BIOTIC

BIOTIC Species Information for Helcion pellucidum
All Taxonomy Biology Distribution Reproduction

Researched by	Dr Harvey Tyler-Walters	Data supplied by	MarLIN
Refereed by	Dr David McGrath
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?	No
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of specimens from Norway, which he suggested were caused by the interrupted growth of the mantle edge when the adult was retracted in response to severe wave action during heavy storms.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,