Oyster Mudworm

Polydora websteri Hartman

Polydora ciliata.—Procter, 1933, p. 142.—Kavanaugh, 1941, pp. 32–34.—Lunz, 1940, p. 310; 1941, pp. 273–283.—Abbott, 1946, pp. 15–18, pl. 3.—Medcof, 1946, pp. 498–515.—Plaine, 1952, pp. 121–123, fig. 1.—Turner and Hanks, 1959, pp. 109–111.—Landers, 1967, pp. 63–66, figs. 1–2. Not Johnston, 1838.

Polydora caeca.—Webster, 1879a, pp. 252–253, pL 9: figs. 119–122.—Andrews, 1891a, p. 291. Not Oersted, 1843.

Polydora websteri.—Hartman, 1943, pp. 70–72, fig. 1; 1945, p. 33; 1951, pp. 81–82; 1954, p. 415; 1961, pp. 99–100, pls. 16–17; 1966b, p. 223; 1969, pp. 151–152, 4 figs.—Loosanoff and Engle, 1943, pp. 69–78.—Grice, 1951, pp. 1–10.—Mackin and Cauthron, 1952, pp. 14–24.—Menzel, 1955, p. 112.—Hopkins, 1958, pp. 268–277, figs. 1–6.—Owen, 1957, pp. 35–46.—Rioja, 1960, p. 304.—MacKenzie and Shearer, 1961, pp. 105–111.—Wells and Gray, 1964, p. 73.—Galtsoff, 1964, pp. 421–425.—Forbes, 1966, pp. 280–281.—Davis, 1967, pp. 67–72, figs. 2–3.—Evans, 1969, pp. 775–782.—Blake, 1969a, pp. 814–815, fig. 2; 1969b, pp. 10–16, figs. 5–11.—Haigler, 1969, pp. 821–828, figs. 1–3.

MATERIAL EXAMINED.—Maine (Lamoine Beach; Damariscotta River; Boothbay Harbor region, Ocean Point), Newfoundland (St. Mary’s Bay, 10–20 meters, coll. J. W. Evans), Quebec (Gaspé Peninsula, coll. J. D. Davis), Connecticut (Milford, Type AHF 1569; Noank), Virginia (Gloucester Point, coll. J. L. Simon), North Carolina (Beaufort), South Carolina (Charleston, coll. M. Chamberlain), California (Morro Bay, coll. K. H. Woodwick).

DESCRIPTION.—Polydora websteri is a small slender species, measuring up to 20 mm in length and having about 100 segments. In life it is light tan with red branchiae, palps and blood vessels. Body pigmentation is variable, absent in some specimens while others have dense anterior and posterior black pigment.

A prostomial anterior incision may be distinct, weak or absent (Figure 3a). Specimens from New England and eastern Canada tend to have a weakly incised or rounded prostomium, while in specimens from the middle Atlantic and southern states, it tends to be more strongly incised. Postlarval forms from Maine have a rounded prostomium. The caruncle terminates bluntly on setiger 2. Eyes are present or absent; if present, there are four, disposed as in Figure 3a.

Setiger 1 has only capillary neurosetae and elevated notopodial lobes. Setigers 2–4 have blunt notopodial lobes with fascicles of winged capillary setae. The neuropodial lobes are greatly reduced and contain winged capillary setae. Setiger 6, and those immediately following, contain dorsal fascicles of winged capillary setae. The number of setae per notopodium gradually diminishes in the middle segments. In far posterior segments, only three or four winged capillary setae are found in each notopodium. On setiger 7, bidentate hooded hooks replace the neuropodial winged capillary setae. The hooks number about six in a series and have the main fang at a right angle to the shaft. Each hook has a constriction on the shaft (Figure 3j).

Setiger 5 is twice as large as either 4 or 6; the parapodia contain a row of heavy modified spines (Figure 3b–g) alternating with pennoned companion setae (Figure 3h). One or two superior dorsal, winged setae (Figure 3i) and a ventral fascicle of short winged setae are present. The modified spines are falcate and have a lateral flange or sheath. Figure 3b–g illustrates different views and degrees of wear of these spines.

Branchiae begin on setiger 7. They are small at first, reaching full size on setigers 11 and 12 and are absent from posterior segments.

The pygidium is cup-shaped with a distinct dorsal notch (Figure 3k, l).

DISTRIBUTION.—East coast of North America from Quebec and Newfoundland to Florida, Gulf of Mexico, California, Oregon, and Hawaii.

northern Gaspe waters, upstream and downstream part of middle St. Lawrence estuary, lower St. Lawrence estuary, Magdalen Islands (from Eastern Bradelle valley to the west, as far as Cape North, including the Cape Breton Channel), Prince Edward Island (from the northern tip of Miscou Island, N.B. to Cape Breton Island south of Cheticamp, including the Northumberland Strait and Georges Bay to the Canso Strait causeway), middle North Shore (from Sept -Iles to Cape Whittle, including the Mingan Islands); western slope of Newfoundland, including the southern part of the Strait of Belle Isle but excluding the upper 50m in the area southwest of Newfoundland; to Cape Hatteras

intertidal and infralittoral of the Gulf and estuary