Polykrikaceae Explained

The Polykrikaceae (also known as Polykrikidae) are a family of athecate dinoflagellates of the order Gymnodiniales. Members of the family are known as polykrikoids. The family contains two genera: Polykrikos and Pheopolykrikos.[1]

Characteristics

The most distinctive feature of polykrikoids is their formation of multinucleate "pseudocolonies" consisting of an even number of subunit zooids. The two genera differ in number of nuclei; possessing two nuclei regardless of the number of zooids is a synapomorphy for Polykrikos, whereas Pheopolykrikos possess equal numbers of nuclei and zooids.[2]

Along with the Warnowiaceae (warnowiids), polykrikoids are known for possessing unusually complex subcellular structures. In particular, an extrusome complex of two organelles called the nematocyst and taeniocyst is considered a synapomorphy for Polykrikos.[3] Molecular phylogenetics studies suggest some inconsistency in the taxonomy of this group, particularly in the assignment of species to one of the two genera.[4] [5]

Habitat and life cycle

Most polykrikoids are planktonic, although one species - P. lebourae - is benthic. The family includes photosynthetic, heterotrophic, and mixotrophic species. Some species, such as P. kofoidii, are of scientific interest due to their status as predators of other dinoflagellates, a behavior that is significant in the regulation of algal blooms.[6] [7] Others, such as Ph. hartmanii (which has been reclassified P. hartmanii)[5] are themselves causes of ichthyotoxic algal blooms.[8] P. hartmanii is capable of both heterothallic (outcrossing) and homothallic (self-fertilizing) sexual reproduction.[9]

The reproductive behaviors of polykrikoids are mostly not well understood, although P. kofoidii has been studied and found to have a complex life cycle of both vegetative (asexual) and sexual reproduction complicated by its pseudocolonial structure.[10]

Evolution

The family demonstrates a complex evolutionary history indicating multiple instances of loss of photosynthetic plastids in different lineages.[11] The distinctive pseudocolonial structure may have arisen in multiple evolutionary lineages from ancestors capable of forming chains of distinct individual cells.

Notes and References

  1. Michael D. Guiry. 2015 . Polykrikaceae Kofoid & Swezy, 1921 . 109413 . 8 August 2015 . AlgaeBase.
  2. Hoppenrath. Mona. Character Evolution in Polykrikoid Dinoflagellates. Leander. Brian S.. Journal of Phycology. April 2007. 43. 2. 366–377. 10.1111/j.1529-8817.2007.00319.x. 2007JPcgy..43..366H . 16821791 .
  3. Hoppenrath. M. Bachvaroff. TR. Handy. SM. Delwiche. CF. Leander. BS. Molecular phylogeny of ocelloid-bearing dinoflagellates (Warnowiaceae) as inferred from SSU and LSU rDNA sequences.. BMC Evolutionary Biology. 25 May 2009. 9. 116. 19467154. 10.1186/1471-2148-9-116. 2694157. free. 2009BMCEE...9..116H.
  4. Reñé. Albert. Camp. Jordi. Garcés. Esther. Diversity and Phylogeny of Gymnodiniales (Dinophyceae) from the NW Mediterranean Sea Revealed by a Morphological and Molecular Approach. Protist. May 2015. 166. 2. 234–263. 10.1016/j.protis.2015.03.001. 25847865. 10261/116250. free.
  5. Hoppenrath. Mona. Yubuki. Naoji. Bachvaroff. Tsvetan R.. Leander. Brian S.. Re-classification of Pheopolykrikos hartmannii as Polykrikos (Dinophyceae) based partly on the ultrastructure of complex extrusomes. European Journal of Protistology. January 2010. 46. 1. 29–37. 10.1016/j.ejop.2009.08.003. 19767184.
  6. Matsuyama. Y. Miyamoto. M. Kotani. Y. Grazing impacts of the heterotrophic dinoflagellate Polykrikos kofoidii on a bloom of Gymnodinium catenatum. Aquatic Microbial Ecology. 1999. 17. 91–98. 10.3354/ame017091. free.
  7. JEONG. HAE JIN. KIM. SOO KYEONG. KIM. JAE SEONG. KIM. SEONG TAEK. YOO. YEONG DU. YOON. JOO YIH. Growth and Grazing Rates of the Heterotrophic Dinoflagellate Polykrikos kofoidii on Red-Tide and Toxic Dinoflagellates. The Journal of Eukaryotic Microbiology. May 2001. 48. 3. 298–308. 10.1111/j.1550-7408.2001.tb00318.x. 11411838. 27126586 .
  8. Tang. Ying Zhong. Harke. Matthew J.. Gobler. Christopher J.. Cock. M.. Morphology, phylogeny, dynamics, and ichthyotoxicity of (Dinophyceae) isolates and blooms from New York, USA. Journal of Phycology. December 2013. 49. 6. 1084–1094. 10.1111/jpy.12114. 27007629 . 2013JPcgy..49.1084T . 12140986 .
  9. Z Chai, Z Hu, Y Liu, Y Tang 2020. Proof of homothally of Pheopolykrikos hartmannii and details of cyst germination process Journal of Oceanology and Limnology 38 (1), 114-123
  10. Tillmann. Urban. Hoppenrath. Mona. Life Cycle of the pseudocolonial dinoflagellate (Gymnodiniales, Dinoflagellata). Journal of Phycology. April 2013. 49. 2. 298–317. 10.1111/jpy.12037. 27008517. 2013JPcgy..49..298T . 30674349 .
  11. Gavelis. Gregory S.. White. Richard A.. Suttle. Curtis A.. Keeling. Patrick J.. Leander. Brian S.. Single-cell transcriptomics using spliced leader PCR: Evidence for multiple losses of photosynthesis in polykrikoid dinoflagellates. BMC Genomics. 17 July 2015. 16. 1. 528. 10.1186/s12864-015-1636-8. 26183220. 4504456 . free .

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