The early developmental process of Acanthaster solaris in the South China Sea

Crown-of-thorns sea star (CoTS), a well-known coral predator, has triggered severe ecological disaster on coral reefs in the South China Sea. In order to clarify the early development process of this coral predator and better explain the formation process of CoTS outbreak, an artificial breeding was conducted for the outbreak population of Acanthaster solaris in the South China Sea with the method of reproductive biology. The result demonstrated 1-methyl-adenine was effectively induced to foster A. solaris to spawn. When under the temperature of 28 ℃ and salinity of 33 as the natural seawater of coral reefs, a batch of embryos completed incubation process and developed into bipinnaria larva. With feeding on Chaetoceros muelleri, two newly-formed arm protruded from the anteroventral part of the planktonic larva after 12 d post-fertilization, a feature designated as early branchiolaria larva. Upon two days metamorphosis, larva was successfully developed into 5-arms settled juvenile with totally 410 juveniles and the average size of (445.88 ± 50.63) μm (mean ± SD). It was found that in the comparison between artificial food and natural food, artificial food could not promote the conversion of planktic larvae into branchiolaria larvae and natural food was still needed for the planktic development. Notably, in the experiment of present or absent attached bases, coral stone can effectively promote the metamorphosis development of settled juveniles with the mean metamorphosis rate 2.59%, higher than that of no attached bases with the value only 0.31%. In this study, a number of progenies of A. solaris population were successfully bred in artificial breeding, revealing their early developmental process. The result here provided basic data for investigation, monitoring, early warning, disaster reduction, prevention and control, and disaster management of A. solaris, which finally fostered the ecological security of islands and reefs in the South China Sea.