Action Mechanisms of the Secondary Metabolite Euplotin C: Signaling and Functional Role in Euplotes

Among secondary metabolites, the acetylated hemiacetal sesquiterpene euplotin C has been isolated from the marine, ciliated protist Euplotes crassus, and provides an effective mechanism for reducing populations of potential competitors through its cytotoxic properties. However, intracellular signaling mechanisms and their functional correlates mediating the ecological role of euplotin C are largely unknown. We report here that, in E. vannus (an Euplotes morphospecies which does not produce euplotin C and shares with E. crasssus the same interstitial habitat), euplotin C rapidly increases the intracellular concentration of both Ca2+ and Na+, suggesting a generalized effect of this metabolite on cation transport systems. In addition, euplotin C does not induce oxidative stress, but modulates the electrical properties of E. vannus through an increase of the amplitude of graded action potentials. These events parallel the disassembling of the ciliary structures, the inhibition of cell motility, the occurrence of aberrant cytoplasmic vacuoles, and the rapid inhibition of phagocytic activity. Euplotin C also increases lysosomal pH and decreases lysosomal membrane stability of E. vannus. These results suggest that euplotin C exerts a marked disruption of those homeostatic mechanisms whose efficiency represents the essential prerequisite to face the challenges of the interstitial environmental.L'articolo è disponibile sul sito dell'editore http://onlinelibrary.wiley.com

Exposure to anti-mosquito insecticides utilized in rice fields affects survival of two non-target species, Ischnura elegans and Daphnia magna

Insecticides are commonly utilized to control mosquito larvae in rice fields. They can, however, have negative effects on both vertebrates and non-target invertebrate species. In this study, we examined the effects of pulse exposition to different concentrations of cypermethrin (0.15, 0.015, 0.0015 mg/L) and diflubenzuron (0.15, 0.015, 0.0015 mg/L) on egg hatching rate, larval growth, and larval survival in a damselfly, Ischnura elegans, and on survival of a crustacean, Daphnia magna. Insecticide exposure had significant negative effects on hatching rate in damselfly eggs. Exposed damselfly larvae also grew less and showed a higher mortality than control larvae. In Daphnia, the acute toxicity test (ISO 6341 in Water quality\u2014determination of the inhibition of the mobility of Daphnia magna Straus (Cladocera, Crustacea)\u2014acute toxicity test, Int Organ Stand Geneve, Geneva, 2012) showed an increased inhibition of mobility in the presence of insecticides. We observed a proportional response in relation to insecticide concentration, such that the highest exposure levels showed the largest reduction of vital performances. Our highest tested values correspond to those currently employed in agriculture. This study suggests that exposure to two common insecticides strongly affects non-target invertebrates even at very low concentration levels (cypermethrin 0.0015 mg/L and diflubenzuron 0.0015 mg/L)