Karenia(dinoflagellate)
| Karenia | |
|---|---|
| |
| Karenia brevis | |
Scientific classification
| |
| Domain: | Eukaryota |
| Clade: | Diaphoretickes |
| Clade: | SAR |
| Clade: | Alveolata |
| Phylum: | Myzozoa |
| Superclass: | Dinoflagellata |
| Class: | Dinophyceae |
| Order: | Gymnodiniales |
| Family: | Kareniaceae |
| Genus: | Karenia Gert Hansen & Moestrup |
| Type species | |
| Karenia brevis (C.C.Davis) Gert Hansen & Moestrup
| |
Kareniais a genus that consists of unicellular, photosynthetic, planktonic organisms found in marine environments.[1]The genus currently consists of 12 described species.[1]They are best known for their dense toxic algal blooms andred tidesthat cause considerable ecological and economical damage; someKareniaspecies cause severe animal mortality.[1]One species,Karenia brevis,is known to cause respiratory distress andneurotoxic shellfish poisoning(NSP) in humans.[1]
Taxonomy
[edit]The genusKareniais named for Dr. Karen Steidinger for her exceptional contributions to dinoflagellate research.[1]She has spent many decades researchingKarenia brevis.[1]
12 species have been described in the genusKareniathus far:[1]
- Karenia asterichroma
- Karenia bicuneiformis
- Karenia brevis
- Karenia brevisulcata
- Karenia concordia
- Karenia cristata
- Karenia digitata
- Karenia longicanalis
- Karenia mikimotoi
- Karenia papilionacea
- Karenia selliformis
- Karenia umbella
History of knowledge
[edit]Characteristic fish killings described by 15th and 16th century Spanish explorers were likely the earliest recorded sightings ofKarenia.[2]Other major fish killings were documented in 1844 off of the coast of Florida.[1]Oda, in 1935, was the first to name any species in what is now the genusKarenia:[3]Gymnodinium mikimotoibut was later renamedKarenia mikimotoi.[1]Davis in 1948 was the first to document that the cause of the fish kills was the dinoflagellateGymnodinium breve,[4]which was renamedPtychodiscus brevisand since 2001 is now known asKarenia brevis.[1]
Description
[edit]Kareniaare naked, flat, unicellular, photosynthetic cells that are quite pleomorphic: size tends to range from about 20–90 um.[1]The cell contains a straight apical groove, and differences in apical grooves (acrobases) are often used to distinguish between species.[5]Thecal plates are not present.[6]The cell body can be divided into an episome and a hyposome like other dinoflagellates.[6]Two dissimilar flagella that are involved in locomotion are present in the cingulum and sulcus.[6]The cytoplasm contains many yellow-green chloroplasts.[7]The plastid ofKareniais especially notable as it is the product of tertiary endosymbiosis, by uptake of a haptophyte.[7]Therefore, they lack the typical dinoflagellate pigmentperidininand have a plastid with pigments chlorophylls a+c and 19′-hexanoyloxyfucoxanthin, typically haptophyte pigments.[7]A nucleus is also found in the cell and its location and shape can distinguish between species.[5]
Habitat and ecology
[edit]Kareniais found throughout the world in both oceanic and coastal waters.[2]It is relatively sporadic in abundance, but it can form large blooms in the summer or fall which can have severe ecological and economical consequences.[8]These blooms are generally referred to asharmful algal blooms(HABs), but are also sometimes referred to as red tides.[2]Kareniais known to divide very slowly, but are able to form dense blooms probably due to their ability to swim quickly, which likely allows them access to higher concentrations of nutrients.[2]Many of these blooms consist of more than one type ofKareniaspecies.[1]The cause of the blooms is still poorly understood.[8]
When a large bloom occurs, resources become limited, and this means greater competition for space and sunlight between several marine organisms—as the genusKareniastart dying they release theirneurotoxins,which can kill fish and other organisms.[8]The dense blooms can also cause animal mortalities through anoxia.[8]Karenia brevisalso causes distress in humans in the form ofneurotoxic shellfish poisoning(NSP) which gets biomagnified up the food chain.[2]Kareniaspecies produce a variety of toxins, with many probably producing more than one.[2]
Kareniaare considered autotrophic organisms primarily, but some have been found to be mixotrophic as they can ingest microbes as well.[2]
Microbes have also been seen to be capable of attackingKareniaspecies, although their role in population dynamics is not well understood.[1]
Biology
[edit]Life cycle
[edit]Although the genusKareniaconsists of 12 described species, most research on life cycles has been done onKarenia breviswhich will be outlined here.Kareniafollow the typical life cycle of a dinoflagellate with a motile,haploid,asexual cell with regular mitotic divisions.[1]Thisbinary fissionreproduction occurs once about every 2–10 days, and division occurs primarily at night (Brand et al., 2012).[1]They occasionally produce diploid planozygotes (mobile zygotes) implying they are capable of sexual reproduction.[1]They have been observed to be in what appears to be the process of conjugation, a type of unicellular sexual reproduction.[1]They can enter a hypnozygote cyst stage, which is an often thick walled, resting cyst that results from sexual fusion.[1]This occurs when environmental conditions are adverse and allows it to be dormant and spread to grow algal blooms elsewhere.[1]
