Pseudopolydora achaeta Radashevsky & Hsieh, 2000

Fig. 3

Pseudopolydora achaeta Radashevsky & Hsieh, 2000: 223−226, figs 4–5, 11a.

Pseudopolydora achaeta – Lana et al. 2006: 50. — Zvyagintsev et al. 2011: 53. — Abe et al. 2014: 3−5; 2016: 654−656, fig. 3; 2019: 6−11. — Bogantes et al. 2021: 581, fig. 2a–b.

Pseudopolydora aff. achaeta – Abe & Sato-Okoshi 2021: 56−57, fig. 9a–b (larval morphology).

Pseudopolydora sp. A – Radashevsky & Migotto 2006: fig. 1c.

Description

Two specimens were found in Sulaibikhat Bay, Kuwait, comprising 20-chaetiger anterior fragment of a small juvenile and a 70-chaetiger complete female about 16 mm long and 0.8 mm wide (MIMB 40934; Fig. 3A–B). Transverse bands of diffused black pigment present on dorsal side of up to 15 anterior chaetigers; small middorsal melanophores present from chaetigers 4−6 to chaetigers 10−12. Prostomium anteriorly weakly incised, notched or almost blunt, posteriorly extending to end of chaetiger 2 as a low caruncle. Occipital antenna present. Chaetiger 1 reduced, weakly separated from peristomium, with small notopodial and well developed neuropodial lamellae; notochaetae absent; neurochaetae comprising 1−5 very fine, hair-like capillaries. Chaetiger 5 same in size as chaetigers 4 or 6, with dorsal superior and ventral capillaries same in shape and number as those chaetae on chaetigers 4 or 6; two kinds of heavy spines arranged in a vertical slightly curved double row; noto- and neuropodial postchaetal lamellae present (Fig. 3 C−E). Anterior-row spines pennoned, with curved pointed tip, without subdistal constriction (Fig. 3F), up to 22 in a series; posterior-row spines simple falcate (Fig. 3G), up to 19 in a series. Bidentate hooded hooks in neuropodia from chaetiger 8, up to 15 in a series. Branchiae from chaetiger 7 to chaetiger 15. Pygidium flaring disc with wide dorsal gap and dorso-lateral processes (Fig. 3H–I). Glandular pouches in neuropodia from chaetiger 1, largest and paired in each neuropodium in chaetigers 6 and 7, single in other neuropodia.

MG staining

Intensely stained ventral and lateral sides and notopodial postchaetal lamellae of 15–16 anterior chaetigers, outer edges of branchiae (Fig. 3C); narrow transverse bands on dorsal side of branchiate chaetigers.

Remarks

Pseudopolydora achaeta was originally described from the South China Sea, Taiwan, as a common polychaete inhabiting tubes in soft sediments in brackish-water environments (Radashevsky & Hsieh 2000). Since then, the species was reported from Paraná and São Paulo (Brazil) (Lana et al. 2006; Radashevsky & Migotto 2006), Sea of Japan (Russia) (Zvyagintsev et al. 2011), Pacific side of Honshu Island (Japan) (Abe et al. 2014, 2016, 2019; Abe & Sato-Okoshi 2021), and from Florida (USA) (Bogantes et al. 2021). Here, for the first time, we report it for the Arabian Gulf (Kuwait). The only female had small oocytes up to 65 µm in diameter developing from chaetiger 15 onwards (Fig. 3J). The morphology of the specimens fits the diagnostic characters of P. achaeta . The same pattern of methylene green staining was observed in the type specimens of P. achaeta from Taiwan (MIMB 3401). The wide distribution of this species outside of its native area in the Northwest Pacific can be explained by unintentional human-mediated transportations of larvae with ballast water of ships, followed by successful invasions.

Distribution

South China Sea: Taiwan; Japan: Pacific side of Honshu Island; Brazil: Paraná, São Paulo; Atlantic USA: Florida; Arabian Gulf: Kuwait.