Effect of Copper Sulphate (CuSO4) on Freshwater Snail, Physa acuta Draparnaud, 1805: A Histopathological Evaluation

Impact of copper sulphate treatment on cyanobacterial blooms and subsequent water quality risks

Control of algal blooms and associated biologically-induced water quality risks in drinking reservoirs is problematic. Copper sulphate (CuSO4) treatment is one intervention that has been utilised for >100 years. Evidence indicates a favourable short-term reduction in Cyanobacterial biomass (e.g. bloom termination), but here we indicate that it may also increase longer-term water quality risk. In 2022, we investigated the impacts of CuSO4 spraying on Cyanobacterial communities and nutrient levels within a drinking water supply reservoir using environmental DNA (eDNA) to assess community shifts, alongside monitoring nutrient fractions, orthophosphate (OP) and total phosphate (TP), post-treatment. CuSO4 application successfully reduced Cyanobacterial abundance, however elimination of Cyanobacteria resulted in a shift in bacterial dominance favouring Planctomycetota throughout the summer and a combination of Actinobacteriota and Verrucomicrobiota, throughout autumn. As Cyanobacterial abundance recovered post-treatment, Cyanobacterial genera demonstrated greater diversity compared to only three Cyanobacterial genera present across samples pre-treatment, and included taxa associated with water quality risk (e.g. taste and odour (T&O) metabolite and toxin producers). The increase in Cyanobacteria post-treatment was attributed to an increase in biologically available nutrients, primarily a significant increase in OP. Overall, findings suggest that the significant shift in biodiversity likely induces a less stable ecosystem with greater plasticity of response to changing environmental and biogeochemical variables. Legacy implications of CuSO4 spraying, in terms of shifts in ecosystem and nutrient balance over time, may have implications for drinking water quality, but importantly also for reservoir management options. As such, the effects of CuSO4 spraying should be considered carefully before consideration as a contender for in-reservoir biological control.

Metabolomic changes in Cryptocaryon irritans from Larimichthys crocea after exposure to copper plate

Cryptocaryon irritans is a highly detrimental parasite in mariculture, causing significant economic losses to the aquaculture industry of Larimichthys crocea. In recent years, copper and copper alloy materials have been used to kill parasites. In this study, the effect of copper plates on the tomont period of C. irritans was explored. The findings indicated that copper plates effectively eradicated tomonts, resulting in a hatching rate of 0. The metabolomic analysis revealed that a total of 2,663 differentially expressed metabolites (1,032 up-regulated and 1,631 down-regulated) were screened in the positive ion mode, and 2,199 differentially expressed metabolites (840 up-regulated and 1,359 down-regulated) were screened in the negative ion mode. L-arginine and L-aspartic acid could be used as potential biomarkers. Copper plate treatment affected 25 metabolic pathways in the tomont, most notably influencing histidine metabolism, retinol metabolism, the biosynthesis of phenylalanine, tyrosine, and tryptophan, as well as arginine and proline metabolism. It was shown that high concentrations of copper ions caused a certain degree of disruption to the metabolome of tomonts in C. irritans, thereby impacting their metabolic processes. Consequently, this disturbance ultimately leads to the rapid demise of tomonts upon exposure to copper plates. The metabolomic changes observed in this study elucidate the lethal impact of copper on C. irritans tomonts, providing valuable reference data for the prevention and control of C. irritans in aquaculture.

Histopathological Evaluation of the Curative Effects of EDTA on Lymnaea stagnalis Exposed to Subacute Cadmium

We investigated the therapeutic effects of EDTA application for 14 and 28 days on cadmium (Cd) induced pond snail Lymnaea stagnalis (Linnaeus, 1758). The sublethal concentration of cadmium (63.4 mg/l Cd) caused tissue damages to the snail after an exposure for 28 days.In the groups treated with EDTA, the concentration of Cd in the foot, mantle and hepatopancreas tissues showed significantly decreased during the recovery period. The curative effects of EDTA on Cd-induced damage were assessed using a scoring system. Cadmium exposure led to histopathological changes including increased mucositis, pigment and protein cells, foot epithelium desquamation, muscle fibril damage, connective tissue cell atrophy, and increased lipid vacuoles in the mantle and hepatopancreas. However, these changes were less severe in snails treated with EDTA (2.00 mL/L for 28 day), indicating that EDTA reduces their susceptibility to heavy metal toxicity.

