MarLIN

information on the biology of species and the ecology of habitats found around the coasts and seas of the British Isles

A bristleworm (Aphelochaeta marioni)

Distribution data supplied by the Ocean Biogeographic Information System (OBIS). To interrogate UK data visit the NBN Atlas.

Researched byWill Rayment Refereed byDr Peter Gibbs
Authority(Saint-Joseph, 1894)
Other common names- SynonymsTharyx marioni (Saint-Joseph, 1894)

Summary

Description

Aphelochaeta marioni is a thin, thread like, segmented worm. The fifth segment bears a pair of grooved tentacles, or palps, which are used for deposit feeding. The palps, which are tightly coiled when retracted, are approximately equal in length to the body. Numerous filamentous cirri, which act as gills, are arranged in pairs on each of the segments of the anterior half of the body. The bristles (chaetae) are very fine and hair like. Aphelochaeta marioni is reddish-brown in colour and typically between 20 and 35 mm in length, although individuals can reach 100 mm in length.

Recorded distribution in Britain and Ireland

Patchily distributed all around the British coast where suitable substrata exist. Occurs on the south west and south coasts of the Isle of Man and has also been recorded in north east Ireland.

Global distribution

Recorded from parts of the North Atlantic, North Sea, western Baltic, Mediterranean, South Pacific and the Indian Ocean.

Habitat

Aphelochaeta marioni lives buried in soft sediments in the intertidal and subtidal. The majority of individuals live in the upper 4 cm of the sediment, with the smaller animals nearer the surface. It is sometimes present in sandy sediments, but predominates in zones of muddy sand or silt, especially in areas where the surface of the sediment consists of diatom ooze. It is occasionally found in the sediment that accumulates in rock crevices or around seaweed holdfasts.

Depth range

Mid shore to 5000 m

Identifying features

  • Body with 200 segments or more.
  • First segment (prostomium) is a blunt cone without eyes.
  • Following 3 segments achaetous.
  • Pair of coiling palps located on first chaetiger.
  • Long, contractile gill filaments present from first chaetiger to mid-point of body.
  • Chaetae very fine and hair like.

Additional information

The name change from Tharyx marioni to Aphelochaeta marioni occurred recently and some authors still use the previous name. Therefore, care should be taken when searching the literature on this species. In this review, where the species was researched under the former name, the species name is given as Aphelochaeta marioni (studied as Tharyx marioni). Aphelochaeta marioni is very difficult to identify (Mike Kendall, pers. comm.) and some authors (e.g. Farke, 1979) have commented that specimens that have been the subject of published research may have been misidentified.

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Biology review

Taxonomy

PhylumAnnelidaSegmented worms e.g. ragworms, tubeworms & fanworms
ClassPolychaetaBristleworms, e.g. ragworms, scaleworms, paddleworms, fanworms and tubeworms
OrderTerebellida
FamilyCirratulidae
GenusAphelochaeta
Authority(Saint-Joseph, 1894)
Recent SynonymsTharyx marioni (Saint-Joseph, 1894)

Biology

Typical abundanceHigh density
Male size range10-100mmMale size at maturity10mm
Female size range10mmFemale size at maturity
Growth formVermiform segmentedGrowth rate1-1.5mm/month
Body flexibilityHigh (greater than 45 degrees)Mobility
Characteristic feeding methodNot relevant, Surface deposit feeder
Diet/food source
Typically feeds onOrganic debris, diatoms
Sociability Environmental positionInfaunal
DependencyIndependent.
SupportsNone
Is the species harmful?No information

Biology information

Abundance
Gibbs (1969) studied the abundance of Aphelochaeta marioni (studied as Tharyx marioni) in Stonehouse Pool, Plymouth Sound. In silt/clay sediments at 5 m depth, the species occurred at a maximum density of 108,000 individuals/m2. In silt/clay and fine sand at the low water mark, the maximum density was 61,150 individuals/m2. Farke (1979) studied the abundance of Aphelochaeta marioni (studied as Tharyx marioni) in the Wadden Sea, Netherlands. In the intertidal, the maximum recorded abundance was 71,200 individuals/m2 in muddy sand.

