Brackish sea fir (Pachycordyle michaeli)

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

Summary

Description

A simple hydroid consisting of an erect, unbranched stem, up to 5 mm in height, with a single terminal polyp (hydranth). Each upright stem rises from a creeping stolon (hydrorhiza). The stem is sheathed by a chitinous sheath, the perisarc. The perisarc is often wrinkled, especially near the base, and terminates below the hydranth. The hydranth bears 8 to 16 tentacles in 2 to 4 alternating whorls, depending on hydranth size. It is creamy white in colour, with hints of pink around the mouth of the hydranth. The reproductive bodies (gonophores) are borne on short stalks in an irregular spiral below the hydranth.

Recorded distribution in Britain and Ireland

Widewater lagoon, West Sussex.

Global distribution

Recorded from only 3 locations worldwide: Kiel Canal, Widewater lagoon in Sussex and attached to a ship's hull in South Africa.

Habitat

Grows on algae such as Chaetomorpha. It has only ever been recorded in the vicinity of ports and harbours.

Depth range

-

Identifying features

  • Stem simple and unbranched bears a single terminal hydranth.
  • Hydranth with 2-4 whorls of tentacles close to mouth.
  • Gonophores in the form of fixed sporosacs.
  • Planulae develop within apical part of gonophore.

Additional information

The systematic status of this species was revised by Stepanjants et al. (2000) who placed Clavopsella navis and Clavopsella quadrangularia in the new genus Thieliana. Subsequent revision by Schuchert (2004, 2007; cited in Calder, 2012) placed the species in the genus Pachycordyle. Pachycordyle navis was subsequently synonymized with Pachycordyle michaeli (WoRMS, 2021). 

Biology review

Taxonomy

LevelScientific nameCommon name
PhylumCnidaria
ClassHydrozoa
OrderAnthoathecata
FamilyBougainvilliidae
GenusPachycordyle
Authority(Berrill, 1948)
Recent SynonymsClavopsella navis (Millard, 1959)Rhizorhagium navis (Millard, 1959)Pachycordyle navis (Millard, 1959)

Biology

ParameterData
Typical abundanceData deficient
Male size range0.39-1.29 mm
Male size at maturity
Female size rangeVery small(<1cm)
Female size at maturity
Growth formTurf
Growth rateData deficient
Body flexibilityHigh (greater than 45 degrees)
MobilitySessile, permanent attachment
Characteristic feeding methodPassive suspension feeder
Diet/food sourceOmnivore
Typically feeds on
Sociability
Environmental positionEpifaunal
Dependency-
Supports-
Is the species harmful?Data deficient

Biology information

Size refers to length of hydranth.

Habitat preferences

ParameterData
Physiographic preferencesIsolated saline water (Lagoon)
Biological zone preferencesData deficient
Substratum / habitat preferencesMacroalgae
Tidal strength preferencesWeak < 1 knot (<0.5 m/sec.)
Wave exposure preferencesVery sheltered
Salinity preferencesReduced (18-30 psu)
Depth range
Other preferencesNo text entered
Migration PatternNon-migratory or resident

Habitat Information

Pachycordyle navis is presumed to be an introduced species since it has only ever been recorded in the vicinity of ports and harbours. It is probably transported on ships hulls. It was first recorded in the UK in 1973 in Widewater Lagoon, Shoreham, West Sussex (Eno et al., 1997). It was last recorded there (as Clavopsella navis) by Sheader (1990) in 1990 when it was relatively abundant attached to algae. It is presumed extinct in South Africa as it has only been recorded from one ship's hull in 1959. The condition of the population in Kiel is not known.

Life history

Adult characteristics

ParameterData
Reproductive typeGonochoristic (dioecious)
Reproductive frequency
Fecundity (number of eggs)2-10
Generation timeInsufficient information
Age at maturity
SeasonInsufficient information
Life spanInsufficient information

Larval characteristics

ParameterData
Larval/propagule type-
Larval/juvenile development
Duration of larval stageNo information
Larval dispersal potential No information
Larval settlement period

Life history information

Female gonophores contain about 8 eggs, which develop directly into planulae. There is no free-living medusoid stage.

Sensitivity reviewHow is sensitivity assessed?

