Oreaster reticulatus

The cushion seastar, Oreaster reticulatus, ranges from around South Carolina to the Caribbean Islands, and is most common in the shallow waters in the Carribean. The cushion seastar has been introduced to the Cape Verde Islands in Western Africa. (Wulff, 1995)

Oreaster reticulatus is found in calm, shallow, subtropical and tropical water. A majority of individuals tend to be found on coarse, calcereous sandy bottoms that are isolated or surrounded by seagrass. However, this seastar can also be located in soft sand and mud substrates that are associated with shallow reefs, mangroves, or lagoons. (Guzman and Guevara, 2002; Puglisi, 2000)

Oreaster reticulatus is a large seastar with a central disc from which its five tapered arms radiate. The cushion seastar can grow up to 0.50 m in diameter, depending on food availability. The seastar's body is covered by a hard outer shell with knobby spines, or ossicles, that extend away from the surface. Oreaster reticulatus is not polymorphic and can be easily distinguished from closely related species by their hard shell and short tapered arms. Individuals vary in color and can be brown, red, orange, or yellow. The juveniles are green, which provides camouflage from predators. (Puglisi, 2000)

Oreaster reticulatus lays large and bouyant eggs in water currents. The planktonic larvae will be completely developed but will loose their bouyancy, settle and metamorphose in seagrass beds within 23 days at 23 degrees C. Sexual maturity is reached at a radius of 0.12 m. The last juvenile stage measures 0.06-0.12 m in length. (Metaxas, et al., 2008)

Fertilization is external. Sperm and eggs are released when a male and a female seastar are in close proximity. The seastars will reproduce when there are dense aggregations, up to 14 per square meter. Having large numbers of males and females ensures eggs will be fertilized. ("Seastar", 2009; Puglisi, 2000)

In subtropical areas, Oreaster reticulatus reproduces synchronously during the summer. In warmer areas, asynchronous spawning can occur year round. (Puglisi, 2000)

Parental care is negligible. The planktonic larvae are dispersed over long distances and feed on their own. (Puglisi, 2000)

The lifespan of the cushion seastar depends on food availability. If there is low food availability, the cushion star will re-absorb its own tissue, which leads to a reduction in size. (Puglisi, 2000)

The cushion seastar is a solitary species and moves around slowly using its tube feet. It can move approximately 0.12-0.33 m per minute and is active during the day. (Freeman, 2011)

Cushion seastars recognize when a potential mate is in close proximity. To increase chances of fertilization, individuals aggregate when ready to spawn. These events rely on environmental cues, such as the length of daylight. Seastars are able to sense light and dark, and therefore movement, through a microscopic eye called an ocellus. The seastars may use chemical signals to indicate that they are ready. ("Seastar", 2009; Hutchins, 2004)

The cushion seastar is an omnivore and also a deposit feeder. Oreaster reticulatus feeds on echinoids, holothuroid juveniles, and other invertebrates including polychaete worms, copepods, ostracods, crab larvae and sponge tissue. The seastar piles sediments and everts its large cardiac stomach, which allows it to surround the food. Digestive juices are then excreted to break down the food. (Guzman and Guevara, 2002; Puglisi, 2000)

Seastars are most vulnerable to predation at the larval and juvenile stages, and are presumably preyed upon by fish or other echinoderms. Juvenile O. reticulatus are green, which provides camouflage.

The only recorded predator for an adult cushion seastar is the triton Charonia variegata, which is a gastropod. The cushion seastar's daily activities coincide with the changes in light intensity, usually around dusk and dawn. This allows them to avoid predators and arrange foraging activity with the activity of their prey. ("Seastar", 2009; Hutchins, 2004; Scheibling, 1980)

Via feeding, the cushion seastar can turn over sediment at a rate of 1.9 times in a 24-hour period. (Puglisi, 2000)

Cushion seastars are large and easily seen and are thus of sight-seeing value. They have also been heavily harvested as souvenirs. (Hutchins, 2004)

There are no known adverse effects of Oreaster reticulatus on humans.

This species is not listed on the IUCN Red List, CITES appendices, the United States Endangered Species Act list, but it is protected in the Carribean because of over-exploitation by souvenir hunters. (Puglisi, 2000)