Feeding
Aphelochaeta marioni is a deposit feeder, feeding at the surface of the sediment at night. While feeding the animal remains in its burrow and the two palps roam at the surface transporting sand, debris and diatoms to the mouth along a tentacle canal crenulated with cilia. Farke (1979) is unsure whether Aphelochaeta marioni is a selective feeder, but it seems not, as sand grains have been found in the gut of the animal.

Habitat preferences

Physiographic preferencesOpen coast, Offshore seabed, Strait / sound, Estuary, Enclosed coast / Embayment
Biological zone preferencesBathybenthic (Bathyal), Circalittoral offshore, Lower circalittoral, Lower eulittoral, Lower infralittoral, Mid eulittoral, Sublittoral fringe, Upper circalittoral, Upper infralittoral
Substratum / habitat preferencesFine clean sand, Mud, Muddy sand, Sandy mud
Tidal strength preferencesModerately Strong 1 to 3 knots (0.5-1.5 m/sec.), Very Weak (negligible), Weak < 1 knot (<0.5 m/sec.)
Wave exposure preferencesExtremely sheltered, Sheltered, Very sheltered
Salinity preferencesFull (30-40 psu), Low (<18 psu), Reduced (18-30 psu), Variable (18-40 psu)
Depth range Mid shore to 5000 m
Other preferences
Migration PatternNon-migratory / resident

Habitat Information

Aphelochaeta marioni has been recorded from a variety of different sediment types. In the intertidal area of the Wadden Sea, it achieved highest abundance where the sediment fraction smaller than 0.04 mm diameter was greater than 10% of the total sediment (Farke, 1979). In the Severn Estuary, Aphelochaeta marioni (studied as Tharyx marioni) characterized the faunal assemblage of very poorly oxygenated, poorly sorted mud with relatively high interstitial salinity (Broom et al., 1991). In fact, Aphelochaeta marioni displays a remarkable tolerance for salinity range. Wolff (1973) recorded Aphelochaeta marioni (studied as Tharyx marioni) from brackish inland waters in the Netherlands with a salinity of 16 psu, but not in areas permanently exposed to lower salinities. Farke (1979) reported that the species also penetrated into areas exposed to salinities of 4 psu during short periods at low tide when the freshwater discharge from rivers was high.

Life history

Adult characteristics

Reproductive type Gonochoristic (dioecious) Reproductive frequency Annual episodic
Fecundity (number of eggs) 100-1,000 Generation time 1-2 years
Age at maturity 1 year Season See additional information
Life span 2-3 years

Larval characteristics

Larval/propagule type - Larval/juvenile development Lecithotrophic
Duration of larval stage Not relevant Larval dispersal potential See additional information
Larval settlement period

Life history information

The lifecycle of Aphelochaeta marioni varies according to environmental conditions. In Stonehouse Pool, Plymouth Sound, Aphelochaeta marioni (studied as Tharyx marioni) spawned in October and November (Gibbs, 1971) whereas in the Wadden Sea, Netherlands, spawning occurred from May to July (Farke, 1979). Spawning, which occurs at night, was observed in a microsystem in the laboratory by Farke (1979). The female rose up into the water column with the tail end remaining in the burrow. The eggs were shed within a few seconds and sank to form puddles on the sediment. The female then returned to the burrow and resumed feeding within half an hour. Fertilization was not observed, probably because the male does not leave the burrow. The embryos developed lecithotrophically and hatched in about 10 days (Farke, 1979). The newly hatched juveniles were ca 0.25 mm in length with a flattened, oval body shape, and had no pigment, chaetae, cirri or palps. Immediately after hatching, the juveniles dug into the sediment. Where the sediment depth was not sufficient for digging, the juveniles swam or crawled in search of a suitable substratum (Farke, 1979). In the microsystem, juvenile mortality was high (ca 10% per month) and most animals survived for less than a year (Farke, 1979). In the Wadden Sea, the majority of the cohort reached maturity and spawned at the end of their first year, although some slower developers did not spawn until the end of their second year (Farke, 1979). However, the population of Aphelochaeta marioni in Stonehouse Pool spawned for the first time at the end of the second year of life (Gibbs, 1971). There was no evidence of a major post-spawning mortality and it was suggested that individuals may survive to spawn over several years. Gibbs (1971) found that the number of eggs laid varied from 24-539 (mean=197) and was correlated with the female's number of genital segments, and hence, female size and age.

