Ophiothela mirabilis

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Ophiothela mirabilis
Ophiothela mirabilis.jpg
Ophiothela mirabilis on a horned sea star in Philippines
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Echinodermata
Class: Ophiuroidea
Order: Ophiurida
Family: Ophiotrichidae
Genus: Ophiothela
Species:
O. mirabilis
Binomial name
Ophiothela mirabilis
(Verrill, 1867)

Ophiothela mirabilis is a species of ophiuroid brittle star within the family Ophiotrichidae . O. mirabilis is an epizoic species which have a non-parasitic relationship with host sponges or gorgonians. Although native to the Pacific Ocean, it has invaded the Caribbean and southwestern Atlantic since late 2000. [1] Many of its characteristics, including reproduction and diet, allow O. mirabilis opportunities to quickly propagate and spread through habitats.

Contents

Characteristics

Ophiothela mirabilis is a very minute brittle star, which rarely reaches more than 1 cm including arms. It has in general 6 arms, however because of its mode of reproduction by division (scissiparity), its shape is often very irregular (one half more developed than the other, only 4 or 5 arms, or on the contrary 7 or 8...).

Its coloration is extremely variable and made believe for a long time in a complex of several species: it can thus be orange plain or white mottled with bright colors (in particular yellow and blue) with ringed arms. [2]

All have arms with delicate translucent, thorny spines. The arms are flexible in all directions. The jaws contain clusters of well-developed tooth papillae on the apex but not on the sides. There are no mouth papillae. Inside the mouth edge there is a second pair of tube feet. The dorsal surface of the disc is covered with spines and thorny towers.

The former species Ophiothela danae is now considered a junior synonym of Ophiothela mirabilis. [2]

Reproduction

Many fissiparous ophiuroid species can undergo asexual or sexual reproduction, but asexual reproduction is the prime method for most, including Ophiothela mirabilis. According to a study from the Marine Biodiversity Journal, sexual reproduction was not evident in O. mirabilis due to lack of gonads among multiple populations. [3] They reproduce asexually through fragmentation: an organism can split into fragments and each fragment will eventually generate into fully mature individuals. Echinoderms use a specific form of fragmentation called fissiparity where some species intentionally divide through autotomy. Autotomy, also known as self-amputation, is a defensive mechanism where an organism can dissociate from a body part to escape high-stress situations, such as predation. [4] This is helpful for species who inhabit irregular environments: hooking onto sponges or gorgonians can subject O. mirabilis to erratic movements where they may separate their disc tissues. O. mirabilis is able to regenerate a fragment into a whole organism, a whole disc with arms and organs, in less than a month. [3] These reproductive methods allow for rapid propagation and abundance throughout an ecosystem.

Diet

Ophiothela mirabilis, like most species of Ophiuroidea, has a simple digestive system with a short esophagus and a pouch-like stomach. [5] Due to their lack of an anus, ophiuroids are selective in their nutrient uptake because they are unable to obtain nutrients from large quantities of ingested mud. Instead, their feeding strategies vary between suspension and deposit feeding. Organisms who use suspension feeding capture and ingest food particles suspended in water; those who use deposit feeding crawl along the seafloor to intake nutrients from sedimentary deposits. O. mirabilis may be able to switch between the two and alter their diet, depending on their developmental stage. Epizoic species, such as O. mirabilis, do not feed on their hosts; they can eat settled detritus, filamentous algae, or mucus from their coral colony. Habitation on a host aids suspension feeding by providing an elevated position for easier access to capture plankton with their feet and arm spines. [5]

Life-cycle

Ophiothela mirabilis has a life cycle of a typical brittle star. However, their complete life cycle has not been studied and further research needs to be conducted on the species. The brittle star typically goes through a pelagic phase suspended in the water as plankton and a benthic phase on the seafloor or attached to a substrate such as bryozoans, tunicates, sponges, or corals. [6]

The first stage in the life cycle of Ophiothela mirabilis is the planktonic larval stage, during which the larvae are free-swimming and drift with ocean currents. According to a study, these larvae have a bilaterally symmetrical body plan and undergo significant morphological changes during their development. [6] The larvae feed on planktonic organisms and have a ciliated band (tiny hairs) that helps them to move and capture food. [6] This stage can last for several weeks or months, depending on environmental conditions.