Recent Trends in S. aureus and E. coli-Based Endometritis, and the Therapeutic Evaluation of Sodium Alginate-Based Antibiotics and Nanoparticles

Postpartum infection of the uterus by pathogenic bacteria is exacerbated due to a lack of sufficient epidemiological studies and evidence-based therapeutics. Therefore, this study was planned to find the prevalence, risk factors, and drug-resistance profile of S. aureus and E. coli isolated from bovine endometritis and to evaluate the antibacterial potential of sodium alginate-based antibiotics and nanoparticles. The study revealed 34.21% S. aureus and 31.57% E. coli, whereas most of the assumed risk factors presented significant association in this study. S. aureus showed the highest resistance against fusidic acid (60%) and cefoxitin (50%), while the highest resistance in E. coli was found against fusidic acid (60%), gentamicin (60%), chloramphenicol (50%), and cefoxitin (50%). Tylosin coupled with MgO nanoparticles stabilized in sodium alginate gel (Tylo + MgO + gel) presented significantly lower minimum inhibitory concentration (MIC) against E. coli, showing 13.88 ± 4.51 µg/mL after 24 h incubation. On the other hand, gel-based preparations showed MIC as 31.25 ± 0 µg/mL (Tylo + gel + MgO) and 26.04 ± 9.02 µg/mL (Tylo + Gel) against S. aureus. Generally, the MICs of non-gel-based preparations were significantly higher against bacteria except ampicillin against S. aureus in this study. The toxicity analysis of MgO nanoparticles presented 20-80% mortality of snails against a wider range of 0.01 mg/mL-10 mg/mL. The histopathological parameters concluded MgO nanoparticles safe to use on off targets. The current study thus concludes the rise in antimicrobial resistance while the gel-based products appearing as effective antimicrobials with sufficient safety margins for off-targets. The study thus invites further investigation for the development of suitable and affordable modified therapeutics for better health and production of animals.

Evaluation of Sodium Alginate Stabilized Nanoparticles and Antibiotics against Drug Resistant Escherichia coli Isolated from Gut of Houbara Bustard Bird

Alternative approaches and/or modified approaches to tackle resistance in gut microbes are need of the hour. The current study was planned to find the resistance modulation and toxicity potential of sodium alginate stabilized MgO nanoparticles and antibiotics against Escherichia coli (E. coli) isolated from the gut of Houbara bustard bird ( $n=105$ fecal samples). The preparations consisted of gel stabilized ampicillin (G+A), gel stabilized MgO and ampicillin (G+M+A), gel stabilized MgO and cefoxitin (G+M+C), gel stabilized tylosin (G+T), gel stabilized MgO and tylosin (G+M+T), and gel stabilized MgO (M+G). The fecal samples showed 53% (56/105) prevalence of E. coli which was found to be significantly ( $p<0.05$ ) associated with most of the assumed factors and resistant to multiple drugs. G+M+T showed the lowest ( $4.883\pm 0.00$ μg/mL) minimum inhibitory concentration (MIC) followed G+M+C, G+M+A, G+A, M+G, and G+T. Significant reduction ( $p<0.05$ ) in MIC with respect to incubation interval found at the 16th hr for G+M+A, G+A, and G+M+C that further remained nonsignificant ( $p>0.05$ ) onwards until the 24th hr of incubation. In the case of G+T and M+G, significant reduction in MIC was found at the 20th hr and 24th hr of incubation. Ecotoxicology and histopathology trials on snails showed mild changes in MICs of the preparations. The study thus concluded increasing drug resistance in E. coli of houbara bird while sodium alginate stabilized MgO nanoparticles and antibiotics were effective alternative antibacterial composites with mild toxicity.

