''Cenometra bella'' is a species of crinoids belonging to the genus ''

Cenometra ''Cenometra'' is a genus of crinoids belonging to the family Colobometridae. Species Species within this genus include: * '' Cenometra bella'' (Hartlaub, 1890) * '' Cenometra emendatrix'' (Bell, 1892) References Colobometridae Crinoid ...

''. They can have up to 30 arms Lisa Kirkendale and Charles Messin
An annotated checklist and key to the Crinoidea of Guam and the Commonwealth of the Northern Marianas Islands
Micronesica, vol. 35, n. 36, 2003, pg. 523-546 and can be of variable colours but are often characterised by a marked contrast between the extending free-arms and the feathery

pinnules 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. Co ...

(for example, dark brown and white). This species clings to its support and moves around by its feet-like cirri.

Morphology

Like many other

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 ...

s, ''C. bella'' is visually comparable to both a flowering plant and a

sea star Starfish or sea stars are Star polygon, star-shaped echinoderms belonging to the class (biology), class Asteroidea (). Common usage frequently finds these names being also applied to brittle star, ophiuroids, which are correctly referred to ...

.Feng, Yunjiang, et al. “Crinoids: Ancient Organisms, Modern Chemistry.” Natural Product Reports, vol. 34, no. 6, 2017, pp. 571–584., doi:10.1039/c6np00093b This species evolutionary morphology has remained fairly constant with minimal changes in their appearance. These small featherstars are predominantly dark brown on their underside. The underside reveals its finger-like brachials and cirri they use to walk and anchor themselves to objects.Arguelles, Carmen C, et al. “Identification of Feather Stars (Echinodermata: Crinoidea: Comatulida) at Subic Bay, Zambales, Philippines.” Philippine Journal of Science, vol. 139, no. 1, June 2010, pp. 51–60.Sadhukhan, Koushik, and C. Raghunathan. “New Record of Five Feather Stars (Class: Crinoidea) from Andaman and Nicobar Islands.” Zoological Survey of India, vol. 2, no. 1, 2012. The centrodorsal plate is the round ‘body’ that holds its brachials and arms together, and averages at 4.181mm in diameter. The mouth is located at the center of this plate. ''C. bella'' typically has five short, stiff and stout bifurcating arm bases that radiate from the centrodorsal plate of the comatulid ray, but this number can vary per individual. These arm bases branch out into two

ossicles The ossicles (also called auditory ossicles) are three irregular bones in the middle ear of humans and other mammals, and are among the smallest bones in the human body. Although the term "ossicle" literally means "tiny bone" (from Latin ''ossi ...

, giving them a total of ten or more free-arms. The longer non-branching portion of the arms makes up the majority of the arm length, much like many other members of the comatulida order. On average these non-branching feathery arms are 8.5 cm long for an adult ''C. bella''. Each arm has a long white central ridge with dark brown spotted pinnules that project outwards, and slightly taper inwards at the distal end, much like that of a

fern The ferns (Polypodiopsida or Polypodiophyta) are a group of vascular plants (plants with xylem and phloem) that reproduce via spores and have neither seeds nor flowers. They differ from mosses by being vascular, i.e., having specialized tissue ...

plant. Not all of their arms are regenerating, but every crinoid will have at least a few that are capable of regeneration.Baumiller, Tomasz K., and Angela Stevenson. “Reconstructing Predation Intensity on Crinoids Using Longitudinal and Cross-Sectional Approaches.” Swiss Journal of Palaeontology, vol. 137, no. 2, 2018, pp. 189–196., doi:10.1007/s13358-018-0169-6. Skeletally, the brachitaxes are composed of two ossicles, with ambulacral appendices. The second pinnule is massive, hard and curved. The basal segment of the proximal pinnules is curved or rounded.

Reproduction & development

There are male and female sexes of ''C. bella''. These

gonochoric In biology, gonochorism is a sexual system where there are two sexes and each individual organism is either male or female. The term gonochorism is usually applied in animal species, the vast majority of which are gonochoric. Gonochorism contrast ...

crinoids shed their

ova , abbreviated as OVA and sometimes as OAV (original animation video), are Japanese animated films and special episodes of a series made specially for release in home video formats without prior showings on television or in theaters, though the ...

sperm Sperm (: sperm or sperms) is the male reproductive Cell (biology), cell, or gamete, in anisogamous forms of sexual reproduction (forms in which there is a larger, female reproductive cell and a smaller, male one). Animals produce motile sperm ...

from ruptured pinnules into the water. After

fertilisation Fertilisation or fertilization (see spelling differences), also known as generative fertilisation, syngamy and impregnation, is the fusion of gametes to give rise to a zygote and initiate its development into a new individual organism or of ...

