Starfishes Class Asteroidea Profile
Saltwater Guides Invertebrate Profiles
Sea Stars & Cushion Stars
The Asteroidea class, also referred to as asteroids, under the family Ophidiasteridae contains about 31 genera with more than 1,500 species that have flexible arms (also called rays) that can fluidly move over objects of any shape, but can contract become stiff when handled.
The internal skeletal plates or ossicles are never fused, the surface of the body can be knobby, spiny, bristly or smooth, and depending on the species can have up to 50 arms, but the usual number is five (5). Cushion Stars of the family Oreasteridae in this class have a solid domed form or shape to the body with extremely short arms, or no arms at all.
Starfish in theclass Asteroidea are characteristically carnivorous, feeding on a wide range of invertebrates. For example, what are often referred to as "knobby" sea stars, species such as the Chocolate Chip Star (Protoreaster nodosus) and others of genera Protoreastor, Pentaster and Pentaceastor, along with some species such as Choriaster granulatus (Doughboy Sea Star) and those of genus Culcita (Cushion Stars) are less desirable because of their predatory nature towards sessile mollusks and all forms of soft and stony corals.
Some of the more desirable species are of the genus Fromia such as F. elegans and monilis respectively, genus Linckia/Linkia such as the Spotted or Comet Star (L. multiflora) and Blue Star (L. laevigata), along with the Purple "Linckia" (Tamaria stria) and the ever popular White Burrowing / White Sand Star (Archaster typicus). However, watch out for the size on many of these species. For example, even though L. multiflora only reaches a diameter of about 10-15 cm (about 4-6 inches), L. laevigata grows to a diameter of 30 cm (about 12 inches) or more, and the Green Star (Linckia guildingi) up to about 41 cm (16 inches). Also be careful with species identification in this group, as there are many other colorful, similar looking starfish that are sold as "true" Linckias, but are not and may be quite predatory. Some other genera under the family Ophidiasteridae often seen in aquariums are Neoferdina, Nardoa, Ceratonardoa, Ophidiaster, Phataria, Pharia and Leiaster.
Depending on the species, starfish in this group reproduce in two ways:
- Most have opposite sexes that spawn by the synchronized release of eggs and sperm, where fertilization takes place in the water and the eggs hatch into free-swimming larvae that drift as plankton for days or weeks before coming to settle on the ocean floor and transform into juveniles.
- In a some cases, such as with the Spotted or Comet Star (L. multiflora) and Green Linckia (Linckia guildingi), they can drop or detach an arm that then grows into a complete new starfish. This is often why these sea stars may have one or a few shorter arms than the others.
- "Sea Stars, Class Asteroidea" by Robert Fenner.
- Sea Stars FAQs I from Robert Fenner.
- Sea Stars FAQs II from Robert Fenner.
- More Starfish Care & Photo Resources
- "Hawai'i's Marine Creatures: A Guide To Hawai'i's Marine Invertebrates" by John. P. Hoover
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