Yellow cluster anemone

Photo: Sylvain Le Bris · CC BY-NC

Parazoanthus axinellae forms the visually dominant invertebrate layer on Monte da Guia's caldera walls, its colonies of brilliant yellow polyps covering sections of rock from 15 metres to depth. Colonial zoanthids like this species are filter feeders that exploit the persistent north Atlantic current flow to intercept suspended plankton. Their colouration derives from symbiotic pigment-producing bacteria rather than the zooxanthellae found in tropical corals, an adaptation to the low-light, cool-water Azorean environment.