Mud worms: Streblospio benedicti

Description

Streblospio benedicti is a segmented marine polychaete (family Spionidae) with paired, paddle-like appendages (parapodia) on each segment. Its conical head (prostomium) is equipped with four eyes, coiling tentacles (palps), two banded gills, and an impressive array of sensory organs (Speer 1997). Its partially translucent body is reddish-brown with dark green gill bands (Weiss 1995), and it typically grows to 6 millimeters (Gosner 1978). S. benedicti live in soft gray mucoid tubes located at and slightly below the sediment surface (Hartman 1947, Weiss 1995).

Background

Distribution. S. benedicti are common along the entire Atlantic coast, and are commonly found in fine sands and silty sediments (Franz and Harris 1988, Steimle and Caracciolo-Ward 1989). These worms are abundant in polyhaline and mesohaline portions of the Hudson River estuary (Ristich et al. 1977), and S. benedicti is one of the most abundant and ubiquitous benthic invertebrate species throughout New York/New Jersey Harbor (Diaz and Boesch 1982, Cerrato 1986, Franz and Harris 1988, this study).

Feeding. S. benedicti consumes mud and detritus captured by sweeping its palps across the sediment or through the water column (Gosner 1978).

Life Cycle

Polychaete gonads appear as swellings during the breeding season, and gametes are shed into the coelom (epithelium-lined body cavity between the body wall and the digestive tract) and expelled through the nephridia or via the rupturing of the body wall. Fertilization is external, and development proceeds through larval and juvenile stages (Myers 1997, Speer 1997).

Environmental Influences

Salinity. S. benedicti is generally sensitive to changes in salinity, and its distribution in estuaries often reflects the salinity structure. Abundance decreases as salinity lowers, and even high amounts of rain can affect S. benedicti distribution (Reish 1979). This species most commonly occurs in polyhaline waters (18 to 30 practical salinity units [psu]), but has been observed in the mesohaline waters (5 to 18 psu) of the Hudson River estuary (Ristich et al. 1977).

Predation. Like many polychaetes, S. benedicti is an important food source for various species of fish, such as spot (Leiostomus xanthurus) and winter flounder (Pleuronectes americanus) in New York/New Jersey Harbor (Grosslein and Azarovitz 1982).

Pollution. Polychaete distributions and dominance patterns are often used as indicators of pollution, as many species (including S. benedicti) are relatively tolerant to high levels of sediment organics (Reish 1979). Often, pollution-tolerant polychaetes remain in areas where more sensitive species have left or died, though heavily polluted areas eventually become completely devoid of life. Dredging activities can also negatively affect S. benedicti distributions through burial, removal of suitable habitat, resuspension of silts, and release of sediment-bound contaminants. Recolonization by most polychaetes can occur in less than a month, but some studies have indicated that several months to a year may be needed (Reish 1979).

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