BIOTIC Species Information for Nephtys hombergii
|Researched by||Lizzie Tyler||Data supplied by||University of Sheffield|
|Refereed by||This information is not refereed.|
|Scientific name||Nephtys hombergii||Common name||Catworm|
|MCS Code||P499||Recent Synonyms||None|
|Additional Information||The different species of Nephtys are difficult to identify, requiring detailed examination of the parapodia and chaetae. Reference to Rainer (1991) is recommended.
Two other Nephtys species have previously been synonymous with Nephtys hombergii. Nephtys assimilis and Nephtys kersivalensis are now recognized as separate species as described in Rainer (1989) and Rainer (1991). Consequently, some records of the geographical distribution of Nephtys hombergii should be viewed with caution (Olive & Morgan, 1991).
|Taxonomy References||Rainer, 1989, Rainer, 1990, Hayward & Ryland, 1995b, Hayward et al., 1996, Rainer, 1991, Fish & Fish, 1996, Fauchald. 1963,|
|Growth form||Vermiform segmented
|Typical food types||Molluscs, crustaceans & other polychaetes.||Habit||Free living|
|Bioturbator||Diffusive mixing||Flexibility||High (>45 degrees)|
|Height||Not relevant||Growth Rate||Insufficient information|
|Adult dispersal potential||100-1000m||Dependency||Independent|
|General Biology Additional Information||Abundance
Clay (1967f) lists densities of Nephtys hombergii reported by various authors from locations in the British Isles, which range from 570 per m² in the Tamar Estuary to 2 per m² at a location on the Northumbrian coast.
Nephtys hombergii excavates no permanent burrow but continually changes course in the sediment in the hunt for food, so that a maze of temporary burrows is made, marked only by a mucilage lining. These tunnels are located 5 to 15 cm beneath the surface (Linke, 1939; Holme, 1949). The sampling technique of Vader (1964) showed that the worm can move very quickly through the substratum, downwards on the ebb tide and up again on the flood tide (Clay, 1967f). Nephtys hombergii is also capable of swimming short distances with an undulatory movement.
Adults of the species are carnivorous and captures prey with its eversible, papillated proboscis.
|Biology References||Holme, 1949, Linke, 1939, Vader, 1964, Clay, 1967(f), Arndt & Schiedek, 1997, Beukema, 1987, Hayward & Ryland, 1990, Julie Bremner, unpub data,|
|Distribution and Habitat|
|Distribution in Britain & Ireland||Found throughout Britain and Ireland.|
|Global distribution||Found from the northern Atlantic, from such areas as the Barents Sea, the Baltic and the North Sea, to the Mediterranean. Nephtys hombergii has been reported from as far south as South Africa.|
|Biogeographic range||Not researched||Depth range|
|Migratory||Non-migratory / Resident|
|Distribution Additional Information||Maximum densities of Nephtys hombergii tend to occur in the lower part of the intertidal that is also occupied by %Arenicola marina% (Clark & Haderlie, 1960; Clark et al., 1962) but Nephtys hombergii has been collected from dredge hauls at various depths.
On some shores, the intertidal zonation of Nephtys hombergii is probably determined by the type of substratum found at various levels (Clark & Haderlie, 1960).
Although the species may colonize a variety of substrata, Nephtys hombergii may be found in higher densities in muddy environments and this tends to isolate it from %Nephtys cirrosa%,
which is characteristic of cleaner, fairly coarse sand.
High densities of Nephtys hombergii were found in substrata of 0.3% particles >0.25mm and 5.8% <0.125mm in diameter but the worm tolerated up to 3.8% 0.25mm and 2.2-15.9% <0.125mm (Clark et al.,1962).
Nephtys species penetrate into the mouths of estuaries and estuarine lagoons until the salinity falls below 20 psu, but Nephtys hombergii occasionally extends into waters with a salinity <18 psu (Barnes, 1994). Clark & Haderlie (1960) found Nephtys hombergii in the Bristol Channel at salinities between 15.9 psu and 25.1 psu.
