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Bat Star

Asterina miniata

One of the most common varieties of star in the Eastern Pacific, the Bat Star range is from Sitka, Alaska down to Baja Mexico. Also known as the Webbed Star and Broad-disk Star, they are easily recognized due their distinctive shape. Bat Stars are usually reddish orange, but can be found in other colors such as white, green, purple and pink. A characteristic that separates them from other stars is that the body core is always wider than the arms are long. Tube feet operate by use of a water vascular system and provide movement, feeding and respiration functions. Like all stars, they can regenerate lost arms.

They play an important role in the ecosystem as scavengers who keep sea floors clean of dead and decaying animals, control algae growth, the balance of sea urchins and small invertebrate populations. An increase in Bat Star populations can have a negative impact on kelp beds and the many marine animals which they support, as the stars consume more algae.

It’s previous scientific name, Patiria miniata was changed to Asterina miniatea as it is the only member of the family Asterinidae.

purple urchin and a red and orange bat star in a tide pool

Credit: Aquarium of the Pacific / Anitza Valles

SPECIES IN DETAIL

Bat Star

Asterina miniata

CONSERVATION STATUS: Not evaluated

CLIMATE CHANGE: Uncertain

At the Aquarium

Coastal Corner Touch Lab.

Geographic Distribution

Eastern Pacific from Alaska to Mexico.

Habitat

They live on the Pacific coast from Alaska to Mexico. Bat stars live in low intertidal zones in depths up to 3oo m. (984 ft.). They are found in rocky and hard sandy bottoms and in eelgrass beds.

Physical Characteristics

Typically, they are reddish orange but can be found in a variety of colors such as white, green, purple and pink. They have a distinctive shape with a center disk that is always wider than their arms are long, providing a web like appearance. Adults can reach up to 24 cm (10 in) wide. Bat Stars usually have 5 arms, but may have from 4 to 9. A hard spiny skin acts as a deterrent to predators. Tube feet on the bottom of their arms provide multiple functions including mobility, respiration and feeding. Bat Stars have a single photosensitive eye spot on the end of each arm that allows them to recognize prey.

Size

Adults 24 cm (10 in.) however the central disk is always wider than arms are long. Weight unknown.

Diet

Bat stars are omnivores and scavengers. They feed on eelgrass, algae, sea urchins, sponges, and other small invertebrates. The star has a cardiac stomach that is extended from the mouth to surround and consume food.

Reproduction

Females and males will broadcast eggs and sperm all year long. Fertilized eggs will turn into a motile embryo and later into a minute larva.

Behavior

Bat stars move slowly across the sandy and hard surface bottom using tube feet. When males encounter other males, they can become aggressive and get into “fights” for territory, which look more like pushing contests. When confronted by predators, they can secrete a chemical compound, which triggers a flee mechanism in the predator. Bat stars can also dislodge an arm to allow for escape.

Adaptation

Sea star fossils dating back 435 million years indicate that they have had lots of time to adapt to their environment. Sea stars can regenerate lost arms, protecting them from all but the most severe attacks. They also have eye spots at the end of each arm to aid in finding food. Bat stars also come in a variety of different colors which may help protect them by blending in with their surrounding habitat.

Longevity

In controlled environments they can live up to 35 years.

Conservation

Bat stars are one of the most common stars along the Eastern Pacific shoreline and provide an important role, as a scavenger, in keeping the ocean floor clean. While not endangered they are subject to the condition known as Sea Star Wasting Disease Syndrome. The condition has been observed every decade since the 1970’s the size and range has intensified with each decade. While several theories have been advanced, and much research is being done no clear clause of the syndrome has been determined.

They can also have a negative impact on marine ecology if their population is not controlled; they can decimate kelp beds which provide an important role in the lives of many marine species.

Special Notes

The average number of arms on the star is 5 but may be from 4 to 9. Studies indicate that the larger the number of arms the slower the speed of movement.

Bar stars can regenerate lost arms that have fallen off.

Since the bat star has no central brain, radial symmetry, and each arm acts independently, it has no sense of direction and is unable to make controlled movements in a specific direction.

They have eye spots on the end of each arm that can detect light.

SPECIES IN DETAIL | Print full entry

Bat Star

Asterina miniata

CONSERVATION STATUS: Not evaluated

CLIMATE CHANGE: Uncertain

Eastern Pacific from Alaska to Mexico.

They live on the Pacific coast from Alaska to Mexico. Bat stars live in low intertidal zones in depths up to 3oo m. (984 ft.). They are found in rocky and hard sandy bottoms and in eelgrass beds.

Typically, they are reddish orange but can be found in a variety of colors such as white, green, purple and pink. They have a distinctive shape with a center disk that is always wider than their arms are long, providing a web like appearance. Adults can reach up to 24 cm (10 in) wide. Bat Stars usually have 5 arms, but may have from 4 to 9. A hard spiny skin acts as a deterrent to predators. Tube feet on the bottom of their arms provide multiple functions including mobility, respiration and feeding. Bat Stars have a single photosensitive eye spot on the end of each arm that allows them to recognize prey.

Adults 24 cm (10 in.) however the central disk is always wider than arms are long. Weight unknown.

Bat stars are omnivores and scavengers. They feed on eelgrass, algae, sea urchins, sponges, and other small invertebrates. The star has a cardiac stomach that is extended from the mouth to surround and consume food.

Females and males will broadcast eggs and sperm all year long. Fertilized eggs will turn into a motile embryo and later into a minute larva.

Bat stars move slowly across the sandy and hard surface bottom using tube feet. When males encounter other males, they can become aggressive and get into “fights” for territory, which look more like pushing contests. When confronted by predators, they can secrete a chemical compound, which triggers a flee mechanism in the predator. Bat stars can also dislodge an arm to allow for escape.

Sea star fossils dating back 435 million years indicate that they have had lots of time to adapt to their environment. Sea stars can regenerate lost arms, protecting them from all but the most severe attacks. They also have eye spots at the end of each arm to aid in finding food. Bat stars also come in a variety of different colors which may help protect them by blending in with their surrounding habitat.

In controlled environments they can live up to 35 years.

Bat stars are one of the most common stars along the Eastern Pacific shoreline and provide an important role, as a scavenger, in keeping the ocean floor clean. While not endangered they are subject to the condition known as Sea Star Wasting Disease Syndrome. The condition has been observed every decade since the 1970’s the size and range has intensified with each decade. While several theories have been advanced, and much research is being done no clear clause of the syndrome has been determined.

They can also have a negative impact on marine ecology if their population is not controlled; they can decimate kelp beds which provide an important role in the lives of many marine species.

The average number of arms on the star is 5 but may be from 4 to 9. Studies indicate that the larger the number of arms the slower the speed of movement.

Bar stars can regenerate lost arms that have fallen off.

Since the bat star has no central brain, radial symmetry, and each arm acts independently, it has no sense of direction and is unable to make controlled movements in a specific direction.

They have eye spots on the end of each arm that can detect light.