Neanthes succinea (Leuckart, 1847) – clam worm; pile worm
Synonyms: Alitta succinea; Nereis succinea; Nectoneanthes alatopalpis Wu et al., 1985; Nectoneanthes oxypoda Imajima, 1972; Nereis (Neanthes) australis Treadwell, 1923; Nereis (Neanthes) saltoni Hartman, 1936; Nereis alatopalpis Wesenberg-Lund, 1949; Neanthes perrieri Saint-Joseph, 1898; Nereis belawanensis Pflugfelder, 1933; Nereis acutifolia Ehlers, 1901; Nereis glandulosa Ehlers, 1908; Nereis limbata Ehlers, 1868; Nereis reibischi Heinen, 1911
Common names: Pileworm, clam worm (U.K., USA);
This is a rather large polychaete worm; it may be almost 20 cm long. Macroscopically it is similar to other nereid species occurring in Nordic waters, e.g. N. virens (M. Sars, 1835), Nereis pelagica Linnaeus, 1758 and N. diversicolor (=Hediste d.) (O.F. Müller, 1776), i.e. it has one pair of antennae, one pair of palps and 4 pairs of tentacles. Microscopically it has a distinct pattern of paragnaths (small chitinous spines on the eversible pharynx), and also the lobes of the parapodia are distinct for the different species. The body in N. succinea is divided into two regions, the posterior part having much enlarged lobes on the parapodia. The head region is dark brownish and the posterior part is greenish yellow. During swarming the color is pale reddish.
Neanthes succinea, full body. Photo by Kathe Rose Jensen
Neanthes succinea, close-up. Photo by Kathe Rose Jensen
Neanthes succinea (from Kirkegaard 1992)
A: Anterior end with everted proboscis showing jaws and paragnaths. Arrow points to group of paragnaths that are specific for this species.
B: Parapodium from anterior end
Parapodium from posterior end with enlarged dorsal lobe.
Fore more information on the three common species (see below).
Native distribution: This is a cryptogenic species. It was originally described from Helgoland in 1847 (Bakken & Wilson, 2005), but it took almost 100 years before it was recorded in other places. However, Wolff (1973) claims that it may have been present in the Netherlands since the 18th century, and there are museum records from 1899.
Introduced distribution: This species is found almost worldwide, but has been considered native of the North(east) Atlantic and then introduced to other regions. It was first recorded from Danish waters in 1953, but later a few specimens, which had been collected in 1949, were found in the Zoological Museum, Copenhagen (Muus, 1967). It was first found in Sweden on the west coast in 1940 (Smith, 1963). It is often associated with mussel beds (Muus, 1967; Rasmussen, 1973).
On the west coast of the USA N. succinea lives in a land-locked salt-lake, Salton Sea, below sea level (Kuhl & Oglesby, 1979).
The species recorded as Nereis succinea in the Caspian Sea has turned out to be Hediste diversicolor (=Nereis d.) (Muus, 1967).
Neanthes succinea occurs in Iranean Gulf (as Nereis alatopalpis) and in southeastern Australia, where it was forst recorded in 1978 (Hewitt et al., 2004).
N. succinea is a deposit-feeder preferentially inhabiting soft bottoms from intertidal to about 20 m depth (Wolff, 1973). It may also be a voracious predator or scavenger, feeding on amphipods or other small invertebrates (Rasmussen, 1973; Hardege et al., 1990). It burrows in the sediment and may form semi-permanent U-shaped tubes or complex gallery burrows, depending on the sediment (Rasmussen, 1973; Kirkegaard, 1992). It may occur in densities of 600 individuals per m² (Rasmussen, 1973). It is highly tolerant for kinds of pollution and extremely euryhaline (Kuhl & Oglesby, 1979) and is able to take up sediment-associated pollutants through the gut (Ahrens et al., 2001). It is often associated with mussel and oyster beds. It is an excellent food for many fish species (Carpelan & Linsley, 1961; Neuhoff, 1979), and is also used for bait by sport fishermen. During swarming they are often prey of sea birds from above and jellyfish from below (Rasmussen, 1973).
Reproduction: In N. succinea both sexes show swarming behavior in connection with reproduction. Swarming takes place in the summer at temperatures above 13° C, and usually during the night at new moon (Kirkegaard, 1992), though it occurred in bright sunshine in the Isefjord (Rasmussen, 1973). The the Salton Sea swarming does not seem to follow a monthly cycle (Carpelan & Linsley, 1972). In N. virens only the males form "heteronereis" or epitoke body forms with enlanrged parapodial lobes on part of the body (Bass & Brafield, 1972). H. diversicolor does not change in body form in connection with reproduction (Kirkegaard, 1992). In all three species the worms die soon after spawning (Muus, 1967; Kirkegaard, 1992). Spawning period for N. succinea is June to September, for N. virens April to May, and for H. diversicolor June to August (Neuhoff, 1979). Gonads mature while the animals are still in their tubes while they wait for the adequate signal to initiate swarming (Hardege et al., 1990). The body is divided into 3 regions during the swarming period; only the middle section is used for swimming. Males are bright red in the middle section and females greenish brown (Rasmussen, 1973). Many studies have been carried out on the role of pheromones in the reproduction of this species (Zeeck et al., 1990; Ram et al., 1999, 2008; Watson et al., 2003; Hardege et al., 2004). Swarming is controlled by temperature and lunar phase (Hardege et al., 1990).
As it is considered native in many European countries, impacts have not been identified except for Australia and the west coast of the USA. It has a high potential for bioturbation and the impacts associated with this, e.g. oxygenation in deeper layers, bioavailability of pollutants buried in the sediment, increased activity of meiofauna and micro-organisms. It is able to bioaccumulate a number of pollutants and may be used as a biomonitor. Competition with other nereid species has been suggested as H. diversicolor seems to become rare where N. succinea becomes common (Smith, 1963).
Nereis succinea and the other nereid species are commonly used as bait.