, their embryos grow into

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 later sink to a substrate surface, like gorgonian coral. The growing larvae, once attached to a surface undergoes

metamorphosis Metamorphosis is a biological process by which an animal physically develops including birth transformation or hatching, involving a conspicuous and relatively abrupt change in the animal's body structure through cell growth and different ...

into a small crinoid and remains mostly sessile during growth.

Feeding

The beautiful crinoid is a

suspension 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 spec ...

. They filter feed on marine microorganisms like algae, diatoms, and larvae. They also consume

marine snow In the deep ocean, marine snow (also known as "ocean dandruff") is a continuous shower of mostly organic detritus falling from the upper layers of the water column. It is a significant means of exporting energy from the light-rich photic zone to ...

(detritus). This filtration occurs on their cirri, which is linked to the gut near the mouth and anus on the centrodorsal plate.

Behaviour

These featherstars are mostly sessile, anchoring themselves to hard substrate surfaces or the sea floor using their cirri ‘legs’. However, they are also free-moving creatures capable of traveling short distances to escape their predators or other threats. As nocturnal critters, they partially hide, sessile, within rocks and corals during the day with their mouths oriented upwards. Though their centrodorsal plate remains sheltered during the day as they wait till night to come out and feed, their free-arms can remain fully exposed in a circular fan-like arrangement outside of their habitat, throughout the day.

Distribution & habitat

''Cenometra bella'' typically occupies shallow tropical waters,Baumiller, Tomasz K., and Forest J. Gahn. “Reconstructing Predation Pressure on Crinoids: Estimating Arm-Loss Rates from Regenerating Arms.” Paleobiology, vol. 39, no. 1, 2013, pp. 40–51., doi:10.1666/0094-8373-39.1.40. living in open-surfaces Tinkova, T. V., et al. “Deterrence of Feather Stars (Crinoidea, Comatulida) from Southern Vietnam for the Indo-Pacific Sergeant-Fish Abudefduf Vaigiensis.” Doklady Biological Sciences, vol. 456, no. 1, 2014, pp. 195–198., doi:10.1134/s0012496614030107. below depths of 5 meters. They are more commonly located around large coral species in coral reefs, and sometimes found in the intertidal zone. However, in rare cases, they have been found to establish habitat in the deeper ocean (up to 55mJeng, M.-S. 1998 Shallow-water echinoderms of Taiping Island in the South China Sea. Zoological Studies 37(2):137-153.
/ref>). These featherstars are often exposed on top of a gorgonian coral, under a reef flat, or clinging to sea whips. This shallow water species is present in the Indo-West

Pacific Ocean The Pacific Ocean is the largest and deepest of Earth's five Borders of the oceans, oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean, or, depending on the definition, to Antarctica in the south, and is ...

, thriving around South and South East Asia: India, the Philippines, China, South Japan, the Maldives, South Pacific Islands. ''C. bella'' has also been found in the

Great Barrier reef The Great Barrier Reef is the world's largest coral reef system, composed of over 2,900 individual reefs and 900 islands stretching for over over an area of approximately . The reef is located in the Coral Sea, off the coast of Queensland, ...

Threat & survival adaptations

Being mainly sessile creatures, ''C. bella'' is highly susceptible to

predators Predation is a biological interaction in which one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill ...

like large fish and other marine organisms. They may also lose limbs due to

abiotic stress Abiotic stress is the negative impact of non-living factors on the living organisms in a specific environment. The non-living variable must influence the environment beyond its normal range of variation to adversely affect the population performan ...

ors like great salinity and temperature fluctuations. On average, the feather-star is reported to lose an arm every 8 to12 days. As a survival mechanism, this crinoid has evolved to be able to lose and regenerate lost limbs, much like a sea-star. Their pinules are also spiked to protect them from

. In addition, ''C. bella'' are able to produce aversive tasting and toxic chemicals to deter predators from consuming their arms that remain exposed out of their habitat throughout the day. The deterrent taste not only provides immediate protection from their predators but also forms long-term negative

conditioning Conditioning may refer to: Science, computing, and technology * Air conditioning, the removal of heat from indoor air for thermal comfort ** Automobile air conditioning, air conditioning in a vehicle ** Ice storage air conditioning, air conditio ...

to prevent large fish from attacking again. These antifeedant chemicals also provide the beautiful crinoid's colour.

References

{{Taxonbar, from=Q20722429 Colobometridae