Physical pressures

Use / to open/close text displayed

 IntoleranceRecoverabilitySensitivityEvidence / Confidence
Substratum loss [Show more]

Substratum loss

Benchmark. All of the substratum occupied by the species or biotope under consideration is removed. A single event is assumed for sensitivity assessment. Once the activity or event has stopped (or between regular events) suitable substratum remains or is deposited. Species or community recovery assumes that the substratum within the habitat preferences of the original species or community is present. Further details

Evidence

Pachycordyle navis lives attached to algae, so would be removed with the algae upon substratum loss. There would be no recovery of the population because only two extant populations of Pachycordyle navis are known: Widewater lagoon, Sussex and Kiel Canal, Germany.

High None Very High Very low
Smothering [Show more]

Smothering

Benchmark. All of the population of a species or an area of a biotope is smothered by sediment to a depth of 5 cm above the substratum for one month. Impermeable materials, such as concrete, oil, or tar, are likely to have a greater effect. Further details.

Evidence

The species would be affected by smothering if the algae on which it lives is completely covered in the sediment. If the algae protrudes sufficiently above the sediment the hydroid may escape the effects of smothering.

Intermediate Low High Very low
Increase in suspended sediment [Show more]

Increase in suspended sediment

Benchmark. An arbitrary short-term, acute change in background suspended sediment concentration e.g., a change of 100 mg/l for one month. The resultant light attenuation effects are addressed under turbidity, and the effects of rapid settling out of suspended sediment are addressed under smothering. Further details

Evidence

Pachycordyle navis is likely to have some tolerance to siltation as it inhabits lagoons where siltation frequently occurs. The algae on which the species lives will also lift the hydroid above the accumulation of silt. However, the heath of the host algae may be adversely affected by siltation.

Intermediate Very low / none High Very low
Decrease in suspended sediment [Show more]

Decrease in suspended sediment

Benchmark. An arbitrary short-term, acute change in background suspended sediment concentration e.g., a change of 100 mg/l for one month. The resultant light attenuation effects are addressed under turbidity, and the effects of rapid settling out of suspended sediment are addressed under smothering. Further details

Evidence

No information
Desiccation [Show more]

Desiccation

  1. A normally subtidal, demersal or pelagic species including intertidal migratory or under-boulder species is continuously exposed to air and sunshine for one hour.
  2. A normally intertidal species or community is exposed to a change in desiccation equivalent to a change in position of one vertical biological zone on the shore, e.g., from upper eulittoral to the mid eulittoral or from sublittoral fringe to lower eulittoral for a period of one year. Further details.

Evidence

The species is vulnerable to desiccation because it is soft bodied and has no protection from the drying effects of sun and wind. Some of the population may be sheltered from desiccation if they are present on the underside of the algal frond. However, if the whole population is destroyed recoverability would be non-existent because only two populations of Thieliana navis occur worldwide.

Intermediate None Very High Very low
Increase in emergence regime [Show more]

Increase in emergence regime

Benchmark. A one hour change in the time covered or not covered by the sea for a period of one year. Further details

Evidence

The species is vulnerable to emergence because it is soft bodied and has no protection from desiccation. Some of the population may be sheltered from desiccation if they are present on the underside of the algal frond. However, if the whole population is destroyed recoverability would be very low because only two populations of Pachycordyle navis occur worldwide.

Intermediate None Very High Very low
Decrease in emergence regime [Show more]

Decrease in emergence regime

Benchmark. A one hour change in the time covered or not covered by the sea for a period of one year. Further details

Evidence

No information
Increase in water flow rate [Show more]

Increase in water flow rate

A change of two categories in water flow rate (view glossary) for 1 year, for example, from moderately strong (1-3 knots) to very weak (negligible). Further details

Evidence

The species would probably not be affected by a change in water flow because it is permanently attached to the algae and may be able to withstand high water flow rates because they have been transported long distances on ships hulls.

Tolerant Not relevant Not sensitive Very low
Decrease in water flow rate [Show more]

Decrease in water flow rate

A change of two categories in water flow rate (view glossary) for 1 year, for example, from moderately strong (1-3 knots) to very weak (negligible). Further details

Evidence

No information
Increase in temperature [Show more]

Increase in temperature

  1. A short-term, acute change in temperature; e.g., a 5°C change in the temperature range for three consecutive days. This definition includes ‘short-term’ thermal discharges.
  2. A long-term, chronic change in temperature; e.g. a 2°C change in the temperature range for a year. This definition includes ‘long term’ thermal discharges.

