BIOTIC

BIOTIC Species Information for Hediste diversicolor
All Taxonomy Biology Distribution Reproduction

Researched by	Georgina Budd	Data supplied by	MarLIN
Refereed by	Mike Kendall
General Biology
Growth form	Vermiform segmented	Feeding method	Surface deposit feeder Omnivore Scavenger Sub-surface deposit feeder Passive suspension feeder
Mobility/Movement	Burrower Swimmer Crawler	Environmental position	Infaunal
Typical food types	Mud, sand & detritus. Phytoplankton & plankton. Other macrofauna.	Habit	Burrow dwelling
Bioturbator	Diffusive mixing	Flexibility	High (>45 degrees)
Fragility	Fragile	Size	Medium(11-20 cm)
Height	Not relevant	Growth Rate	Insufficient information
Adult dispersal potential	1km-10km	Dependency	Independent
Sociability	Solitary
Toxic/Poisonous?	No
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. Colour The variable colours of Hediste diversicolor approaching maturity and during spawning (see reproduction) are due to varying proportions of green (biliverdin), orange and brown (carotenoids) pigments. The green colour of mature males and females is caused by biliverdin present in the gut wall, the epidermis and coelomic cells and is formed by the breakdown of haemoglobin in the blood. In males, the white mass of sperm in the coelom gives it a lighter green colour (Dales, 1950). In mature specimens during and after spawning, the green appearance is also enhanced by a complete extraction of carotenoids from the body wall (Dales & Kennedy, 1954).
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,