Flame shells are bivalve molluscs. They take their name from the bright red/orange filamentous fringe or mantle and tentacles which are permanently on display. The tentacles (a mixture of red and white) waft around in passing currents resembling flames.

Behaviour

Flame shell beds develop mostly on sea beds of coarse sand, gravel and shells, often in areas with moderate or strong water currents, usually at depths of between 5m and 30m.

When threatened, it may escape by clapping its valves together, propelling it through the water, with assistance from its tentacles. Due to their inability to retract their mantle and tentacles into the shell, flame shells hide by burrowing under the top layer of sediment.

Flame shells build ‘nests’ on the sea bed. Each shellfish swims around looking for shells and gravels which they collect in their tentacles and bring back to their chosen underwater home, before gluing them together into a nest using sticky byssal threads. Individual nests expand over time, eventually overlapping with other nests and consequently forming expansive reefs. These reefs can support hundreds of other species. However, these nests are fragile and vulnerable to physical disturbances, such as scallop dredging.

Size

Length: 2.5-4cm

Status

Flame Shell beds are a priority marine feature in Scotland’s seas and are protected in six locations around Scotland by a suite of Marine Protected Areas. In May 2019, part of Loch Carron containing flame shells was confirmed as a new Marine Protected Area.

Distribution

In the British Isles, the distribution of this species is primarily restricted to the west coast of Scotland from the sub-littoral (below low tide), down to 100m. Beds can be found at the mouths of a handful of sea lochs around the west coast, such as Loch Carron, Loch Sunart, Loch Fyne, and in a few remnant patches near Ullapool, and the Isles of Lismore and Rum. A study in 2000 indicated that flame shell beds have been lost from their former widespread distribution, including in the Clyde and around the Isle of Man.

When to see

January to December

Facts

• The flame shell’s vibrant red colour is due to the large amount of carotenoids (yellow, orange, and red organic pigments) found within their body.
• Flame shells are considered of national importance in Scotland. In 2012, more than 100 million flame shells were found during a survey of Loch Alsh, a tiny stretch of sea between the Isle of Skye and the Scottish mainland. The colony has formed a reef five miles long and may be the largest grouping of flame shells anywhere in the world.