For intertidal species or communities, the range of temperatures includes the air temperature regime for that species or community. Further details

Evidence

The temperature resistance of the Pachycordyle navis is not known.

No information Not relevant No information Very low
Decrease in temperature [Show more]

Decrease in temperature

  1. A short-term, acute change in temperature; e.g., a 5°C change in the temperature range for three consecutive days. This definition includes ‘short-term’ thermal discharges.
  2. A long-term, chronic change in temperature; e.g. a 2°C change in the temperature range for a year. This definition includes ‘long term’ thermal discharges.

For intertidal species or communities, the range of temperatures includes the air temperature regime for that species or community. Further details

Evidence

No information
Increase in turbidity [Show more]

Increase in turbidity

  1. A short-term, acute change; e.g., two categories of the water clarity scale (see glossary) for one month, such as from medium to extreme turbidity.
  2. A long-term, chronic change; e.g., one category of the water clarity scale (see glossary) for one year, such as from low to medium turbidity. Further details

Evidence

The species is unlikely to be affected by a change in turbidity as it is not dependant on light availability and it would not interfere with its feeding. However, the host algae may be adversely affected by a reduction in light availability.

Low Moderate Low Very low
Decrease in turbidity [Show more]

Decrease in turbidity

  1. A short-term, acute change; e.g., two categories of the water clarity scale (see glossary) for one month, such as from medium to extreme turbidity.
  2. A long-term, chronic change; e.g., one category of the water clarity scale (see glossary) for one year, such as from low to medium turbidity. Further details

Evidence

No information
Increase in wave exposure [Show more]

Increase in wave exposure

A change of two ranks on the wave exposure scale (view glossary) e.g., from Exposed to Extremely exposed for a period of one year. Further details

Evidence

A change in wave exposure is unlikely to occur in a lagoon unless one of the lagoon boundaries is breached. The species would probably not be affected by an increase in wave exposure because it does not present a large surface area to wave action. However, it's host algae may be intolerant of wave exposure and may be washed away.

Tolerant Not relevant Not sensitive Very low
Decrease in wave exposure [Show more]

Decrease in wave exposure

A change of two ranks on the wave exposure scale (view glossary) e.g., from Exposed to Extremely exposed for a period of one year. Further details

Evidence

No information
Noise [Show more]

Noise

  1. Underwater noise levels e.g., the regular passing of a 30-metre trawler at 100 metres or a working cutter-suction transfer dredge at 100 metres for one month during important feeding or breeding periods.
  2. Atmospheric noise levels e.g., the regular passing of a Boeing 737 passenger jet 300 metres overhead for one month during important feeding or breeding periods. Further details

Evidence

Insufficient
information

No information Not relevant No information Very low
Visual presence [Show more]

Visual presence

Benchmark. The continuous presence for one month of moving objects not naturally found in the marine environment (e.g., boats, machinery, and humans) within the visual envelope of the species or community under consideration. Further details

Evidence

Insufficient
information

No information Not relevant No information Very low
Abrasion & physical disturbance [Show more]

Abrasion & physical disturbance

Benchmark. Force equivalent to a standard scallop dredge landing on or being dragged across the organism. A single event is assumed for assessment. This factor includes mechanical interference, crushing, physical blows against, or rubbing and erosion of the organism or habitat of interest. Where trampling is relevant, the evidence and trampling intensity will be reported in the rationale. Further details.

Evidence

The species and its host algae are flexible so will 'give' under abrasion. However, they occur on top of the sediment and would probably be removed, along with surface substratum by a passing scallop dredge (or equivalent force). The impact is likely to be equivalent to substratum loss. Therefore, an intolerance of high has been recorded.
Hydroids are generally regarded as opportunistic species with good recruitment, the ability to reproduce asexually or sexually, colonize space rapidly and with good powers of recovery from damage (see Boero, 1984; Gili & Hughes, 1995). Hydroids can form highly resistant resting stages and recover or spread by fragmentation (Gili & Hughes 1995). Therefore, hydroids are likely to recover rapidly from physical disturbance from resting stages or pieces of hydrorhizae on the remaining substratum, or fragments. However, Pachycordyle navis releases planulae from its gonothecae that probably have limited dispersal capability (see Sommer, 1992; Gili & Hughes, 1995). It is an introduced species thought to have been transported by shipping, either on the hull or in the ballast water (Reise et al., 1999) but has a very limited distribution, which suggests either a limited recruitment capability and/or a narrow range of environmental preferences. Although it was recorded in the Widewater lagoon in 1973, its has not been recorded from any other sites in the UK since. It seems unlikely that it can recruit from other areas, or extremely slowly, save by the chance anthropogenic introductions, e.g. via shipping. If the population was completely destroyed by physical disturbance then recovery is unlikely. Nevertheless, the population may recover from resting stages or fragments. Therefore, a recoverability of low has been recorded.

