Predatory dinoflagellates arepredatoryheterotrophic ormixotrophicalveolates that derive some or most of theirnutrients from digesting other organisms. About one half of dinoflagellates lack photosynthetic pigments and specialize in consuming other eukaryotic cells, and even photosynthetic forms are often predatory.[1][2]
Organisms that derive their nutrition in this manner includeOxyrrhis marina, which feeds phagocytically onphytoplankton,[3]Polykrikos kofoidii, which feeds on several species of red-tide and/or toxic dinoflagellates,[4]Ceratium furca, which is primarily photosynthetic but also capable of ingesting other protists such as ciliates,[5]Cochlodinium polykrikoides, which feeds on phytoplankton,[6]Gambierdiscus toxicus, which feeds on algae and produces atoxin that causesciguatera fish poisoning when ingested,[7] andPfiesteria and related species such asLuciella masanensis, which feed on diverse prey including fish skin and human blood cells.[8][9] Predatory dinoflagellates can kill their prey by releasing toxins or phagocytize small prey directly.[10]
Some predatory algae have evolved extreme survival strategies. For example,Oxyrrhis marina can turncannibalistic on its own species when no suitable non-self prey is available,[11] andPfiesteria and related species have been discovered to kill and feed on fish, and since have been (mistakenly) referred to as carnivorous "algae" by the media.
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The media has applied the term carnivorous or predatory algae mainly toPfiesteria piscicida,Pfiesteria shumwayae and otherPfiesteria-likedinoflagellates implicated inharmful algal blooms andfish kills.[12][13]Pfiesteria is named after the American protistologistLois Ann Pfiester. It is anambush predator that utilizes a hit and run feeding strategy by releasing a toxin that paralyzes the respiratory systems of susceptible fish, such asmenhaden, thus causing death bysuffocation. It then consumes the tissue sloughed off its dead prey.[14]Pfiesteria piscicida (Latin:fish killer) has been blamed for killing more than one billion fish in theNeuse andPamlico riverestuaries inNorth Carolina and causingskin lesions in humans in the 1990s.[13] It has been described as "skinning fish alive to feed on their flesh"[13] or chemically sensing fish and producing lethal toxins to kill their prey and feed off the decaying remains.[12] Its deadly nature has led toPfiesteria being referred to as "killer algae"[15][16] and has earned the organism the reputation as the "T. rex of the dinoflagellate world"[17] or "the Cell from Hell."[18]
The prominent and exaggerating media coverage ofPfiesteria as carnivorous algae attacking fish and humans has been implicated in causing "Pfiesteria hysteria" in theChesapeake Bay in 1997 resulting in an apparent outbreak of human illness in thePocomoke region inMaryland.[19] However, a study published the following year concluded the symptoms were unlikely to be caused bymass hysteria.[20]
During the media coverage in the 1990s,Pfiesteria has been referred to as "super villain"[16] and subsequently has been used as such in several fictional works. APfiesteria subspecies killing humans featured inJames Powlik's 1999 environmental thrillerSea Change. InFrank Schätzing's 2004science fiction novelThe Swarm,lobsters andcrabs spread the killer algaPfiesteria homicida to humans.
InYann Martel's 2001 novelLife of Pi, the protagonist encounters a floating island of carnivorous algae inhabited bymeerkats while shipwrecked in thePacific Ocean. At a book reading inCalgary, Alberta,Canada, Martel explained that the carnivorous algae island had the purpose of representing the more fantastical of two competing stories in his novel and challenge the reader to a "leap of faith."[21]
In the 2005National Geographic TV showExtraterrestrial, the alien organism termedHysteria combines characteristics ofPfiesteria with those ofcellular slime molds. LikePfiesteria,Hysteria is a unicellular, microscopic predator capable of producing a paralytic toxin. Like cellular slime molds, it can release chemical stress signals that cause the cells to aggregate into aswarm which allows the newly formed superorganism to feed on much larger animals and produce a fruiting body that releasesspores for reproduction.[22]
