Toxic Effects And Toxic Mechanisms Of Two Red-tide Algae On Artemia Salina

In recent years,toxic and harmful red-tide occurred frequently in the coastal of China,which have posed serious ecological risks to marine organisms.In this study,the adverse effect of the two toxic algae--Alexandrium minutum,Prorocentrum lima and their excreted toxins Gonyautoxin2/3(GTX2/3)and Okadaic acid(OA)on Artemia salina were studied.In addition,the toxic mechanisms of two red-tide algae and their toxins to A.salina were also investigated by transcriptomic analysis.The research results showed that A.minutum and GTX2/3 have no effect on the hatching of A.salina cysts,both larvae and 14 day adult were also not sensitive to A.minutum or GTX2/3.The full transcriptome of adult A.salina after exposure A.minutum and GTX2/3was assembled and functionally annotated,and a total of 599,286 transcripts were obtained which were clustered into 515,196 unigenes.Results of transcriptional effect level index(TELI)revealed that direct exposure to the toxic algae A.minutum induced much higher toxicity at transcriptomic level than exposure to its excreted GTX2/3.In addition,compare with control group,for A.minutum treated group,20189 differentially expressed genes(DEGs)was identified,254 DEGs for GTX2/3 treated group.Among these DEGs,40 up-regulated and 79 down-regulated DEGs were communally altered for both treatment groups.These DEGs are mainly enriched in the related metabolic function pathways,e.g.,amino sugar metabolic process,chitin metabolic process,etc.but the A.minutum treated group regulated much more function pathways than GTX2/3 treated group,which indicated that the toxic mechanisms of A.minutum exposure or GTX2/3 exposure on A.salina were different from each other.Exposure to A.minutum could regulate ribonucleoprotein complex formation and metabolism of amino acid and lipid in A.salina.Unlikely,GTX2/3 exposure could inhibit the expression of chitin metabolism related genes which might result in disruption of molting process or disturbed sheath morphogenesis.P.lima was more toxic than its excreted toxin OA to A.salina.Although P.lima and OA did not effect the hatching of A.salina cysts.However,P.lima has lethal effect for three different stages(Instar I< 2 h,Instar II= 24 h,Instar III= 48 h)of A.salina larvae,and their LC50 was 5.28 cells/m L,4.56 cells/m L and 5.12 cells/m L,respectively.For OA treated group,the LC50 value were 196.4 ?g/L,123.5 ?g/L and 179.9 ?g/L,respectively.Besides,the two treatment groups have lethal effect for 14-day A.salina adults(14 days post hatch)as well.Atotal of 474366 unigenes were obtained from the transccriptome sequencing,compare with solvent control group,there were 1010,2138 and 2069 DEGs for P.lima,OA-L and OA-H group respectively.In the most functional pathways regulated by these related DEGs,OA-L and OA-H have highly overlapping parts,e.g.,chitin binding,chitin metabolic process,chitin deacetylase activity,amino sugar metabolic process and chitinase activity,etc.,but the two OA groups are significantly different from P.lima treated group.