Higher order taxa
Eukaryota; Myzozoa; dinophyceae; Gymnodiniales; Kareniaceae [Others may be used. Use NCBI link to find]
Karlodinium veneficum (taxonomic synonym K. micrum)
Description and significance
K. veneficum is part of the Eukarya domain and a marine planktonic dinoflagellate found in oceans and estuaries all around the world. It is a photosynthetic species that contains multiple chloroplasts.
Gymnodinium veneficum was originally named and discovered by Mary Parke and D. Ballantine in 1956 (4). It was found to be very closely related to Gymnodinium vitiligo, due to its small size and similar structural characteristics (4). The most distinct difference between G. veneficum and G. vilitgo was that, G. veneficum produced and released toxins. After more research was performed on this particular species, the genus name was changed from Gymnodinium to Karlodinium. The species was renamed Karlodinium veneficum due to the discovery of harmful toxins produced by this species which has been known to cause harmful algae blooms and kill fish in marine ecosystems (8). Multiple articles including Algaebase (which is a database of information on algae that includes terrestrial, marine and freshwater organisms) have stated that Karlodinium micrum is a taxonomic synonym of Karlodinium veneficum. In the article by Bergholtz et al. 2005, it was stated that K. micrum should be changed to K. veneficum due to the fact that they are identical in size, both have golden brown chloroplasts with pyrenoids and an epicone (part that is located near the apical groove in dinoflagellate) present.
The complete sequencing of the genome for K. veneficum has not fully been studied, but parts of the nucleotide sequence has been tagged and sequenced. On the NCBI (National Center for Biotechnology Information) website, there are two pages for both K. veneficum and K. micrum. Both have similar small subunit ribosomal RNA gene sequences. See links below for more information.
K. veneficum RNA gene sequence, http://www.ncbi.nlm.nih.gov/nuccore/jn986578
K. micrum RNA gene sequence, http://www.ncbi.nlm.nih.gov/nuccore/eu038293
Cell and colony structure
K.veneficum cells are quite small ranging from 7-14 micrometers in width and 9-18 micrometers in length. The structure of K. veneficum contains approximately four irregular shaped golden brown chloroplasts that contain many pyrenoids and a centrally located nucleus (4). K. veneficum also has one or two flagella that are located in opposites directions of each other (2). Along the anterior end of the cell there is a shallow sulcus (a depression or fissure). K. veneficum is a relatively small microorganism so it is overlooked quite often.
K.veneficum is structurally similar to Karlodinium armiger in the sense that both microbes contain flagella and contain the same type of pyrenoids within the chloroplasts. They differ in respect to the color of the chloroplasts, which in K. armiger are a yellow-green color, and also in the length of the apical groove (2).
The cells of K. veneficum reproduce asexually through binary fission, but it is suggested that an individual cell will soon die out due to environment around it (4).
Metabolic activity of K. veneficum is not fully understood. K. veneficum has been known to rely on photosynthesis and mixotrophy for growth. A mixotrophic species are able to take advantage of different environment conditions by using different sources of carbon and energy. Because K. veneficum is a photosynthetic species, light can have a huge impact on the organisms feeding capabilities. If K. veneficum is exposed to prolonged darkness, this can have a negative effect on its feeding capabilities (2). Under conditions where nutrients are limited, K.veneficum will start to feed on other organisms as a substitute for necessary nutrients (5). It has been suggested that mixotrophy is an adaptive strategy for survival under extreme conditions due to the toxins produced by this species (5). Under conditions where nutrients are limited, K. veneficum utilizes phagotrophy (form of feeding by ingesting inorganic particles) as an alternative mechanism for necessary nutrients to survive (5).
K. veneficum was first isolated off the coast of the English Channel near the city of Plymouth in Devon, United Kingdom. K. veneficum has also been found in many other places all around the world. It has been found along the Chesapeake Bay and parts of Florida in the United States, other parts of Europe, Africa, Asia and Australia (3). It is suggested that the location of K.veneficum is more widespread around the world, but because of its small size it has probably been overlooked.
K. veneficum produces three harmful karlotoxins called Tx1, Tx2 and Tx3. These karlotoxins have been known to cause harmful algae blooms across the world and may be the result of some recent fish kills along the Chesapeake Bay and a few other places. These karlotoxins have the ability to slow the mobility of other organisms, including fish, in order for K. veneficum to obtain necessary nutrients for food (4). The release of these karlotoxins has been known to contribute to survival strategies of K. veneficum that involve the capturing of prey (4). Tx1 has been found to be more toxic than Tx2 and Tx3, but the functions of all three karlotoxins are similar.
K. veneficum is not known to be pathogenic at this time.
 Bergholtz, Trine., Daugbjerg, Niels., Moestrup, Ojvind., and Fernandez-Tejedor, Margarita (2005). On the Identity of Karlodinium veneficum and description of Karlodinium armiger sp. Nov. (Dinophyceae), Based on Light and Electron Microscopy, Nuclear-encoded LsU rDNA, and Pigment Composition. Phycological Society of America, 42, 170-193, DOI: 10.1111/j.1529-8817.2006.00172.x.
 Calbet, Albert., Bertos, Mirela., Feuentes-Grunewald, Claudia., Alacid, Elizabet., Figueroa, Rosa., Renom, Berta., Garces, Esther (2011) Intraspecific Variability in K. veneficum: Growth rates, mixotrophy, and lipid composition. Harmful Algae, 10, 654-667; doi:10.1016/j.hal.2011.05.001
 Galimany, Eva., Place, Allen R., Ramon, Montserrat., Justson, Maria., Pipe, Richard K. (2008) The effects of Feeding Karlodinium veneficum (PLY #103, Gymnodinium veneficum Ballantine) to the Blue Mussel Mytilus edulis. Harmful Algae, 7, 91-98; doi: 10.1016/j.hal.2007.05.004
 Place, Allen R., Bowers, Holly A., Bachvaroff, Tsetvan t., Adolf, Jason E., Deeds, Jonathan R., and Sheng, Jian (2012). Karlodinium veneficum- the little dinoflagellate with a big bite.Harmful Algae, 14, 179-195; doi:10.1016/j.hal.2011.10.021
 R.K. Naik, R.R. Chitari and A. C. Anil (2010). Karlodinium veneficum in India: Effect of Fixatives on Morphology and Allelopathy in Relation to Skeletonema costatum. Current Science, 99, 1112-1116.
 Van Wagoner, Ryan M., Jonathan R. Deeds, Masayuki Satake, Anthony A. Ribeiro, Allen R. Place, Jeffrey L.C. Wright. Isolation and characterization of karlotoxin 1, a new amphipathic toxin from Karlodinium veneficum. Tetrahedron Lett. Author manuscript; available in PMC 2010 August 25. Published in final edited form as: Tetrahedron Lett. 2008 November 3; 49(45): 6457–6461. doi: 10.1016/j.tetlet.2008.08.103. Accessed on 2012-03-20
Edited by Caitlyn Thiboutot of Dr. Lisa R. Moore, University of Southern Maine, Department of Biological Sciences, http://www.usm.maine.edu/bio