|Substratum preferences||Coarse clean sand
Fine clean sand
|Physiographic preferences||Open coast
Enclosed coast / Embayment
|Biological zone||Mid Eulittoral
|Wave exposure||Moderately Exposed
|Tidal stream strength/Water flow||Insufficient information
||Salinity||Variable (18-40 psu)
Reduced (18-30 psu)
|Habitat Preferences Additional Information||None entered|
|Distribution References||Rainer, 1989, Rainer, 1990, Hayward & Ryland, 1995b, Hayward et al., 1996, Rainer, 1991, Fish & Fish, 1996, Clark & Haderlie, 1960, Clark et al., 1962, Barnes, 1994, Clay, 1967(f), Alheit, 1978, Hayward & Ryland, 1990, Julie Bremner, unpub data,|
|Reproductive Season||See additional information||Reproductive Location||Sediment surface|
|Reproductive frequency||Annual protracted||Regeneration potential||No|
|Life span||3-5 years||Age at reproductive maturity||1-2 years|
|Generation time||1-2 years||Fecundity||>10,000 eggs per year|
|Egg/propagule size||150 µm diameter||Fertilization type||External|
|Reproduction Preferences Additional Information||Spawning
Sexes are separate. Nephtys hombergii remains in the sediment during spawning and eggs and sperm are released on to the surface of the sediment during low tide. Bentley (1989) gives an ultrastructural description of oogenesis in Nephtys hombergii. Mean size of oocytes was reported to be between 140 and 160 µm in Arcachon Bay, France, 200 µm in Southampton Water and between 100 to 140 µm on the Northumbrian coast (Mathivat-Lallier & Cazeau, 1991; Oyenenkan, 1986). The animals spawn via the anus. Histological examination by Bentley et al. (1984) revealed the development of a cleft in the central part of the gut in the prepygidial segment which serves to deliver the mature gametes to the anus for spawning. This system is developed only in mature worms of both sexes. Bentley et al. (1984) suggested that this represents the normal pathway for the discharge of gametes in the Nephtyidae, which lack functional coelomoducts. A spawning hormone (SH) released from the supraoesophageal ganglion brings about spawning in mature individuals (Olive, 1976; Olive & Bentley, 1980). Nephtys hombergii is a broadcast spawner, so it is advantageous that the spawning of a given individual coincides with that of several others of the same species. In addition to endocrine control, environmental factors, such as temperature, day-length, and tidal or lunar cycles, have been implicated in the timing of spawning of the Nephtyidae, in particular the spring tide phase of the lunar cycle (Bentley et al., 1984).
The planktonic cycle of Nephtys hombergii was described by Cazaux (1970), who defined five stages: two trochophore stages (2-3 days) and three metatrochophore stages. The first trochophore stage is lecithotrophic and successive four other stages are planktotrophic. The pelagic life cycle of Nephtys hombergii lasts seven to eight weeks at the end of which larvae metamorphose into benthic juveniles. Newly metamorphosed juveniles have an average width of 0.2 mm and eight or nine segments (Mathivat-Lallier & Cazaux, 1991).
Observation of the reproductive patterns of the Nephtyidae suggest that they are related to environmental conditions in central parts of the range of each species, marginal populations of some species exhibit occasional reproductive failures, e.g. Nephtys cirrosa, whose reproductive physiology is not sufficiently well adapted to conditions experienced in the northern limit of its range (Olive & Morgan, 1991). In the British Isles Nephtys hombergii has been observed to spawn in May and June in northern Britain, sometimes successfully but also unsuccessfully, to be followed by a period of oosorption (internal breakdown of gametes) overlapping with the subsequent cycle of gamete production. Olive & Morgan (1991) found reproductive failure in this species difficult to explain, as distribution records inferred Nephtys hombergii to be in the centre of its range in northeast England. They suggested for the relatively long-lived Nephtys hombergii that spawning failure could be part of an adaptive response in which adult survivorship is maintained at the expense of reproductive output (see Lewis et al., 1962; Grémare & Olive, 1986). The endocrine system of Nephtys hombergii (see Bentley & Pacey, 1992) is able to control spawning by failing to secrete gonadotrophic hormone (GH), withdrawing GH secretion during the vitellogenic phase, or failing to secrete spawning hormone. Such endocrine responses may result from the receipt of inappropriate environmental signals from the soma (Bentley & Pacey, 1992). Olive et al. (1985) suggested that when energy levels of the soma fall below some critical level (which may reduce survival chances of the individual) then reproductive failure through GH withdrawal may result.
In the Tyne Estuary spawning of Nephtys hombergii occurred in May and September, whilst in Southampton Water the species spawned throughout the year with peaks in July and November (Wilson, 1936; Oyenekan, 1986). In Århus Bay, Denmark, Nephtys hombergii spawned in August and September, but a decrease in the number of individuals bearing gametes in May and June suggested that at least part of the population spawned in early summer (Fallesen & Jørgensen, 1991).
|Reproduction References||Cazeau, 1970, Mathivat-Lallier & Cazaux, 1991, Oyenekan, 1986, Olive & Morgan, 1991, Grémare & Olive, 1986, Lewis et al., 1982, Fallesen & Jørgensen, 1991, Olive, 1976, Olive & Bentley, 1980, Bentley & Pacey, 1992, Bentley et al., 1984, Bentley, 1989, Eckert, 2003, Julie Bremner, unpub data, Olive, 1977,|