Diadema setosum Breeding Guide: Long-Spine Urchin Spawning
The long-spine sea urchin is a broadcast spawner with planktonic larvae; it is not bred in home aquaria. Handle its venomous spines with care.
Overview
Diadema setosum is a long-spined sea urchin in the family Diadematidae, class Echinoidea, and one of the oldest known living members of its genus. It ranges across the Indo-Pacific from the Red Sea eastward to Australia, north to Japan and south along East Africa, and has been recorded as invasive in the Mediterranean off Turkey. Its very long, hollow spines carry mild venom; it is an effective grazer of tropical reef algae.
Reproductive Mode
The species is a broadcast spawner with temperature-dependent timing. Temperatures above 25 °C have been cited as a possible spawning cue, equatorial populations spawn year-round, Persian Gulf populations spawn around April to May, and full-moon phases also influence spawning.
Sexual Reproduction
As a free-spawning echinoid, males and females release gametes into the water, where fertilisation occurs externally and the embryos develop into planktonic larvae that drift before settling and metamorphosing into juveniles. This dispersal-dependent larval phase is the only reproductive route in this species.
Common Challenges
The planktonic larval cycle cannot be completed in home aquaria, which lack the open-water dispersal and larval microfood it requires. Sea urchins do not reproduce asexually, so there is no fragmentation route either. The long, brittle spines are mildly venomous and demand caution during maintenance.