Pseudopolydora arabica Radashevsky & Al-Kandari, 2020

Figs 1B, 5D, 10

Pseudopolydora arabica Radashevsky & Al-Kandari, 2020: 2−10, figs 2−7.

Pseudopolydora sp. B – Al-Kandari et al. 2019: 9. — Radashevsky et al. 2020: table 1, fig. 1.

Pseudopolydora paucibranchiata – Swaleh & Mustaquim 1993: 204, fig. 2. — Not Okuda 1937.

Adult diagnostic features

Adults up to 20 mm long, 1 mm wide with 80 chaetigers (Fig. 10A). Live individuals with yellowishwhite pigment on lateral sides of prostomium and dorsal side of 3−5 anterior chaetigers (most intense on chaetigers 1−2), and up to 50 yellowish-white ramified chromatophores on each palp in (Fig. 10A– B); chromatophores not visible after fixation. Prostomium anteriorly narrow and rounded (Fig. 10B). Caruncle extending to end of chaetiger 4. Occipital antenna present. Chaetiger 1 with short capillaries in neuropodia; notochaetae absent. Anterior-row capillaries in notopodia from chaetiger 7 to chaetigers 10−20 with wide subtriangular, pennoned limbation. Chaetiger 5 almost as same in size as chaetigers 4 and 6 (Fig. 10B); dorsal superior capillaries slightly shorter and fewer than those capillaries on chaetigers 4 and 6; ventral capillaries as same as those on chaetiger 4; two kinds of notopodial spines arranged in a double J-shaped row; outer (anterior-row) notopodial spines with geniculate distal tip with wide limbation; inner (posterior-row) notopodial spines simple falcate (Fig. 10C). Bidentate hooded hooks in neuropodia from chaetiger 8. Branchiae from chaetiger 7 to chaetiger 30, up to 24 pairs. Pygidium small, cup-shaped, with dorsal gap. Glandular pouches in neuropodia from chaetiger 1, largest in chaetigers 6 and 7, single pouch in each neuropodium.

MG staining

Intensely stained dorsal side of the prostomium in front of eyes, dorsal side of the peristomium, and ventral side of chaetigers: complete transverse paired bands moderate intense on chaetigers 1–4, very intense complete transverse paired bands on chaetigers 5–7, and paired transverse bands split into three parts from chaetiger 8 onwards (Fig. 10D–G). Remarkably, the three-parts banding was associated with the start of the hooded hooks in neuropodia and was invariable in all examined specimens.

Remarks

Pseudopolydora arabica Radashevsky & Al-Kandari, 2020 was originally described from the Arabian Gulf as one of the common polychaetes inhabiting soft sediments. The population density of the species in some places reaches 50 000 individuals per 1 m 2.

Distribution

Arabian Gulf: Kuwait (Fig. 1B).