Biodiversity & Conservation

Limaria hians beds in tide-swept sublittoral muddy mixed sediment



Image Sue Scott - Gaping file shell nest on mixed muddy substratum, with nest opened and Limaria hians exposed. Image with ca 15 cm.
Image copyright information

  • #
Distribution map

SS.SMx.IMx.Lim recorded (dark blue bullet) and expected (light blue bullet) distribution in Britain and Ireland (see below)

  • EC_Habitats
  • UK_BAP

Ecological and functional relationships

The information below is based on survey data and the few detailed studies available: Gilmour (1967), Minchin (1995), Connor et al. (1997), JNCC (1999), and Hall-Spencer & Moore (2000b). Limaria hians is an active suspension feeder on phytoplankton, bacteria, and detritus.

The carpet of byssus threads, coarse sediment, and shell produced by Limaria hians provides refugia, and substratum for attachment for a wide variety of sessile and sedentary species.

Other suspension feeders include sponges, hydroids (e.g. Kirchenpaueria pinnata, Nemertesia spp., and Tubularia spp.), bryozoans (e.g. Bugula spp.) , soft corals (e.g. Alcyonium digitatum), epifaunal and infaunal bivalves (e.g. Modiolus modiolus and Mya truncata respectively), tube worms (e.g. Pomatoceros triqueter), ascidians and small crustaceans. If present, the brittlestars, e.g. Ophiura spp. or Ophiopholis aculeata, may also suspension feed.

Kelp (e.g. Laminaria hyperborea) and foliose red algae (e.g. Delesseria sanguinea or Phycodrys rubens) probably provide primary production in the form of detritus and dissolved organic matter, and via grazing by amphipods, isopods, chitons, gastropods (e.g. Gibbula cineria, Tectura virginea or Calliostoma zizyphinum) or sea urchins (e.g. Psammechinus miliaris). Suspension feeders, including Limaria hians obtain primary productivity from phytoplankton and benthic and epiphytic microalgae.

The faunal turf of hydroids and bryozoans is probably grazed by echinoderms (e.g. Henricia oculata and Echinus esculentus) or gastropods (e.g. Calliostoma zizyphinum) or preyed on by polychaetes (e.g. the sea mouse Aphrodite aculeata), nudibranchs (e.g. Onchidoris sp.) and pycnogonids (e.g. Achelia echinata) (Gordon, 1972; Salvini-Plawen, 1972: Ryland, 1976).

Mobile predators include crabs such as Cancer pagurus and Necora puber, which probably eat a variety of epifauna including gastropods, small crustacea and bivalves. The nests of Limaria hians provide a defence against most predators (Merrill & Turner, 1963: Gilmour, 1967). In addition, Limaria hians can also discard its tentacles leaving a predator with a sticky, unpalatable meal while the rest of the animal makes its escape by swimming. The tentacles of Limaria hians (especially the longer tentacles) secrete an adhesive and irritant mucus, that has been shown to deter a variety of predators from crabs to fish; e.g. the flounder was reported to spit out Limaria hians (Gilchrist, 1896; Merrill & Turner, 1963; Gilmour, 1967). However, the starfish Asterias rubens and Marthasterias glacialis prey on a wide range of epifauna and molluscs including Limaria hians (Minchin, 1995).

Fish such as juvenile cod Gadus morhua, small-spotted catshark (dogfish) Scyliorhinus canicula, and dragonets Callionymus lyra and gobies probably prey on mobile and sessile epifauna on the reef and may take damaged specimens of Limaria hians (JNCC, 1999; Hall-Spencer & Moore, 2000b).

Starfish, brittlestars, hermit crabs (e.g. Pagurus bernhardus), crabs and the common whelk Buccinum undatum probably act as epifaunal scavengers within this biotope (JNCC, 1999; Hall-Spencer & Moore, 2000b).

