Dipolydora quadrilobata (Jacobi 1883)

Polydora quadrilobata Jacobi

Polydora quadrilobata Jacobi, 1883, pp. 1–37, 2 pls.—Mesnil, 1897, pp. 87–88, pl. 3: figs. 9–11.—McIntosh, 1909, pp. 170–172, pl. 5:figs. 2–3; 1915, p. 236, pl. 98:figs. 13, 17, pl. 106: fig. 4.—Eliason, 1920, pp. 45–46; 1962, p. 52.—Fauvel, 1927, p. 52, figs. 18 l–n.—Annenkova, 1931, pp. 203–205; 1932, p. 139, figs. 6–9.—Procter, 1933, p. 142—Friedrich, 1938, p. 133.—Berkeley and Berkeley, 1943, p. 130; 1954, p. 464.—Uschakov, 1955, p. 273, figs. 94a–d; 1965, p. 250, fig. 94a–d.—Rasmussen, 1956, p. 64.—Hannerz, 1956, pp. 122–123.—Hempel, 1957a, pp. 276–278; 1957b, pp. 100–135, fig. 5.—Hartman, 1961, p. 29; 1969, pp. 145–146, 4 figs.—Khlebovitsch, 1961, p. 201.—Jones, 1961, p. 288.—Blake, 1969b, pp. 37–51, figs. 27–37.

Polydora tubifex Verrill, 1885b, pp. 438–439.—Sumner et al., 1913, p. 624.

Polydora littorea.—Hartman, 1944, pl. 18: fig. 9. Not Verrill, 1881.

MATERIAL EXAMINED.—Maine (Cobscook Bay; Lamoine Beach; Damariscotta River), Connecticut (Noank), Sweden and Denmark (NMGS).

DESCRIPTION.—Individuals measure up to 15 mm in length and have about 70 segments. The anterior end has brown, reticulated pigmentation dispersed on the sides of the peristomium and on the anterior and posterior margins of setigers 1–7. The intensity of the pigmentation varies between individuals, but has been found in some degree on all specimens examined from New England. The color in life is light tan, with red blood prominent in the branchiae, palps, and blood vessels.

The prostomium is distinctly bifid on its anterior margin and continues posteriorly as an indistinct caruncle to about the middle of setiger 3 (Figure 9a). Four to six eyes are present in nearly a straight transverse line. The two outer pairs may be fused into a single mass. The palps are long and flexible, with a prominent ciliated groove.

Setiger 1 has capillary notosetae and neurosetae (Figure 9b). Setigers 2–4 and 6 have neuropodial fascicles of finely-winged, capillary setae. The notosetae of setigers 2–4 are winged capillaries (Figure 9c). Bidentate hooded hooks begin on setiger 7 (Figure 9i) and are accompanied by two or three fine capillary setae. There are usually no more than three or four hooks in any one parapodium. The notosetae of setiger 6 and succeeding setigers include fascicles of winged capillaries. The number of capillary notosetae diminishes in the middle segments, and they are completely replaced by heavier, sharply pointed spines in far posterior segments. These spines are disposed in a semicircular arrangement and give the posterior end a spinous appearance (Figure 9j–k).

Setiger 5 lacks parapodial lobes and has three types of setae (Figure 9d). The dorsal setae consist of a horizontally curved row of heavy, modified spines (Figure 9e, f) and a vertical curved row of shorter limbate setae (Figure 9g, h) located at the anterior end of the horizontal row, resulting in a J-shaped arrangement when the specimen is viewed from the sides. The heavy spines have a unique structure (Figure 9e, f). The distal end curves and is bifurcated at the tip, forming two nearly equal teeth between which is located a fine bushy tuft. When worn, the teeth and tufts may be reduced. A small fascicle of winged setae is located ventral to the modified spines.

Branchiae begin on segment 7. They are short and stubby, not reaching full size until setiger 12 or 13. They are absent from the posterior third of the body.

The pygidium has four subequal lobes (Figure 9k). When seen on living specimens under reflected light, they are white.

DISTRIBUTION.—Europe, eastern Canada, New England, southern California, western Pacific.