Euplokamis

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Euplokamis
Temporal range: 540–0  Ma
Bioluminescence emitted by comb jelly of genus Euplokamis.jpg
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Ctenophora
Class: Tentaculata
Order: Cydippida
Family: Euplokamididae
Mills, 1987
Genus: Euplokamis
Chun, 1879
Synonyms [1]

Euplokamidae Mills, 1987

Euplokamis is a genus of ctenophores, or comb jellies, belonging to the monotypic family Euplokamididae. [2] It shares the common name sea gooseberry with species of the genus Pleurobrachia. Despite living for hundreds of millions of years in marine environments, there is minimal research regarding Euplokamis, because they are uncommon. Research on the evolution of the basic body structures of diploblastic metazoans revealed that there are four major phyla, including the Ctenophores. [3] Although the morphology of Euplokamis often resembles the medusa stage of Cnidarians, their eight rows of combs are one distinguishing feature that led to the official classification of Ctenophores. [4] After being originally described by Chun (1879), the family Euplokamididae was expanded by Mills (1987) due to the discovery of a new species, Euplokamis dunlapae . [5] Further research indicated that Euplokamis should be identified from Mertensiidae due to the rows of combs and some compression. [6] They may also be distinguished from the genus Pleurobrachia due to their more elongated shape. [6] Additionally, various adaptations of Euplokamis have been observed such as the use of tentacles for movement/feeding, a complex nervous system, and bioluminescent capabilities. Other characteristics including a defined mesoderm, lack of stinging cells, developmental differences, and symmetry supported the reclassification of these organisms. [7]

Contents

Distribution & Habitat

Euplokamis have been found in fossil records dating back to the Cambrian period, part of the Paleozoic Era, and it is estimated that some species may have evolved before this period. [3] Originally, Cnidarians and Ctenophores were classified under the same phyla, Coelenterata. Ctenophore bodies are made up of a gelatin substance, similar to Cnidarians, but the multiple rows of combs present in fossil records are unique to ctenophores. [8] Records of Euplokamis sp. indicate they are distributed widely around the world, but are most often found in warm coastal waters. [9] Euplokamis prefer marine, or saltwater, environments and are classified as free swimmers, due to their ability to move through the water column. [4] They have been identified in the Mediterranean Sea, the North Pacific, the Gulf of Maine, and off the coast of Sweden. [10] [5] However, since this genus was originally grouped in the family Pleurobrachiidae, there is limited information regarding their actual distribution and habitat.

Figure 1. Pelagic ctenophores: (a) Beroe ovata, (b) unidentified cydippid (c) "Tortugas red" cydippid, (d) Bathocyroe fosteri, (e) Mnemiopsis leidyi, and (f) Ocyropsis sp. from Wikipedia Commons Pelagic ctenophores.png
Figure 1. Pelagic ctenophores: (a) Beroe ovata, (b) unidentified cydippid (c) "Tortugas red" cydippid, (d) Bathocyroe fosteri, (e) Mnemiopsis leidyi, and (f) Ocyropsis sp. from Wikipedia Commons

Anatomy & Morphology

Ctenophores are divided into two classes based on either the presence(Tentaculat)) or the lack (Nuda) of tentacles. [9] Within each class, there are multiple orders to further distinguish their structures and characteristics. The class Tentaculata contains the following orders: Cydippida, Lobata, and Cestida. [11] The genus Euplokamis is part of the class tentaculate, which indicates that tentacles are present. [7] They are also part of the order Cydippida, distinguished by their tentacles and their round body shape. [7] Euplokamis tentacles are long, with side branches, and have a sheath allowing them to be retracted inside of the body. [9] The tentacle side branches are known as tentilla, which in the case of Euplokamis are held tightly in coils except during the act of prey capture. [12] Further, the widely spaced tentillia droplets allow for organisms to be classified to the genus level and are one of the only examples of striated muscle found in ctenophores. [13]