High Low High Very low
Displacement [Show more]

Displacement

Benchmark. Removal of the organism from the substratum and displacement from its original position onto a suitable substratum. A single event is assumed for assessment. Further details

Evidence

Pachycordyle navis is permanently attached to algae and would be unable to re-attach itself if removed. If the whole population is destroyed recoverability would be very low because only two populations of Pachycordyle navis occur worldwide.

High None Very High Very low

Chemical pressures

Use [show more] / [show less] to open/close text displayed

 IntoleranceRecoverabilitySensitivityEvidence / Confidence
Synthetic compound contamination [Show more]

Synthetic compound contamination

Sensitivity is assessed against the available evidence for the effects of contaminants on the species (or closely related species at low confidence) or community of interest. For example:

  • evidence of mass mortality of a population of the species or community of interest (either short or long term) in response to a contaminant will be ranked as high sensitivity;
  • evidence of reduced abundance, or extent of a population of the species or community of interest (either short or long term) in response to a contaminant will be ranked as intermediate sensitivity;
  • evidence of sub-lethal effects or reduced reproductive potential of a population of the species or community of interest will be assessed as low sensitivity.

The evidence used is stated in the rationale. Where the assessment can be based on a known activity then this is stated. The tolerance to contaminants of species of interest will be included in the rationale when available; together with relevant supporting material. Further details.

Evidence

Insufficient
information

No information Not relevant No information Very low
Heavy metal contamination [Show more]

Heavy metal contamination

Evidence

Insufficient
information

No information Not relevant No information Not relevant
Hydrocarbon contamination [Show more]

Hydrocarbon contamination

Evidence

Insufficient
information

No information Not relevant No information Not relevant
Radionuclide contamination [Show more]

Radionuclide contamination

Evidence

Insufficient
information

No information Not relevant No information Not relevant
Changes in nutrient levels [Show more]

Changes in nutrient levels

Evidence

Insufficient
information

No information Not relevant No information Not relevant
Increase in salinity [Show more]

Increase in salinity

  1. A short-term, acute change; e.g., a change of two categories from the MNCR salinity scale for one week (view glossary) such as from full to reduced.
  2. A long-term, chronic change; e.g., a change of one category from the MNCR salinity scale for one year (view glossary) such as from reduced to low. Further details.

Evidence

Evidence suggests that the species is tolerant of fully saline conditions because it can survive on ships hulls. The species must be tolerant of reduced salinity because it occurs in lagoons but the tolerance of the species to very reduced salinities is not known.

No information Not relevant No information Not relevant
Decrease in salinity [Show more]

Decrease in salinity

  1. A short-term, acute change; e.g., a change of two categories from the MNCR salinity scale for one week (view glossary) such as from full to reduced.
  2. A long-term, chronic change; e.g., a change of one category from the MNCR salinity scale for one year (view glossary) such as from reduced to low. Further details.

Evidence

No information
Changes in oxygenation [Show more]

Changes in oxygenation

Benchmark.  Exposure to a dissolved oxygen concentration of 2 mg/l for one week. Further details.

Evidence

Insufficient
information

No information Not relevant No information Not relevant

Biological pressures

Use [show more] / [show less] to open/close text displayed

 IntoleranceRecoverabilitySensitivityEvidence / Confidence
Introduction of microbial pathogens/parasites [Show more]

Introduction of microbial pathogens/parasites

Benchmark. Sensitivity can only be assessed relative to a known, named disease, likely to cause partial loss of a species population or community. Further details.

Evidence

Insufficient
information

No information Not relevant No information Not relevant
Introduction of non-native species [Show more]

Introduction of non-native species

Sensitivity assessed against the likely effect of the introduction of alien or non-native species in Britain or Ireland. Further details.

