Mnemiopsis

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Mnemiopsis
Sea walnut, Boston Aquarium (cropped).jpg
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Ctenophora
Class: Tentaculata
Order: Lobata
Family: Bolinopsidae
Genus: Mnemiopsis
Agassiz, 1860
Species:
M. leidyi
Binomial name
Mnemiopsis leidyi
A. Agassiz, 1865
Synonyms

Mnemiopsis gardeniAgassiz, 1860
Mnemiopsis mccradyiMayer, 1900

Contents

Mnemiopsis leidyi, the warty comb jelly or sea walnut, [1] is a species of tentaculate ctenophore (comb jelly). 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. [2]

Description and ecology

Mnemiopsis have an oval-shaped and transparent lobed body, with four rows of ciliated combs that run along the body vertically and glow blue-green when disturbed. They have several feeding tentacles. Unlike cnidarians, Mnemiopsis does not sting. Their body comprises 97% water. They have a maximum body length of roughly 7–12 centimetres (3–5 in) and a diameter of 2.5 centimetres (1 in).

It is euryoecious, tolerating a wide range of salinity (2 to 38 psu), temperature (2–32 °C or 36–90 °F), and water quality.

Mnemiopsis is a carnivore that consumes zooplankton including crustaceans, [3] other comb jellies, and eggs and larvae of fish. Many of its predators are vertebrates, including birds and fish. Others are members of gelatinous zooplankton such as Beroe ctenophores and various Scyphozoa (jellyfish).

The comb jelly has the capacity for self-fertilization, as they are hermaphroditic. They have gonads that contain the ovary and spermatophore bunches in their gastrodermis. It carries 150 eggs along each meridional canal. Eggs and sperm are released into the water column where fertilization takes place. The spawning commences at late evening or at 1:00 or 2:00 a.m. The spawning eggs develop a thick outer layer within a minute of encountering seawater. As many as 10,000 eggs are produced from large specimens in areas with abundant prey. Egg production can start when the animals reach about 15 mm in length. Egg production increases with ctenophore size, and it is unclear when senescence occurs. Indeed, much like the so-called Immortal jellyfish, Mnemiopsis leidyi can undergo reverse development, namely reverting into a previous life cycle stage. [4]

It has a transient anus, which means that it appears only during defecation. There is no permanent connection between the gut and the rear of the body. Instead, as waste accumulates, part of the gut starts to balloon out until it touches the outer layer, or epidermis. The gut then fuses with the epidermis, forming an anal opening. Once excretion is complete, the process is reversed and the anus vanishes. The animals defecate at regular intervals: once an hour in the 5-centimetre-long adults, and once every 10 minutes or so in the larvae. [5] [6]

The species moves so slowly that it is referred to as "sea walnut". [7]

As an invasive species

Mnemiopsis leidyi Comb jelly.tif
Mnemiopsis leidyi

1980s – Black Sea

Mnemiopsis leidyi was introduced in the Black Sea in the 1980s, where only one species of comb jelly, the small sea gooseberry Pleurobrachia pileus occurred until then. The most likely cause of its introduction is accidentally by merchant ships' ballast water. The first Black Sea record was in 1982. [8]

By 1989, the Black Sea population had reached the highest level, with some 400 specimens per m3 of water (>10 animals/cubic foot) in optimal conditions. [3] Afterwards, due to depletion of foodstocks resulting in lower carrying capacity, the population dropped somewhat.

In the Black Sea, M. leidyi eats eggs and larvae of pelagic fish. It caused a dramatic drop in fish populations, notably the commercially important anchovy Engraulis encrasicholus (known locally as hamsi, hamsiya, hamsa, etc.), by competing for the same food sources and eating the young and eggs. [3] Biological control was tried with Beroe ovata , another comb jelly, with some degree of success; it appears as if a fairly stable predator-prey dynamic has been reached. [9]

1999 – Caspian Sea

In 1999 the species was introduced in the Caspian Sea via the Unified Deep Water System of European Russia. The establishment of this population led to a 60% reduction in the number of sprat, which in turn led to a reduction in the population of sturgeon and seals. [10]

Worldwide distribution of Mnemiopsis leidyi. Native range in red, colonized areas in pink Mnemiopsis.svg
Worldwide distribution of Mnemiopsis leidyi. Native range in red, colonized areas in pink

2006 – North and Baltic Seas

Since then, the species has apparently spread throughout the Mediterranean basin and the northwestern Atlantic. In 2006, it was first recorded in the North Sea, [11] and since October 17, 2006 [12] in the western Baltic Sea, namely the Kiel Fjord and The Belts. Up to 100 animals per cubic metre were counted in the Baltic, whereas the population density in the North Sea was at a much lower 4 animals/m3 at most. [3]

