BIOTIC Species Information for Chthamalus stellatus
Researched byKaren Riley Data supplied byMarLIN
Refereed byProf. Alan J. Southward
General Biology
Growth formConical
Feeding methodActive suspension feeder
Mobility/MovementPermanent attachment
Environmental positionEpifaunal
Typical food typesGenerally feeds on plankton. HabitAttached
BioturbatorNot relevant FlexibilityNone (< 10 degrees)
FragilityRobust SizeSmall(1-2cm)
HeightInsufficient information Growth Rateca. 10-55 µm / day
Adult dispersal potentialNone DependencyIndependent
General Biology Additional InformationFeeding

Chthamalus stellatus / Chthamalus montagui generally feed on small plankton. They can consume diatoms, but were found not to grow under a regime dominated by diatoms (Barnes & Barnes, 1965). Normal feeding of chthamalids involves a cirral beat. This cirral beat is also noted to be a respiratory mechanism (Anderson & Southward, 1987). However, in high wave exposure they tend to hold their cirri out stiffly against the water current for a long period of time, retracting when food is captured (Crisp, 1950). Barnacles living in wave exposed conditions may benefit from this passive suspension feeding habit where cirral beating and consequent energy expenditure are minimised (Crisp, 1950).
Rates of cirral beat decrease with age and size, but increase with temperature (Anderson & Southward, 1987). Green (1961) reported that barnacles higher up on shore had a higher cirrial beat frequency than those at lower levels. However, Southward (1955; 1964(b)) found no similar trends.

Southward (1955) found that there was no response of Chthamalus stellatus / Chthamalus montagui in still water and that cirrial beating was only induced at a current of approximately 10 cm / sec. The extension response was also sometimes shown. The cirrial beating frequency is also related to temperature, shown by experiments by Southward (1955). Chthamalus stellatus / Chthamalus montagui barnacles kept at a temperature of 0 °C did not react to touch after an hour. He also found that they remained inactive at a temperature up to 5 °C. Between 5 and 30 °C there was a linear increase to 10 beats every 10 seconds. This slowly declined above 33 °C and dropped rapidly at 36 °C. Although the species resisted coma above a temperature of 40 °C, all cirrial beating ceased at 37.5 °C.


Sessile barnacles have a pair of gills: pleats of the mantle wall, attached to the mantle cavity (Stubbings, 1975). Rainbow (1984) also stated that the cirri might also play an important role in respiration. There is usually a slow respiratory pumping beat, with varied emergence of the cirri.


Barnacles need to moult in order to grow. Feeding rate and temperature determine the frequency of moulting. Moulting does not take place during winter when phytoplankton levels and temperatures are low (Crisp & Patel, 1960).


Once the barnacle is fixed in place it is unable to detach again (Crisp, 1955). All species grow faster in early life and slower in later life, and chthamalids tend to become tubular when crowded (Southward & Crisp, 1965). The growth rate varies with a variety of biological and environmental factors, including current flow, orientation with respect to current, food supply, wave exposure, shore height, surface contour, and intra- or inter-specific competition. Growth in Chthamalus spp. takes place along the whole internal surface of the one layered plates (Bourget, 1977). The growth rate for Chthamalus stellatus / Chthamalus montagui has been reported by Barnes (1956; Crisp & Bourget (1985) as between 10 - 55 µm per day (relatively slow) in the linear phase. Crisp (1950) noticed that Chthamalus stellatus / Chthamalus montagui reached a maximum size of 0.2 to 1.4 cm. Chthamalus stellatus / Chthamalus montagui was found to have a lower growth rate than many other species of barnacles (Relini, 1983). The species reached a basal diameter of 2-2.5 mm in 3 months, 3.5-4 one year later, up to 8 mm in the 2nd year of growth, but generally no more than about 5-6 mm (Relini, 1983). Sometimes a decrease in size was noticeable, due to abrasion. This low growth rate was found to be associated with a low metabolic rate, or low oxygen consumption, by Barnes & Barnes (1965). Benedetti-Cecchi et al. (2000) observed that Chthamalus stellatus barnacles in the north west Mediterranean were significantly larger the higher up shore that they were found. However, no significant difference in growth rate was noted by Benedetti-Cecchi et al. (2000), with the growth rate of juveniles being between 0.4 and 0.8 mm per year, and that greater mortality of young and adults in a low shore environment.

Parasites and epizoites

Healy (1986, in O'Riordan et al., 1992) observed the parasitic isopod, Hemioniscus balani in Chthamalus stellatus and Chthamalus montagui in Ireland, although it was never present in Lough Hyne populations. However, Southward & Crisp (1954) found that although it attacks and sterilises Semibalanus balanoides individuals, it does not normally attack chthamalids on British shores.

Further Information

  • The dog whelk, Nucella lapillus, feeds on barnacles. The species of Chthamalus spp. are less at risk of this due to their smaller size in comparison with Semibalanus balanoides, but nevertheless it can still have a negative impact on their abundance.
  • Other predators which pull shells or cirri of barnacles off the rock, include crabs, amphipods, shore fish such as wrasse and sometimes herring gulls (Moore & Kitching, 1939), in particular, the shanny Blennius pholis (Kendall & Bedford, 1987). Another possible predator is the polychaete, Eulalia viridis (Moore & Kitching, 1939). Chthamalus spp. is also known to be displaced by Patella spp. and smothered by Mytilus spp. and algae at lower shore levels (Moore & Kitching, 1939).
  • Empty barnacle cases provide homes for small periwinkles, , small bivalves and the isopod, Campecopea hirsuta (Fish & Fish, 1996).
  • In order to protect themselves from changes in temperature, desiccation and a lowering of salinity, intertidal barnacles are usually able to close their aperture tightly (Moore & Kitching, 1939).
Biology References Barnes & Barnes, 1965, Anderson & Southward, 1987, Crisp, 1950, Southward, 1964, Crisp & Patel, 1960, Stubbings, 1975, Crisp, 1955, Southward & Crisp, 1965, Bourget, 1977, Crisp & Bourget, 1985, Relini, 1983, Benedetti-Cecchi et al., 2000, Moore & Kitching, 1939, Southward, 1955, Crisp et al., 1981, Southward & Crisp, 1954, Barnes et al., 1963, Kendall & Bedford, 1987, Bassindale, 1964, Southward, 1964(b), Bassindale, 1964,
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