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

A hydroid (Pachycordyle navis)

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

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.  

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Biology review

Taxonomy

PhylumCnidaria
ClassHydrozoa
OrderAnthoathecata
FamilyBougainvilliidae
GenusPachycordyle
Authority(Millard, 1959)
Recent SynonymsClavopsella navis (Millard, 1959)Rhizorhagium navis (Millard, 1959)

Biology

Typical abundanceData deficient
Male size range0.39-1.29mm
Male size at maturity
Female size rangeVery small(<1cm)
Female size at maturity
Growth formTurf
Growth rateData deficient
Body flexibility
Mobility
Characteristic feeding methodNo information, Passive suspension feeder, Predator
Diet/food source
Typically feeds on
Sociability
Environmental positionEpifaunal
Dependency-
Supports-
Is the species harmful?Data deficient

Biology information

Size refers to length of hydranth.

Habitat preferences

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

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

Larval characteristics

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

 IntoleranceRecoverabilitySensitivityEvidence/Confidence
High None Very High Very low

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.

Intermediate Low High Very low

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 Very low / none High Very low

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.

No information
Intermediate None Very High Very low

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

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.

No information
Tolerant Not relevant Not sensitive Very low

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.

No information
No information Not relevant No information Very low

The temperature resistance of the Pachycordyle navis is not known.

No information
Low Moderate Low Very low

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.

No information
Tolerant Not relevant Not sensitive Very low

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.

No information
No information Not relevant No information Very low

Insufficient
information

No information Not relevant No information Very low

Insufficient
information

High Low High Very low

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 None Very High Very low

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.

Chemical pressures

 IntoleranceRecoverabilitySensitivityEvidence/Confidence
No information Not relevant No information Very low

Insufficient
information

Heavy metal contamination
No information Not relevant No information Not relevant

Insufficient
information

Hydrocarbon contamination
No information Not relevant No information Not relevant

Insufficient
information

Radionuclide contamination
No information Not relevant No information Not relevant

Insufficient
information

Changes in nutrient levels
No information Not relevant No information Not relevant

Insufficient
information

No information Not relevant No information Not relevant

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
No information Not relevant No information Not relevant

Insufficient
information

Biological pressures

 IntoleranceRecoverabilitySensitivityEvidence/Confidence
No information Not relevant No information Not relevant

Insufficient
information

No information Not relevant No information Not relevant

Insufficient
information

No information Not relevant No information Not relevant

Insufficient
information

No information Not relevant No information Not relevant

Insufficient
information

Additional information

Importance review

Policy/legislation

Wildlife & Countryside ActSchedule 5, section 9
UK Biodiversity Action Plan Priority
Species of principal importance (England)
Features of Conservation Importance (England & Wales)

Status

Non-native

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. 

Citation

This review can be cited as:

White, N. 2005. Pachycordyle navis A hydroid. 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/1152

Last Updated: 24/06/2005