M. leidyi at the Monterey Bay Aquarium Warty comb jelly (mnemiopsis) 2.jpg
M. leidyi at the Monterey Bay Aquarium

One year later, the Baltic population of M. leidyi was found to have spread east to the Gotland Basin and the Bay of Puck. [13] The impact of the species on the already heavily stressed Baltic ecosystem is unknown. The species overwinters in the deep waters where the temperature does not drop below 4 °C (39 °F); the fact that the Baltic is heavily stratified, with the waters above and below the halocline mixing little, is believed to aid its survival. [3]

Apart from the widespread P. pileus, three comb jelly species occasionally drift into the Baltic from the North Sea but do not seem to be present as a stable population of significant size: Bolinopsis infundibulum , Beroe cucumis and Beroe gracilis . The second species might potentially be used for biological control. [2] [3]

The route of dispersal of M. leidyi to the North Sea/Baltic region is unknown. It might have occurred naturally by drifting individuals, or with ballast water of ships, either from its natural range or from the Black Sea, via the Mediterranean and eastern Atlantic. [14] At least technically possible given the species' euryhaline habits is an alternative route of dispersal through continental Europe, being carried with ballast water in ships travelling from the Black Sea to the Rhine Estuary via the Rhine-Main-Danube Canal. The latter route is known to be the point of entry into continental Europe for numerous invasive freshwater neozoons from the Ponto-Caspian region, such as the zebra mussel, the quagga mussel, the amphipods Dikerogammarus villosus and Chelicorophium curvispinum , and the polychaete Hypania invalida .

Genomics

Both the nuclear and mitochondrial genomes of Mnemiopsis leidyi have been sequenced, providing insight into the evolutionary position of Ctenophora (comb jellies). [15] [16]

In the original 2013 paper reporting the nuclear genome sequence, phylogenetic analysis of the presence and absence of genes, introns, and amino acid alignments suggested that the comb jelly is the sister lineage to the rest of all animals. [15] [17] However, a 2015 study applied different methodologies and found support for Porifera as the sister group to all other animals, and confirmed findings from the original study that amino acid alignments gave mixed support for this hypothesis. [18] The position of Ctenophora and Porifera is currently being actively debated. [19] [20]

Its mitochondrion shows several interesting features. [21] It is 10 kilobases in length making it the smallest animal mitochondrial DNA sequence known to date. It has lost at least 25 genes, including MT-ATP6 and all the tRNA genes. The atp6 gene has been relocated to the nuclear genome and has acquired introns and a mitochondrial targeting presequence. All tRNA genes have been genuinely lost along with nuclear-encoded mitochondrial aminoacyl tRNA synthetases. The mitochondrial rRNA molecules possess little similarity with their homologs in other organisms and have highly reduced secondary structures.

The genome of Mnemiopsis leidyi appears to lack recognizable microRNAs, as well as the nuclear proteins Drosha and Pasha, which are critical to canonical microRNA biogenesis. It is the only animal thus far reported to be missing Drosha. MicroRNAs play a vital role in the regulation of gene expression in all non-ctenophore animals investigated thus far except for Trichoplax adhaerens , one of three known members of the phylum Placozoa. [22]

In Mnemiopsis leidyi, NOS is present both in adult tissues and differentially expressed in later embryonic stages suggesting the involvement of NO in developmental mechanisms. Ctenophores also possess soluble guanylyl cyclases as potential NO receptors with weak but differential expression across tissues. Combined, these data indicate that the canonical NO-cGMP signaling pathways existed in the common ancestor of animals and could be involved in the control of morphogenesis, cilia activities, feeding and different behaviors. [23]

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 fresh water and marine environments, including jellyfish, hydroids, sea anemones, 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. Cnidarians are also some of the only animals that can reproduce both sexually and asexually.

<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">Mitochondrial DNA</span> DNA located in mitochondria

Mitochondrial DNA is the DNA located in the mitochondria organelles in a eukaryotic cell that converts chemical energy from food into adenosine triphosphate (ATP). Mitochondrial DNA is a small portion of the DNA contained in a eukaryotic cell; most of the DNA is in the cell nucleus, and, in plants and algae, the DNA also is found in plastids, such as chloroplasts.

<span class="mw-page-title-main">Tentaculata</span> Class of comb jellies

Tentaculata is a class of comb jellies, one of two classes in the phylum Ctenophora. The common feature of this class is a pair of long, feathery, contractile tentacles, which can be retracted into specialised ciliated sheaths. In some species, the primary tentacles are reduced and they have smaller, secondary tentacles. The tentacles have colloblasts, which are sticky-tipped cells that trap small prey.

