Biodiversity & Conservation

Neocrania anomala and Protanthea simplex on very sheltered circalittoral rock



Image Sue Scott - Circalittoral cliff face with dense brachiopods Neocrania anomala and Terebratulina retusa, the anemone Protanthea simplex and the ascidian Ciona intestinalis. Loch Duich, Highland. Image width ca 1 m.
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Distribution map

CR.LCR.BrAs.NeoPro recorded (dark blue bullet) and expected (light blue bullet) distribution in Britain and Ireland (see below)

  • EC_Habitats

Ecological and functional relationships

In this circalittoral biotope and similar sub-biotopes there are few algal species and limited primary production. The fauna is dominated by encrusting / attached species such as anemones, hydroids, brachiopods and solitary ascidians. The fauna consists predominantly of passive and active suspension feeders. There are a few errant predators and scavengers such as Cancer pagurus, and Asterias rubens. Particularly dense assemblages with abundant solitary sea squirts may provide shelter for other small fauna. Additional shelter may be provided by large sponges, particularly in the sub-biotopes.

Seasonal and longer term change

Ciona intestinalis is typically an annual species, particularly in reduced salinity water although reproduction can occur throughout the year. There will be some temporal changes in the coverage and shelter provided by this species. Otherwise, it is unlikely that there will be any seasonal or other temporal changes in the biotope.

Habitat structure and complexity

The sheltered conditions of the landward basins of sea lochs can allow quite species-rich assemblages to develop. Several tube worm species, including Chaetopterus variopedatus can be used by Protanthea simplex as a substratum. Larger species, including sponges and solitary ascidians provide greater spatial complexity. Higher densities of the hard, permanently attached Neocrania anomala may exclude other species.


Primary productivity in this biotope is low although coralline algae were recorded in more than half of the records of this biotope and the brown algae Pseudolithoderma extensum in approximately one quarter of all records (JNCC, 1999). However, quite high densities of encrusting or attached organisms, primarily brachiopods, sea loch anemones, solitary ascidians and tube worms can result in quite high secondary productivity through suspension feeding.

Recruitment processes

Recruitment is primarily through pelagic larvae. Intense local recruitment can occur with Ciona intestinalis where sticky mucus strings containing eggs and larvae are trapped round nearby adults or other objects. Dispersal ability of Neocrania anomala may be limited and only occur from local populations. Protanthea simplex with is long-lived pelagic larval stage has considerable dispersal potential.

Time for community to reach maturity

None of the main characterizing species are particularly long lived. Neocrania anomala survives for possibly up to 10 years. Ciona intestinalis lives typically only for a year and populations can reproduce throughout the year. Large sponges may have considerably greater longevity and slower growth. It may take over five years for the community to reach maturity.

Additional information

This review can be cited as follows:

Jackson, A. 2005. Neocrania anomala and Protanthea simplex on very sheltered circalittoral rock. 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: <>