Effects of predator lipids on dinoflagellate defence mechanisms - increased bioluminescence capacity

Abstract

Short flashes of blue light (bioluminescence) from dinoflagellates can reduce copepod grazing of light-emitting cells. Other protective strategies against grazing are toxicity, reduced cell chain length and altered swimming patterns in different phytoplankton. Both toxicity and bioluminescence capacity in dinoflagellates decrease in copepod-free cultures, but toxin production can be restored in response to chemical alarm signals from copepods, copepodamides. Here we show that strains of the dinoflagellates Lingulodinium polyedra and Alexandrium tamarense, kept in culture for 14 and 9 years respectively, are capable of increasing their total bioluminescence capacity in response to copepodamides. The luminescence response to mechanical stimulation with air bubbles also increases significantly in L. polyedra after exposure to copepodamides. Effects on size, swimming speed and rate of change of direction in L. polyedra and A. tamarense were not detected, suggesting that post-encounter mechanisms such as bioluminescence and toxin production may constitute the dominating line of defence in these taxa. To our knowledge, this study provides the first evidence of changes in bioluminescence physiology as a response to chemical cues from natural enemies and emphasizes the importance of bioluminescence as an anti-grazing strategy.

Induction of defensive traits in marine plankton—new copepodamide structures

“…Measurements of chain length over time confirm that chain length is negatively correlated to copepod abundance in nature too (Bjærke et al ). Based on the results reported here and earlier findings—a previous study shows that copepodamides induce bioluminescence in L. polyedra and Alexandrium tamarense (Lindström et al )—we conclude that copepodamide presence induces a broad range of defensive traits in phylogenetically distant groups which may cause indirect cascading effects in plankton food webs. In particular, copepods and copepodamides will both favor smaller and/or more defended phytoplankton phenotypes.…”

“…Copepodamides trigger paralytic shellfish and amnesic shellfish toxin production in dinoflagellates and diatoms (Selander et al ; E. Selander et al unpubl. ), increased bioluminescence in Alexandrium tamarense and Lingulodinium polyedra (Lindström et al ), and chain length shortening in chain forming diatoms (E. Selander et al unpubl. ).…”

“…Selander et al unpubl. ), increased bioluminescence in Alexandrium tamarense and Lingulodinium polyedra (Lindström et al 2017), and chain length shortening in chain forming diatoms (E. Selander et al unpubl. ).…”

Toxic dinoflagellates produce true grazer deterrents

“…Bioluminescence triggered by prey handling may be another way to signal toxicity (Lindström et al. ).…”

Molecular and biochemical basis for the loss of bioluminescence in the dinoflagellateNoctiluca scintillansalong the west coast of the U.S.A.

“…Flash responses to predator contact serve to startle predators (Buskey et al 1983;Buskey and Swift 1985) and to act as a light alarm to attract secondary visual predators of the dinoflagellate predators (Morin 1983;Mensinger and Case 1992;Abrahams and Townsend 1993;Fleisher and Case 1995;Cusick and Widder 2014). Cells also increase their bioluminescence when chemical cues from predators are present (Lindström et al 2017). Despite the ecological significance of dinoflagellate bioluminescence, some species have bioluminescent and nonbioluminescent strains (Valiadi et al 2012).…”