Dispersal
Under stable conditions, adult and juvenile Aphelochaeta marioni disperse by burrowing (Farke, 1979). In the microsystem, a glass barrier in the sediment prevented the movement of animals to new areas over a period of some months, even though dispersal could have occurred by creeping on the surface or swimming. When the barrier was removed, the new areas were soon colonized (Farke, 1979). Farke (1979) reported that Aphelochaeta marioni (studied as Tharyx marioni) was capable of swimming but only did so under abnormal circumstances, e.g. when removed from the sediment. Farke (1979) suggested that as there was no pelagic stage, dispersal and immigration to new areas must mainly occur during periods of erosion when animals are carried away from their habitat by water currents.

Sensitivity reviewHow is sensitivity assessed?

Physical pressures

 IntoleranceRecoverabilitySensitivityEvidence/Confidence
High High Moderate Low
Aphelochaeta marioni lives infaunally in soft sediments. The physical removal of its substratum, e.g. as a result of channel dredging activities, would also remove the entire population of Aphelochaeta marioni and hence, intolerance is recorded as high. Aphelochaeta marioni has no pelagic phase in its lifecycle, and dispersal is limited to lateral movement by the slow burrowing of the adults and juveniles (Farke, 1979). Recoverability is recorded as high (see additional information below).
Low Immediate Not sensitive Low
Aphelochaeta marioni lives infaunally in soft sediments and moves by burrowing. It deposit feeds at the surface by extending contractile palps from its burrow. An additional 5 cm layer of sediment would result in a temporary cessation of feeding activity, and therefore growth and reproduction are likely to be compromised. However, Aphelochaeta marioni would be expected to quickly relocate to its favoured depth, with no mortality, and hence an intolerance of low is recorded. Once the animals have relocated to the surface, feeding activity should return to normal and therefore a recoverability of immediate is recorded.
Tolerant* Not relevant Not sensitive* Low
Aphelochaeta marioni is not likely to be perturbed by an increase in suspended sediment because it lives infaunally in soft sediment (Brenchley, 1981). It is a surface deposit feeder. While feeding, the animal remains in its burrow and the two palps roam at the surface transporting sand, debris and diatoms to the mouth along a tentacle canal crenulated with cilia (Farke, 1979). An increased rate of siltation may result in an increase in food availability and therefore growth and reproduction of Aphelochaeta marioni may be enhanced. However, food availability would only increase if the additional suspended sediment contained a significant proportion of organic matter and the population would only be enhanced if food was previously limiting.
Low Immediate Not sensitive Low
Aphelochaeta marioni is a surface deposit feeder and therefore relies on a supply of nutrients at the sediment surface. A decrease in the suspended sediment would result in a decreased rate of deposition on the substratum surface and therefore a reduction in food availability for Aphelochaeta marioni. This would be likely to impair growth and reproduction. The benchmark states that this change would occur for one month and therefore would be unlikely to cause mortality. An intolerance of low is therefore recorded. As soon as suspended sediment levels increased, feeding activity would return to normal and hence recovery is recorded as immediate.
Not relevant Not relevant Not relevant Not relevant
Aphelochaeta marioni lives infaunally in sediment that has a high silt content and retains a large amount of water. It is therefore protected from desiccation stress.
Intermediate High Low Low
