Feather Star

The Feather Star, scientifically known as Comaster schlegelii, is a captivating macro species frequently encountered by divers across the Indo-West Pacific. While previously classified as Comanthina schlegeli, recent research has reclassified it into the genus Comaster. This echinoderm is a vibrant inhabitant of coral reefs, known for its striking appearance and graceful movements. It holds a conservation status of Least Concern, indicating a stable population. As a filter-feeder, it plays an important ecological role in its marine environment, perching on exposed coral heads and gorgonians to capture nutrients from the water column. Divers often observe this species at dive sites such as Admiralty Anchor, where it is abundant, and Washing Machine (Verde Island), where it is common.

Identification

• Size: This is a large feather star, capable of reaching an impressive arm span of up to 35 cm.
• Coloration: Comaster schlegelii is renowned for its highly variable and often spectacular coloration. Individuals can be plain golden yellow, pale brown, or black. Many are multicoloured, frequently displaying combinations of green with bands of orange, white, and black on their arms and pinnules. Some specimens exhibit red ribs on their arms with dark pinnules tipped in white, or dark arms with scattered short segments of white. The specific coloration can depend on the collection area.
• Arms and Pinnules: The Feather Star possesses numerous flexible arms, which can range from 10 to 90, though typically 32-60 arms are observed. These arms are formed from many jointed calcareous plates called ossicles and can be coiled. Short side branches, known as pinnules, extend from either side of each arm.
• Attachment and Movement: On its underside, the feather star has claw-like appendages called cirri, which it uses to cling to the substrate. Unlike some other feather star species that stand tall on their cirri, Comaster schlegelii tends to "squat," with its cirri often hidden by its curving arms, which also assist in anchoring. If disturbed or seeking a new location, it can "walk" on its cirri or swim with a slow, undulating motion of its many arms.
• Habitat and Depth: This species is typically found in the Indo-West Pacific, inhabiting coral reefs, coral rubble, and rock outcrops. While most common on reef crests down to about 5 m, it has been observed at depths ranging from 0 to 278 m. It thrives in waters with temperatures between 15.4–28°C.

The Feather Star, Comanthina schlegeli, is a striking inhabitant of the Indo-West Pacific's vibrant coral reef ecosystems. This species thrives in environments characterized by clear, warm waters and moderate currents, which are essential for its filter-feeding lifestyle.

Typically found in shallow, sunlit reef environments, Comanthina schlegeli is most commonly observed on exposed reef crests and current-swept coral heads. Divers can encounter this species across a broad depth range, from the immediate surface down to approximately 278 meters, though it is most prevalent in shallower waters, often within the first 5 meters of the reef crest. Preferred water temperatures for this feather star generally fall between 22–28°C.

Regarding substrate preference, Comanthina schlegeli is a master of attachment, using its claw-like cirri to firmly cling to various hard substrates. These include:

• Live or dead corals
• Sponges
• Rocky seabeds and coral rubble

During daylight hours, these feather stars often remain cryptic, tucking their central body into crevices or under coral ledges, with only their numerous arms visible. As nocturnal filter feeders, they extend their feathery arms into the water column at night to capture plankton, detritus, and other fine organic particles drifting by.

Comanthina schlegeli plays an integral role in its ecosystem, not only as a filter feeder but also by forming symbiotic relationships with other marine life. Its intricate arms provide shelter for various small organisms, including crinoid shrimp, crinoid squat lobsters, and even small fish. These associations highlight the feather star's importance as a microhabitat within the larger reef structure.

Notable dive sites where Comanthina schlegeli is frequently observed include Admiralty Anchor, where it is abundant, and Washing Machine (Verde Island), where it is commonly found, both locations indicative of its preference for current-rich reef environments.

The Feather Star, Comanthina schlegeli (now scientifically recognized as Comaster schlegelii), is a captivating macro invertebrate frequently encountered by divers across Indo-Pacific dive sites, including Admiralty Anchor and Washing Machine (Verde Island). This echinoderm, known for its vibrant colors and intricate, feathery arms, can reach an arm span of up to 25 cm (10 in).

• Underwater Encounter Behavior: During daylight hours, the Feather Star is typically sedentary, often found clinging to coral heads, gorgonians, or hidden within crevices, with only its numerous arms extended into the water column to feed. While generally stationary, it possesses the remarkable ability to detach from its perch and swim gracefully, though sometimes erratically, through the water using alternating sweeps of its arms when disturbed or seeking a new feeding location. Divers should exercise caution, as the feather star's arms are delicate and can be quite sticky, easily tearing if brushed against. A notable defense mechanism is its ability to autotomize (shed) an arm when threatened, which it can later regenerate.
• Feeding Habits: As a filter feeder, Comaster schlegelii primarily feeds on tiny drifting organisms and particles, including plankton and detritus. It maximizes its feeding efficiency by extending its many feathery arms into the current, often forming a parabolic shape to capture food. Tiny tube feet lining the mucus-covered arms flick edible bits into grooves, which are then slowly transported to the upward-facing mouth located on the central disc. While some species may feed during the day, many feather stars are primarily nocturnal, emerging from their hiding spots at night to feed.
• Social Structure: Feather stars are often observed clustering together in groups, a behavior that may offer safety in numbers and facilitate resource sharing. Within these aggregations, they may communicate through subtle movements and arm positioning, signaling about food availability or changes in their environment. These aggregations can also increase gamete encounter rates during spawning.
• Notable Seasonal Patterns: Reproduction in feather stars typically involves broadcast spawning, where males and females release their gametes (sperm and eggs) into the water column for external fertilization. This process often occurs during warmer months and can be synchronized by environmental triggers such as lunar or seasonal cycles. The fertilized eggs develop into free-swimming larvae that drift as plankton before settling on the seabed and metamorphosing into juvenile stalked forms, eventually becoming free-moving adults.

These fascinating creatures inhabit shallow coral reefs and rocky substrates in the Indo-West Pacific, typically encountered at depths ranging from a few meters to over 200 m, though they are most common on reef crests down to about 5 m. They are also known to host a variety of symbiotic organisms, such as crinoid shrimp, squat lobsters, and even some fish like the ornate ghost pipefish, which find shelter and food among their arms.