Chemical Defense by Erythrolactones in the Euryhaline Ciliated Protist, Pseudokeronopsis erythrina.
Pseudokeronopsis erythrina produces three new secondary metabolites, erythrolactones A2, B2 and C2, and their respective sulfate esters (A1, B1, C1), the structures of which have been recently elucidated on the basis of NMR spectroscopic data coupled to high resolution mass measurements (HR-MALDI-TOF). An analysis of the discharge of the protozoan pigment granules revealed that the non-sulfonated erythrolactones are exclusively stored in these cortical organelles, which are commonly used by a number of ciliates as chemical weapons in offense/defense interactions with prey and predators. We evaluated the toxic activity of pigment granule discharge on a panel of free-living ciliates and micro-invertebrates, and the activity of each single purified erythrolactone on three ciliate species. We also observed predator-prey interactions of P. erythrina with unicellular and multicellular predators. Experimental results confirm that only P. erythrina cells with discharged pigment granules were preferentially or exclusively hunted and eaten by at least some of its predators, whereas almost all intact (fully pigmented) cells remained alive. Our results indicate that erythrolactones are very effective as a chemical defense in P. erythrina.
1 Laboratory of Protistology and Biology Education, Department of ECHT, University of Macerata, Piazzale Bertelli, 1, 62100 Macerata, Italy.
Federico
F
Buonanno
2 Bioorganic Chemistry Laboratory, Department of Physics, University of Trento, Via Sommarive 14, 38123 Povo (Trento), Italy.
Andrea
A
Anesi
3 Department of Biology, University of Pisa, Via Alessandro Volta 4, 56126, Pisa, Italy.
Graziano Di
GD
Giuseppe
2 Bioorganic Chemistry Laboratory, Department of Physics, University of Trento, Via Sommarive 14, 38123 Povo (Trento), Italy.|4 Biophysical Institute, CNR, Via alla Cascata 56/C, 38123 Povo (Trento), Italy.
Graziano
G
Guella
1 Laboratory of Protistology and Biology Education, Department of ECHT, University of Macerata, Piazzale Bertelli, 1, 62100 Macerata, Italy.
Claudio
C
Ortenzi
D000818:Animals; D016798:Ciliophora / Q000235:genetics / Q000378:metabolism*; D007448:Invertebrates; D007783:Lactones / Q000737:chemistry* / Q000378:metabolism / Q000633:toxicity*; D015394:Molecular Structure; D010802:Phylogeny; D011235:Predatory Behavior
D007783:Lactones
Pseudokeronopsis; extrusomes; natural lactones; natural toxins; predator-prey interaction