<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 known 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">Coelenterata</span> Term encompassing animal phyla Cnidaria and Ctenophora

Coelenterata is a term encompassing the animal phyla Cnidaria and Ctenophora. The name comes from Ancient Greek κοῖλος (koîlos) 'hollow' and ἔντερον (énteron) 'intestine', referring to the hollow body cavity common to these two phyla. They have very simple tissue organization, with only two layers of cells, along with a middle undifferentiated layer called mesoglea, and radial symmetry. Some examples are corals, which are typically colonial; hydrae, jellyfish, sea anemones, and Aurelia, which are solitary; Pennatula; Portuguese man o' war; Gorgonia; and Physalia. Coelenterata lack a specialized circulatory system, relying instead on diffusion across the tissue layers.

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

Platyctenida, also known as benthic comb jellies, is an order of comb jellies in the class Tentaculata. Platyctenids display a generally benthic lifestyle in contrast to most ctenophores being largely pelagic. Platyctenids display widely differing morphological characteristics from their pelagic counterparts, being highly flattened on their oral-aboral axis and having lost many key traits associated with the phylum.

<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>Beroe</i> (ctenophore) Genus of comb jellies

Beroe, commonly known as the cigar comb jellies, is a genus of comb jellies in the family Beroidae. Beroe exhibits bioluminescence.

<span class="mw-page-title-main">ParaHoxozoa</span> Clade of all animals except sponges and comb jellies

ParaHoxozoa is a clade of animals that consists of Bilateria, Placozoa, and Cnidaria.

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

Beroe ovata is a comb jelly in the family Beroidae. It is found in the South Atlantic Ocean and the Mediterranean Sea and has been introduced into the Black Sea, the Aegean Sea, the Sea of Azov and the Caspian Sea. It was first described by the French physician and zoologist Jean Guillaume Bruguière in 1789.

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

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<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.

<i>Euplokamis</i> Genus of ctenophores

Euplokamis is a genus of ctenophores, or comb jellies, belonging to the monotypic family Euplokamididae. It shares the common name sea gooseberry with species of the genus Pleurobrachia. 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. Further research indicated that Euplokamis should be identified from Mertensiidae due to the rows of combs and some compression. They may also be distinguished from the genus Pleurobrachia due to their more elongated shape. 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.