The nest galleries support a number of detrivores, deposit feeders, scavengers and predators. For example, polychaetes (e.g. Polynoe spp. and Flabelligera affinis), flatworms and small crustaceans are probably scavengers within the nests, preyed on by polychaetes such as Glycera lapidum and Nephtys hombergi and ribbon worms) (Hall-Spencer & Moore, 2000b).

Seasonal and longer term change

Seasonal change
In the Plymouth area, Limaria hians breeds between early spring to late summer, the larvae present in the water column from August to the following April, with a peak of larval abundance in October at Plymouth or in late summer in Mulroy Bay, Co. Donegal (Lebour, 1937b, MBA, 1957; Allen, 1962; Minchin, 1995).

The macroalgae in the biotope may be expected to show seasonal changes in growth and development; for examples see Delesseria sanguinea and Laminaria hyperborea reviews. In temperate waters most bryozoan species tend to grow rapidly in spring and reproduce maximally in late summer, depending on temperature, day length and the availability of phytoplankton (Ryland, 1970). Several species of bryozoans and hydroids demonstrate seasonal cycles of growth in spring/summer and regression (die back) in late autumn/winter, over-wintering as dormant stages or juvenile stages (see Ryland, 1976; Gili & Hughes, 1995; Hayward & Ryland, 1998). For example, the fronds of Bugula species are ephemeral, surviving about 3-4 months but producing two frond generations in summer before dying back in winter, although the holdfasts are probably perennial (Eggleston, 1972a; Dyrynda & Ryland, 1982). The hydroid Tubularia indivisa is annual, dying back in winter (Fish & Fish, 1996), while the uprights of Nemertesia antennina die back after 4-5 months and exhibit three generations per year (spring, summer and winter) (see reviews; Hughes, 1977; Hayward & Ryland, 1998; Hartnoll, 1998). Many of the bryozoans and hydroid species are opportunists (e.g. Bugula flabellata) adapted to rapid growth and reproduction (r-selected), taking advantage of the spring/summer phytoplankton bloom and more favourable (less stormy) conditions (Dyrynda & Ryland, 1982; Gili & Hughes, 1995). Some species such as the ascidians Ciona intestinalis and Clavellina lepadiformis are effectively annual (Hartnoll, 1998). Therefore, the biotope is likely to demonstrate seasonal changes in the abundance or cover of the epifauna and macroalgae.

Temporal change
Hall-Spencer & Moore (2000b) studied a Limaria hians bed over a 5 year period, while Minchin (1995) reported the that Limaria hians was abundant in the Moross Channel, Mulroy Bay from 1978-1982 and had been recorded from Mulroy Bay a hundred years previously. This suggests that Limaria hians beds, once established, are probably relatively stable unless affected by human impacts or storms (see sensitivity).

Habitat structure and complexity

The gaping file shell Limaria hians can build extensive nests made of shell, stones debris and maerl (when present) interlaced by several hundred byssus threads, and lined by mucus, mud and their faeces (Gilchrist, 1896; Hall-Spencer & Moore, 2000b). Nests may be constructed by expansion of smaller burrows, in gravel, shell sand or laminarian holdfasts, or may be simply composed of byssus threads (see Merrill & Turner (1963) and Gilmour (1967) for details). Nests are about the maximum gape of shell in diameter by about twice the length of the animal, with holes for the entrance and exit of water. Nests vary in size and complexity with individual Limaria hians being recorded from nests of 2-5 cm diameter, while larger nests of up to 25 cm diameter and 10 cm in length consisted of numerous ventilated holes and galleries (Gilmour, 1967; Tebble, 1976; Hall-Spencer & Moore, 2000b). Hall-Spencer & Moore (2000b) reported that six of these large nests contained 24-52 small and 25-40 large individuals of Limaria hians, with adult individuals occupying single galleries with two ventilation holes, while juveniles occupied complex galleries with multiple ventilation holes. Limaria hians can also occur individually or in small numbers, for example in kelp holdfasts, or under stones intertidally (Jason Hall-Spencer, pers com.).

