Host Preferences and Colouration of Christmas Tree Worms, Spirobranchus corniculatus (Grube, 1862) from Bidong Island, South China Sea

Abstract

Polychaetes from genus Spirobranchus is one of the distinctive organisms in the coral reef ecosystem due to a unique, colourful ‘Christmas tree’ shape of radiolar crown. The presence of Christmas Tree Worm (CTW) on hard coral species and its colour variations can be potentially used to determine the coral health status and tourism attractions. Nevertheless, information on CTW in Malaysia is lacking; thus, the specific habitat and colour variety for CTW, particularly at the east coast of Peninsular Malaysia are not well understood. Hence, the objectives of this study are to investigate the coral preferences and colour variety of Pacific CTW, Spirobranchus corniculatus at Pantai Pasir Cina, Bidong Island, South China Sea. Underwater surveys were done using a belt transect technique by SCUBA divers in three depth ranges, i.e. 2–4 m, 5–7 m, and 8–10 m during high tide. Numbers of S. corniculatus per coral colony and coral species were recorded. Everted CTWs were digitally photographed and colour corrected to reveal the true colour. A total of 274 S. corniculatus were found along the belt transects on the coral reef at Pantai Pasir Cina. The major percentage (60.2%) of S. corniculatus was found in depth between 5 and 7 m and live on hermatypic coral from genus Porites. However, only a small number of CTW were recorded living on other coral genera including Astreopora spp., Montastrea spp. and Montipora sp., and no CTW was recorded live as a symbiont with Acropora species. The CTW at Pantai Pasir Cina has five plain and four patterns of colours dominated by blue, followed by yellow, orange, green, white, striped blue, striped purple, striped white and striped brown. This study revealed the importance of massive coral in particular Porites species as CTW host at Pantai Pasir Cina, Bidong Island. The information could be beneficial for determining the coral reef status using CTW as indicator species and for proper underwater tourism management.KeywordsChristmas tree worm Spirobranchus corniculatus Coral reefBidong IslandSouth China Sea