Aphelochaeta marioni lives in the intertidal zone in significant numbers (Gibbs, 1969; Farke, 1979). The species lives infaunally and hence is not likely to suffer from desiccation stress. However, Aphelochaeta marioni can only feed when immersed and therefore will experience reduced feeding opportunities. Over the course of a year the resultant energetic cost is likely to cause some mortality. In addition, increased emergence will increase the vulnerability to predation from shore birds. An intolerance of intermediate is therefore recorded. Recoverability is recorded as high (see additional information below).
Tolerant Not relevant Not sensitive High
Aphelochaeta marioni thrives in the subtidal zone and therefore could potentially benefit from a decreased emergence regime. It is possible that decreased emergence would allow the species to colonize further up the shore.
Intermediate High Low Low
An increase in water flow rate is not likely to affect Aphelochaeta marioni directly as it lives infaunally. However, increased water flow rate will change the sediment characteristics in which the species lives, primarily by re-suspending and preventing deposition of finer particles (Hiscock, 1983). The preferred habitat of Aphelochaeta marioni has a high silt content (Gibbs, 1969), a substratum which would not occur in very strong tidal streams. Therefore, the species would be outside its habitat preference and some mortality would be likely to occur. Additionally, the consequent lack of deposition of particulate matter at the sediment surface would reduce food availability. The resultant energetic cost over one year would also be likely to result in some mortality. An intolerance of intermediate is therefore recorded. Recoverability is recorded as high (see additional information below).
Tolerant* Not relevant Not sensitive* High
Aphelochaeta marioni thrives in areas with low water flow, including the lowest category on the water flow scale (Connor et al., 1997), and is tolerant of hypoxia (Broom et al., 1991). Hence, the species is likely to tolerate a reduction in water flow. However, decreased water movement would result in increased deposition of suspended sediment (Hiscock, 1983). An increased rate of siltation may result in an increase in food availability for Aphelochaeta marioni and therefore growth and reproduction may be enhanced, but only if food was previously limiting.
Low Very high Very Low Low
Aphelochaeta marioni is distributed over a wide temperature range. It has been recorded from the Mediterranean Sea and Indian Ocean (Hartmann-Schröder, 1974; Rogall, 1977; both cited in Farke, 1979) and therefore the species must be capable of tolerating higher temperatures than it experiences in Northern Europe. Furthermore, Aphelochaeta marioni lives infaunally and so is likely to be insulated from rapid temperature change. An increase in temperature would be expected to cause some physiological stress but no mortality and therefore an intolerance of low is recorded. Metabolic activity should quickly return to normal when temperatures decrease and so a recoverability of very high is recorded.
Low Very high Very Low Low
Aphelochaeta marioni is distributed over a wide temperature range. It has been recorded from the Western Baltic Sea, South Atlantic Ocean and North Sea (Hartmann-Schröder, 1974; Rogall, 1977: both cited in Farke, 1979) and therefore the species must be capable of tolerating low temperatures. Aphelochaeta marioni lives buried in sediment and is therefore well insulated from decreases in temperature. In the Wadden Sea, the population was apparently unaffected by a short period of severe frost in I973 (Farke, 1979). A decrease in temperature would be likely to cause some physiological stress but no mortality and therefore an intolerance of low is recorded. Metabolic activity should quickly return to normal when temperatures increase and so a recoverability of very high is recorded.
Low Very high Very Low Low
