The Bat Star (Patiria miniata) is a common sea star species found along the Pacific coast of North America, recognized for its distinctive, webbed appearance. Understanding its specific dietary habits and unique feeding mechanism provides insight into its function as a widespread marine scavenger. This exploration will detail the Bat Star’s physical traits, the items it consumes, and the specialized biological process it uses for feeding.
Identifying the Bat Star
The Bat Star gets its common name from the thick webbing of skin that connects its short, broad arms, giving it a pentagonal or bat-like shape. While most individuals possess five arms, specimens with four to nine rays are not uncommon. The central disk is noticeably wider than the rays are long, contributing to its distinct, flattened profile.
Its coloration is highly variable, making identification by color alone unreliable; Bat Stars can be solid or mottled in shades of red, orange, yellow, brown, green, or purple. Reaching a diameter of up to 20 centimeters (about 8 inches), the skin on the aboral (top) surface has a rough, sandpaper-like texture due to flattened, crescent-shaped skeletal plates called ossicles. This sea star is abundant along the Pacific coast, ranging from Sitka, Alaska, down to Baja California. It inhabits rocky intertidal zones, kelp forests, and subtidal areas down to depths of about 300 meters (980 feet).
Primary Food Sources
The Bat Star is classified as an opportunistic omnivore and detritivore, meaning its diet is highly flexible, consisting of both plant and animal matter, alive or dead. A significant portion of its intake comes from organic detritus found on the seafloor, making it an important cleaner in its environment.
This sea star actively consumes various small, attached invertebrates. Prey includes sessile organisms like hydroids, sponges, bryozoans (especially Tubulipora species), and colonial tunicates. Plant material, such as algae, surfgrass, and organic films that coat rocks, are also regularly consumed. The diet is largely determined by local availability; Bat Stars in a kelp forest consume more drift algae, while those in a rocky intertidal zone focus on biofilms and small epifauna. They also scavenge on the carcasses of dead fish and other animals, demonstrating their role as recyclers in the marine ecosystem.
The Unique Feeding Process
The Bat Star employs a specialized biological mechanism known as stomach eversion to consume its food. When the sea star locates a food source, it positions itself over the item and uses hydraulic pressure from its water vascular system to push its cardiac stomach out through its mouth, which is located on the underside.
This flexible, sac-like stomach is molded directly onto the surface of the food item. Once the stomach is extended and in contact with the meal, the Bat Star releases digestive enzymes externally. These enzymes break down and liquefy the organic matter outside of the body. The Bat Star then absorbs the partially digested, soupy material through the walls of the everted stomach before retracting the cardiac stomach back into its body cavity. The tube feet, powered by the water vascular system, also manipulate and move the food mass toward the central mouth opening.