Evidence

Insufficient
information

No information Not relevant No information Not relevant
Extraction of this species [Show more]

Extraction of this species

Benchmark. Extraction removes 50% of the species or community from the area under consideration. Sensitivity will be assessed as 'intermediate'. The habitat remains intact or recovers rapidly. Any effects of the extraction process on the habitat itself are addressed under other factors, e.g. displacement, abrasion and physical disturbance, and substratum loss. Further details.

Evidence

Insufficient
information

No information Not relevant No information Not relevant
Extraction of other species [Show more]

Extraction of other species

Benchmark. A species that is a required host or prey for the species under consideration (and assuming that no alternative host exists) or a keystone species in a biotope is removed. Any effects of the extraction process on the habitat itself are addressed under other factors, e.g. displacement, abrasion and physical disturbance, and substratum loss. Further details.

Evidence

Insufficient
information

No information Not relevant No information Not relevant

Additional information

Importance review

Policy/legislation

DesignationSupport
Wildlife & Countryside ActSchedule 5, section 9
UK Biodiversity Action Plan PriorityYes
Species of principal importance (England)Yes

Status

Non-native

ParameterData
Native-
Origin-
Date Arrived1973

Importance information

-none-

Bibliography

  1. Anonymous, 1999s. Saline lagoons. Habitat Action Plan. In UK Biodiversity Group. Tranche 2 Action Plans. English Nature for the UK Biodiversity Group, Peterborough., English Nature for the UK Biodiversity Group, Peterborough.

  2. Barnes, R.S.K., 1994. The brackish-water fauna of northwestern Europe. Cambridge: Cambridge University Press.

  3. Boero, F., 1984. The ecology of marine hydroids and effects of environmental factors: a review. Marine Ecology, 5, 93-118.

  4. Eno, N.C., Clark, R.A. & Sanderson, W.G. (ed.) 1997. Non-native marine species in British waters: a review and directory. Peterborough: Joint Nature Conservation Committee.

  5. Gili, J-M. & Hughes, R.G., 1995. The ecology of marine benthic hydroids. Oceanography and Marine Biology: an Annual Review, 33, 351-426.

  6. Howson, C.M. & Picton, B.E., 1997. The species directory of the marine fauna and flora of the British Isles and surrounding seas. Belfast: Ulster Museum. [Ulster Museum publication, no. 276.]

  7. Millard, N.A.H., 1975. Monograph of the Hydroida of Southern Africa. Annals of the South Africa Museum, 68, 1-513.

  8. Reise, K., Gollasch, S. & Wolff, W.J., 1999. Introduced species of the North Sea coasts. Helgoland Meeresuntersuchungen, 52, 219-234.

  9. Sheader, M. & Sheader, A., 1990. A survey of Widewater saline lagoon to determine the current status of the site, with special reference to Ivell's sea anemone, Edwardsia ivelli. Preliminary Report, Peterborough. Nature Conservancy Council. NCC CSD Report 1176.

  10. Sommer, C., 1992. Larval biology and dispersal of Eudendrium racemosum (Hydrozoa, Eudendriidae). Scientia Marina, 56, 205-211. [Proceedings of 2nd International Workshop of the Hydrozoan Society, Spain, September 1991. Aspects of hydrozoan biology (ed. J. Bouillon, F. Cicognia, J.M. Gili & R.G. Hughes).]

  11. Stephanjants, S.D., Timoshkin, O.A., Anokhin, B.A. & Napara, T.A., 2000. A new species of Pachycordyle (Hydrozoa, Clavidae) from Lake Biwa (Japan), with remarks on this and related Clavid genera. Scientia Marina, 64 (Suppl. 1), 225-236.

  12. Calder, D.R., 2012. On a collection of hydroids (Cnidaria, Hydrozoa, Hydroidolina) from the west coast of Sweden, with a checklist of species from the region. Zootaxa, 3171, 1-77. 

Datasets

  1. NBN (National Biodiversity Network) Atlas. Available from: https://www.nbnatlas.org.

  2. OBIS (Ocean Biodiversity Information System),  2024. Global map of species distribution using gridded data. Available from: Ocean Biogeographic Information System. www.iobis.org. Accessed: 2024-05-28

Citation

This review can be cited as:

White, N. 2005. Pachycordyle michaeli Brackish sea fir. In Tyler-Walters H. Marine Life Information Network: Biology and Sensitivity Key Information Reviews, [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 28-05-2024]. Available from: https://marlin.ac.uk/species/detail/1152

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Last Updated: 24/06/2005