Aphelochaeta marioni typically inhabits turbid waters such as estuaries. It does not require light and therefore is not directly affected by an increase in turbidity for the purposes of light attenuation. An increase in turbidity may affect primary production in the water column and therefore reduce the availability of diatom food sinking to the sediment surface. In addition, primary production by the micro-phyto benthos on the sediment surface may be reduced, further decreasing food availability. However, phytoplankton will also immigrate from distant areas and so the effect may be decreased. As the turbidity increase only persists for a year, decreased food availability would probably only affect growth and fecundity and an intolerance of low is recorded. As soon as light levels return to normal, primary production will increase and hence recoverability is recorded as very high.
Tolerant Not relevant Not sensitive High
Aphelochaeta marioni does not require light and therefore would not be affected by a decrease in turbidity for light attenuation purposes.
High High Moderate Low
Aphelochaeta marioni characteristically inhabits soft sediments in sheltered areas. This suggests that it would be intolerant of wave exposure to some degree. An increase in wave exposure by two categories for one year would be likely to affect the species in several ways. Fine sediments would be eroded (Hiscock, 1983) resulting in the likely reduction of the habitat of Aphelochaeta marioni and a decrease in food availability. Strong wave action is also likely to cause damage or withdrawal of delicate feeding and respiration structures resulting in loss of feeding opportunities and compromised growth. Furthermore, individuals may be damaged or dislodged by scouring from sand and gravel mobilized by increased wave action. It is likely that high mortality would result from the considerations discussed above and therefore an intolerance of high is recorded. Recoverability is recorded as high (see additional information below).
Tolerant Not relevant Not sensitive High
Aphelochaeta marioni characteristically inhabits soft sediments in sheltered areas and is tolerant of hypoxia (Broom et al., 1991). It is therefore likely to tolerate a decrease in wave exposure.
Tolerant Not relevant Not sensitive Low
No information was found concerning the intolerance of Aphelochaeta marioni to noise. However, it is unlikely to be affected by noise and vibration at the level of the benchmark.
Low Immediate Not sensitive High
Aphelochaeta marioni is only active at night (Farke, 1979). Farke (1979) noted their intolerance to visual disturbance in a microsystem in the laboratory. In order to observe feeding and breeding in the microsystem, the animals had to be gradually acclimated to lamp light. Even then, additional disturbance, such as an electronic flash, caused the retraction of palps and cirri and cessation of all activity for some minutes. Visual disturbance, in the form of direct illumination during the species' active period at night, may therefore result in loss of feeding opportunities, which may compromise growth and reproduction. Hence, an intolerance of low is recorded. When the visual disturbance is removed feeding activity should return to normal immediately.
Intermediate High Low Low
Aphelochaeta marioni is a soft bodied organism which exposes its palps and cirri at the surface while feeding. The species lives infaunally in soft sediment, usually within a few centimetres of the sediment surface. Physical disturbance, such as dredging or dragging an anchor, would be likely to penetrate the upper few centimetres of the sediment and cause physical damage to Aphelochaeta marioni. An intolerance of intermediate is therefore recorded. Recoverability is recorded as high (see additional information below).
Tolerant Not relevant Not sensitive High
Farke (1979) noted the effects of displacement on Aphelochaeta marioni (studied as Tharyx marioni) while performing experiments on intolerance to salinity changes. It was observed that when an individual was removed from its habitat and displaced to a similar habitat, it took approximately one minute to dig itself into the sediment. Aphelochaeta marioni is therefore recorded as not sensitive to displacement.

