BIOTIC Species Information for Hediste diversicolor
|Click here to view the MarLIN Key Information Review for Hediste diversicolor|
|Researched by||Georgina Budd||Data supplied by||MarLIN|
|Refereed by||Mike Kendall|
|Scientific name||Hediste diversicolor||Common name||Ragworm|
|MCS Code||P462||Recent Synonyms||Nereis diversicolor
Nereis (Hediste) diversicolor
|Additional Information||The form and distribution of paragnaths on the pharynx can be very useful in identification and Kinberg (1866, cited in Chambers & Garwood, 1992) assigned roman numerals to eight different areas of the pharynx that bear paragnaths. However, the number of paragnaths can vary considerably both within and between populations and this variation is thought to be a result of habitat and feeding preferences (Barnes & Head, 1977).
See Chambers & Garwood (1992) for further description and detail on identification.
|Taxonomy References||Hayward & Ryland, 1995b, Fauchald, 1977, Barnes, 1994, Chambers & Garwood, 1992, Barnes & Head, 1977,|
|Growth form||Vermiform segmented
||Feeding method||Surface deposit feeder
Sub-surface deposit feeder
Passive suspension feeder
|Typical food types||Mud, sand & detritus. Phytoplankton & plankton. Other macrofauna.||Habit||Burrow dwelling|
|Bioturbator||Diffusive mixing||Flexibility||High (>45 degrees)|
|Height||Not relevant||Growth Rate||Insufficient information|
|Adult dispersal potential||1km-10km||Dependency||Independent|
|General Biology Additional Information||Feeding
Hediste diversicolor is omnivorous and exhibits a diversity of feeding modes; carnivory, scavenging, filter feeding on suspended particles and deposit-feeding on materials in and on the surface layers of the sediment (Barnes, 1994).
Hediste diversicolor feeds using an eversible pharynx and the sensory appendages on the head, namely palps and tentacles (M. Kendall, pers. comm.).
A conspicuous difference between Hediste diversicolor and the closely related polychaete Nereis virens is the unique ability of Hediste diversicolor to satisfy its metabolic requirements from a diet of phytoplankton, like a typical obligate filter-feeder (Nielsen et al., 1995).
The filter feeding mechanism was described by Harley (1950). A funnel-shaped net consisting of fine mucous threads is drawn across the burrow and a water current is driven through the net by undulating body movements (Fauchald & Jumars, 1979). This is best observed in a tank (M. Kendall, pers. comm.). When sufficient particles have accumulated on the net, they are consumed along with the entire net (Fauchald & Jumars, 1979). After an interval, the net is replaced (M. Kendall, pers. comm.). Riisgård (1991) suspected that Hediste diversicolor is a hitherto undervalued key organism in the control of phytoplankton in shallow brackish waters. It is unknown to what extent Hediste diversicolor utilizes its potential to subsist on suspended food particles in nature but can be considered a suspension feeder when a sufficient number of algal cells are present in the water (Riisgård, 1991).
When deposit feeding, Esnault et al. (1990) recognized two main types of searching behaviour exhibited by Hediste diversicolor. The first involved the worm crawling on the surface of the substratum prospecting for food, catching it with its jaws and ingesting it immediately. The second type saw the worm depositing a string of mucous on either side of its body on the substrate surface. When the worm retreated back into its burrow the mucous was brought back and built it into a pellet which can be consumed there and then or stored for consumption later on (Esnault et al., 1990).
Olivier et al. (1995) found that juvenile Hediste diversicolor can select detritus on the sediment surface and accumulate it in their burrow. The juveniles irrigate the burrows thereby maintaining an aerobic condition that favours the decaying process of the plant debris by stimulating bacterial growth ('gardening').
Lucas & Bertru (1997) found bacteriolytic activity in the digestive system of Hediste diversicolor thus highlighting the ability of this species to feed on bacteria.
|Biology References||Hayward & Ryland, 1995b, Fauchald, 1977, Barnes, 1994, Dales & Kennedy, 1954, Harley, 1950, Riisgård, 1991, Riisgård, 1994, Nielsen et al., 1995, Lucas & Bertru, 1997, Esnault et al., 1990, Olivier et al., 1995, Fauchald & Jumars, 1979, Scaps, 2002,|
|Distribution and Habitat|
|Distribution in Britain & Ireland||Widespread along all British coasts where suitable habitat and substratum exist.|
|Global distribution||Hediste diversicolor is widely distributed throughout north-west Europe on the Baltic Sea, North Sea and along Atlantic coasts to the Mediterranean.|
|Biogeographic range||Not researched||Depth range||Intertidal|
|Migratory||Non-migratory / Resident|
|Distribution Additional Information||
Distribution & density
In estuaries the maximum density of the Hediste diversicolor population normally occurs in the middle regions, with density decreasing both towards the head and mouth of the estuary. Smith (1956), found that the maximum population density of Hediste diversicolor in the Tamar estuary corresponded to that portion of the estuary with the greatest salinity variation. The density of worms varies between locations and throughout the reproductive cycle. Numbers of juveniles may be over 100 000 per m² (Clay, 1967(c)). In the Ythan Estuary, Scotland, the density of adult Hediste diversicolor was reported to be 961 per m² (Chambers & Milne, 1975).Burrows
The entrance to the burrows of Hediste diversicolor are 1-2 mm wide in soft mud and are best seen when a fork is inserted into the sediment and the handle pulled towards the user (M. Kendall, pers. comm.). Short shallow depressions radiate from the opening: these are made by the anterior part of the worm's body as it searches for food around it's hole, with the tail firmly anchored within the burrow. Burrow depth increases with body size (Esselink & Zwarts, 1989). Whilst feeding at the mud surface the worm is particularly prone to predation by wading birds and fish. The burrow is thus an important refuge in which to retreat. Esselink & Zwarts (1989) found a seasonal variation in the depth of burrows of Hediste diversicolor. The deepest burrows were seen in winter and it is likely that this deeper burrowing is an adaptation to escape low temperatures. Burrow depth was seen to level off at 15 cm because at this depth the worm can retreat from the reach of most deep-probing predators including curlews and oyster catchers. The individual burrow is a well-delimited territory but this territoriality is not extended outside the burrow (Scaps, 2002).
