BIOTIC

BIOTIC Species Information for Helcion pellucidum

Researched by

Dr Harvey Tyler-Walters

Data supplied by

MarLIN

Refereed by

Dr David McGrath

Taxonomy

Scientific name

Helcion pellucidum

Common name

Blue-rayed limpet

MCS Code

W234

Recent Synonyms

Patina pellucida, Patina laevis, Helcion laevis

Phylum

Mollusca

Subphylum

Superclass

Class

Gastropoda

Subclass

Prosobranchia

Order

Patellogastropoda

Suborder

Family

Pattelidae

Genus

Helcion

Species

pellucidum

Subspecies

Additional Information

Specimens found in cavities in holdfasts develop into the laevis form (Helcion pellucidum var. laevis). The laevis form has a taller, more robust opaque shell, ledged in profile, with blue rays that alternate with reddish brown rays. The most noticeable ledge of the shell indicates the size at which the individual enters the holdfast. Weber et al. (1997) suggested that Helcion pellucidum was genetically distinct from its South African con-geners and may have arisen independently. Recent studies of morphological features (Ridgeway et al., 1998) and molecular characteristics (Koufopanou et al., 1999) suggest that Helcion pelludicum belongs to the genus Patella.

Taxonomy References

Fish & Fish, 1996, Hayward & Ryland, 1995b, Weber et al., 1997, Ridgeway et al., 1998, Fretter & Graham, 1994, Koufopanou, 1999,

General Biology

Growth form

Conical

Feeding method

Herbivore

Mobility/Movement

Temporary attachment
Crawler

Environmental position

Epifaunal

Typical food types

%Laminaria hyperborea%, %Laminaria digitata%, %Alaria esculenta%, %Sacchoriza polyschides%, %Fucus serratus%, and when young %Himanthalia elongata% and %Mastocarpus stellatus%.

Habit

Free living

Bioturbator

Not relevant

Flexibility

None (< 10 degrees)

Fragility

Robust

Size

Small(1-2cm)

Height

Growth Rate

1-2 mm/month

Adult dispersal potential

Very limited (<1m)

Dependency

Independent

Sociability

Solitary

Toxic/Poisonous?

General Biology Additional Information

Growth is rapid in summer, autumn and winter but slow in winter. Population studies suggest that few individuals survive to their second year (Fretter & Graham, 1976; Graham & Fretter, 1947). Vahl (1971) noted growth irregularities or 'checks' in the shell of specimens from Norway, which he suggested were caused by the interrupted growth of the mantle edge when the adult was retracted in response to severe wave action during heavy storms.

Adults can recolonize vacant fronds (McGrath, 1997), perhaps via the surface of the substratum or by mucus rafting, and if dislodged adults can right themselves and be carried to neighbouring plants by currents by secreting a mucus 'sail' (Vahl ,1983).

Kain & Svendsen (1969) provide pictures of Helcion pellucidum on blades of Laminaria hyperborea together with the cavities grazed in the fronds and in holdfasts. Kain & Svendsen (1969) noted that in Norwegian populations severe grazing by Helcion pellucidum may result in perforation of blades by autumn (before new blades develop) and in some cases grazing where the blade and stipe meet may 'cut off' the blade.

Biology References

Fish & Fish, 1996, Fretter & Graham, 1976, Graham & Fretter, 1947, McGrath, 1992, McGrath, 1997, Vahl, 1983, Fretter & Graham, 1994, Kain & Svendsen, 1969, Vahl, 1971,

Distribution and Habitat

Distribution in Britain & Ireland

Recorded on all coasts of Britain and Ireland, except the coast surrounding the Wash.

Global distribution

Occurs in Iceland and from north Norway to south Portugal. It is found on the west coasts of Denmark, and Sweden south to Oresund. However it is absent from the Baltic sea and the east coasts of Denmark, Belgium and Holland.

