The bat star, scientifically known as Patiria miniata, is a common inhabitant of the Pacific coast of North America. This marine invertebrate, often called the sea bat or webbed star, is recognized by the distinctive webbing between its arms. While typically found in shades of red or orange, they can also display a wide array of colors including white, green, purple, and pink. Residing across the intertidal and subtidal zones from Alaska to Baja California, it plays a role in its marine ecosystem through its feeding habits.
The Bat Star’s Diverse Diet
Bat stars are omnivorous scavengers, consuming a broad array of food items that become available in their marine habitats. Their diet regularly includes various forms of algae, such as diatoms, microalgae, and thin algal films scraped directly from surfaces. They also graze on larger marine plants like eelgrass and surfgrass, providing a plant-based component. This plant-based consumption is supplemented by their intake of small colonial animals, including bryozoans and colonial tunicates, which are often found growing on underwater surfaces.
As active detritivores, bat stars play a role in cleaning the seafloor by consuming decaying organic matter. Their diet includes dead organisms, marine snow, and various types of carrion, such as remnants of dead fish or other marine animals that settle on the seabed. They also prey on small invertebrates like tiny crustaceans, hydroids, and sessile organisms such as sponges and tunicate worms. They may also consume other sea stars or sea urchins.
Unique Feeding Strategies
The bat star employs distinct feeding strategies. A notable method involves the eversion of its cardiac stomach. When the bat star locates food, it extends this stomach out through its mouth, directly over the prey. This external positioning of the stomach enables the bat star to envelop the food item, even those larger than its mouth opening.
Once the cardiac stomach is everted and covering the food, it secretes powerful digestive enzymes. These enzymes begin to break down the food externally, effectively liquefying it before it is ingested. After the food is partially digested, the bat star retracts its stomach, along with the now-liquefied material, back into its body for final absorption.
The bat star’s numerous tube feet, located on the underside of its arms, assist in manipulating food particles and adhering to surfaces while grazing on algal films and detritus. In instances where larger food is scarce, they can also extend their stomach into the water column to capture suspended microorganisms, acting as a filter feeder.
Habitat and Food Availability
The bat star’s diet is linked to its habitat and food availability. These sea stars are common inhabitants of the Pacific coast, thriving across a range of depths from the intertidal zone down to approximately 300 meters. They can be found in diverse settings, including rocky shores, tide pools, kelp forests, and both sandy and muddy bottoms, each offering distinct food opportunities. Their presence in these varied microhabitats exposes them to a wide array of potential food sources.
The bat star’s opportunistic feeding strategy allows it to adjust its diet based on the abundance of food. When preferred food items are scarce, they can readily switch to consuming other available organic matter, such as detritus or microorganisms, demonstrating considerable dietary flexibility. This adaptability is crucial for their survival in dynamic marine ecosystems where food resources can fluctuate. As scavengers and detritivores, bat stars perform an important ecological function by helping to clean the seafloor of dead organisms and excess algae, thus facilitating the recycling of nutrients back into the food web. Their actions support the overall health and balance of these underwater communities.