Asterina Star Care Guide
Asterina spp. are tiny starfish that arrive as live-rock hitchhikers and reproduce by splitting. Most graze detritus and algae, but a few nibble corals.
Compiled by Aquairi from published sources · Published · Updated
Overview
Asterina is a genus of small sea stars in the family Asterinidae, commonly encountered in reef aquaria as hitchhikers on live rock and coral frags. Individuals are tiny, typically about 0.5–1.5 cm across and reaching a maximum of roughly 2 cm, with an often asymmetrical, grey to cream body. Because the home-aquarium animals lumped under the name span many species that are hard to tell apart, behaviour varies, and most are harmless members of a mature reef community.
Taxonomy
- Class: Asteroidea
- Order: Valvatida
- Family: Asterinidae
- Genus: Asterina (Nardo, 1834)
- Scientific name: Asterina spp.
- Type species: Asterina gibbosa (Pennant, 1777)
Habitat
Asterina occur in warm and temperate seas; the type species and its closest relatives are Atlantic, while many small reef-tank specimens come from tropical live rock. In the aquarium they hide and graze on rockwork, glass and substrate, emerging across hard surfaces wherever biofilm and detritus accumulate.
Tank requirements
- Minimum tank volume: 30 L
- Temperature: 24–26 °C (75–79 °F)
- pH: 8.1–8.4
- Carbonate hardness (dKH): 8–11
- Specific gravity: 1.024–1.026
- Adult diameter: about 0.5–2 cm
No special provision is needed; population size tracks the amount of available food, so tanks cleaned diligently and fed sparingly tend to hold only a few individuals.
Diet
Most Asterina act as detritivores, grazing detritus, algal film and biofilm. In the absence of other food some are reported to consume corals, with zoanthids a noted target; darker individuals or those with red or brown markings are more often associated with coral grazing than near-white ones.
Reproduction
Asterina reproduce asexually by fission (fissiparous reproduction): the body splits and loses one or two arms at a time, each fragment regrowing into a new star. Under abundant food this allows populations to multiply rapidly.
Compatibility
By and large Asterina are innocuous in a mature reef. If jagged white marks appear on corals or zoanthids the responsible stars should be removed; harlequin shrimp are an effective biological control, hunting sea stars but then requiring a continued supply of them as food.
Asterina Breeding Guide: Fission and the Pest Question
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.