title: Loss of phototaxis and degeneration of an eyespot in long-term algal cultures: evidence from ultrastructure and behaviour in the dinoflagellate Kryptoperidinium foliaceum.
abstract: Phototaxis provides phytoplankton with the means to orient themselves in a light gradient. This is accomplished using an eyespot and associated organelles. For the dinoflagellate Kryptoperidinium foliaceum, which has been described as having one of the most elaborate eyespot complexes known, positive phototaxis has hitherto not been reported. In this study, we show that a newly isolated strain of K. foliaceum is indeed capable of positive phototaxis with a mean vector (± 95% confidence interval) of 352°± 2.2, where 0/360° indicates the position of the light source. A study of three strains (UTEX 1688, CCMP 1326, and MBL07) of K. foliaceum showed that the eyespot in two of these strains has degenerated following decades in culture. Thus, previous studies have failed to report positive phototaxis due to loss of directionality caused by the degenerated eyespot. The results are discussed in a broader context and we conclude that studies on algal morphology and physiology may result in erroneous conclusions if based on algal cultures maintained under laboratory conditions for extended periods.
authors.affiliation: Academia Sorana, Akademigrunden 8, 4180 Sorø, Denmark. mo@soroe-akademi.dk
authors.forename: Morten
authors.initials: M
authors.lastname: Moldrup
authors.forename: Øjvind
authors.initials: Ø
authors.lastname: Moestrup
authors.forename: Per Juel
authors.initials: PJ
authors.lastname: Hansen
mesh_terms: D004141:Dinoflagellida / Q000502:physiology* / Q000528:radiation effects / Q000648:ultrastructure*; D008027:Light; D008124:Locomotion / Q000528:radiation effects*; D046529:Microscopy, Electron, Transmission; D015388:Organelles / Q000502:physiology / Q000528:radiation effects / Q000648:ultrastructure; D010788:Photosynthesis / Q000502:physiology
keywords: Protist; algae; lamellar body; light gradient; morphology; photoreceptor; photosynthetic; unicellular