|Substratum preferences||Sandy mud
Enclosed coast / Embayment
Ria / Voe
|Biological zone||Upper Littoral Fringe
Lower Littoral Fringe
|Tidal stream strength/Water flow||Weak (<1 kn)
Very Weak (negligible)
|Salinity||Low (<18 psu)
Reduced (18-30 psu)
Variable (18-40 psu)
|Habitat Preferences Additional Information||None entered|
|Distribution References||Hayward & Ryland, 1995b, Fauchald, 1977, Clay, 1967 (c.), Chambers & Milne, 1975, Esselink & Zwarts, 1989, Smith, 1956, Kristensen, 1988, Scaps, 2002, Beukema, 1990,|
|Reproductive Season||Spring - summer||Reproductive Location||Adult burrow|
|Reproductive frequency||Semelparous||Regeneration potential||No|
|Life span||1 year||Age at reproductive maturity||<1 year|
|Generation time||1-2 years||Fecundity||Insufficient information|
|Egg/propagule size||Insufficient information||Fertilization type||External|
|Reproduction Preferences Additional Information||
Nereidae are monotelic, that is, they reproduce only once in their lifetime and then die (Olive & Garwood, 1981). Hediste diversicolor is gonochoristic (dioecious) and remains atokous throughout its life (Scaps, 2002).
In summer and autumn the sexes are externally indistinguishable being both reddish brown in colour. In any one population females are predominant, although to varying extent between localities (Dales, 1950; Clay, 1967 (c) and references therein). This observation led early workers to suggest parthenogenetic reproduction and hermaphroditism within Hediste diversicolor (Dales, 1950) but it is now acknowledged that these reproductive mechanisms are not found in Hediste diversicolor. Hediste diversicolor does not display epitoky or swarming behaviour associated with sexual reproduction like other nereid polychaetes, such as Nereis succinea and Nereis virens. The sex ratio in populations of Hediste diversicolor is heavily biased towards females. Olive & Garwood (1981) reported a ratio of females to males of approximately 4.6 : 1 in northeastern England.
Maturation & spawning
Colour differences between the sexes become more apparent upon maturation. Maturation and spawning are induced by a temperature rise in early spring to between 6°C and 11°C following a period of low winter temperatures. The male becomes bright green in colour. In contrast, the female appears darker green in colour which may be lacking on the ventral side. Reddish brown pigments may also still be visible in the female.
Bartels-Hardege & Zeeck (1990) induced spawning in the laboratory, in specimens of Hediste diversicolor from tidal flats of the Jadebusen (North Sea), outside the normal spawning period of early spring. Temperatures were not lowered to simulate winter conditions but maintained at 16°C. Mature specimens appeared after four weeks and released gametes after a further four weeks according to a semilunar cycle. Reproduction was sustained for a period of four months. Such an extended spawning was witnessed on the Jadebusen following an unusually warm winter. Spawning occurred from February until May and was less synchronized. In contrast, the same population spawned within two months (February - March) following lower winter temperatures in another year. They concluded that not only a threshold temperature was important for synchronized spawning but the timing of the rise in temperature following winter was also a significant factor (Bartels-Hardege & Zeeck, 1990).
Age at maturity
Generally Hediste diversicolor is reported to reach maturity between one and three years of age. Populations appear to show local characteristics in terms of spawning periods. Spawning may be limited to a short period in spring or extend over the summer. In the Thames Estuary, Dales (1950) reported specimens growing to maturity within one year, spawning in February, with some individuals surviving up to 18 months. Mettam et al. (1982), reported that Hediste diversicolor from the Severn Estuary matured rapidly in the spring and spawned at two years old. Olive & Garwood (1981), found that females in the Blyth Estuary, Northumberland, were in their second year before eggs began to appear, so most probably spawned in their third year. However, these authors also reported that spermatogenesis was only found to take about six months in the Blyth. They therefore suggested that there is a variable age at maturity and that this could have arisen either because the population were polymorphic in terms of their genetically determined age at maturity or if the age at maturity was variable and influenced by the environmental conditions (Olive & Garwood, 1981). Golding & Yuwono (1994) showed that, although full maturation of the gametes occurred, spawning was blocked by implanting cerebral ganglia from immature donors into the body cavity of adult hosts.
In the Ythan Estuary, Scotland, Chambers & Milne (1975) witnessed two spawning peaks in the population of Hediste diversicolor, the first occurring between January and March, and another between June and August.
|Reproduction References||Barnes, 1994, Clay, 1967 (c.), Chambers & Milne, 1975, Dales, 1950, Mettam et al., 1982, Olive & Garwood, 1981, Bachelet, 1987, Bentley & Pacey, 1992, Bartels-Hardege & Zeeck, 1990, Chambers & Garwood, 1992, Scaps, 2002, Golding & Yuwono, 1994,|