Chemical pressures

 IntoleranceRecoverabilitySensitivityEvidence/Confidence
High High Moderate Very low
There is no evidence directly relating to the effects of synthetic chemicals on Aphelochaeta marioni. However, there is evidence from other polychaete species. Collier & Pinn (1998) investigated the effect on the benthos of ivermectin, a feed additive treatment for infestations of sea-lice on farmed salmonids. The polychaete Hediste diversicolor was particularly susceptible, exhibiting 100% mortality within 14 days when exposed to 8 mg/m2 of ivermectin in a microcosm. Arenicola marina was also intolerant of ivermectin through the ingestion of contaminated sediment (Thain et al., 1998; cited in Collier & Pinn, 1998) and it was suggested that deposit feeding was an important route for exposure to toxins. Beaumont et al. (1989) investigated the effects of tri-butyl tin (TBT) on benthic organisms. At concentrations of 1-3 µg/l there was no significant effect on the abundance of Hediste diversicolor or Cirratulus cirratus (family Cirratulidae) after 9 weeks in a microcosm. However, no juvenile polychaetes were retrieved from the substratum and hence there is some evidence that TBT had an effect on the larval and/or juvenile stages of these polychaetes. The high mortality of polychaetes due to exposure to ivermectin suggests a high intolerance to synthetic chemicals, but this decision is made with very low confidence. Recoverability is recorded as high (see additional information below).
Heavy metal contamination
Low Very high Very Low Low
Bryan (1984) suggested that polychaetes are rather tolerant of heavy metals. In Restronguet Creek, the sediments contained levels of arsenic, copper and tin two orders of magnitude higher than in unpolluted estuaries, while levels of silver and zinc were approximately forty times higher (Bryan & Gibbs, 1983). The presence of Aphelochaeta marioni in this area (Bryan & Gibbs, 1983) suggests that the species is tolerant of heavy metal contamination. Furthermore, Aphelochaeta marioni was shown to accumulate arsenic (Gibbs et al., 1983). Aphelochaeta marioni (studied as Tharyx marioni) was found to have whole body concentrations of arsenic greater than 2000 µg/g dry weight (even when living under low ambient arsenic conditions). For reference, other Cirratulids, e.g. Cirriformia tentaculata, from the same habitat contained arsenic at concentrations lower than 100 µg/g dry weight. The purpose of the arsenic accumulation is unclear. Trials with gobies failed to confirm that it was a predator deterrent mechanism and it is probably not a detoxification mechanism as arsenic accumulations were similar for worms living in widely varying arsenic concentrations. Hence, there is no evidence to suggest that Aphelochaeta marioni is intolerant of heavy metal contamination. However, other annelids have been shown to be intolerant of heavy metal contamination (e.g. see review by Crompton, 1997) and therefore an intolerance of low is recorded. Due to their tolerance, a recoverability of very high is recorded.
Hydrocarbon contamination
Tolerant* Not relevant Not sensitive* Moderate
Cirratulids seem to be mostly immune to oil spills, probably because their feeding tentacles are protected by a heavy secretion of mucus (Suchanek, 1993). This is supported by observations of Aphelochaeta marioni following the Amoco Cadiz oil spill in March, 1978 (Dauvin, 1982, 2000). Prior to the spill, Aphelochaeta marioni (studied as Tharyx marioni) was present in very low numbers in the Bay of Morlaix, western English Channel. Following the spill, the level of hydrocarbons in the sediment increased from 10 mg/kg dry sediment to 1443 mg/kg dry sediment 6 months afterwards. In the same period, Aphelochaeta marioni increased in abundance to a mean of 76 individuals/m2, which placed it among the top five dominant species in the faunal assemblage. It was suggested that the population explosion occurred due to the increased food availability because of accumulation of organic matter resulting from high mortality of browsers. Six years later, abundance of Aphelochaeta marioni began to fall away again, accompanied by gradual decontamination of the sediments. Aphelochaeta marioni is therefore recorded as not sensitive, with a potential to benefit from hydrocarbon contamination.
Radionuclide contamination
No information Not relevant No information Not relevant
No evidence was found concerning the intolerance of Aphelochaeta marioni to radionuclide contamination.
Changes in nutrient levels
Intermediate High Low Very low
