Crown-of-thorns starfish reproduce by spawning, in which males and females release their gametes into the seawater, where fertilization occurs. Unlike some other starfish, which can reproduce through somatic fission or arm autonomy, A. planci is not known to reproduce asexually. There is evidence that A. planci releases chemicals that induces spawning in nearby individuals. However, not all individuals in a given population spawn at the same time.

When spawning, A. planci will climb to a high place on a coral outcrop, then arch its body. Gametes are released through five pores on the aboral surface of the body, as the animal waves its arms and moves its tubefeet vigorously.

Mating System: polygynandrous (promiscuous)

Acanthaster planci spawns seasonally during summer months, according to each population’s location. Populations in the northern hemisphere generally spawn between May and August, while populations in the southern hemisphere spawn between November and February. These seasons have been roughly correlated with periods of warmer water temperature in the respective habitats. Gravid females may contain anywhere from 12 to 24 million eggs, and may produce as many as 60 million eggs throughout a season.

Breeding interval: Acanthaster planci breeds once a year.

Breeding season: This species breeds in the summer months in the northern and southern hemispheres.

Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization (External ); broadcast (group) spawning; oviparous

As this asteroid is a broadcast spawner with a planktonic larval stage, there is no parental investment in offspring.

Parental Investment: no parental involvement