Once the larvae have reached a certain size, they undergo metamorphosis and settle onto a suitable substrate, where they begin their sessile juvenile stage. [6] The metamorphosis of brittle stars involves the breakdown of the ciliated band, the growth of tube feet and arms, and the development of a hard exoskeleton to protect the juvenile as it transitions to a sessile lifestyle. [6] During this stage, they attach themselves to the substrate using their arms and secrete a hard exoskeleton, which protects them from predators. [6] The juveniles are also capable of filter feeding, using their arms to catch planktonic organisms. [6] After several months, the juveniles reach maturity and develop into fully grown adult forms, which can reproduce and continue the life cycle. The adult forms are not sessile and fully mobile.

Lastly, there is an additional developmental stage between the metamorphosis and planktonic phase called vitellaria. [6] This stage is characterized by the presence of ciliated bands and tube feet, which help the vitellaria move around and explore the surrounding environment before settling down. [6] Therefore, this allows the brittle star to search for a suitable place to attach itself to the seafloor and grow into an adult.

Movement

Like other brittle stars, O. mirabilis uses a variety of muscles to move its arms and body. The muscles of brittle stars are arranged in a complex network, allowing for a wide range of movements such as twisting, bending, and coiling. Bending involves the curvature of the arms, while twisting involves the rotation of the arms around their longitudinal axis. [7] Coiling is a more complex movement that involves the wrapping of the arms around a central point, such as the arm of another brittle star or a piece of substrate. [7] These movements are controlled by a combination of muscles and skeletal elements called ossicles, which are interconnected to provide support for the arms while still allowing for flexibility and movement. [7] Similarly, bending movements of brittle stars are controlled by a complex network of muscle fibers that run along the arms and disk. These muscle fibers are able to contract and relax to control the bending movements of the arms. [8]

There are two types of muscles for movement observed in brittle stars: radial and longitudinal. [9] Radial muscles run along the length of the arms and are responsible for bending the arms. The muscles of brittle stars work in a coordinated manner to produce movement. When the radial muscles contract, the arms bend. This movement is controlled by a system of nerves that runs along the arms and connects to the central nervous system. [10] When the longitudinal muscles contract, the arms coil around a central point, such as the arm of another brittle star or a piece of substrate. [10] Longitudinal muscles run from the base of the arms to the center of the body and are responsible for coiling and uncoiling the arms. Moreover, it has been examined that the longitudinal muscles are essential in the process of arm regeneration, having the ability to lose and regenerate its arms. [11]

Additionally, O. mirabilis uses rowers, which is a specialized type of tube foot, for locomotion and navigation. [12] The rowers are located along the undersides of the arms and are arranged in a single row. [13] The rowers are covered in cilia, which beat in a coordinated fashion to generate a wave-like motion that propels the brittle star forward. [13] It has been investigated that O. mirabilis uses a lead arm to direct its movement, being able to choose which arm to use as the lead arm, depending on the direction it wants to move. [13] The lead arm is responsible for initiating the rowing motion, while the other arms coordinately follow. [13]

Overall, Ophiothela mirabilis is a highly mobile species of brittle star that uses a combination of bending, twisting, coiling, and rowing to move and respond to changes in its environment. Its movements are coordinated by a network of muscles that allow for a wide range of motions. However, further research is needed to fully understand the movement and behavior of Ophiothela mirabilis.

Geographical distribution

Ophiothela mirabilis is found at latitudes between 33° South and 38° North. [14] O. Miralibis are native to 3 marine realms: the Tropical Eastern Pacific, Temperate North Pacific, and East Indo-Pacific. [14] Recently, invasive O. Mirabilis have been observed in two additional marine realms: the Tropical Atlantic and Temperate South American. [14] The first observed occurrence of O. Miralibis in the Atlantic Ocean was reported off the coast of Rio De Janeiro, Brazil in 2000. [1] Shipping activity is cited as the most likely cause of invasive O. Mirabilis presence due to their high presence in proximity to ports. [15] Non-Native populations also exhibit increased survivability compared to native populations, likely due harsh conditions and increased competition during transport. [15] More research is needed as to current O. Mirabilis population data and to future expansion potential.

