Biodiversity & Conservation

Mytilus edulis and piddocks on eulittoral firm clay


<i>%Mytilus edulis%</i> and piddocks on eulittoral firm clay
Distribution map

LR.MLR.MytPid recorded (dark blue bullet) and expected (light blue bullet) distribution in Britain and Ireland (see below)

  • EC_Habitats

Species indicative of sensitivity

To assess the sensitivity of the biotope, the sensitivity of component species is reviewed. Those species that are considered to be particularly indicative of the sensitivity of the biotope, and for which research has been undertaken in detail are shown below (see selection criteria). The biology of other component species of the biotope is also taken into account wherever information is known to the researcher.

Community Importance Species name Common Name
Key Structuring Barnea candida White piddock
Key Structuring Pholas dactylus Common piddock
Key Structuring Petricola pholadiformis American piddock
Key Structuring Mytilus edulis Common mussel


The piddocks Barnea candida, Pholas dactylus and Petricola pholadiformis and the mussel Mytilus edulis are the key structuring species. The piddocks create an uneven surface, and empty burrow holes in clay platforms that provide habitats for other animals, greatly increasing species diversity of the biotope (Pinn et al., in press). The Mytilus edulis patches between the burrows also provide some heterogeneity to the substratum and additional surface area for attachment for epibionts including algal species. Within the mussel matrix, associated fauna may find refuge. In Mytilus edulis islands, biological activities such as suspension feeding and the production of biodeposits affect the process of community organization of the associated fauna (Tsuchiya & Nishihira, 1986). The periwinkle Littorina littorea is a grazer commonly associated with this biotope. However, it is unlikely to affect the community structure.

Additional information

The MNCR reported 42 species from this biotope, although not all species occur in all examples of the biotope (JNCC, 1999). Tsuchiya & Nishihira (1986) found more than 40 different species associated with mussel patches approximately 500 cm² in size.

This review can be cited as follows:

Marshall, C.E. 2008. Mytilus edulis and piddocks on eulittoral firm clay. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 30/11/2015]. Available from: <>