Raman & Ganapati (1983) studied the distribution of Aphelochaeta marioni (studied as Tharyx marioni) in relation to a sewage outfall in Visakhaptnam Harbour, Bay of Bengal. Aphelochaeta marioni was found to be dominant in the 'semi-healthy zone' characterized by high dissolved oxygen (median 7.2 mg/l), low biological oxygen demand (9.6 mg/l) and low nutrients (nitrate 0.02 mg/l, phosphate 0.88 mg/l). Aphelochaeta marioni was not found in high numbers in the polluted zone close to the sewage outfall, characterized by low dissolved oxygen (median 6.0 mg/l), high biological oxygen demand (14-60 mg/l) and high nutrients (nitrate 0.042-0.105 mg/l, phosphate 2.35-3.76 mg/l). This would suggest that Aphelochaeta marioni is intolerant of eutrophication. However, it would be expected that an increase in organic nutrients would lead to increased food availability for the deposit feeding Aphelochaeta marioni and that the species would thrive provided it could tolerate the increase in biological oxygen demand. Broom et al. (1991) stated that Aphelochaeta marioni was characteristic of faunal assemblages in the Severn Estuary with very poorly oxygenated mud and Thierman et al. (1996) noted that Aphelochaeta marioni "does not have a massively adverse reaction to sulphidic conditions". Furthermore, Dauvin (1982, 2000) recorded an increase in abundance of Aphelochaeta marioni following an oil spill which resulted in an explosion of plant growth due to high mortality of grazers. Therefore, the available evidence on intolerance of Aphelochaeta marioni to nutrient changes does not allow consistent conclusions to be drawn. The worst case scenario is that nutrient enrichment will lead to reduced abundance of Aphelochaeta marioni so an intolerance of intermediate is recorded, with very low confidence. Recoverability is recorded as high (see additional information below).
Tolerant Not relevant Not sensitive High
Populations of Aphelochaeta marioni inhabit the open coast where sea water is at full salinity. They are clearly capable of thriving in fully saline conditions and hence probably relatively tolerant of increases in salinity. No information was found concerning the reaction to hypersaline conditions (>40psu). Farke (1979) studied the effects of changing salinity on Aphelochaeta marioni (studied as Tharyx marioni) in a microsystem in the laboratory. Over several weeks, the salinity in the microsystem was increased from 25-40 psu and no adverse reaction was noted. However, when individuals were removed from the sediment and displaced to a new habitat, they only dug into their new substratum if the salinities in the two habitats were similar. If the salinities differed by 3-5 psu, the worms carried out random digging movements, failed to penetrate the sediment and died at the substratum surface after a few hours. This would suggest that Aphelochaeta marioni can tolerate salinity changes when living infaunally but is far more intolerant when removed from its habitat.
Tolerant Not relevant Not sensitive High
Aphelochaeta marioni thrives in estuaries and is therefore likely to be tolerant of decreases in salinity. It has been recorded from brackish inland waters in the Southern Netherlands with a salinity of 16 psu, but not in areas permanently exposed to lower salinities (Wolff, 1973). However, it also penetrates into areas exposed to salinities as low as 4 psu for short periods at low tide when fresh water discharge from rivers is high (Farke, 1979). The distribution of Aphelochaeta marioni, therefore, suggests that it is very tolerant of low salinity conditions.
Low Very high Very Low Low
Connor et al. (1997) described sediments in which Aphelochaeta marioni is commonly found as usually with a "black anoxic layer close to the sediment surface." Broom et al. (1991) recorded that Aphelochaeta marioni (studied as Tharyx marioni) characterized the faunal assemblage of very poorly oxygenated mud in the Severn Estuary. They found Aphelochaeta marioni to be dominant where the redox potential at 4 cm sediment depth was 56 mV and, therefore, concluded that the species was tolerant of very low oxygen tensions. Thierman et al. (1996) studied the distribution of Aphelochaeta marioni in relation to hydrogen sulphide concentrations. The species was found to be abundant at low sulphide concentrations (<50 µM) but only occasional at concentrations from 75-125 µM. They concluded that Aphelochaeta marioni does not display a massively adverse reaction to sulphidic conditions and is able to tolerate a low amount of sulphide. The evidence suggests that Aphelochaeta marioni is capable of tolerating hypoxia but it is difficult to determine to what degree. It is likely that feeding, growth and reproduction would be impaired under sustained low oxygen conditions and therefore an intolerance of low is recorded. Activity should return to normal when oxygen tensions increase and therefore a recoverability of very high is recorded.

