ABSTRACT
In Hong Kong, Anthocidaris crassispina commonly feeds on 9 algal species. In winter (December to April), urchins at all localities heavily graze upon Colpomenia sinuosa, Sargassum hemiphyllum and Ulva conglobata. During the warmer months, the urchins graze upon Sargassum spp. and Corallina spp. in localities where macrophytes are perennial. In areas experiencing a summer macrophytic decline, the urchins depend upon coralline (Corallina spp.), filamentous (Cladophora delicatula and Gelidium divaricatum) and encrusting (Lithophyllum) algae. Laboratory food preference experiments performed on 6 common algal species have shown that in terms of percentage total intake, Colpomenia sinuosa was most preferred, followed in order by Petalonia fascia, Sargassum hemiphyllum, Padina australis, Corallina pilulifera and Ulva conglobata. Consumption experiments have shown that urchins of 40-50 mm test diameter feed upon algae (daily percentage biomass) in the following order: Colpomenia sinuosa (5.7%), Ulva fasciata (3.5%), Padina australis (3.0%), Sargassum hemiphyllum (2.6%), Ulva conglobata (2.5%) and Corallina pilulifera (1.4%).
