Polydora websteri Hartman

Polydora websteri Hartman in Loosanoff and Engle, 1943

Figure 3

Polydora websteri Hartman in Loosanoff & Engle, 1943: 70 –72, fig. 1; Hartman 1951: 81 –82; Haigler 1969: 821 –828, figs. 1–3 (boring mechanism); Blake 1969a: 10 –16, figs. 5–11 (larvae); 1969b: 814–815, fig. 2; 1971: 6–8, fig. 3 (synonymy); 1996: 176, Fig. 4.28M–P; Blake & Kudenov 1978: 258 –259, fig. 43k–n; Radashevsky 1999: 110–112, fig. 1A–F (lectotype); Sato-Okoshi 1999: 832 –834, fig. 2B; Surugiu 2005a: 67; Read 2010: 9 –11, figs. 1H–J, 2B, 2D, 2F, 4D–G; Lisitskaya et al. 2010: 75 –77, fig. 1–4.

? Polydora ciliata. Dumitrescu 1962: 66 [in part]; 1973: 43 [in part]; Bäcescu et al. 1963: 139, fig. 3 [in part]; Marinov 1977: 158 –159, pl. XXI, fig. 2c–e [in part]; Surugiu & Manoleli 1998 –1999: 24 [in part]; Kisseleva 2004: 264 –266, fig. 107a–c [in part]; Surugiu 2005a: 66. Non Johnston, 1838.

Material examined. Black Sea: “ Polydora ciliata (Johnston, 1838) (M. Neagrä) Polychaeta 3” MNINGA 30.294 (12); Romania: Sta. AG13, Agigea, 10 m, scrapings from Mytilus galloprovincialis bank, 1 Sep 2004, MNINGA PLY039 (1); Sta. AG34, Agigea, 4 m, scrapings from M. galloprovincialis bank, 16 Apr 2005, MNINGA PLY040 (2); Sta. 99, Eforie Sud (44°01ʹ15.7ʹ N, 28°38ʹ36.9ʹ E), limestone plate covered with mud near sewage outflow, 1.5 m, 5 Aug 2005 (100+); Sta. AG47, Agigea, 14 m, scrapings from M. galloprovincialis bank, 23 Oct 2005, MNINGA PLY041 (6); Sta. AG48, Agigea, 12 m, scrapings from M. galloprovincialis bank, 23 Oct 2005, MNINGA PLY042 (1); Sta. AG52, Agigea, 4 m, scrapings from M. galloprovincialis bank, 23 Oct 2005, MNINGA PLY043 (2); Ukraine: southern Crimea, Katsiveli (44°23ʹN, 33°58ʹ E), on long-line farmed Crassostrea gigas (Thunberg, 1793) shells, 2.5–3.5 m, salinity 17.9–18.6‰, 29 Jun 2011, coll./det. E. Lisitskaya (31).

Description. Adult worms up to 20 mm long, 1.1 mm wide at chaetiger 5 and with up to 116 chaetigers. Colour in life light tan with red branchiae, palps and blood vessels. Preserved specimens pale yellowish. Dorsal black pigmentation absent in adults. Distal 3/4–2/3 of palps with a dark brown, almost black sinuous line along edges of ciliated food groove, persisting in preserved specimens. Pygidium white in colour due to presence of numerous glandular epithelial cells.

Prostomium with anterior margin slightly incised, caruncle extending back to posterior end of chaetiger 2 (Fig. 3 A). Occipital antenna absent. Eyes usually absent in adults; juveniles with 1–4 small rounded eyes in trapezoidal arrangement, with anterior pair slightly larger and further apart. Lateral sides of caruncle with narrow ciliated grooves. Two long, easily detachable palps present, capable of extending to chaetiger 15.

Chaetiger 1 only with well-developed neuropodial postchaetal lamellae and a fascicle of capillary neurochaetae; notopodium represented by small notopodial lamellae, notochaetae entirely absent (Fig. 3 B). Chaetigers 2–4 and 6 with well-developed and flattened noto- and neuropodial postchaetal lamellae, with bundles of limbate capillary chaetae.

Modified chaetiger 5 broader and longer than adjacent ones (Fig. 3 A–B), partially covering chaetiger 6, without postchaetal lamellae and bearing an oblique or almost horizontal row of 5–6 thick, falcate spines alternating with companion chaetae. Major spines of chaetiger 5 falcate, distally curved and with broad, subterminal flange on concave side (Fig. 3 C). Companion chaetae slender, pennoned, slightly more ventral and closely adjoining falcate spines (Fig. 3 C–D). Chaetiger 5 with up to six superior dorsal limbate capillary chaetae arranged in vertical row (Fig. 3 C–D) and compact bundle of inferior ventral shorter limbate capillaries.

Neuropodial bidentate hooded hooks from chaetiger 7, up to 11 in a vertical row in middle chaetigers, decreasing to 2–3 posteriorly, without alternating or inferior capillaries on anterior and posterior chaetigers. Hooded hooks with main tooth at right/acute angle to shaft and with wide acute angle (~40°) to smaller apical tooth; with a prominent constriction and distinct manubrium on shaft. Posterior notopodia with slender winged and non-winged capillaries, without special notopodial spines.

