Fluorescence Grass Coral

zooxanthellate

The skeleton of Galaxea is very distinctive. Corallites are extremely plocoid, 3-15 mm tall cylinders set into a flat and rather blistery coenosteum. Further enhancing this appearance of tall corallites are the extremely protuberant primary septa, projecting a further 3 - 5 mm above the corallite wall. Septa usually number over 24 in mature corallites. These are very attractive corals when living, due to the daytime extension of pale yellow, green or blue translucent tentacles. Colonies of this species are commonly less than 40 cm across, forming cushions, or are encrusting to sub-massive. Occasionally, such as in turbid waters, the species can provide over 50% cover over several hundred square metres, and these colonies may develop both foliaceous and sub-ramose parts, with smaller corallites on fast growing extensions. However, on the sub-ramose parts of giant colonies, calices are much smaller and have only 12 septa. (This is a character of Galaxea astreata. Where such fragments come from the same colonies as typical G. fascicularis, it seems likely that they represent young, fast growing edges.) Its depth range is 5-20 m deep (Sheppard, 1998). Small colonies are cushion-shaped or low domes or irregular. Large colonies are of mixed sizes, commonly up to 6 mm in diameter with numerous septa reaching the corallite centre. Colour: Usually green, red and brown in various mixtures. Polyps are frequently extended during the day, and tentacles often have conspicuous white tips. Abundance: very common in a wide range of habitats and may be dominant on inshore fringing reefs, where columnar colonies frequently exceed 5 m in diameter (Veron, 1986). The small, cushion-shaped colonies are readily recognised because of the spiky appearance caused by the protuberant radiating septa of the tubular corallites. Often feeds during the day. Colour: A vivid green, brown or red with white-tipped tentacles. Habitat: diverse, especially in turbid, shallow waters (Richmond, 1997); rocks (Kalk, 1959). Tropical Indo-Pacific in Kalk (1958).