ertan & Çinar, Melih Ertan, 2009, Species of the subgenera Aquilaspio and Prionospio (Polychaeta: Spionidae: Prionospio) from the southern coast of Turkey (Levantine Sea, eastern Mediterranean), with description of a new species and two new reports for the Mediterranean fauna, Zootaxa 2275, pp. 1-20 : 16-17

Prionospio (Aquilaspio) sexoculata Augener, 1918

Figure 8

Prionospio sexoculata Augener, 1918:405 –408, pl. 6, figs. 159, 172. Aquilaspio sexoculata: Foster 1971:106 .

Prionospio (Aquilaspio) sexoculata: Imajima 1990b:2 –5, fig. 3.

Material examined. ESFM –POL/05–210, 8 specimens, 14 September 2005, Iskenderun Bay, K8, 36º45΄40΄΄N, 36º11΄58΄΄E, 5 m, sand; ESFM –POL/05–364, 2 specimens, 14 September 2005, Iskenderun Bay, K9, 36º54΄22΄΄N, 35º58΄0 5΄΄E, 1 m, sand; ESFM –POL/05–1222, 2 specimens, 17 September 2005, Mersin Bay, G6, 36º48΄22΄΄N, 34º41΄39΄΄E, 5 m, black mud; ESFM –POL/05–1402, 38 specimens, 17 September 2005, Mersin Bay, G11, 36º45΄47΄΄N, 34º51΄54΄΄E, 5 m, sandy mud.

Description. Largest specimen incomplete, 7.3 mm long, 0.24 mm wide with 65 chaetigers. Body slender, enlarged anteriorly, gradually tapering to posterior end, color in alcohol pale yellow. Prostomium rectangular, truncate on anterior margin, with small median peak ( Fig. 8 A), slightly inflated at level of eyes, tapering posteriorly, with a narrow caruncle extending to end of chaetiger 1 ( Fig. 8 A). Two pairs of eyes, arranged in rectangle; anterior pair larger than posterior ( Fig. 8 A–B). Peristomium dorsally fused to chaetiger 1, forming moderate lateral wings ( Fig. 8 B).

Branchiae present on chaetigers 2 and 3 ( Fig. 8 A–B), all with digitiform pinnules; first pair longest, extending back to posterior part of chaetiger 8. Second pair extending to middle part of chaetiger 6 ( Fig. 8 A– B).

Parapodia of chaetiger 1 reduced, with only digitiform neuropodial lamellae, notochaetae absent. Parapodia of chaetiger 2 with rectangular-shaped notopodial lamellae and small triangular neuropodial lamellae with tips bending ventrally ( Fig. 8 B). Notopodial postchaetal lamellae of chaetigers 3 and 4 becoming subrectangular, with pointed distal end; neuropodial lamellae of chaetiger 3 rectangular, those of chaetiger 4 rounded. Following notopodial lamellae gradually decreasing in size and becoming rounded. Neuropodial lamellae small, triangular on middle parapodia, digitiform on posterior parapodia. No membranous dorsal crests.

Capillary notochaetae of anterior and middle chaetigers unilimbate, arranged in two rows, those of anterior row being shorter, with wider sheaths than those of posterior row ( Fig. 8 F). Both types of chaetae with granulations on distal half of shaft. Capillary neurochaetae unilimbate, arranged in two rows, also with granulations on shaft; inferior sabre chaetae from neuropodia of chaetiger 10 ( Fig. 8 E). Neuropodial hooded hooks present from chaetiger 16, numbering up to six per fascicle. Notopodial hooded hooks present from chaetiger 33, numbering up to three per fascicle. Hooks accompanied by capillaries throughout, with four tiers of two small teeth and one apical tooth above main fang ( Fig. 8 D).

Pygidium with a long dorsomedial cirrus and two short ventrolateral cirri ( Fig. 8 C).

Ecology. The highest population density (380 individuals.m -2) of this species was found on sandy mud substratum at 5 m depth at station G11 (Mersin Bay).

Distribution. South east Atlantic, Northwest Pacific ( Imajima 1990b); Mediterranean Sea, Red Sea, Indian Ocean ( Amoureux et al. 1978, Ben-Eliahu 1995); intertidal to 20 m. It was previously considered as a Lessepsian migrant (Ben-Eliahu 1995).

Figures

FIGURE 8. Prionospio (Aquilaspio) sexoculata. A, anterior end, dorsal view; B, anterior end, lateral view; C, posterior end, dorsal view; D, neuropodial hooded hook on chaetiger 30; E, ventral sabre chaeta on chaetiger 16; F, notopodial capillary chaeta on chaetiger 10. Scale: A – B = 0.1 mm, C = 250 µm, D = 10 µm, E – F = 20 µm, D = 10 µm.