Heliocidaris crassispina

Heliocidaris crassispina is a small sea urchin, reaching a maximum length of up to 7.7 cm. It can be identified by its robust body and spines, which are adapted to its benthic lifestyle. This species is typically found in shallow waters, often residing at depths ranging from 0 to 70 meters. It prefers rocky substrates and can be seen clustered in rock crevices or at the bases and undersides of boulders, both in sheltered and exposed shore environments. This clustering behavior may help it adapt to wave turbulence in its habitat. Feeding primarily on algae, Heliocidaris crassispina is an opportunistic feeder. Its diet consists mainly of available algal growth in its surroundings. The species exhibits external fertilization, and members are gonochoric, meaning they have distinct male and female individuals. Brooding is common, with eggs being held on the peristome or in the concavities on the petaloids. After fertilization, embryos develop into planktotrophic larvae, which remain in the water column for several months before settling to the seafloor and metamorphosing into juvenile urchins. Encounters with Heliocidaris crassispina during dives may reveal them nestled among rocks, often in groups. Divers may observe their feeding behavior as they graze on algae. This species has been recorded in various locations, particularly in the Northwest Pacific region, such as Hong Kong. The conservation status of Heliocidaris crassispina has not been evaluated, leaving its long-term viability uncertain.