This biotope is characterized by dense populations of Limaria hians where the nests coalesce into a carpet or reef over the sedimentary substratum, and in which individual Limaria hians are not visible (Connor et al., 1997; JNCC, 1999). For example, in the Creag Gobhainn area of Loch Fyne, Limaria hians formed a reef 10-20cm high, composed of >700 individuals/m² and covering several hectares (Hall-Spencer & Moore, 2000b) and 216-584 /m² were reported in the Moross Channel, Mulroy Bay in 1980 (Hobson, 1980 cited in Minchin, 1995). The carpet of nests covers and hence stabilizes the substratum. In addition, the carpet of nests provides substratum for the attachment for a diverse array of sessile and sedentary invertebrates, niches and refugia for mobile epifauna, and the nests themselves support a burrowing infauna and scavengers. The exact composition of the associated community probably varies with location depending on the species present in the surrounding area.

  • In shallow examples of this biotope the Limaria hians carpet provides substratum for macroalgae, including the kelps Saccorhiza polyschides, Laminaria digitata and Saccharina latissima (studied as Laminaria saccharina and their associated flora and fauna (e.g. see EIR.LhypR) , which would otherwise be unable to attach to a sedimentary substratum (Minchin, 1995).
  • Sessile epifauna attached to the nests and any available hard substrata such as stones include, sponges (e.g. Esperiopsis fucorum), hydroids (e.g. Kirchenpaueria pinnata, Nemertesia spp., and Tubularia spp.), soft corals (e.g. Alcyonium digitatum), anemones (e.g. Urticina felina and Metridium senile), bryozoans (e.g. Bugula spp.), barnacles (e.g. Balanus crenatus), amphipods (e.g. Ampelisca spp. and Jassa spp.), ascidians (e.g. Ciona intestinalis and Corella parallelogramma), tube worms (e.g. Pomatoceros triqueter), and bivalves (e.g. the horse mussel Modiolus modiolus and scallops Pecten maximus and Chlamys varia) (Connor et al., 1997; JNCC, 1999; Hall-Spencer & Moore, 2000b).
  • Mobile epifauna include flatworms, ribbon worms (Nemertea), polychaetes (e.g. the sea mouse Aphrodite aculeata), pycnogonids, amphipods, shrimp, hermit crabs (e.g. Pagurus bernhardus), crabs (e.g. Cancer pagurus, Hyas araneus, and Necora puber), gastropods (e.g. Gibbula spp., Calliostoma zizyphinum, and Buccinum undatum), nudibranchs (e.g. Onchidoris spp.), sea urchins (e.g. Psammechinus miliaris), brittlestars (e.g., Ophiothrix fragilis and Ophiocomina nigra), and starfish (e.g. Asterias rubens, Crossaster papposus and Marthasterias glacialis) (Connor et al., 1997; JNCC, 1999; Hall-Spencer & Moore, 2000b).
  • The galleries of the nests also supported scavengers such as scale worms (e.g. Polynoe sp.) and predatory polychaetes (e.g. Lepidonotus squamatus and Glycera lapidum), while the polychaetes Flabelligera affinis and the bivalve Mysella bidentata were associated with the faeces-lined walls of nest galleries (Hall-Spencer & Moore, 2000b).
  • Hall-Spencer & Moore (2000b) reported that the sediment underneath the Limaria hians bed supported a diverse infaunal community including burrowing bivalves (e.g. Mya truncata, Dosinia exoleta and Tapes rhomboides), the heart urchin Echinocardium pennatifidum and the holothurian Thyonidium drummondi. The high infaunal biodiversity observed in their study area was attributed to the porosity of the Limaria hians beds and the locally strong currents, that allowed adequate exchange of oxygenated water and nutrient. Examples of this biotope that occur in areas of low water movement (i.e. weak currents and wave sheltered conditions) may not exhibit such as diverse community.


