''Metacrinus rotundus'', the Japanese sea lily, is a

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

of stalked

crinoid Crinoids are marine invertebrates that make up the class Crinoidea. Crinoids that remain attached to the sea floor by a stalk in their adult form are commonly called sea lilies, while the unstalked forms, called feather stars or comatulids, are ...

in the family Isselicrinidae. It is a species found off the west coast of Japan, near the edge of the

continental shelf A continental shelf is a portion of a continent that is submerged under an area of relatively shallow water, known as a shelf sea. Much of these shelves were exposed by drops in sea level during glacial periods. The shelf surrounding an islan ...

at a depth of around deep. This is the shallowest-living species among the extant stalked crinoids.

Description

In appearance, the Japanese sea lily resembles a

feather duster A feather duster is a cleaning tool that is typically made from a wooden dowel handle onto which feathers are wound with a wire. The feathers are most often long. Some dusters have a retractable casing instead of a dowel handle and these are t ...

. It has a central mouth surrounded by a crown of many-branched feeding arms. These are jointed and can coil up or unroll to expose the feathery

pinnule A leaflet (occasionally called foliole) in botany is a leaf-like part of a compound leaf. Though it resembles an entire leaf, a leaflet is not borne on a main plant stem or branch, as a leaf is, but rather on a petiole or a branch of the leaf. C ...

s on either side to the current. Each pinnule has several rows of

tube feet Tube or tubes may refer to: * Tube (2003 film), ''Tube'' (2003 film), a 2003 Korean film * "Tubes" (Peter Dale), performer on the Soccer AM#Tubes, Soccer AM television show * Tube (band), a Japanese rock band * Tube & Berger, the alias of dance/e ...

and a central

ambulacral Ambulacral is a term typically used in the context of anatomical parts of the phylum Echinodermata or class Asteroidea and Edrioasteroidea. Echinoderms can have ambulacral parts that include ossicles, plates, spines, and suckers. For example, sea ...

groove that leads to a groove on the arm that continues down to the mouth. The crown is supported by a tough stalk composed of

calcareous Calcareous () is an adjective meaning "mostly or partly composed of calcium carbonate", in other words, containing lime (mineral), lime or being chalky. The term is used in a wide variety of Science, scientific disciplines. In zoology ''Calcare ...

ossicles bound together by ligaments. At the base of the stalk is a disc-like sucker and the sides of the stalk bear five whorls of cirri (clawed appendages). The stalk continues lengthening during the animal's life and may reach and the arms can grow to half that length.

Distribution and habitat

The Japanese sea lily occurs off the western coast of Japan. It is usually found within the depth range . Abundant collection records are available from

Sagami Bay lies south of Kanagawa Prefecture in Honshu, central Japan, contained within the scope of the Miura Peninsula, in Kanagawa, to the east, the Izu Peninsula, in Shizuoka Prefecture, to the west, and the Shōnan coastline to the north, while the i ...

and

Suruga Bay Suruga Bay (駿河湾, ''Suruga-wan'') is a bay on the Pacific coast of Honshū in Shizuoka Prefecture, Japan. It is situated north of a straight line from Omaezaki Point to Irōzaki Point at the tip of the Izu Peninsula and surrounded by Honsh� ...

. It is found attached by its stem to rocks, shells and other hard surfaces, using its cirri to anchor itself into position. It can move across the seabed using its arms but seldom does so.

Biology

The Japanese sea lily is a

filter feeder Filter feeders are aquatic animals that acquire nutrients by feeding on organic matters, food particles or smaller organisms (bacteria, microalgae and zooplanktons) suspended in water, typically by having the water pass over or through a s ...

. It extends its arms towards the current, spreads its pinnules and gathers

plankton Plankton are the diverse collection of organisms that drift in Hydrosphere, water (or atmosphere, air) but are unable to actively propel themselves against ocean current, currents (or wind). The individual organisms constituting plankton are ca ...

and other particles floating past. These are transferred into the groove by its tube feet, wrapped in mucus and moved along the groove by the

cilia The cilium (: cilia; ; in Medieval Latin and in anatomy, ''cilium'') is a short hair-like membrane protrusion from many types of eukaryotic cell. (Cilia are absent in bacteria and archaea.) The cilium has the shape of a slender threadlike proj ...

that line it. If the Japanese sea lily is damaged, it can regenerate its arms and even the whole crown can be regenerated above the stalk. In favorable locations, there may be a dense bed of sea lilies and it may form part of a rich micro-habitat with bivalve mollusks and

brittle star Brittle stars, serpent stars, or ophiuroids (; ; referring to the serpent-like arms of the brittle star) are echinoderms in the class Ophiuroidea, closely related to starfish. They crawl across the sea floor using their flexible arms for locomot ...

s. Like other sea lilies,

gamete A gamete ( ) is a Ploidy#Haploid and monoploid, haploid cell that fuses with another haploid cell during fertilization in organisms that Sexual reproduction, reproduce sexually. Gametes are an organism's reproductive cells, also referred to as s ...

s are produced in specialized areas of the pinnules and liberated into the sea. After fertilization the

eggs An egg is an organic vessel in which an embryo begins to develop. Egg, EGG or eggs may also refer to: Biology * Egg cell, the female reproductive cell (gamete) in oogamous organisms Food * Eggs as food Places * Egg, Austria * Egg, Switzerland ...

hatch into barrel-shaped

larva A larva (; : larvae ) is a distinct juvenile form many animals undergo before metamorphosis into their next life stage. Animals with indirect development such as insects, some arachnids, amphibians, or cnidarians typically have a larval phase ...

e that are planktonic for a few days before settling on the seabed, cementing themselves to hard surfaces, undergoing metamorphosis and developing into juvenile sea liliesAmemiya, S., Omori, A., Tsurugaya, T., Hibino, T., Yamaguchi, M., Kuraishi, R., Kiyomoto, M. and Minokawa, T. 2016. Early stalked stages in ontogeny of the living isocrinid sea lily Metacrinus rotundus. Acta Zoologica, 97: 102–116. DOI: 10.1111/azo.12109

References

{{Taxonbar, from=Q2459287 Isselicrinidae Animals described in 1885