Alcyonidium gelatinosum

Colonies form extensive encrusting sheets. Colonies are light brown, with conspicuous white walls defining the outline of autozooids during the late summer and autumn months. The autozooids are polygonal in shape, dimensions: 0.3-0.5 x 0.2-0.4mm. Space-filling kenozooids interspersed among the autozooids. Colonies are well developed and abundant in the late summer. With bright pink embryos developing in them they form a conspicuous part of the benthic fauna.

A. gelatinosum occurs commonly on the undersides of rocks and Fucus serratus plants in the intertidal zone and on bedrock down into the shallow sublittoral.

This species broods coronate larvae. These are pink in colour and are present in the late summer and autumn.

Well-developed colonies can grow up to 10cm across.