Additionally, these organisms have bi-radial symmetry with a mouth on their front end and a statocyst, or sense organ, at the other end. [7] The sides of their stomachs are lined with distinct bulbs, shaped like tadpoles, [12] and unlike other well-known jellyfish, Euplokamis do not have any nematocytes, known as stinging cells. The mouth is connected to the digestive tract via the pharynx. The digestive system, or gastrovascular cavity, is made up of intricate canals that allow for both digestion and circulation to occur. [7] They also lack an anus but are able to excrete some waste through pores on the adoral end. Typically, Euplokamis are small, only growing up to approximately 20 millimeters (mm) in length. [12]

Another distinct feature of this genus is the eight rows of combs present. While they are known as comb plates, they are actually made up of large cilia, which are hair-like structures. [13] These plates are unique because they consist of some of the largest known cilia found on any organism. [13] Additionally, the combs primarily function in movement, allowing some species to move forward and backward. [4] Since their bodies are made of the mesoglea—a translucent, gelatin-like substance—the 8 comb rows can be easily identified. These combs function in movement, due to their large ciliary structures. [13]

Behaviors & Adaptations

Tentacles: Movement and Feeding Behavior

Figure 3. Structure of Ctenophora: Order Cypiddia from Wikipedia Commons Mertensia ovum.png
Figure 3. Structure of Ctenophora: Order Cypiddia from Wikipedia Commons

Euplokamis have long tentacles with branches that are used for feeding and movement. These branches are known as tentilla and are held tightly in coils, forming droplet shapes. [12] The tentilla are usually held in coils but can be uncoiled to aid in movement. [14] Further, these organisms can move their tentilla in slow spontaneous movements or in rapid extensions. [14] According to research, Euplokamis are carnivorous, like all other known species of Ctenophores. [15] They are known to feed primarily on rotifers and other small crustaceans: including copepods, amphipods, and some planktonic larvae. [15] To catch prey, they will extend the tentilla and wrap them around copepods. [16] The tentilla are covered in sticky colloblasts, which keep the prey stuck in place. [14] Not only can the tentilla be released at high velocities to quickly capture prey, but they also can be released in a slow and controlled manner, likely to attract prey. [14] Additionally, the cilia that make up the comb plate move by making a stroke in a certain direction. After capturing prey, they can reverse the stroke, or beat, in the other direction on two rows, while the other rows continue to beat in the normal direction. [13] They are then able to push the prey to their mouth in a sweeping motion, and the ciliary reversal causes the organism to rotate, which tangles the prey further into its mouth. [13]

Nervous System

Despite their simple exterior, research on the nervous system of Euplokamis sp. indicates the use of more complex systems, including axons. The use of these axons has allowed some species of Euplokamis sp. to swim backward rapidly. The direction of the cilia comb plate may be reversed causing them to move backward. [10] These organisms are unique due to the presence of giant axons in their combs that allow for a rapid escape response. [17] Additionally, Euplokamis sp. has an aboral sensory organ, which is bypassed to produce this escape response. [18]

Bioluminescence

Figure 4. Bioluminescent Euplokamis sp. from Wikipedia Commons Bioluminescence emitted by comb jelly of genus Euplokamis.jpg
Figure 4. Bioluminescent Euplokamis sp. from Wikipedia Commons

Another adaptation that many ctenophores have developed is bioluminescence, or the ability to produce light. For example, Euplokamis dunlapae were found to produce light off the coast of Washington when exposed to stimuli. [10] After physical stimulation, they produced bright flashes of light, consistent with bioluminescence. According to research, bioluminescence in Euplokamis sp. is both intrinsic and extrinsic, because light can appear in the comb rows or as bursts of light in the water. [19] Additionally, off the coast of Maine, Euplokamis sp. was found to be one of the two brightest species to have bioluminescence. [20] Research suggests that bioluminescence in Euplokamis sp. may function as a defense mechanism. [20] The bursts of light were only observed directly in response to a disturbance or stimulation, likely to distract or blind predators when they are sensed. [21] Additionally, some produce light as a warning signal, or to expose nearby predators. The various strategies may impact predator-prey relationships or other the population dynamics in an area. [20]

Taxonomy [11]

Related Research Articles

<span class="mw-page-title-main">Cnidaria</span> Aquatic animal phylum having cnydocytes

Cnidaria is a phylum under kingdom Animalia containing over 11,000 species of aquatic animals found both in freshwater and marine environments, including jellyfish, hydroids, sea anemone, corals and some of the smallest marine parasites. Their distinguishing features are a decentralized nervous system distributed throughout a gelatinous body and the presence of cnidocytes or cnidoblasts, specialized cells with ejectable flagella used mainly for envenomation and capturing prey. Their bodies consist of mesoglea, a non-living jelly-like substance, sandwiched between two layers of epithelium that are mostly one cell thick.