Biological pressures

 IntoleranceRecoverabilitySensitivityEvidence/Confidence
Low Very high Very Low Low
Gibbs (1971) recorded that nearly all of the population of Aphelochaeta marioni in Stonehouse Pool, Plymouth Sound, was infected with a sporozoan parasite belonging to the acephaline gregarine genus Gonospora, which inhabits the coelom of the host. No evidence was found to suggest that gametogenesis was affected by Gonospora infection and there was no apparent reduction in fecundity. However, any parasitic infection is likely to impair the host in some way and an intolerance of low is recorded. If the parasite were to be removed, the host would be likely to return to normal health quickly so a recoverability of very high is recorded. No other information was found concerning infection of Aphelochaeta marioni by microbial pathogens.
No information Not relevant No information Not relevant
No information was found concerning non-native species which would be likely to compete with Aphelochaeta marioni.
Not relevant Not relevant Not relevant Not relevant
There is no evidence that Aphelochaeta marioni is extracted deliberately.
Intermediate High Low Very low
Commercial extraction of other infaunal species is likely to have an effect on Aphelochaeta marioni where their distributions overlap. Hall & Harding (1997) demonstrated that commercial cockle harvesting by suction dredging had significant effects on soft-sediment infaunal communities. Following dredging, species numbers were reduced by up to 30% and abundances by up to 50%. In Maine, USA, commercial digging for worms and clams was studied by Brown & Wilson (1997). Following experimental digging for two and a half months, the densities of three polychaete species, including Tharyx acutus, were significantly reduced, as was the total number of taxa present. It should be noted that Tharyx acutus is a surface dweller and therefore has a different lifestyle to Aphelochaeta marioni. Hence, the inferences that can be drawn are limited. However, it seems likely that the disruption of the infaunal community caused by commercial harvesting would result in mortality of Aphelochaeta marioni and therefore an intolerance of intermediate is recorded. Recoverability is recorded as high (see additional information below).

Additional information

Aphelochaeta marioni has no pelagic phase in its lifecycle, and dispersal is limited to the slow burrowing of the adults and juveniles (Farke, 1979). The blow lug, %Arenicola marina%, has similar dispersal capabilities and its recoverability has been well studied. Heavy commercial exploitation in Budle Bay in winter 1984 removed 4 million worms in 6 weeks, reducing the population from 40 to <1 per m². Recovery occurred within a few months by recolonization from surrounding sediment (Fowler, 1999). However, Cryer et al. (1987) reported no recovery for 6 months over summer after mortalities due to bait digging. Beukema (1995) noted that the lugworm stock recovered slowly after mechanical dredging, reaching its original level in at least three years. Fowler (1999) pointed out that recovery may take a long time on a small pocket beach with limited possibility of recolonization from surrounding areas. Therefore, if adjacent populations are available recovery will be rapid. However where the affected population is isolated or severely reduced, recovery may be extended. Recoverability for Aphelochaeta marioni is therefore recorded as high.

Importance review

Policy/legislation

- no data -

Status

National (GB) importance-Global red list (IUCN) category-

Non-native

Native-
Origin- Date ArrivedNot relevant

Importance information

Reise (1977) reported that Aphelochaeta marioni (studied as Tharyx marioni) was food for Crangon crangon, Carcinus maenas, Pomatoschistus microps and young Pleuronectes platessa.

Bibliography

  1. Beaumont, A.R., Newman, P.B., Mills, D.K., Waldock, M.J., Miller, D. & Waite, M.E., 1989. Sandy-substrate microcosm studies on tributyl tin (TBT) toxicity to marine organisms. Scientia Marina, 53, 737-743.

  2. Beukema, J.J., 1995. Long-term effects of mechanical harvesting of lugworms Arenicola marina on the zoobenthic community of a tidal flat in the Wadden Sea. Netherlands Journal of Sea Research, 33, 219-227.

  3. Brenchley, G.A., 1981. Disturbance and community structure : an experimental study of bioturbation in marine soft-bottom environments. Journal of Marine Research, 39, 767-790.

  4. Broom, M.J., Davies, J., Hutchings, B. & Halcrow, W., 1991. Environmental assessment of the effects of polluting discharges: stage 1: developing a post-facto baseline. Estuarine, Coastal and Shelf Science, 33, 71-87.

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Citation

This review can be cited as:

Rayment, W.J. 2007. Aphelochaeta marioni A bristleworm. In Tyler-Walters H. and Hiscock K. (eds) Marine Life Information Network: Biology and Sensitivity Key Information Reviews, [on-line]. Plymouth: Marine Biological Association of the United Kingdom. Available from: http://www.marlin.ac.uk/species/detail/1556

Last Updated: 08/06/2007