Little information on productivity was found. However, phytoplankton, benthic microalgae, kelps and other macroalgae probably make an important contribution to primary productivity where abundant. Dame (1996) suggested that dense beds of bivalve suspension feeders increase turnover of nutrients and organic carbon in estuarine (and presumably coastal) environments by effectively transferring pelagic phytoplanktonic primary production to secondary production in the sediments (pelagic-benthic coupling). The Limaria hians beds probably also provide secondary productivity in the form of tissue, faeces and pseudofaeces.

Recruitment processes

Limaria hians is dioecious (Ansell, 1974) and can reproduce in its second summer (Minchin, 1995). Hrs-Benko (1973) reported that Limaria hians in the northern Adriatic were sexually active throughout the year, with a main spawning period between late spring and summer, while Minchin (1995) noted that settlement normally occurred in August to September in Mulroy Bay. Veligers of Limaria hians were collected between August and the following April in the Plymouth area, absent in early summer with a peak in abundance in October (Lebour, 1937b). Limaria hians veligers are distinctive and triangular in shape (80-320 µm in length). Larvae reach 320 µm in length within a few weeks in the laboratory, after which metamorphosis occurs, suggesting that the veligers could spend at least a few weeks in the plankton. Newly metamorphosed juveniles grow rapidly, reaching 2 mm in length within about 2.5 months (Lebour, 1937b). Minchin (1995) noted that Limaria hians laid down two growth rings per year after their first year, and reported a mean shell length of 2 cm in their third summer. Hrs-Benko (1973) noted that individuals >2.7-3 cm in size died in the Adriatic population, while Minchin (1995) recorded 5 year classes and 6 year old specimens in Mulroy Bay. However, Limaria hians populations are dependant on recruitment to maintain their abundance as recruitment failure in the Moross Channel, Mulroy Bay , associated with tri-butyl tin (TBT) contamination, resulted in loss of the resident population (Minchin, 1995).

The associated macroalgae, epifauna and interstitial fauna probably depend on locality and recruit from the surrounding area. Many hydroids and most bryozoans, ascidians and probably sponges have short lived plankton or demersal larvae with relatively poor dispersal capabilities. Exceptions include Nemertesia antennina and Alcyonium digitatum and hydroids that produce medusoid life stages, which probably exhibit relatively good dispersal potential. Hydroids and bryozoans are opportunistic, rapid growing species, with relatively widespread distributions, which colonize rapidly and are often the first groups of species to occur on settlement panels. Sponges and anemones may take longer to recruit to the habitat but are good competitors for space. Recruitment in epifauna communities is discussed in detail in the faunal turf biotopes MCR.Flu, CR.Bug and in Modiolus modiolus beds (MCR.ModT).

Mobile epifaunal species, such as echinoderms, crustaceans, and amphipods are fairly vagile and capable of colonizing the community by migration from the surrounding areas, probably attracted by the refugia and niches supplied by the Limaria hians carpet. In addition, most echinoderms and crustaceans have long-lived planktonic larvae with high dispersal potential, although, recruitment may be sporadic, especially in echinoderms.

Time for community to reach maturity

The time taken for the biotope to develop would depend on the time required for the Limaria hians population to increase in abundance and develop a carpet or bed of byssal nests. Colonization by macroalgae, epifauna, and mobile species would probably be rapid and may enhance development of the byssus reef (Jason Hall-Spencer pers comm.). The recovery of the Limaria hians beds in Moross Channel, Mulroy Bay was studied by Minchin (1995). The population was reduced to only <2% of its 1980 abundance by 1986 (Minchin et al., 1987). In the follow up study, Minchin (1995) reported that after successful spat falls in 1989 onwards, the population, carpet and associated community had returned to their 1980 state by 1994, presumably due to recruitment from a few surviving old specimens or populations in other areas of Mulroy Bay. Therefore, it is likely that a recognizable biotope could develop within 5 years once successful recruitment of Limaria hians occurred. However, the associated community may take longer to develop, especially in the case of long-lived species.

Additional information

None entered

This review can be cited as follows:

Tyler-Walters, H. 2003. Limaria hians beds in tide-swept sublittoral muddy mixed sediment. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 25/11/2015]. Available from: <>