<span class="mw-page-title-main">Jellyfish</span> Soft-bodied, aquatic invertebrates

Jellyfish and sea jellies are the common names given to the medusa-phase of certain gelatinous members of the subphylum Medusozoa, which is a major part of the phylum Cnidaria.

<span class="mw-page-title-main">Ctenophora</span> Phylum of gelatinous marine animals

Ctenophora comprise a phylum of marine invertebrates, commonly known as comb jellies, that inhabit sea waters worldwide. They are notable for the groups of cilia they use for swimming, and they are the largest animals to swim with the help of cilia.

<span class="mw-page-title-main">Nerve net</span> Nervous systems lacking a brain

A nerve net consists of interconnected neurons lacking a brain or any form of cephalization. While organisms with bilateral body symmetry are normally associated with a condensation of neurons or, in more advanced forms, a central nervous system, organisms with radial symmetry are associated with nerve nets, and are found in members of the Ctenophora, Cnidaria, and Echinodermata phyla, all of which are found in marine environments. In the Xenacoelomorpha, a phylum of bilaterally symmetrical animals, members of the subphylum Xenoturbellida also possess a nerve net. Nerve nets can provide animals with the ability to sense objects through the use of the sensory neurons within the nerve net.

<span class="mw-page-title-main">Beroidae</span> Family of comb jellies without tentacles

Beroidae is a family of ctenophores or comb jellies more commonly referred to as the beroids. It is the only family within the monotypic order Beroida and the class Nuda. They are distinguished from other comb jellies by the complete absence of tentacles, in both juvenile and adult stages. Species of the family Beroidae are found in all the world's oceans and seas and are free-swimmers that form part of the plankton.

<span class="mw-page-title-main">Lobata</span> Order of comb jellies

Lobata is an order of Ctenophora in the class Tentaculata with smaller tentacles than other ctenophores, and distinctive flattened lobes extending outwards from their bodies.

<span class="mw-page-title-main">Tentacle</span> Varied organ found in many animals and used for palpation and manipulation

In zoology, a tentacle is a flexible, mobile, and elongated organ present in some species of animals, most of them invertebrates. In animal anatomy, tentacles usually occur in one or more pairs. Anatomically, the tentacles of animals work mainly like muscular hydrostats. Most forms of tentacles are used for grasping and feeding. Many are sensory organs, variously receptive to touch, vision, or to the smell or taste of particular foods or threats. Examples of such tentacles are the eyestalks of various kinds of snails. Some kinds of tentacles have both sensory and manipulatory functions.

<span class="mw-page-title-main">Siphonophorae</span> Order of colonial hydrozoans with differentiated zooids

Siphonophorae is an order within Hydrozoa, which is a class of marine organisms within the phylum Cnidaria. According to the World Register of Marine Species, the order contains 175 species thus far.

Colloblasts are unique, multicellular structures found in ctenophores. They are widespread in the tentacles of these animals and are used to capture prey. Colloblasts consist of a collocyte containing a coiled spiral filament, internal granules and other organelles.

<i>Mnemiopsis</i> Genus of comb jellies

Mnemiopsis leidyi, the warty comb jelly or sea walnut, is a species of tentaculate ctenophore. It is native to western Atlantic coastal waters, but has become established as an invasive species in European and western Asian regions. Three species have been named in the genus Mnemiopsis, but they are now believed to be different ecological forms of a single species M. leidyi by most zoologists.

<i>Lampocteis</i> Genus of comb jellies

Lampocteis is a monotypic genus of comb jellies, the only genus in family Lampoctenidae. The sole species in this new genus is Lampocteis cruentiventer, the bloodybelly comb jelly. This ctenophore was first collected in the Pacific Ocean off the coast of San Diego, California, in 1979. It was described in 2001. The generic name was formed from the Ancient Greek lampós and kteís ("comb"), referring to the iridescence of its "combs"; the specific epithet was formed from the Latin cruentus ("blood-red") and venter ("belly"). Two morphological differences separating it from previously known comb jellies warranted the naming of a new family for this animal. These jellies are typically found at a depth of 250-1,500 meters deep in the North Pacific Ocean.