Habitat

Ophiothela mirabilis are found on host organisms in shallow waters. [16] They do not always stay with their original host for extended periods of time; they may leave their host to find another. [17] The species most frequently and densely colonized by O. Mirabilis are Octocorals, however O. Mirabilis is known to colonize over 20 species, including Sea Sponges, Cnidarians, Bryozoans, Sea Urchins, and Algae. [16] [17] O. Mirabilis require appropriate aquatic conditions to inhabit an environment, including a mean calcite concentration of 0.53 × 10−4 to 0.051 mol.m−3, a mean surface sea temperature of over 20.23 °C, a Chlorophyll concentration from 0.004 to 1.64 mg/m3, and a mean water pH level over 7.64. [15]

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<span class="mw-page-title-main">Echinoderm</span> Exclusively marine phylum of animals with generally 5-point radial symmetry

An echinoderm is any member of the phylum Echinodermata. The adults are recognisable by their radial symmetry, and include starfish, brittle stars, sea urchins, sand dollars, and sea cucumbers, as well as the sea lilies or "stone lilies". Adult echinoderms are found on the sea bed at every ocean depth, from the intertidal zone to the abyssal zone. The phylum contains about 7,000 living species, making it the second-largest grouping of deuterostomes, after the chordates. Echinoderms are the largest entirely marine phylum. The first definitive echinoderms appeared near the start of the Cambrian.

<span class="mw-page-title-main">Starfish</span> Class of echinoderms, marine animal

Starfish or sea stars are star-shaped echinoderms belonging to the class Asteroidea. Common usage frequently finds these names being also applied to ophiuroids, which are correctly referred to as brittle stars or basket stars. Starfish are also known as asteroids due to being in the class Asteroidea. About 1,900 species of starfish live on the seabed in all the world's oceans, from warm, tropical zones to frigid, polar regions. They are found from the intertidal zone down to abyssal depths, at 6,000 m (20,000 ft) below the surface.

<span class="mw-page-title-main">Brittle star</span> Echinoderms, closely related to starfish

Brittle stars, serpent stars, or ophiuroids are echinoderms in the class Ophiuroidea, closely related to starfish. They crawl across the sea floor using their flexible arms for locomotion. The ophiuroids generally have five long, slender, whip-like arms which may reach up to 60 cm (24 in) in length on the largest specimens.

<span class="mw-page-title-main">Amphiuridae</span> Family of brittle stars

Amphiuridae are a large family of brittle stars of the suborder Gnathophiurina. Some species are used to study echinoderm development and bioluminescence.

Ophiocanops fugiens is a living species in the brittle star family Ophiocanopidae. Though once considered to be the only one living species in this brittle star family, recent research has brought to light three specimens of Ophiocanops that differ substantially from O. fugiens. It has been regarded as the most primitive brittle star, close to Paleozoic forms, though other authors have disagreed with the view. Classification of O. fugiens is highly argued. Ophiocanops is usually placed in the order Oegophiurida or regarded as a genus incertae sedis or even given its own subclass Oegophiuridea. Some recent data suggest its relationship to the extant family Ophiomyxidae.

<i>Ophiura ophiura</i> Species of brittle star

Ophiura ophiura or the serpent star is a species of brittle star in the order Ophiurida. It is typically found on coastal seabeds around northwestern Europe.

<i>Amphiodia pulchella</i> Species of brittle star

Amphiodia pulchella is a species of brittle star belonging to Amphiuridae, a diverse family of the Ophiurida order.

<i>Ophiocoma scolopendrina</i> Species of brittle star

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. Unlike other Ophiocoma brittle stars, they are known for their unique way of surface-film feeding, using their arms to sweep the sea surface and trap food. Regeneration of their arms are a vital component of their physiology, allowing them to efficiently surface-film feed. These stars also have the ability to reproduce throughout the year, and have been known to have symbiotic relationships with other organisms.

