Tripneustes gratilla Breeding Guide

How the collector urchin Tripneustes gratilla reproduces by broadcast spawning into planktonic echinopluteus larvae, why it is not home-bred, and its role in aquaculture.

Overview

Tripneustes gratilla, the collector or pincushion urchin, is an Indo-Pacific echinoid that grazes on algae, periphyton and seagrass at depths of about 2 to 30 metres. It is valued in aquaculture because it produces bright orange roe (gonads), and it has been raised in hatcheries for both food production and reef restoration.

Reproductive Mode

Like other members of the class Echinoidea, T. gratilla is gonochoric, with separate male and female individuals that show no external sexual distinction. It is a broadcast spawner: males and females release sperm and eggs directly into the water column, where fertilisation takes place. Spawning typically occurs during the warmer months.

Sexual Reproduction

Fertilised embryos develop into free-swimming planktotrophic echinopluteus larvae that feed in the plankton for several months before sinking to the seabed and metamorphosing into juvenile urchins. The echinopluteus is a weak swimmer and is largely carried by oceanographic processes. Hawaiian hatchery work has reared the species at scale, with one program producing tens of thousands of juveniles that reached at least 15 mm in about five months.

Common Challenges

Because the planktonic larvae require months of suspended development on cultured microalgae under controlled conditions, this urchin is effectively impossible to breed in a typical home reef aquarium. Spawning may occur, but larvae are consumed by filtration and tank mates long before settlement.