<i>Ocyropsis</i>

Ocyropsis is a genus of Ctenophores, which are commonly known as Comb Jellies. Ocyropsis belong to the family of Ocyropsidae. Ocyropsis possesses two large lateral muscular lobes and four auricles, and appear pale and translucent in color. Ocyropsis habitat is not precise as their gelatinous composition can make it difficult to study. They have been found in warm and cold waters. Unlike other, slow swimming Ctenophores, Ocyropsis are efficient in evading their predators. They use their oral lobes for additional propulsion and a secrete luminous mucous in efforts to evade predators. The muscular oral lobes of the Ocyropsis are used to grab its prey, and then moved to the prehensile mouth for absorption.

<span class="mw-page-title-main">Cydippida</span> Order of comb jellies with retractable branched tentacles

Cydippida is an order of comb jellies. They are distinguished from other comb jellies by their spherical or oval bodies, and the fact their tentacles are branched, and can be retracted into pouches on either side of the pharynx. The order is not monophyletic, that is, more than one common ancestor is believed to exist.

<span class="mw-page-title-main">Platyctenida</span> Order of benthic ctenophores

Platyctenida is an order of comb jellies.

<i>Pleurobrachia bachei</i> Species of comb jelly

Pleurobrachia bachei is a member of the phylum Ctenophora and is commonly referred to as the Pacific sea gooseberry. These comb jellies are often mistaken for medusoid Cnidaria, but lack stinging cells.

<i>Mertensia ovum</i> Species of comb jelly

Mertensia ovum, also known as the Arctic comb jelly or sea nut, is a cydippid comb jelly or ctenophore first described as Beroe ovum by Johan Christian Fabricius in 1780. It is the only species in the genus Mertensia. Unusually among ctenophores, which normally prefer warmer waters, it is found in the Arctic and adjacent polar seas, mostly in surface waters down to 50 metres (160 ft).

<i>Pleurobrachia pileus</i> Species of comb jelly

Pleurobrachia pileus is a species of comb jelly, commonly known as a sea gooseberry. It is found in open water in the northern Atlantic Ocean, the North Sea, the Baltic Sea and the Black Sea, and was first described by the Danish zoologist Otto Friedrich Müller in 1776.

<i>Coeloplana astericola</i> Species of comb jelly

Coeloplana astericola, the creeping comb jelly, is a species of benthic comb jelly from the tropical western Indo-Pacific region that lives as an episymbiont on starfish such as Echinaster luzonicus.

<i>Beroe abyssicola</i> Species of comb jelly

Beroe abyssicola is a species of beroid ctenophore, or comb jelly. It is largely found in deep waters in the North Pacific Ocean, and is common in Japan and the Arctic Ocean. A predator, Beroe feeds mostly on other ctenophores by swallowing them whole. Like other ctenophores, B. abyssicola has a simple nervous system in the form of a nerve net, which it uses to direct its movement, feeding, and hunting behaviors.

Euplokamis dunlapae is a marine species of ctenophore. It is the first species of ctenophora reported to have giant axons controlling the comb rows. They control the ciliary beating, allowing for rapid change in the speed and direction of the cilia, likely evolved as an escape mechanism.

