Bis-(2-ethylexhyl) phthalate impairs spermatogenesis in zebrafish (Danio rerio)

Bis-(2-ethylhexyl) phthalate (DEHP) is a widely used industrial additive for increasing plastic flexibility. Its metabolites are known to exert toxic effects on reproduction and development of mammals. The aim of this study was to evaluate the effects of environmentally relevant concentrations of DEHP (0.2 and 20 μg/L) on the reproductive biology of adult male zebrafish (Danio rerio). The effects of DEHP and 17β-ethynylestradiol (a positive control) were determined after one or three weeks of exposure by TUNEL assay, histomorphometric analysis and evaluation of reproductive performance. DEHP impaired reproduction in zebrafish by inducing a mitotic arrest during spermatogenesis, increasing DNA fragmentation in sperm cells and markedly reducing embryo production (up to 90%). In conclusion, relatively short-term exposure to environmentally relevant concentrations of DEHP is able to alter spermatogenesis and affect reproduction in zebrafish

Cytogenetic characterization of the holocentric chromosomes in the aphids Myzus varians and Myzus cerasi

Cytogenetic investigations on the holocentric chromosomes of Myzus varians and Myzus cerasi have been carried out using silver staining and C-banding followed by chromomycin A3 (CMA3) and DAPI staining in order to improve our knowledge of these pest crop species and facilitate their identification. In M. varians C-banding pattern is pecu-: liar of each chromosome pair thus allowing the identification of all homologues and the reconstruction of a reliable karyotype whereas in M. cerasi, C-positive regions result to be limited to both the telomeric regions of the X chromosomes. In both species, silver staining localizes rDNA genes on one telomere of each X chromosome; such telomeres are the unique brightly fluorescent C-positive regions after CMA3 staining, whereas all other heterochromatic bands result DAPI positive

Biochemical and molecular diagnosis of insecticide resistance conferred by esterase, MACE, kdr and super-kdr based mechanisms in Italian strains of the peach potato aphid, Myzus persicae (Sulzer)

In this paper we analysed the basis of insecticide resistance in 59 Italian strains of the peach potato aphid Myzus persicae using both molecular and biochemical assays. Our data as a whole clearly indicate that most M. persicae strains (76.3%) have high or extremely high production of an esterase enzyme which sequester and detoxify insecticides with esteric group. Kdr genotypes conferring resistance towards pyrethoids are present in 57.7% of the analysed populations. Moreover, 26.5% of the kdr positive strains possess also the M918T mutation conferring super-kdr phenotype. Strains with modified AChE (MACE) are not so numerous (27.1%), although they can be found almost everywhere in Italy. Considering all the strains analysed, both MACE and kdr phenotypes are associated with high levels of esterase activity. In Central\u2013Southern regions, kdr and MACE resistance mechanisms resulted in linkage disequilibrium. Bioassays performed in order to evaluate the efficacy of a pyrethroid insecticide against a strain possessing a F979S mutation within its paratype sodium channel gene suggests that this amino acid substitution could affect the sodium channel responsivity to pyrethroids

Genetic variability among different Italian populations of the aphid Myzus persicae

Aphids life cycle includes cyclical or obligate parthenogenesis, therefore low genetic variation is expected in these insects. Genetic diversity in crop pest aphids such as Myzus persicae, is also influenced by the extensive use of insecticides which favoured the selection of few resistant strains. In the present work, 18 M. persicae populations collected in different Italian regions, were studied by RAPD-PCR (Random Amplified Polymorphic DNA) to assess genetic variability among populations. Twelve different random primers, selected out of 24 previously investigated, were employed for genomic DNA amplification. A total of 150 fragments from the aphid M. persicae populations, and 31 fragments in two outgroups were identified. An UPGMA cluster analysis based on Nei and Li\u2019s genetic distance revealed that the M. persicae populations could be divided into two groups: aphids from Central and Southern Italy were generally located in the same cluster, while aphids from Northern Italy were more often located in the other. The presence of a positive correlation between genetic and geographical distance suggests that at least a portion of the interpopulation polymorphism evidenced could be caused by restricted gene flow