الفهرس 
Neonicotinoid insecticidesOnly 14 pages are availabe for public view
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Abstract
Bivalve mollusks are avid filter feeders. They filter significant amounts of
algae, bacteria, sediment, nutrients, and other particles from the waters, playing a key
benthopelagic regulatory role on freshwater ecosystems. Freshwater clam performs
many important functions in aquatic ecosystems, which can in turn be framed as the
ecosystem services that they contribute to or provide. These include supporting
services such as nutrient recycling and storage, substrate and food web modification,
and use as environmental monitors; regulating services such as water purification
(biofiltration), Therefore, in order to identify the possibility of using freshwater
oysters as a biofilter for the removal of pesticides from water, to determine the toxic
effects of genes related to growth and oxidative stress, and to determine
histopathological damage resulting from exposure to insecticides in fish.
Three different unionid bivalves were collected from North of the River Nile,
belonging to genera Coelatura, Mutela, and Chambardia. They were subjected to
DNA barcoding, through sequencing the hypervariable barcode region of the
mitochondrial cytochrome oxidase subunit I gene (COI), and phylogenetically
analyzed, In order to detect their exact types. Also, the resulting barcodes were used
to design species-specific PCR assays that were tested over waters where the three
species were co-incubated. The results revealed that the collected species were mainly
Mutela rostrata and Chambardia rubens. The third species showed barcoding and
phylogenetic proximity to Coelatura aegyptiaca, yet mixed identity was found with
two other Northeastern African Coelatura species. eDNA-based PCRs provided
specific, clear amplicons for the three species.
One of the three species of clam, Chambardia rubens, was selected for its
ability to modify the effects of insecticides which enter the aquatic ecosystem by drift,
wash off and drains from farm lands or by deliberate application for weeds and other
pest management in water on zebrafish (Danio rerio), whereas, both neonicotinoids
were chosen because they have the high water solubility which causes these
compounds to be highly mobile and, as a consequence, they could easily be
transported into aquatic ecosystems, acetamiprid was selected from neonicotinoids
because it is a widely used insecticide to protect vegetables and fruits, however its
various uses cause environmental pollution, including soil, water, and even food
products and the scarcity of research that has studied its toxic effects on non-target
organisms such as fish and zebrafish was chosen not only to assess toxic effects on
aquatic biota (especially vertebrate ones) but also to bridge the gap to other
vertebrates more difficult to study (such as humans) because it has Several
characteristics make it a convincing tool in drug discovery, such as low maintenance
costs, rapid embryogenesis, transparency, high similarity between the human and
zebrafish genomes. Median Lethal Concentration (LC50) & Time was determined for
acetamiprid, then Fish were exposed to levels of acetamiprid representing 1/10 and
1/25 of the LC50, with and without C. rubens in fishes’ aquaria. Fish incubated with
clams showed significant elevation of transcripts for catalase (cat), glutathione
peroxidase (gpx), and superoxide dismutase (sod). Liver triglycerides rose 5-6-fold in
response to both acetamiprid doses in the “Fish-Only” groups, indicating oxidative
damage induced by acetamiprid. Total H2O2-scavenging activities were the highest in
the “Fish+Clam” groups. Furthermore, in the absence of clams, the high acetamiprid
dose significantly lowered cat, gpx, and sod, and decreased H2O2-scavenging
activities. Meanwhile, total mRNA, Insulin-like growth factor 1 (igf1) transcripts, andfish body mass were in higher fish co-cultured with clams, even though exposure to
acetamiprid decreased igf1 transcripts in both “Fish+Clam” and “Fish-Only” groups,
and the histopathological results showed that increasing the acetamiprid dose toward
the LC50 increased the degenerative changes in both liver and kidney representative
tissues. However, accompanying this addition with the presence of clam reduced the
degree of pathological lesions in both organs at each associated acetamiprid dose.
Acetamiprid removal from water by mussels was measured using LC-MS/MS and the
results showed that mussels could remove significant amount of acetamiprid from
waters, being the digestive gland the most organ accumulating it. Removal of
pesticide by mussels peaked at day 1 after pesticide addition, then clearance rates kept
at the same levels until day 14.
The results strongly recommended to extend the application for molecular
tools for further investigation of hidden diversity in the world of River Nile bivalves
in Egypt, to detect their exact species, abundance, and status of conservation and these
findings suggest that in the environment, the Nile clam could reduce the oxidative
stress, metabolic changes and histopathological lesions induced in fish by the
neonicotinoid insecticide acetamiprid.