Potentially Misidentified Species:
Neanthes succinea is similar in appearance to several polychaetes,
particularly those belonging to the same family. Descriptive
characteristics and habitat traits described here may aid in positive
identification, although polychaete taxonomy is generally considered beyond
the scope of amateur naturalists.
II. HABITAT AND DISTRIBUTION
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).
Neanthes succinea occurs throughout the IRL system.
III. LIFE HISTORY AND POPULATION BIOLOGY
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.
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 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 US coastal waters from
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.
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
IV. PHYSICAL TOLERANCES
The reported reproductive temperature range of the species is 12-35°C (Neuhoff 1979, Kuhl and Oglesby 1979).
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
V. COMMUNITY ECOLOGY
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
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 Ám) 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
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.
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
Water column larvae are vulnerable to predation by fish and birds (Craig et
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.
Neanthes succinea is an active forager primarily at night, spending most of the day in a mucous-lined tube (Craig et al. 2003).
VI. SPECIAL STATUS
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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Mullet. Copeia 4:705-707.
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Salton Sea: distribution and seasonal dynamics, Hydrobiologia 473:139-160.
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feeding guilds. Oceanography and Marine Biology Annual Review 17:193-284.
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Neanthes succinea in San Francisco Bay. Pacific Science 41:37-43.
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epitokal metamorphosis in Neanthes succinea (Frey et Leuckart) from
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pheromones in female Nereis succinea. Peptides 25:1517-1522.
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sediments of a subestuary of central Chesapeake Bay. Estuaries 8:296-304.
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region of Chesapeake Bay. Estuaries 8:93-113.
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succinea. Global Invasive Species database. Available online.
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the colonization of a dredged channel. Marine Biology 32:193-204.
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Nereis succinea in higher Salton Sea salinities. Biological Bulletin
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canvasbacks, Aythya valisineria, on Chesapeake Bay. Estuaries
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(Denmark). Ophelia 11:1-507.
Theede H. 1980. Physiological responses of estuarine animals to cadmium
pollution. Helgolander Meeresunters 33:26-35.
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dynamics in the Salton Sea, California, 1997-1999, Hydrobiologia
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Species FactSheet. USGS Nonindigenous Aquatic Species Database,
Gainesville, FL. Available online.
J. Masterson, Smithsonian Marine Station
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Page last updated: October 1, 2008