<i>Ophionereis reticulata</i> Species of brittle star

Ophionereis reticulata, the reticulated brittle star, is a brittle star in the family Ophionereididae. It is found in shallow parts of the western Atlantic, Caribbean Sea and Gulf of Mexico.

<i>Amphiura filiformis</i> Species of brittle star

Amphiura filiformis is a species of brittle star belonging to the family Amphiuridae. It is found on the seabed in the north east Atlantic Ocean and adjoining seas to a depth of 200 metres (660 ft). It digs itself a shallow burrow in the sand and waves its arms in the water above to suspension feed on plankton.

<i>Astroboa nuda</i> Species of brittle star

Astroboa nuda is a type of basket star from Gorgonocephalidae family. Its large arms are highly branched. It inhabits reef slopes exposed to current in diverse places such as the Red Sea and New Caledonia. During the day it coils into a tight ball. At night it spreads arms to form a basket to feed on plankton. They are part of the class Ophiuroidea, which is the largest class of echinoderms. The name Ophiuroidea comes from the roots, ophis, meaning snake and oura, which means tail, referring to the thin, spiraling shape of the basket stars’ arms.

<i>Gorgonocephalus arcticus</i> Species of brittle star

Gorgonocephalus arcticus is a species of basket star in the class Ophiuroidea. The genus name comes from the Greek, gorgós meaning "dreaded" and cephalus meaning "head", and refers to the similarity between these echinoids and the Gorgon's head from Greek myth with its coiled serpents for hair.

<i>Ophiocoma echinata</i> Species of brittle star

Ophiocoma echinata, the spiny ophiocoma, is a species of brittle star belonging to the family Ophiocomidae. It is the type species of the genus Ophiocoma and is found in the tropical west Atlantic Ocean, the Caribbean Sea and the Gulf of Mexico.

<i>Ophiactis savignyi</i> Species of brittle star

Ophiactis savignyi is a species of brittle star in the family Ophiactidae, commonly known as Savigny's brittle star or the little brittle star. It occurs in the tropical and subtropical parts of all the world's oceans and is thought to be the brittle star with the most widespread distribution. It was first described by the German zoologists Johannes Peter Müller and Franz Hermann Troschel in 1842. The specific name honours the French zoologist Marie Jules César Savigny.

<i>Astrobrachion adhaerens</i> Species of brittle star

Astrobrachion adhaerens is a basket star in the Euryalidae family. Along with A. constrictum, it is one of only two species in the genus Astrobrachion. Both species live in association with soft corals in moderately deep water. It is endemic to the west, north and east coasts of Australia, the Kermadec Islands and Lord Howe Island.

<i>Acrocnida</i> Genus of echinoderms

Acrocnida is a genus of brittle stars in the family Amphiuridae. The genus contains three members: Acrocnida brachiata, Acrocnida semisquamata, and Acrocnida spatulispina. There has also been observed hybridization between both Acrocnida brachiata and Acrocnida spatulispina. It is a fairly common genus, usually found along the coasts of Northwestern Europe, but with some species like semisquamata appearing around West Africa. Members of this genus primarily prefer intertidal and sub-tidal habitats, and they are they are less likely to be found in intertidal areas by comparison. This genus was not officially classified until 1926, by T. Gislén. One study found that due to the increased calcification that Acrocnida brachiata causes could be a potential source of Carbon Dioxide for not only the warm, shallow environments they live in, but also for the atmosphere.

<i>Ophionereis schayeri</i> Species of brittle star

Ophionereis schayeri, Schayer's brittle star, is a brittle star in the family Ophionereididae.

<i>Amphiodia occidentalis</i> Species of brittle star

Amphiodia occidentalis, the long-armed brittle star, is a species of brittle star belonging to the family Amphiuridae. It is found in the Eastern Pacific coast from Alaska to USA, often on the seafloor within intertidal and subtidal zones. Within these areas, it is often found buried a few centimeters under the sand with 2 or 3 arms extending through the surface.

