Glyphosate herbicide toxicity effects on red hybrid tilapia (Oreochromis sp.)
Glyphosate [N-(phosphonomethyl) glycine] is among the most broadly and generally recognised broad-spectrum herbicides used in agriculture due to its low cost and effectiveness in weed management. The pollution of glyphosate in the aquatic environment can be via water ru...
Saved in:
| Main Author: | |
|---|---|
| Format: | Thesis |
| Language: | English |
| Published: |
2019
|
| Subjects: | |
| Online Access: | http://psasir.upm.edu.my/id/eprint/84643/1/FBSB%202019%2021%20-%20ir.pdf |
| Tags: |
Add Tag
No Tags, Be the first to tag this record!
|
| Summary: | Glyphosate [N-(phosphonomethyl) glycine] is among the most broadly and
generally recognised broad-spectrum herbicides used in agriculture due to its low cost and
effectiveness in weed management. The pollution of glyphosate in the aquatic environment
can be via water run-off from agricultural lands, or by spray drift, aerial spraying or due to
industrial discharge, which may be seen as a threat to aquatic biota. Fish is one of the best
organisms to study the toxicological aspects of glyphosate. To date, very few studies have been
done with high purity glyphosate due to the cost factor, of which this study aims to accomplished.
Fish was procured and acclimatized to the laboratory condition within ten days
before the commencement of the experiment. A 4 days bioassay was carried out using red
hybrid tilapia (Oreochromis sp.) as the test organisms to ascertain lethal
concentration (LC50) of glyphosate using arithmetic and probit methods. After determining
the LC50, fish were exposed to different concentrations (0, 25, 50, 100 and 150 mg/L) of glyphosate
herbicide for 4- and 49-days to evaluate its toxicity through changes in fish behaviour,
hematological, biochemical, histopathological as well as changes in the growth pattern of the
fish. The major physicochemical parameters of the water were ascertained. The water quality
parameters during the experiments ranged are temperature (25-29℃), dissolved oxygen (5.3-9.3
mg/L) and pH (6.5-7.4) respectively. The LC50 values of glyphosate were 250 mg/L
(arithmetic) and 215 mg/L with 162 and 282 mg/L as lower and upper 95% confidence
limit (Probit). Fish mortality rate positively correlated with the increase in glyphosate
concentration. Glyphosate exerts fewer effects on the behaviour of red hybrid tilapia at low
concentrations, but at higher concentrations of 50 mg/L and above various behavioural changes
including air gasping, erratic swimming, fin movement, mucus secretions, hemorrhages, and loss of
scale were evident. There was significant concentration-dependent decrease between the control and
exposed fish in all haematological parameters examined. The total serum protein showed a
significant decrease between the control and exposed fish. There was an increase in the values of total bilirubin, alkaline phosphatase, aspartate aminotransferase,
alanine aminotransferase, and gamma-glutamyl transferase in both 4- and 49-days exposure periods. A
significant decline was recorded in the cholinesterase enzyme activities in all organs and
substrate except the spleen, kidney and gills using PTC substrate during 4 days exposure and gills
using BTC substrate during the 49 days glyphosate exposure. BTC and ATC substrates recorded
higher activities in the liver and brain both during 4- and 49-days exposure periods. Glyphosate
herbicide significantly declined the protein content in all organs during 4- and 49-days
toxicity testing with the exception of ovary which shows no significant changes during both
toxicity testing. The overall growth performance of the fish was hindered due to
exposure to glyphosate herbicide with a reduction in the length (26.3±2.4 to 23.3±1.6 cm),
weight (198±5.9 to 175±2.79 g), food conversion ratio
(0.21 to 0.02), specific growth rate (4.6 to 4.57), and condition factor (1.28 to 0.95) between
the control and glyphosate treated fish. A significant decrease was observed in the
hepato-somatic and gonadal-somatic indices of the fish exposed to glyphosate. Glyphosate
exposure also resulted in different histopathological changes, with fewer changes in
the ovary of red hybrid tilapia. In the liver, hepatopancreas degeneration and its partial
detachment from the liver parenchyma, congested blood capillaries, necrosis, hemosiderin
deposit, reduced number of mitochondria, pyknosis, degeneration of nucleolus, cytoplasmic
vacuolation, and damaged mitochondria result histopathological changes recorded as a result
of glyphosate exposure to red hybrid tilapia. Hemosiderin deposit, mitochondria
vacuolation, the rapture of the nuclear membrane, margination of chromatin as well as melanin
deposit were seen in the spleen of fish. Lifting and congestion of primary and secondary gill
lamellae, oedema of interdigitate area, hyperplasia, hypertrophy, mitochondrial degeneration,
karyolysis, cellular membrane degeneration were observed in the gills of the fish after
glyphosate exposure. Widening of the Bowman’s corpuscular space, infiltration of
inflammatory cells, tubular degeneration and necrosis, hemosiderin deposit,
karyolysis, mitochondria degeneration and vacuolation and dissolution of the cellular
membrane were the resulted histopathological alterations seen in the kidney of the fish
exposed to glyphosate herbicide. In the brain, partial detachment of the neuronal cells, necrosis
of neuronal and glial cells, congestion and dilation of blood vessels, vacuolation of neurophil and
glial cells axonal and mitochondrial degeneration and cytoplasmic oedema were the changes
observed. Reduced number of previtellogenic follicles and mature yolk granules, increased empty
spaces within the mature follicles and degeneration and vacuolation of mitochondria were observed
in the ovary of the fish exposed to glyphosate herbicide. According to the findings of this
research, exposure of red hybrid tilapia to glyphosate herbicide resulted into overall decline in
the health status of the fish. These findings may indicate a health risk for red hybrid
tilapia and other aquatic animals exposed to glyphosate in aquatic
ecosystems. |
|---|