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References

  1. ↑ "Common Names for Sea Walnut (Mnemiopsis leidyi)". Encyclopedia of Life. Retrieved 13 December 2013.
  2. 1 2 Hansson, Hans G. (2006). "Ctenophores of the Baltic and adjacent Seas - the invader Mnemiopsis is here!". Aquatic Invasions. 1 (4): 295–298. doi: 10.3391/ai.2006.1.4.16 .
  3. 1 2 3 4 5 6 Kube, Sandra; Postel, Lutz; Honnef, Christopher; Augustin, Christina B. (2007). "Mnemiopsis leidyi in the Baltic Sea - distribution and overwintering between autumn 2006 and spring 2007". Aquatic Invasions. 2 (2): 137–145. doi: 10.3391/ai.2007.2.2.9 .
  4. ↑ Soto-Angel, Joan J.; Burkhardt, Pawel (2024-11-05). "Reverse development in the ctenophore Mnemiopsis leidyi". Proceedings of the National Academy of Sciences. 121 (45). doi:10.1073/pnas.2411499121. ISSN   0027-8424.
  5. ↑ Michael Le Page (March 2019). "Animal with an anus that comes and goes could reveal how ours evolved". New Scientist.
  6. ↑ Tamm, Sidney L. (2019). "Defecation by the ctenophore Mnemiopsis leidyi occurs with an ultradian rhythm through a single transient anal pore". Invertebrate Biology. 138: 3–16. doi: 10.1111/ivb.12236 .
  7. ↑ Abigail Tucker (September 2012). "How Can a Jellyfish This Slow Be So Deadly? It's Invisible". Smithsonian Magazine. Archived from the original on 2013-04-11. Retrieved 2013-02-21.
  8. ↑ Zaika, V. Ye.; Sergeyeva, N. G. (1990). "Morphology and development of Mnemiopsis mccradyi (Ctenophora, Lobata) in the Black Sea". Zoologicheskii Zhurnal. 69 (2): 5–11.
  9. ↑ Kideys, Ahmet E (2002). "Fall and rise of the Black Sea ecosystem". Science . 297 (5586): 1482–1484. doi:10.1126/science.1073002. PMID   12202806. S2CID   43042123.
  10. ↑ Zarina Akhmedova (November 8, 2010). "Борьба против вредоносного мнемиопсиса в водах Каспия дала первые результаты - минэкологии" [Initial Results in the Fight Against the Malicious Mnemiopsis in Caspian Waters – Ministry of the Environment]. Trend News Agency. Retrieved September 14, 2016.(in Russian)
  11. ↑ Faasse, Marco A.; Bayha, Keith M. (2006). "The ctenophore Mnemiopsis leidyi A. Agassiz 1865 in coastal waters of the Netherlands: an unrecognized invasion?". Aquatic Invasions. 1 (4): 270–277. doi: 10.3391/ai.2006.1.4.9 .
  12. ↑ Javidpour, Jamileh; Sommer, Ulrich; Shiganova, Tamara A. (2006). "First record of Mnemiopsis leidyi A. Agassiz 1865 in the Baltic Sea". Aquatic Invasions. 1 (4): 299–302. doi: 10.3391/ai.2006.1.4.17 .
  13. ↑ "Invasion der Rippenquallen" [Invasion of the Comb Jellies] (in German). Scinexx. Retrieved January 15, 2011.
  14. ↑ Oliveira, Otto M. P. (2007). "The presence of the ctenophore Mnemiopsis leidyi in the Oslofjorden and considerations on the initial invasion pathways to the North and Baltic Seas". Aquatic Invasions. 2 (3): 185–189. doi: 10.3391/ai.2007.2.3.5 .
  15. 1 2 Ryan, J. F.; Pang, K.; Schnitzler, C. E.; Nguyen, A.-D.; Moreland, R. T.; Simmons, D. K.; Koch, B. J.; Francis, W. R.; Havlak, P.; Smith, S. A.; Putnam, N. H.; Haddock, S. H. D.; Dunn, C. W.; Wolfsberg, T. G.; Mullikin, J. C.; Martindale, M. Q.; Baxevanis, A. D. (2013). "The genome of the ctenophore Mnemiopsis leidyi and its implications for cell type evolution". Science. 342 (6164): 1242592. doi:10.1126/science.1242592. PMC   3920664 . PMID   24337300.
  16. ↑ Moreland, R.T.; Nguyen, A.-D.; Ryan, J.F.; Baxevanis, A.D. (2020). "The Mnemiopsis Genome Project Portal: integrating new gene expression resources and improving data visualization". Database (Oxford). 2020. doi: 10.1093/database/baaa029 . PMC   7211034 . PMID   32386298.
  17. ↑ Rokas, A. (2013). "My Oldest Sister Is a Sea Walnut?". Science. 342 (6164): 1327–1329. Bibcode:2013Sci...342.1327R. doi:10.1126/science.1248424. PMID   24337283. S2CID   33619949.
  18. ↑ Pisani, Davide; Pett, Walker; Dohrmann, Martin; Feuda, Roberto; Rota-Stabelli, Omar; Philippe, Hervé; Lartillot, Nicolas; Wörheide, Gert (2015-11-30). "Genomic data do not support comb jellies as the sister group to all other animals". Proceedings of the National Academy of Sciences of the United States of America. 112 (50): 15402–7. Bibcode:2015PNAS..11215402P. doi: 10.1073/pnas.1518127112 . PMC   4687580 . PMID   26621703.
  19. ↑ Telford MJ, Moroz LL, Halanych KM (2016). "Evolution: A sisterly dispute". Nature. 529 (7586): 286–7. Bibcode:2016Natur.529..286T. doi: 10.1038/529286a . PMID   26791714.
  20. ↑ Halanych KM, Whelan NV, Kocot KM, Kohn AB, Moroz LL (2016). "Miscues misplace sponges". Proceedings of the National Academy of Sciences of the United States of America. 113 (8): E946–7. Bibcode:2016PNAS..113E.946H. doi: 10.1073/pnas.1525332113 . PMC   4776479 . PMID   26862177.
  21. ↑ Pett, W.; Ryan, J.F.; Pang, K.; Mullikin, J.C.; Martindale, M.Q.; Baxevanis, A.D.; Lavrov, D.V. (2011). "Extreme mitochondrial evolution in the ctenophore Mnemiopsis leidyi: Insight from mtDNA and the nuclear genome". Mitochondrial DNA. 22 (4): 130–142. doi:10.3109/19401736.2011.624611. PMC   3313829 . PMID   21985407.
  22. ↑ Maxwell, E.K.; Ryan, J.F.; Schnitzler, C.E.; Browne, W.E.; Baxevanis, A.D. (December 2012). "MicroRNAs and essential components of the microRNA processing machinery are not encoded in the genome of the ctenophore Mnemiopsis leidyi". BMC Genomics. 13 (1): 714. doi: 10.1186/1471-2164-13-714 . PMC   3563456 . PMID   23256903.
  23. ↑ Moroz, Leonid; Mukherjee, Krishanu; Romanova, Daria (2023). "Nitric oxide signaling in ctenophores". Front. Neurosci. 17: 1125433. doi: 10.3389/fnins.2023.1125433 . PMC   10073611 . PMID   37034176.
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