Dysidea etheria, commonly known as the ethereal sponge or heavenly sponge, is a species of lobate sponge within the class Demospongiae. This marine sponge is known for its light blue color and can be found in the Caribbean as well as off the coasts of Florida and Georgia. Like all other poriferans, D. etheria is capable of both sexual and asexual reproduction. The use of spicule collection as well as chemical defenses allows D. etheria to protect itself against predators such as the zebra doris and the orange knobby star. D. etheria is also known as a host species of the invasive brittle star Ophiothela mirabilis. Lastly, various molecular biology studies have utilized D. etheria to both study foreign particle transport in sponges and to isolate novel molecules.

<i>Ophiomusa</i> Genus of echinoderms

Ophiomusa is a genus of echinoderms belonging to the family Ophiolepididae that includes: sea urchins, sand dollars and sea cucumbers. Ophiurida are similar to starfish; they both have a central disc and five arms sprouting from the disc. One of the main distinguishing factors of an Ophiuroid is its arms; the arms of an Ophiurida are longer, thinner, and distinctly separated in comparison to those of a sea star.

References

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  6. 1 2 3 4 5 6 7 8 9 Mladenov, Philip V. (1985). "Development and Metamorphosis of the Brittle Star Ophiocoma pumila: Evolutionary and Ecological Implications". Biological Bulletin. 168 (2): 285–295. doi:10.2307/1541241. ISSN   0006-3185. JSTOR   1541241.
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  8. ↑ Czarkwiani, Anna; Dylus, David V.; Oliveri, Paola (2013). "Expression of skeletogenic genes during arm regeneration in the brittle star Amphiura filiformis". Gene Expression Patterns. 13 (8): 464–472. doi:10.1016/j.gep.2013.09.002. PMC   3838619 . PMID   24051028. S2CID   7826113.
  9. ↑ Zueva, Olga; Khoury, Maleana; Heinzeller, Thomas; Mashanova, Daria; Mashanov, Vladimir (2018-02-01). "The complex simplicity of the brittle star nervous system". Frontiers in Zoology. 15 (1): 1. doi: 10.1186/s12983-017-0247-4 . ISSN   1742-9994. PMC   5796562 . PMID   29434647.
  10. 1 2 Tomholt, Lara; Friesen, Larry J.; Berdichevsky, Daniel; Fernandes, Matheus C.; Pierre, Christoph; Wood, Robert J.; Weaver, James C. (2020). "The structural origins of brittle star arm kinematics: An integrated tomographic, additive manufacturing, and parametric modeling-based approach". Journal of Structural Biology. 211 (1): 107481. doi:10.1016/j.jsb.2020.107481. PMID   32088334. S2CID   211262857.
  11. ↑ Carnevali, Candia (2006). "Regeneration in Echinoderms: repair, regrowth, cloning". Invertebrate Survival Journal. 3 (3): 64–76. ISSN   1824-307X.
  12. ↑ Hitoshi, Wakita, Daiki Kagaya, Katsushi Aonuma (2020-01-08). A general model of locomotion of brittle stars with a variable number of arms. Royal Society. OCLC   1357656981.{{cite book}}: CS1 maint: multiple names: authors list (link)
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  16. 1 2 Glynn, Peter W.; Gillette, Phillip R.; Dettloff, Kyle; Dominguez, Joshua; Martinez, Nicolas; Gross, Julie; Riegl, Bernhard M. (2021-04-01). "Experimental evidence of minimal effects on octocoral hosts caused by the introduced ophiuroid Ophiothela mirabilis". Coral Reefs. 40 (2): 323–334. doi:10.1007/s00338-021-02067-0. ISSN   1432-0975. S2CID   233575907.
  17. 1 2 Mantelatto, Marcelo Checoli; Vidon, Lara Figueiredo; Silveira, Rosana Beatriz; Menegola, Carla; Rocha, Rosana Moreira da; Creed, Joel Christopher (2016-03-30). "Host species of the non-indigenous brittle star Ophiothela mirabilis (Echinodermata: Ophiuroidea): an invasive generalist in Brazil?". Marine Biodiversity Records. 9 (1): 8. doi: 10.1186/s41200-016-0013-x . ISSN   1755-2672. S2CID   51912488.

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