Common names: Bat star, webbed star, sea bat, broad-disk star.
Scientific Name: Asterina miniata
Size Range: Up to 20cm in diameter
The Bat Star generally has five stubby arms, but has been found with as little as four and as many as nine, which stem out of its wide central disk. These arms are connected by webbing, giving them their bat-like appearance. They come in a wide range of solid and mottled colours including brown, yellow, red, orange, purple, gray, and green. Its ossicles-plates on the surface of the star- are large and distinct, giving the appearance of rough shingles.
The Bat Star is found intertidally to 951ft deep off the coasts of Alaska to California in rocky areas covered with algae or surf grass, and among kelp forests, sponges, and bryozoans.
The Bat Star is omnivorous, scavenging on dead or living animals and plants including seaweed, sponges, sea urchins, chitons, barnacles, snails, limpets, sea anemones, and squid eggs. It finds its prey with the help of light sensors on the end of each arm, and consumes its prey by enveloping it with its stomach and secreting digestive juices, creating an ingestible liquid soup. When it is done feeding, it retracts its stomach back into its body. However, it can be difficult for the Bat Star to catch its prey, as the touch of a tube foot or the scent of the star can trigger an escape response.
A. miniata reproduce through spawning, which is not synchronized between individuals. Sperm and eggs are released into the ocean and carried by the current to different places. Eggs are released from pores where the rays connect to the central disk. They can breed anytime during the year-most commonly from May to July-but need two months for their gonads to build up until they are able to spawn again. Their embryos and larvae are transparent, and these stars can live up to 30 years.
Male Bat Stars have also been seen in mating “fights”, which from the outside looks like an arm wrestle-each star vying to place their arm on the others in a sort of slow motion battle.
Photos by Paige Bodin
Sea stars do not have many predators in adulthood, though when exposed at low tide, sea gulls and otters will feed on them, oftentimes leaving partially eaten sea stars to regrow their limbs. Snails and nudibranchs are a threat to the much more vulnerable larvae.