References

  1. ↑ "Euplokamididae". WoRMS. World Register of Marine Species . Retrieved 13 May 2021.
  2. ↑ "Euplokamididae". Global Biodiversity Information Facility . Retrieved 13 May 2021.
  3. 1 2 Giribet, Gonzalo (2002-09-01). "Current advances in the phylogenetic reconstruction of metazoan evolution. A new paradigm for the Cambrian explosion?". Molecular Phylogenetics and Evolution. 24 (3): 345–357. doi:10.1016/S1055-7903(02)00206-3. PMID   12220976.
  4. 1 2 3 Minni, M. (2021). "Phylum Ctenophora – Characteristics, Classification & Examples". Embibe Exams.
  5. 1 2 Mills, Claudia E. (1987). "Revised classification of the genus Euplokamis Chun, 1880 (Ctenophora: Cydippida: Euplokamidae n. fam.) with a description of the new species Euplokamis dunlapae". Canadian Journal of Zoology. 65 (11): 2661–2668. doi:10.1139/z87-404.
  6. 1 2 RITTER, WILLIAM (1906). Zoology: Volume II. Berkley the University Press: University of California Publications. p. 46. ISBN   048477736X.
  7. 1 2 3 4 5 Britannica, T. (2013). "Ctenophore: Marine invertebrate". www.britannica.com. Encyclopedia Britannica.
  8. ↑ Parry, Luke A.; Lerosey-Aubril, Rudy; Weaver, James C. & Ortega-Hernández, Javier (2021-09-24). "Cambrian comb jellies from Utah illuminate the early evolution of nervous and sensory systems in ctenophores". iScience. 24 (9): 102943. Bibcode:2021iSci...24j2943P. doi:10.1016/j.isci.2021.102943. PMC   8426560 . PMID   34522849.
  9. 1 2 3 Shah, R (2016). "Phylum Ctenophora: Features, Characters and Other Details". Biology Discussion.
  10. 1 2 3 Haddock, Steven H. D. & Case, James F. (1995). "Not all ctenophores are bioluminescent: Pleurobrachia". Biological Bulletin. 189 (3): 356–362. doi:10.2307/1542153. JSTOR   1542153. PMID   29244577.
  11. 1 2 World Register of Marine Species, WoRMS (2022). "WoRMS taxon details: Euplokamis". www.marinespecies.org.
  12. 1 2 3 4 Gershwin, L; Lewis, M; Gowlett-Holmes, K & Kloser, R (2014). "The Ctenophores". Pelagic Invertebrates of South-Eastern Australia: A field reference guide. Hobart: CSIRO Marine and Atmospheric Research. pp. 5–6.
  13. 1 2 3 4 5 6 Tamm, Sidney L. (2014). "Cilia and the life of ctenophores". Invertebrate Biology. 133 (1): 1–46. doi:10.1111/ivb.12042. JSTOR   24697149.
  14. 1 2 3 4 Mackie, G. O.; Mills, C. E. & Singla, C. L. (1988). "Structure and function of the prehensile tentilla of Euplokamis (Ctenophora, Cydippida)". Zoomorphology. 107 (6): 319–337. doi:10.1007/bf00312216. S2CID   317017.
  15. 1 2 Wright, Jeremy. "Ctenophora (comb jellies)". Animal Diversity Web. Retrieved 2022-04-10.
  16. ↑ Haddock, Steven H. D. (2007). "Comparative feeding behavior of planktonic ctenophores". Integrative and Comparative Biology. 47 (6): 847–853. doi:10.1093/icb/icm088. JSTOR   4540225. PMID   21669763.
  17. ↑ Mackie, G. O.; Mills, C. E. & Singla, C. L. (1992). "Giant axons and escape swimming in Euplokamis dunlapae (Ctenophora: Cydippida)". The Biological Bulletin. 182 (2): 248–256. doi:10.2307/1542118. JSTOR   1542118. PMID   29303667.
  18. ↑ Norekian, Tigran P. & Moroz, Leonid L. (2019). "Comparative neuroanatomy of ctenophores: Neural and muscular systems in Euplokamis dunlapae and related species". Journal of Comparative Neurology. 528 (3): 481–501. doi:10.1002/cne.24770. PMID   31498892. S2CID   202407426.
  19. ↑ Widder, Edith (January 2002). "Bioluminescence and the Pelagic Visual Environment". Marine and Freshwater Behaviour and Physiology. 35 (1–2): 1–26. doi:10.1080/10236240290025581. S2CID   85259393.
  20. 1 2 3 Widder, E.A.; Greene, C.H. & Youngbluth, M.J. (1992). "Bioluminescence of sound-scattering layers in the Gulf of Maine". Journal of Plankton Research. 14 (11): 1607–1624. doi:10.1093/plankt/14.11.1607.
  21. ↑ Dybas, Cheryl (2013). "RIPPLE MARKS—The Story Behind the Story". Oceanography. 26 (2). doi: 10.5670/oceanog.2013.23 .
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