Biogeographic range

Not researched

Depth range

ca +1 - 25 m

Migratory

Non-migratory / Resident

Distribution Additional Information

Studies in south east Ireland demonstrated that the distribution of Helcion pellucidum on the shore depends on its size and age. McGrath (1992) noted that spat settled with a larval shell attached of ca 0.66 mm. Newly settled spat have a preference for lower shore Lithothamnia (encrusting coralline algae) reaching densities as high as 400 per sq. dm in February. As they grow juveniles (up to 1.8 mm) migrate to Mastocarpus stellatus. The juveniles recruit to Laminarians at about 1.8 mm but are found mainly at the tips of the fronds. Juveniles up to 3 mm may also be found on the receptacles of %Himanthalia elongata%. Dense populations may be found on Fucus serratus, Alaria esculenta, Palmaria palmata and Halidrys siliquosa (McGrath, 1992).

Adults show a seasonal migration on Laminaria hyperborea, migrating down to the stipe before the old blade tissue is discarded in spring to early summer. Larger individuals prefer the lower wave exposure of deeper water (Warburton 1976).

Approximately one third of the population examined by Graham & Fretter (1947) were the laevis form. However, Kain & Svendsen (1969) did not find any specimens in Laminarian holdfasts in Norwegian populations and the laevis form may be absent in Norway.

Substratum preferences

Algae

Physiographic preferences

Open coast
Strait / sound
Sealoch

Biological zone

Lower Eulittoral
Sublittoral Fringe
Upper Infralittoral

Wave exposure

Exposed
Moderately Exposed

Tidal stream strength/Water flow

Moderately Strong (1-3 kn)

Salinity

Full (30-40 psu)

Habitat Preferences Additional Information

None

Distribution References

Hayward & Ryland, 1995b, Fretter & Graham, 1976, Graham & Fretter, 1947, McGrath, 1992, Warburton, 1976, Ebling et al., 1948, Seaward, 1990, Seaward, 1982, Kain & Svendsen, 1969, Vahl, 1971, MBA, 1957,

Reproduction/Life History

Reproductive type

Gonochoristic

Developmental mechanism

Planktotrophic

Reproductive Season

All year with a peak in spring

Reproductive Location

As adult

Reproductive frequency

Annual protracted

Regeneration potential

Life span

1-2 years

Age at reproductive maturity

<1 year

Generation time

<1 year

Fecundity

Insufficient information

Egg/propagule size

Ca 0.16 mm diameter

Fertilization type

External

Larvae/Juveniles
Larval/Juvenile dispersal potential	10-100m	Larval settlement period	Insufficient information
Duration of larval stage	11-30 days

Reproduction Preferences Additional Information

Few individuals survive into their second years. Most specimens >1 year old are found in holdfasts as the laevis form. Breeding occurs throughout the year with a peak in spring. Fertilization is external and eggs are shed singly. The eggs are greenish, ca 0.16 mm across and covered with a gelatinous coat giving an overall diameter of ca 0.32 mm (Fretter & Graham, 1976; Lebour, 1937). Eggs hatch into a 200 micrometer tall trochophore that develops into a 160-180 micrometer veliger larva (Lebour, 1937). Fretter & Graham (1947) state that planktonic life is 'a few weeks'. There is little information on dispersal range, however, 10-100m is assumed given the depth of adult distribution and its settlement on lower shore at least. McGrath (1992) examined recruitment in south east Ireland and reported that newly settled spat have a preference for lower shore Lithothamnia (encrusting corallines). As they grow juveniles (up to 1.8 mm) migrate to Mastocarpus stellatus. The juveniles recruit to Laminarians at about 1.8 mm but are found mainly at the tips of the fronds. Juveniles up to 3 mm may also be found on the receptacles of Himanthalia elongata. McGrath (1992) suggested that larvae settle on Lithothamina and migrate to Mastocarpus stellatus as they grow and finally to Laminaria sp. via Himanthalia elongata.

Reproduction References

Fish & Fish, 1996, Fretter & Graham, 1976, Graham & Fretter, 1947, McGrath, 1992, Fretter & Graham, 1994, Lebour, 1937,