Histological Alterations in Some Organs of African Catfish (Clarias gariepinus) Exposed to Sub-lethal Concentrations of Glyphosate [N-(phosphonomethyl) glycine]

This study used a static bioassay to investigate the histological effects of glyphosate on the gill, liver and muscle of African catfish (Clarias gariepinus) fingerlings. This was done with a view of further characterising the effect of glyphosate on C. gariepinus fingerlings and other aquatic life forms. Six-week old C. gariepinus fingerlings with an average weight of 10.02 ± 0.2 g were stocked into three exposure sets (control, 2.75 ppm (25% of the 96 h LC50 value) and 5.50 ppm (50% of the 96 h LC50 value)) in triplicate at 30 fish per tank for 70 days. The 96 h LC50 value was 11.00 mg/L. Histological examination of the C. gariepinus exposed to various sublethal concentrations of glyphosate showed that major histological changes in their organs were concentration dependent such as gill arch vacuolation, excessive mucosal secretions, lifting of epithelial, and epithelium thickening, hyperplasia and telangiectasis in the gills, discolouration, change in form and consistent alterations involving hyperplasia, narrowing of the central nerve, necrosis, pkynosis, blood congestion and vacuolation of the liver, mild hyperplasia and inflammatory responses in the muscle of the fish. The severity of histological alteration was more pronounced in fish organs exposed to 5.50 ppm of glyphosate concentration. This study concluded that the toxicant (glyphosate) is highly toxic to C. gariepinus particularly at a concentration of 5.50 ppm, therefore its use near farm lands or adjacent water bodies should be discouraged.

Malathion-Induced Hematoxicity and Its Recovery Pattern in Barbonymus gonionotus

An experiment was conducted to assess malathion-induced hematological responses of Barbonymus gonionotus (silver barb) and its recovery patterns in malathion-free water. Fish (45 days old) were exposed to two sublethal concentrations, namely, 25% and 50% (i.e., 3.78 and 7.56 ppm) of LC50 (15.13 ppm) of malathion for 28 days, followed by a postexposure recovery period for the same time. The hematological parameters were examined after 1, 7, 14, 21, and 28 days of exposure as well as after the postexposure recovery time. Except in the case of the control group (0% of malathion), the obtained results revealed that malathion exposure resulted in significantly ( p < 0.05 ) higher prevalence and severity of micronucleus and lower values of Hb, PCV, and RBC and significantly higher values of WBC in a concentration- and time-dependent manner. The values of blood glucose, MCV, MCH, and MCHC showed mixed trends during the experiment. During the recovery period, all blood parameters (micronucleus, glucose, Hb, PCV, RBC, WBC, MCV, MCH, and MCHC) partially recovered, which means that the recovery period was not long enough for the organisms to recover from the previous exposure. The study thus confirms that hematology is a sensitive indicator for fish to detect toxicity caused by different chemicals. Changes in these parameters can provide useful information about environmental conditions and risk assessment of aquatic organisms.

Echinocandin Drugs Induce Differential Effects in Cytokinesis Progression and Cell Integrity

Fission yeast contains three essential β(1,3)-D-glucan synthases (GSs), Bgs1, Bgs3, and Bgs4, with non-overlapping roles in cell integrity and morphogenesis. Only the bgs4+ mutants pbr1-8 and pbr1-6 exhibit resistance to GS inhibitors, even in the presence of the wild-type (WT) sequences of bgs1+ and bgs3+. Thus, Bgs1 and Bgs3 functions seem to be unaffected by those GS inhibitors. To learn more about echinocandins’ mechanism of action and resistance, cytokinesis progression and cell death were examined by time-lapse fluorescence microscopy in WT and pbr1-8 cells at the start of treatment with sublethal and lethal concentrations of anidulafungin, caspofungin, and micafungin. In WT, sublethal concentrations of the three drugs caused abundant cell death that was either suppressed (anidulafungin and micafungin) or greatly reduced (caspofungin) in pbr1-8 cells. Interestingly, the lethal concentrations induced differential phenotypes depending on the echinocandin used. Anidulafungin and caspofungin were mostly fungistatic, heavily impairing cytokinesis progression in both WT and pbr1-8. As with sublethal concentrations, lethal concentrations of micafungin were primarily fungicidal in WT cells, causing cell lysis without impairing cytokinesis. The lytic phenotype was suppressed again in pbr1-8 cells. Our results suggest that micafungin always exerts its fungicidal effect by solely inhibiting Bgs4. In contrast, lethal concentrations of anidulafungin and caspofungin cause an early cytokinesis arrest, probably by the combined inhibition of several GSs.

