Lagoon Brittle Star

Ophiocoma scolopendrina

"Ophiocoma scolopendrina" is a species of brittle star belonging to the family Ophiocomidae. Restricted to life in the intertidal, they live in the Indo-Pacific. They can typically be found within crevices or beneath borders on intertidal reef platforms.
Lagoon Brittle Star (Ophiocoma scolopendrina) Chale Island, Kenya. Mar 8, 2023 Geotagged,Kenya,Ophiocoma scolopendrina,Summer

Appearance

"Ophiocoma scolopendrina", as other brittle stars, have long, thin arms emanating from a small, disk-shaped body and are about the size of an outstretched human hand. They belong to the phylum of echinoderms, which includes sea urchins, sea cucumbers, and sea stars. Dorsal disc and dorsal arm plates vary from variegated black to pale brown. They are irregularly banded. "O. scolopendrina" can reach a length of about 13cm, while the disc diameter can reach up to 25mm. The star's sexes can be identified by checking slits between the arms, which expose the white male spermaries and red female ovaries.

Distribution

"Ophiocoma scolopendrina" can be found in the Red Sea, the tropical Indo-Pacific region, Taiwan, Eastern Africa, Southeastern Polynesia, the Marshall Islands, and Madagascar. Their typical density is about 20 individuals per 1m².

Behavior

When feeding, "O. scolopendrina" changes its location depending on tide positionality. Stars have been observed to be nearly entirely concealed at high tide, and expose themselves progressively as the tide becomes lower.

Unlike other brittle star species"," these stars have evolved an adaptation that lets them participate in surface-film feeding during both low and flooding tides. This adaptation allows them to consume neuston and detrital particles and film that are found suspended on the surface of sea water.

During feeding, "O. scolopendrina" becomes fully exposed and remains attached to the ground by anchoring an arm to a substratum or piece of vegetation. Occasionally, they may also climb vegetation to gain better feeding positionality. The brittle star then utilizes two to four arms to sweep the sea surface, using its arms' ventral sides to trap suspended objects into mucous-covered spines. The food is then transferred to the mouth once the spines have been cleaned by tube feet.

Outside of flooding tide, these brittle stars simply participate in microphagous suspension and deposit-feeding, behavior that is common for other "Ophiocoma" species. During these types of feedings, arms are extended and food is caught from the water column into their mucous-covered spines during this process. This has typically been observed after a high tide.

The unusual feeding pattern observed in "Ophiocoma scolopendrina" has been attributed to a variety of influences, including changes in tidal patterns, the presence of predation, and food availability.

Habitat

These brittle stars are present in crevices and under boulders of intertidal reef platforms in the upper and middle eulittoral. They have also been seen underneath coral rubble. They typically hide amongst concealing vegetation during surface-film feeding. They live primarily in areas with shallow water strictly in the intertidal and are often observed sweeping their arms over sand or coral substrata.

Reproduction

Ovarian substances have been noted to induce male spawn. Adult female stars each contain an estimated 12 * 10⁵ premature oocytes and it is believed that all adult "O. scolopendrina" produce gametes throughout the remainder of their lives. They consistently produce gametes at all studied ages. "O. scolopendrina" reproduce continuously throughout the year, as once gametes are available in the gonads, allowing them to spawn regardless of season.

"Ophiocoma scolopendrina" have planktonic planktotrophic larvae and have been observed to spawn in large numbers.

References:

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Taxonomy
KingdomAnimalia
DivisionEchinodermata
ClassOphiuroidea
OrderOphiacanthida
FamilyOphiocomidae
GenusOphiocoma
SpeciesO. scolopendrina
Photographed in
Kenya