Genetics
[edit]Karenia,like all organisms in the dinoflagellate group, are characteristic for their unique permanently condensedchromatinthat lacksnucleosomesandhistones.[9]The less tightly packed loops of DNA consist of actively transcribed DNA.[8]The haploid genome is large (about 30 times the size of humans), and usually contain a large quantity of repetitive,non-coding DNA.[9]They also portray a uniquemitosiswhere thenuclear envelopestays intact and themitotic spindlehas extra nuclear microtubules that go through the nucleus through cytoplasmic channels.[9]
The genome ofKarenia brevisis estimated to be about 1 x 10^11 bp, although the genome has not been sequenced in any members of this genus.[8]
Toxicity
[edit]Kareniaare well known for their toxic blooms that kill fish, marine organisms, and other animals. These blooms, also called red tides, cause extensive ecological and economic damage. What causes these harmful algal blooms is still poorly understood.[1]
Karenia brevisis of particular importance to humans because it also can cause neurotoxic shellfish poisoning (NSP) and respiratory distress through accumulation of toxins in tissue.[1]These toxins are taken up by molluscs with no detrimental effects, but they distress the humans who ingest the molluscs.[1]The distress is caused by neurotoxins calledbrevetoxins.[10]Brevetoxins are lipid soluble and capable of biomagnification up the food chain.[10]They work by activating voltage-sensitive sodium channels and causing them to remain open for excessive amounts of time, which leads to uncontrolled depolarization of the neural membrane.[10]This results in persistent neuron firing.[10]No deaths have been recorded in association with brevetoxin, but severe effects have been noted, such as nausea, vomiting, and slurred speech.[10]
References
[edit]- ^abcdefghijklmnopqrstuvBrand, Larry E.; Campbell, Lisa; Bresnan, Eileen (2012)."Karenia:The biology and ecology of a toxic genus ".Harmful Algae.14:156–178.doi:10.1016/j.hal.2011.10.020.PMC9891709.PMID36733478.
- ^abcdefgBrand, Larry E.; Compton, Angela (2007)."Long-term increase inKarenia brevisabundance along the Southwest Florida Coast ".Harmful Algae.6(2): 232–252.doi:10.1016/j.hal.2006.08.005.PMC2330169.PMID18437245.
- ^Oda, M (1935). "The red tide of Gymnodinium mikimotoi n.sp. (MS.) and the effect of altering copper sulphate to prevent the growth of it".Dobutsugaku Zasshi, Zoological Society of Japan.
- ^Davis, CC (1948). "Gymnodinium brevis sp. nov., a cause of discolored water and animal mortalities in the Gulf of Mexico".Botanical Gazette.109(3): 358–360.doi:10.1086/335488.JSTOR2472837.S2CID84823699.
- ^abYang, Z. B. (2000). "Karenia digitatasp. nov.(Gymnodiniales, Dinophyceae), a new harmful algal bloom species from the coastal waters of west Japan and Hong Kong ".Phycologia.39(6): 463–470.Bibcode:2000Phyco..39..463Y.doi:10.2216/i0031-8884-39-6-463.1.S2CID85603177.
- ^abcHaywood, Allison J.; Steidinger, Karen A.; Truby, Earnest W.; Bergquist, Patricia R.; Bergquist, Peter L.; Adamson, Janet; Mackenzie, Lincoln (2004-02-01). "Comparative morphology and molecular phylogenetic analysis of three new species of the genusKarenia(Dinophyceae) from New Zealand ".Journal of Phycology.40(1): 165–179.Bibcode:2004JPcgy..40..165H.doi:10.1111/j.0022-3646.2004.02-149.x.ISSN1529-8817.S2CID83753181.
- ^abcGabrielsen, T. M. (2011)."Genome Evolution of a Tertiary Dinoflagellate Plastid".PLOS ONE.6(4): e19132.Bibcode:2011PLoSO...619132G.doi:10.1371/journal.pone.0019132.PMC3082547.PMID21541332.
- ^abcdefVargo, Gabriel A. (2009). "A brief summary of the physiology and ecology ofKarenia brevisDavis (G. Hansen and Moestrup comb. nov.) red tides on the West Florida Shelf and of hypotheses posed for their initiation, growth, maintenance, and termination ".Harmful Algae.8(4): 573–584.doi:10.1016/j.hal.2008.11.002.
- ^abc"Why SequenceKarenia brevis".7 November 2013.
- ^abcdeNaar, Jerome; Bourdelais, Andrea; Tomas, Carmelo; Kubanek, Julia; Whitney, Philip L.; Flewelling, Leanne; Steidinger, Karen; Lancaster, Johnny; Baden, Daniel G. (2002)."A Competitive ELISA to Detect Brevetoxins fromKarenia brevis(FormerlyGymnodinium breve) in Seawater, Shellfish, and Mammalian Body Fluid ".Environmental Health Perspectives.110(2): 179–185.doi:10.1289/ehp.02110179.PMC1240733.PMID11836147.
Further reading
[edit]- Mulholland, M.R. (September 2014). "Contribution of diazotrophy to nitrogen inputs supportingKarenia brevisblooms in the Gulf of Mexico ".Harmful Algae.38:20–29.doi:10.1016/j.hal.2014.04.004.
- Turner, Jefferson; Roncalli, Vittoria; Ciminiello, Patrizia; Dell'Aversano, Carmela; Fattorusso, Ernesto; Tartaglione, Luciana; Carotenuto, Ylenia; Romano, Giovanna; Esposito, Francesco; Miralto, Antonio; Ianora, Adrianna (April 2012). "Biogeographic effects of the Gulf of Mexico red tide dinoflagellateKarenia brevison Mediterranean copepods ".Harmful Algae.16:63–73.doi:10.1016/j.hal.2012.01.006.