Sublethal Effects of Imidacloprid on Fecundity, Apoptosis and Virus Transmission in the Small Brown Planthopper Laodelphax striatellus

Laodelphax striatellus damages plants directly through sucking plant sap and indirectly as a vector of rice stripe virus (RSV), resulting in serious losses of rice yield. It is one of the most destructive insects of rice in East Asia. Insecticides are primarily used for pest management, but the sublethal concentrations of insecticides may benefit several insects. The present research attempted to explore the effects of sublethal concentrations of imidacloprid on the fecundity, apoptosis and RSV transmission in the viruliferous SBPH. The results showed that the fecundity of SBPH was significantly increased after treatment with the LC10 dose of imidacloprid, while the LC30 dose of imidacloprid reduced the fecundity compared with the control. To further investigate the underlying mechanism of increased fecundity after exposure to the LC10 dose of imidacloprid, we examined the expression levels of vitellogenin (Vg), Vg receptor (VgR) and caspases in the ovaries of SBPH, and observed the apoptosis by terminal deoxynucleotidyl transferase (TDT)-mediated dUTP-digoxigenin nick end labeling (TUNEL). qRT-PCR results indicated that the expression levels of Vg, VgR and four caspase genes were all significantly increased by the LC10 dose of imidacloprid, and TUNEL assays suggested that the frequency of apoptosis was significantly higher in the SBPH treated by the LC10 dose of imidacloprid, suggesting a potential correlation between the increased fecundity and the apoptosis of SBPH ovarioles. Additionally, the expression levels of RNA3 and capsid protein (CP) were both increased significantly by the LC10 dose of imidacloprid, whereas were decreased by the LC30 dose of imidacloprid compared to the control. Therefore, this study clarifies the mechanisms of sublethal effects of imidacloprid on viruliferous SBPH and could be used to optimize pest control strategies.

INDUCTION OF MACROCYTIC-NORMOCHROMIC ANAEMIA IN Clarias gariepinus –Siluriform- EXPOSED TO SUB-LETHAL CONCENTRATIONS OF 1, 1-DIMETHYL 4, 4-BIPIRIDILLIUM DICHLORIDE (PARAQUAT) UNDER LABPRATORY CONDITIONS

Introduction: Macrocytic-normochromic anaemia was induced in Clarias gariepinus at intervals of 1, 7 and 14 days. Experimental fish were exposed to test water separately diluted with sub-lethal concentrations of paraquat of 0, 0.03, 0.05, 0.07 and 0.09mg/L. 14 days. No in-depth work has been carried out on Macrocytic-normochromic anaemia in Nigeria. Objective: to evaluate macrocytic-normochromic anaemia in Clarias gariepinus exposed to sublethal concentrations of paraquat. Methods: Blood were collected at intervals of 1, 7 and 14 days .Results: Blood dyscrasias was observed with a significant (p<0.05) decrease in haemoglobin, haematocrit, red blood cells, white blood cells, lymphocytes and monocytes. Mean corpuscular volume (MCV), Mean corpuscular haemoglobin (MCH), Neutrophils, Eosinophil and Basophil increased significantly (p<0.05) with increasing concentrations of the toxicant while Mean corpuscular haemoglobin concentration (MCHC) remained normal. Conclusion: Sublethal concentrations of paraquat induced macrocytic-normochromic anaemia in the exposed Clarias gariepinus.

Antifungal activity of volatile compounds generated by endophytic fungi Sarocladium brachiariae HND5 against Fusarium oxysporum f. sp. cubense

The soil-born filamentous fungal pathogen Fusarium oxysporum f. sp. cubense (FOC), which causes vascular wilt disease in banana plants, is one of the most economically important Fusarium species. Biocontrol using endophytic microorganisms is among the most effective methods for controlling banana Fusarium wilt. In this study, volatile organic compounds (VOCs) showed strong antifungal activity against FOC. Seventeen compounds were identified from the VOCs produced by endophytic fungi Sarocladium brachiariae HND5, and three (2-methoxy-4-vinylphenol, 3,4-dimethoxystyrol and caryophyllene) showed antifungal activity against FOC with 50% effective concentrations of 36, 60 and 2900 μL/L headspace, respectively. Transmission electron microscopy (TEM) and double fluorescence staining revealed that 2-methoxy-4-vinylphenol and 3,4-dimethoxystyrol damaged the plasma membranes, resulting in cell death. 3,4-dimethoxystyrol also could induce expression of chitin synthases genes and altered the cell walls of FOC hyphae. Dichloro-dihydro-fluorescein diacetate staining indicated the caryophyllene induced accumulation of reactive oxygen species (ROS) in FOC hyphae. FOC secondary metabolism also responded to active VOC challenge by producing less fusaric acid and expressions of genes related to fusaric acid production were interrupted at sublethal concentrations. These findings indicate the potential of S. brachiariae HND5 as a biocontrol agent against FOC and the antifungal VOCs as fumigants.

