by Sue Scott DIVE’s marine biologist

COLONIAL ANEMONES

WHITE CLUSTER (TRUMPET) ANEMONE Parazoanthus anguicomus YELLOW CLUSTER (TRUMPET) ANEMONE Parazoanthus axinellae SANDY CREEPLET Epizoanthus couchii GINGER TINY OR PEPPERCORN ANEMONE Isozoanthus sulcatus

Photographs Sue Scott

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For me, a highlight of the Marine Conservation Society dive trip to South Uist (plug – www.seasearch.org.uk) this summer was seeing spectacular sheets of white cluster anemones under overhangs near the tops of cliffs. Although ours are coldwater creatures, I always think colonial anemones have a tropical feel, resembling coral polyps. Colonial anemones are classified as Zoantharia, related to but separate from other anemones and from hard corals. Unlike solitary anemones, the polyps are joined at the base by a sheet of tissue over the rock. They have no hard skeleton, although they often have grains of sand stuck to them. For the past 30 years I’ve been calling these anemones ‘trumpet anemones’, for obvious reasons. However the latest guide

Main photograph: white cluster anemones 1 yellow cluster anemones 2 sandy creeplet anemones

(plug number two – see below), calls the two Parazoanthus species ‘cluster’ anemones, which does avoid confusion with the solitary anemone Aiptaisia mutabilis, also called the trumpet anemone for obvious reasons – yet another example of why biologists use Latin names. Although the yellow trumpet anemone tends to grow in clusters, the white trumpet often has more spread-out colonies. In other countries colonial anemones are also called encrusting anemones or sea mats but we won’t go into that... The two species of Parazoanthus are beautiful and showy; white, orange or yellow, with around 30 to 45 spiky tentacles. The tentacles are alternately held up and folded back, so that they appear to be in two rings. You are unlikely to see both

species together, as the frosty white one, appropriately, lives mainly in the north, while the sunny yellow one lives on southern coasts. Confusingly, the yellow one is occasionally white, but this is rare, like snow in Cornwall! It’s more of a challenge to spot sandy creeplets and ginger tinies, as they are shades of brown, and the base and column are often disguised with silt. Ginger tinies quickly retract into the silt if disturbed. All these colonial anemones catch food from the plankton, together with other small animals that bump into their sticky tentacles. However, ginger tinies are also partly solarpowered. They remain contracted in the dark, but within a few minutes of exposure to light, they open out so that tiny algae in their tissues can photosynthesise, capturing energy

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BRITISH BEASTS

from sunlight as sugars, some of which leak to the anemones. If the water gets too warm, ginger tinies evict their coloured algae, in the same way that corals bleach under stress. New polyps grow from buds on the common base. This swells the existing colony, but to be able to spread to new areas some distance away, something more adventurous is needed. As with other anemones and corals, a tiny swimming larva performs this service. The larvae are produced sexually – in yellow and white trumpet anemones and sandy creeplets, the sexes are separate, with sperm and eggs developing in summer. When writing this piece, I could find little information on our British species, but in tropical colonial anemones spawning is

synchronised, as it is in hard corals, to maximise the chances of fertilisation – all blowing their trumpets together! ■ • Seasearch Guide to Sea Anemones and Corals of Britain and Ireland by Chris Wood, costs £9.95 and is published by the Marine Conservation Society. ISBN: 0948150416.

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BEAST AT A GLANCE

KNOWN HAUNTS Colonial anemones grow on rocks, wrecks, shells and other marine life.

BEST PLACE TO SEE The yellow cluster, ginger tiny and sandy creeplet anemones are found mainly around southern and western coasts of Britain. The white cluster anemone is largely a northern species, but grows further south in deep water.

LIKELY TO APPEAR Most obvious in summer, when their food is abundant.

DISTINGUISHING FEATURES Small trumpet-shaped anemones, joined at the base, forming clusters or spreading colonies. White and yellow cluster anemones are very similar in shape, with tentacles not much longer than the width of the disc. Sandy creeplets are buff-coloured, but with tentacles longer than the body, and with a white tip. Ginger tinies are dark brown.

SIZE The white cluster anemone grows up to 25mm tall; the yellow cluster anemone to 15mm; the sandy creeplet to 12mm and ginger tinies are less than 10mm high. All the colonial anemones can form extensive colonies.

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