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.
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.