Common names: Clam Worm, more...
Synonyms: Alitta succinea Leuckart, 1847, more...
Regional Occurrence: Neanthes succinea is cosmopolitan in distribution and is common in temperate and tropical marine habitats. The putative native range is the Atlantic coast of the Americas, but the species also occurs as an introduced organism along coastal Europe and Africa, in the Black Sea, Caspian and Aral Sea, and southern Australia (Pardo and Dauer 2003, ISSG 2007). N. succinea also occurs along the US Pacific coast as an introduced, non-indigenous species, from Washington State to California (USGS 2008). Introduction pathways have included natural dispersal, ship ballast water, and hull fouling (ISSG 2007).
IRL Distribution: Neanthes succinea occurs throughout the IRL system.
Age, Size, Lifespan: Clam worms grow to approximately 190 mm in length (Craig et al. 2003, ISSG 2007).
NIMPIS (2006) indicates the life cycle takes a minimum of one year to complete.
Abundance: Orth (1973) indicates that Neanthes succinea is at times among the most dominant members of the Chesapeake Bay infaunal Zostera community, occurring in 75% of benthic samples collected in this study.
Clam worms may also occur in considerable abundance, even in marginal habitats (in which polychaetes often appear to thrive). Hamilton, Jr. (1972) reported N. succinea densities of 400/m2 in disturbed, partially anaerobic sediments near Cove Point, in Chesapeake Bay.
Reproduction: Reproduction in clam worms is sexual. Fertilization is external, and the sexes are separate.
When sexual maturity is reached, individuals metamorphose into a nektonic heteronereid form similar in appearance to the non-reproductive form except the parapodia have become enlarged and more lobate (Detwiler et al. 2002, ISSG 2007). This is also referred to as the epitokal stage (Craig et al. 2003) During spawning, heteronereids swim to the surface to spawn en masse. Females die after shedding eggs and males may die after spawning as well (Detwiler et al. 2002, NIMPIS 2006). Reproductive swarming is thought to be triggered by a complex set of exogenous cues including temperature, salinity, photoperiod and lunar period (Hardedge et al. 1990, Fong 1991, ISSG 2007). Swarming has been observed in U.S. coastal waters from March-October.
Laboratory experiments conducted by Hardege et al (1990) revealed that metamorphosis heteronereid stages and swarming could both be induced by raising temperatures at around the time of the new moon. Rasmussen (1973) reports similar circa-lunar periodicity of reproduction in the Ise fjord in Denmark, where swarming individuals could be collected during the summer months from the sea surface, after sunset at the time of the new moon.
Hardege et al. (2004) confirm female clam worms employ a tetra-peptide, cysteinyl-glutathione (CSSG) as mate recognition and gamete release pheromone. The authors demonstrated that female CSSG release during spawning induces male gamete release and also results in increased male swimming activity, possibly facilitating access to slower swimming females.
Embryology: Within 36 hours of fertilization, eggs develop into small, setose, two-segmented larvae. Planktonic larvae remain in the water column until they possess 9-12 segments (NIMPIS 2006 indicates 4-6 segments at settlement), at which time they begin to settle to the benthos (Tiffany et al. 2002).
Temperature: The reported reproductive temperature range of the species is 12-35°C (Neuhoff 1979, Kuhl and Oglesby 1979).
Salinity: Neanthes succinea is euryhaline in its salinity tolerance (Craig et al. 2003). Oglesby (1969) noted that N. succinea was capable of maintaining a hyperosmotic internal environment in response to a hyposaline external environment. Kuhl and Oglesby (1979) conducted laboratory experiments to determine critical upper salinity limits for reproduction and survival of Neanthes succinea. The authors reveal that atokus (immature) individuals survive for extended periods under hypersaline conditions at least as high as 65 ppt, and exhibit short-term survival at salinities as high as 80 ppt. Successful reproduction occurred at salinities as high as 45-50 ppt. Early embryonic stages are less tolerant of hypersalinity than are later developmental stages (e.g., trochophores).
Introduced N. succinea populations in the inland saline Salton Sea of southern California have adapted to elevated salinity levels but may not persist when salinities exceed physiological osmoregulatory limits (Detwiler et al. 2002).
Despite demonstrated salinity tolerance, Holland (1985) notes that N. succinea abundance in of Chesapeake Bay was typically highest in low-salinity years.
Trophic Mode: Neanthes succinea is opportunistic in its feeding. The jawed, eversible proboscis is used primarily to ingest sediment deposits, but it is also capable of grazing some plant material and of facultative capture of small invertebrates (Craig et al. 2003). Small amphipods and polychaetes have been found in N. succinea gut contents (NIMPIS 2006).
Fong (1987) conducted gut analyses of deposit-feeding N. succinea from San Francisco Bay. The authors observed that individuals consumed a wide range (20-300 µm) and that deposit feeding appeared to be largely non-selective feeding. Fauchald and Jumars (1979) indicate the species is primarily a sediment surface feeder.
Cammen (1980) estimated that approximately one-fourth of the organic carbon requirement of North Carolina N. succinea is microbial in origin, with additional sources of carbon derived from direct uptake of plant substratum, ingestion of meiofauna, and possibly uptake of dissolved organic matter.
Competitors: Dietary resources are generally not believed to be limiting to members of the soft sediment deposit feeding guild. As a result competition for dietary resources is not likely to be severe for clam worms.
Predators: A variety of predaceous birds and fish feed extensively on benthic Neanthes succinea (Detwiler et al. 2002). Bishop and Miglarese (1978) observed striped mullet (Mugil cephalus) feeding on swarming water column N. succinea at James Island, South Carolina. Perry and Uhler (1988) reported N. succinea was a minor component in the diet of canvasback geese (Aythya valisineria) wintering on Chesapeake Bay.
Water column larvae are vulnerable to predation by fish and birds (Craig et al. 2003).
Habitats: Neanthes succinea occupies a variety of marine and estuarine intertidal to subtidal infaunal and epifaunal habitats including sand and mud bottoms, seagrass meadows, rocky benthic areas, mussel and oyster beds, and dock pilings (Orth 1973, Craig et al. 2003). Hines and Comtois (1985) report that individuals occurred primarily deeper than 5 cm, with peak abundance between 10-15 cm.
Kaplan et al. (1975) note that N. succinea and other large, mobile species are among the macrobenthos that are quickest to re-colonize sediments that had been disturbed by dredging.
Activity Time: Neanthes succinea is an active forager primarily at night, spending most of the day in a mucous-lined tube (Craig et al. 2003).
Economic/Ecological Importance: Neanthes succinea is an important trophic link between benthic detritus accumulation and energy transfer to higher-level consumers (ISSG 2007). Clam worms also take up and bioaccumulate heavy metals and organic contaminants and may act as a trophic link in moving these materials through the food web (Leatherbarrow et al. 2005, ISSG 2007). Sublethal effects from uptake of the heavy metal cadmium in terms of growth and energy conversion efficiency have been reported by Theede (1980).
Neanthes succinea has significantly altered community structure in some areas where it has been introduced. In the Salton Sea, an inland salt lake in southeastern California, N. succinea had become the dominant benthic detritivore by 1979, and is a critical link in the trophic chain supporting the sport fishery on the lake (Kuhl and Oglesby 1979). Burrowing and feeding by N. succinea can alter sediment nutrient content, potentially altering community composition and also promoting bacterial activity (NIMPIS 2006).
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