Gregarines modulate insect responses to sublethal insecticide residues

Throughout their lifetime, insects face multiple environmental challenges that influence their performance. Gregarines are prevalent endoparasites in most invertebrates that affect the fitness of their hosts, but are often overlooked in ecological studies. Next to such biotic factors, a current common challenge is anthropogenic pollution with pesticides, which causes a major threat to non-target organisms that are readily exposed to lethal or sublethal concentrations. In a laboratory study, we investigated whether the presence of gregarines modulates the food consumption and life history traits of a (non-target) leaf beetle species, Phaedon cochleariae, in response to sublethal insecticide exposure. We show that the larval food consumption of the herbivore was neither affected by gregarine infection nor sublethal insecticide exposure. Nevertheless, infection with gregarines led to a delayed development, while insecticide exposure resulted in a lower body mass of adult males and a reduced reproduction of females. Individuals exposed to both challenges suffered most, as they had the lowest survival probability. This indicates detrimental effects on the population dynamics of non-target insects infected with naturally occurring gregarines that face additional stress from agrochemical pollution. Moreover, we found that the infection load with gregarines was higher in individuals exposed to sublethal insecticide concentrations compared to unexposed individuals. To counteract the global decline of insects, the potential of natural parasite infections in modulating insect responses to anthropogenic and non-anthropogenic environmental factors should be considered in ecological risk assessment.

Haemato-biochemical and ionic regulatory responses of the hybrid catfish, Heteroclarias, to sublethal concentrations of palm oil mill effluents

Background Pollution arising from the noxiousness of palm oil mill effluent (POME) has become a serious threat to aquatic biotas. However, a paucity of information exists on fish response to POME-mediated oxidative stress, lipid peroxidation, haemato-biochemical, enzymatic and ionic changes. This study, therefore, evaluates the effects of 28-day exposure of Heteroclarias, a hybrid catfish, to POME. Juvenile Heteroclarias (n = 350, average weight: 11.90 ± 0.70 g and average length: 9.04 ± 0.71 cm) were exposed to sublethal concentrations (0-control, 4.00, 8.00 and 12.00 mg/l) of POME to determine its effects on red blood cells (RBC), haemoglobin (HB), packed cell volume (PCV), white blood cells (WBC), mean cell haemoglobin (MCH), mean cell haemoglobin concentration (MCHC) and mean cell volume (MCV). The activities of alanine aminotransaminase (ALT), aspartate aminotransaminase (AST), lactate dehydrogenase (LDH), catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPx) and the levels of malondialdehyde (MDA), calcium (Ca+), potassium (K+), magnesium (Mg2+) and sodium (Na+) ions were also assayed in the gill and liver. Results Exposure to POME caused significant (p < 0.05) concentration-dependent decrease in RBC, HB, PCV, MCV, MCH and MCHC values, whereas a significant (p < 0.05) concentration-dependent increase in WBC was observed in POME-exposed fish compared to the control. ALT, AST, LDH, GPx, SOD and CAT activities in the gill and liver significantly (p < 0.05) increased in a concentration-dependent manner. MDA level significantly (p < 0.05) increased in the gill relative to control, while in the liver it was insignificantly different. Both tissues exhibited an increase in Ca+, K+, Mg2+ and Na+ levels at the highest toxicant concentration with a rise of 77.93, 38.46, 109.54 and 41.99% recorded for the electrolytes in the gill and 79.17, 26.92, 55.48 and 38.78% in the liver above the control value, respectively. The levels of all the electrolytes except K+ were higher in the gill than the liver and were in the order: Na+ > K+ > Mg+ > Ca2+ in both tissues. Conclusions These results may be used as a suitable tool for pollution assessment and policy formulation to mitigate the discharge of untreated POME into aquatic ecosystems and their impacts on resident organisms.