Culcita novaeguineae

Lore & Background

The taxonomy of Culcita novaeguineae is complicated by its 'goniasterid' phase: juveniles bear little resemblance to the mature form and gradually change morphology as they grow. Many different 'species' were described in the literature before being recognized as developmental stages of the same species, with some even placed in the family Goniasteridae rather than the correct family Oreasteridae.

Mature individuals are pentagonal to subglobose with an inflated appearance and much-abbreviated arms, growing up to 30 cm in diameter. The armoured body wall consists of calcareous ossicles supported internally by pillars that buttress the ambulacra, and contains pits into which tube feet can be retracted. The body cavity is filled with water, and the dorsal face may be covered with small conical tubercles.

Juvenile cushion stars are star-shaped with five short, broad arms and a low profile. As they grow, the inter-arm areas fill in and expand relative to the tube-feet areas, and the arms become shorter relative to the disc, which becomes inflated and more massive.

Reader's Guide

Culcita novaeguineae is significant as a common and visually distinctive starfish in Indo-Pacific coral reef ecosystems. Its feeding on detritus and small invertebrates, including stony corals, makes it a notable member of the reef community. The species also hosts a variety of commensal and parasitic organisms: the shrimp Periclimenes soror hides under the cushion star; copepods such as Astroxynus culcitae, Stellicola oreastriphilus, and Stellicola parvulipes live parasitically on its exterior; and the star pearlfish (Carapus mourlani) sometimes lives commensally inside the large body cavity, entering through an ambulacral groove and emerging periodically to feed. Its ability to be kept in a reef aquarium of sufficient size, stocked with suitable corals, has also made it of interest to marine aquarists. The species' complex life history, with a juvenile form so different from the adult that it was once classified in a different family, underscores the importance of developmental studies in taxonomy.

Did You Know?

• Culcita novaeguineae can grow to a diameter of 30 cm (12 in).
• The species has numerous synonyms because its juvenile 'goniasterid' phase was once mistaken for different species.