50 research outputs found
Bt Crop Effects on Functional Guilds of Non-Target Arthropods: A Meta-Analysis
Background: Uncertainty persists over the environmental effects of genetically-engineered crops that produce the insecticidal Cry proteins of Bacillus thuringiensis (Bt). We performed meta-analyses on a modified public database to synthesize current knowledge about the effects of Bt cotton, maize and potato on the abundance and interactions of arthropod non-target functional guilds. Methodology/Principal Findings: We compared the abundance of predators, parasitoids, omnivores, detritivores and herbivores under scenarios in which neither, only the non-Bt crops, or both Bt and non-Bt crops received insecticide treatments. Predators were less abundant in Bt cotton compared to unsprayed non-Bt controls. As expected, fewer specialist parasitoids of the target pest occurred in Bt maize fields compared to unsprayed non-Bt controls, but no significant reduction was detected for other parasitoids. Numbers of predators and herbivores were higher in Bt crops compared to sprayed non-Bt controls, and type of insecticide influenced the magnitude of the difference. Omnivores and detritivores were more abundant in insecticide-treated controls and for the latter guild this was associated with reductions of their predators in sprayed non-Bt maize. No differences in abundance were found when both Bt and non-Bt crops were sprayed. Predator-to-prey ratios were unchanged by either Bt crops or the use of insecticides; ratios were higher in Bt maize relative to the sprayed non-Bt control
Centrioles: active players or passengers during mitosis?
Centrioles are cylinders made of nine microtubule (MT) triplets present in many eukaryotes. Early studies, where centrosomes were seen at the poles of the mitotic spindle led to their coining as “the organ for cell division”. However, a variety of subsequent observational and functional studies showed that centrosomes might not always be essential for mitosis. Here we review the arguments in this debate. We describe the centriole structure and its distribution in the eukaryotic tree of life and clarify its role in the organization of the centrosome and cilia, with an historical perspective. An important aspect of the debate addressed in this review is how centrioles are inherited and the role of the spindle in this process. In particular, germline inheritance of centrosomes, such as their de novo formation in parthenogenetic species, poses many interesting questions. We finish by discussing the most likely functions of centrioles and laying out new research avenues
Phylogenetic Distribution of Phenotypic Traits in Bacillus thuringiensis Determined by Multilocus Sequence Analysis
Pathogenicity of entomopathogenic fungi to Thaumetopoea pityocampa (Schiff.) (Lepidoptera: Thaumatopoeidae) larvae in laboratory conditions
The Endosymbiont Arsenophonus Is Widespread in Soybean Aphid, Aphis glycines, but Does Not Provide Protection from Parasitoids or a Fungal Pathogen
Consumption of Immature Stages of Colorado Potato Beetle by Chrysoperla Carnea (Neuroptera: Chrysopidae) Larvae in the Laboratory
The Colorado potato beetle (CPB), Leptinotarsa
decemlineata (Say), has been an important defoliator of potatoes
for 150 years. Although the use of insecticides allowed
drastic reductions of CPB populations, resistance development
against active substances has been observed. In this
context, biological control using predatory larvae of the lacewing
may represent a good alternative. CPB egg and larval
consumption rates have been evaluated for all Chrysoperla
carnea (Stephens) instars for 24 h. While first and second C.
carnea instars only consumed eggs (1.3 and 1.8), first (1.5 and
2.4) and second (0.6 and 0.8) CPB instars, third instar of
lacewing consumed all CPB immature stages: 6.8 CPB eggs,
8.5 first, 4 s, 0.5 third and 0.1 fourth CPB instars. This third
instar killed 4-fold more CPB larvae than other larval stages.
Handling time for third instar lacewing has been evaluated at
52 min on first instar CPB, 102 min on second instar and
164 min on third instar. Our laboratory assays highlight a
potential for lacewing larvae to control CPB immature stages
with a greater efficiency on young CPB larval stages. Fields
assays are however needed to confirm efficiency of this CPB
natural enemy under field conditions