Dipolydora socialis (Schmarda 1861)

Polydora socialis (Schmarda)

Leucodore socialis Schmarda, 1861, p. 64, figs. a–c, pl. 26: fig. 209.

Polydora socialis.—Mesnil, 1896, pp. 193–194, pl. 12: figs. 30–32—Ehlers, 1901, p. 165.—Hartman, 1941, pp. 310–311, pl. 48: figs. 41–42; 1945, pp. 33–35; 1948, p. 37; 1951, p. 83; 1953. pp. 43–44; 1961, p. 29; 1966a, p. 19, pl. 19:figs. 1–2; 1969, pp. 147–148, 2 figs.—Hartman and Reish, 1950, p. 28.—Rioja, 1943, p. 230.—Hartmann-Schröder, 1962, pp. 137–138, figs. 167–168; 1965, pp. 209–211, figs. 200–203—Wells and Gray, 1964, p. 73.—Long, 1968, p. 348.—Blake, 1969a, pp. 816–817, fig. 5; 1969b, pp. 24–31, figs. 19–22.

Polydora socialis plena Berkeley and Berkeley, 1936, pp. 468–469; 1952, p. 22.—Reish, 1968, p. 82.

?Polydora gracilis Verrill, 1880, p. 174.

MATERIAL EXAMINED.—Maine (Damariscotta River), Massachusetts (Cape Cod Bay, coll. SEP), Connecticut (Mystic River), North Carolina (Beaufort), South Carolina (Charleston, coll. M. Chamberlain), California (Mugu Lagoon, AHF N1417; Cayucos), British Columbia (paratypes of P. socialis plena, USNM 32704), Chile (Lund University Chile Expedition 1947–48, deposited AHF).

DESCRIPTION.—Specimens of Polydora socialis from New England measure up to 55 mm in length and have over 400 segments. Individuals examined from North and South Carolina were not as large. Sexually mature females are orange. Larval pigmentation is retained on most adults (Figure 13a), including both dorsal and ventral bands.

The prostomium is deeply notched on its anterior margin. The caruncle extends to setigers 4–9. Eyes are present or absent; when present, they number four to six: a circular pair high up on the prostomial ridge, and more anterior second and third pairs, which may be fused laterally on the prostomial ridge (Figure 13a). The palps are long and prehensile in life; upon preservation, however, they contract and extend posteriorly only to setigers 12–15.

Setiger 1 has capillary setae in both noto- and neuropodia (Figure 14a). Setigers 2–4, 6 and succeeding setigers have two types of posteriorly directed notosetae, an anterior row of short curved capillaries and a posterior row of long, stout capillaries. In far posterior setigers only a few laterally-directed capillary notosetae are present. The neuropodia of setigers 2–4 and 6 have posteriorly directed capillary setae. Bidentate hooded hooks begin on setiger 7. Two or three capillary setae accompany the hooks for several setigers, then disappear, and appear again in far posterior setigers. In anterior setigers, the hooks have a 45° angle between the main fang and the secondary tooth (Figure 14c). In posterior setigers, the main fang is longer and narrower, while the upper tooth is smaller and closely adhering to the shaft and diminishing the angle (Figure 14e).

Setiger 5 is large and well developed (Figure 13a, b). The setae include a small bundle of dorsal geniculate setae lying at the anterior end of a semicircular row of alternating heavy modified spines and smaller pennoned companion setae (Figure 14b). The heavy spines are falcate and have a subterminal protuberance. Ventral and posterior to the above is a small tuft of winged setae.

Branchiae begin on setiger 8 (rarely 7–9) and continue to near the posterior end.

The pygidium typically has a large ventral lobe and two small dorsal ones, with a dorsal gap (Figure 15c, d). In some specimens, however, the three lobes are continuous.

In P. socialis an unusual grinding apparatus has been observed between the esophagus and intestine. In young specimens, this “gizzard-like” structure is thin and transparent, consisting of four teeth, each with a central, inwardly directed cusp. In older specimens, the teeth are fragmented and lie as inclusions in four longitudinal muscles (Figure 14g). This structure is similar to one figured by Carazzi (1893) for P. flava.

DISTRIBUTION.—East and west coasts of North America; Gulf of Mexico; Chile; Falkland Islands.