Molluscicidal and biochemical effects of green-synthesized F-doped ZnO nanoparticles against land snail Monacha cartusiana under laboratory and field conditions

The glass clover snail, Monacha cartusiana (M. cartusiana) is one of the most seriously impacting economic animal pests spreading across Egypt which inflicts severe damages to the agriculture. A green route is developed by deploying an abundant Rosemary plant leaves aqueous extract to synthesize ZnO and F-doped ZnO (F-ZnO) nanoparticles (NPs) that display high molluscicidal activities against the M. cartusiana land snails via leaf dipping and contact techniques. The effect of lethal concentrations, that kills 50% of exposed snails (LC50) value of the treatments, is examined on the activity of alkaline phosphatase (ALP), aspartate aminotransferase (AST), alanine aminotransferase (ALT), enzymes, total protein (TP), total lipids (TL) and cholesterol level of snails, including the histopathological evaluation of the digestive gland and foot of M. Cartusiana. Their molluscicidal activity as poisonous baits under field conditions is also evaluated and compared to the recommended molluscicide, Neomyl. The results show that F^- doping dramatically improves the snail control capability of ZnO NPs, and promotes a considerable increase in both ALT and AST enzymes with an enhancement of TL and Cholesterol levels, but a significant decrease in TP content and ALP activity in treated snails compared to the control group. The LC₅₀ values are found to be 1381.55 and 2197.59 ppm using the leaf dipping for F-ZnO and ZnO, while 237.51 and 245.90 ppm can be achieved using the contact technique, respectively. The greenly synthesized F-ZnO and ZnO NPs induce severe histological alterations in the digestive gland and foot of M. cartusiana, including a complete destruction of the digestive tubules. The histological evaluation of the foot of M. cartusiana exposed to ZnO, shows a rupture of the epithelial layer of the foot sole, while F- ZnO NPs causes the folds of the foot becoming deeper and the rupture of epithelial layer. Our field experiments further demonstrate that F-ZnO achieves 60.08% reduction, while ZnO attains 56.39% diminution in snail population compared to the commercial, Neomyl (69.55%), exhibiting great potentials in controlling the harmful land snail populations.

The Danubian cryptic invader Theodoxus fluviatilis (Gastropoda: Neritidae) in the River Rhine: a potential indicator for metal pollution?

Metal pollution poses a major threat to aquatic systems especially in anthropogenic influenced areas, in as much as metals are persistent in the environment. The freshwater snail Theodoxus fluviatilis has often been used as an indicator species for the ecological status in river monitoring. In the River Rhine, the native Northern-European form of T. fluviatilis is nowadays extinct, whilst the Danubian form is spreading along the river. The aim of our study was to investigate if the cryptic invader is affected by metal exposure present in the River Rhine and to discuss its potential as an indicator for metal pollution. Several environmental abiotic (14 water environmental variables plus five common metal concentrations in water and biofilm) and biotic parameters (biofilm mass) were measured across 23 sites along the River Rhine. Five population and six histopathological parameters were evaluated on snails collected at all 23 sites. Aqueous chromium concentration was positively correlated to the damage of male reproductive organs of T. fluviatilis, and higher ammonium concentration was correlated to a decrease in snail size and an increase in the proportion of juveniles. None of the analysed snail parameters was negatively correlated to concentrations of other metals measured, like copper and zinc. Therefore, based on the parameters evaluated, our results indicate that the Danubian form of T. fluviatilis is only restrictedly suitable as an indicator for metal pollution in the River Rhine system. Further field and laboratory investigations including other stressors are necessary to evaluate the indicator potential of the cryptic invader holistically.

Comparative Assessment of Cadmium and Copper Toxicity to Physa acuta (Draparnaud, 1805)

Cadmium and copper toxicity was investigated using bioassays with neonates of a freshwater gastropod Physa acuta. Mortality, lethal time, and effects on shell length were studied during 28-day chronic exposure experiments. Relative toxicity was assessed from acute and chronic LC values. Copper showed significantly more toxicity at lower concentrations than cadmium ([Formula: see text] < 0.001), causing mortality at the same response levels. Conversely, cadmium affected shell length at lower concentrations than copper, although no significant differences ([Formula: see text] > 0.05) were found in affected shell length between copper and cadmium at the end of the assays. Lethal time (LT[Formula: see text]) was significantly affected by metal concentration ([Formula: see text] < 0.001), with a reduction of 8.28% and 5.90% in time per 0.001 mg/L increase of copper and cadmium, respectively. Physa acuta neonates showed medium to high sensitivity to cadmium and copper compared to other freshwater gastropod species, showing it is a suitable test organism, particularly for chronic ecotoxicological assessment.