Branchiae digitiform, elongated, overlapping middorsally (Fig. 3 E), from chaetiger 7, small at first, reaching maximum length by chaetiger 9–10, and continuing to near the posterior end, absent from last 10–16 chaetigers, decreasing gradually in size in posterior half of the body, free from notopodial postchaetal lamellae.

Pygidium thin, cup-shaped with weakly glandular surface and with anus at base of dorsal gap (Fig. 3 F).

Habitat and ecology. Polydora websteri is a common borer in limestone from the splash zone to the lowest limit of the rocky seabed (~ 20 m). The burrows of P. w e b s t e r i are pear-shaped or sacciform, non-branching, and large enough for the worm to turn and reverse direction. The gallery is lined by a membranous sheath that extends outside the burrow by about 2–3 mm. In areas influenced by sewage discharge, the intense sedimentation of suspended matter covers the substrate in which the worms bore. Under such circumstances the worms will extend their external sheaths well above the substrate, forming dense tube mats that are 2–3 cm thick. Maximum recorded density of this species was 132,500 ind. m–2 at a depth of 0.5 m. The salinity range for this worm in the Black Sea is 9.2–17.8 PSU.

Reproduction and development. According to Lisitskaya et al. (2010) eggs, each measuring 130–150 µm in diameter, were deposited in transparent, elastic, oval-shaped egg capsules 900 µm long and 850 µm wide starting from February. Egg capsules contained 50– 75 eggs and were attached, side-by-side, to the interior wall of the burrow by a thin, 250-µm long stalk. Only 10–15% of the eggs in the capsule were fertilized, the remainder representing nurse eggs. Adelphophagic larvae reared in the laboratory from May to June left the capsules at the 5–6 to 12–13 chaetigers stage and started to swim in the water column. The larvae settled at the 17–18 chaetiger stage. In coastal waters of Crimea planktic larvae of P. websteri were present from May to November (E. Lisitskaya 2012, pers. comm.).

Distribution. Polydora websteri is present in areas where there are cultured edible oysters, especially Crassostrea gigas (Read 2010; Lisitskaya et al. 2010). The worldwide distribution of this species includes the Atlantic (Blake 1971) and Pacific coasts of North America (Hartman 1961; Blake 1996), Gulf of Mexico (Hartman 1951), Caribbean Sea (Foster 1971), Hawaii, Atlantic (Pagliosa 2005) and Pacific coast of South America (Blake 1983); Japan (Sato-Okoshi 1999), southeastern Australia (Blake & Kudenov 1978), and New Zealand (Read 2010). In the Black Sea known records are for coasts of Romania (Surugiu 2005a) and southern Crimea (Lisitskaya et al. 2010).

Remarks. The Black Sea specimens are in good agreement with the description of the type material (Radashevsky 1999). Polydora websteri is very close in morphology to P. haswelli and P. neocaea Williams & Radashevsky, 1999 by having a flange on the major spines of chaetiger 5. However, P. w e bs t e r i can be distinguished from P. haswelli and P. neocaea by pigmentation pattern (Read 2010). Thus palps of P. w e b s t e r i are characterized by continuous black lines along the margins of the ciliated groove, whereas in P. h a s w e l l i and P. neocaea the palps have distinct bands of black pigment. Additionally, dorsal pigmentation is absent in P. w e b s t e r i, whereas in P. h a s w e l l i and P. neocaea there is a conspicuous black pigmentation on the lateral sides of the prostomium and first anterior segments. Slight differences exist also with regard to the shape of the flange on major spines, which is broader, shorter, and almost terminal in P. w e b s t e r i (Fig. 3 C) and is narrower, longer, and subterminal in P. neocaea and P. haswelli (Williams & Radashevsky 1999: Fig. 3 A; Read 2010: Fig. 2 C, Fig. 4 A–C). As noted by Radashevsky et al. (2006) and Read (2010), P. neocaea may be a synonym of P. haswelli.

Polydora websteri is broadly similar in morphology to Polydora ciliata, P. c a l c a re a, and P. limicola. However the latter differ from P. w e b s t e r i in having a distinct lateral triangular tooth on the major modified spines of chaetiger 5 instead of a lateral flange. In some instances P. w e b s t e r i may be also confused with frequently cooccurring Polydora cornuta because on worn spines the flange may have the appearance of a flange and accessory tooth that are not connected, closely resembling the major spines of P. c o r n u t a (Foster 1971; Kudenov 1982: 573; Çinar et al. 2005; Radashevsky 2005; present study). Confusion could be avoided if deeper, unworn chaetae are examined and if the occipital tentacle and the feather-like companion chaetae on chaetiger 5 are observed in P. cornuta. Additional characters that can be used to distinguish between these two species are the palp pigmentation (Haigler 1969) and the angle between the apical tooth and the main fang (present study).