Asterina Breeding Guide: Fission and the Pest Question
Asterina stars reproduce asexually by fission, splitting and regenerating, and can proliferate rapidly in reef tanks; some species nibble coral, making them potential pests.
Overview
Asterina is a genus of small starfish in the family Asterinidae, established by Nardo in 1834 with Asterina gibbosa as the type species. In the reef hobby these tiny grey or cream stars usually arrive as live-rock hitchhikers and become abundant before they are noticed.
Reproductive Mode
Asterina stars reproduce asexually by fission (fissiparous reproduction). The body splits apart, shedding one or two arms at a time, and each fragment regrows into a new star. This is why a handful of tiny stars can seem to cover the rockwork almost overnight.
Asexual Propagation
All Asterina reproduce rapidly by dividing whenever food is available, and once a population is established it becomes difficult to remove them manually. The type species Asterina gibbosa is a protandric hermaphrodite that lays adhesive egg masses with direct development into brachiolaria larvae, but in the aquarium the fission route dominates and drives the population explosions hobbyists observe.
Common Challenges
Most Asterina species are harmless algae and detritus feeders, but it can be difficult to tell which species is present. Some behave like miniature crown-of-thorns and can damage patches of stony coral. Non-predatory forms are usually drab grey or beige, while coral-eating forms often match the colour of the corals they feed on (green, blue or pink). Harlequin shrimp prey on Asterina, but they eat every starfish, so use them with caution.