The effect of copper, zinc, mercury and cadmium on some sperm enzyme activities in the common carp (Cyprinus carpio L.)

Effect of different sizes of nanocopper particles on rainbow trout (Oncorhynchus mykiss W.) spermatozoa motility kinematics

In recent years, nanocopper (Cu NPs) has gained attention due to its antimicrobial properties and potential for industrial, agricultural, and consumer applications. But it also has several effects on the aquatic environment. Widespread use of various nanoproducts has raised concerns about impacts of different nanoparticle size on environment and biological objects. Spermatozoa is a model for studying the ecotoxic effects of pollutants on cells and organisms. This study aimed to investigate the effects of different sizes of copper nanoparticles on rainbow trout spermatozoa motility, and to compare their effects with copper ionic solution. Computer assisted sperm analysis (CASA) was used to detect movement parameters at activation of gametes (direct effect) with milieu containing nanocopper of primary particle size of 40-60, 60-80 and 100 nm. The effect of the elements ions was also tested using copper sulfate solution. All products was prepared in concentration of 0, 1, 5, 50, 125, 250, 350, 500, 750, and 1000 mg Cu L-1. Six motility parameters were selected for analysis. The harmful effect of Cu NPS nanoparticle was lower than ionic form of copper but the effect depends on the motility parameters. Ionic form caused complete immobilization (MOT = 0 %, IC100) at 350 mg Cu L-1 whilst Cu NPs solution only decreased the percentage of motile sperm (MOT) up to 76.4 % at highest concentration tested of 1000 mg Cu L-1 of 40-60 nm NPs. Cu NPs of smaller particles size had more deleterious effect than the bigger one particularly in percentage of MOT and for curvilinear velocity (VCL). Moreover, nanoparticles decrease motility duration (MD). This may influence fertility because the first two parameters positively correlate with fertilization rate. However, the ionic form of copper has deleterious effect on the percentage of MOT and linearity (LIN), but in some concentrations it slightly increases VCL and MD.

Improved Expression of a Thermostable GH18 Bacterial Chitinase in Two Different Escherichia coli Strains and Its Potential Use in Plant Protection and Biocontrol of Phytopathogenic Fungi

Chitinases are enzymes that can break down chitin, a major component of the exoskeleton of insects and fungi. This feature makes them potential biopesticides in agriculture since they are considered a safe and environmentally friendly alternative to synthetic pesticides. In this work, we performed a comparative study between two different bacterial expression strains to produce a recombinant chitinase with improved stability. Escherichia coli strains Origami B and BL21 (DE3) were selected for their distinct cytosolic environment to express BhChitA chitinase of Bacillus halodurans C-125 and to investigate the role of disulfide bond formation and proper folding on its stability and activity. Expression of the recombinant BhChitA in bacterial strain containing oxidative cytosol (Origami B) improved its activity and stability. Although both expression systems have comparable biochemical properties (temperature range 20-80 °C and pH spectrum 3-10), BhChitA expressed in Origami strain seems more stable than expressed in BL21. Furthermore, the optimal expression conditions of the recombinant BhChitA has been carried out at 30 °C during 6 h for the Origami strain, against 20 °C during 2 h for BL21. On the other hand, no significant differences were detected between the two enzymes when the effect of metal ions was tested. These findings correlate with the analysis of the overall structure of BhChitA. The model structure permitted to localize disulfide bond, which form a stable connection between the substrate-binding residues and the hydrophobic core. This link is required for efficient binding of the chitin insertion domain to the substrate. BhChitA exhibited in vitro antifungal effect against phytopathogenic fungi and suppressed necrosis of Botrytis cinerea on detached tomato leaves. In vitro assays showed the influence of BhChitA on growth suppression of Botrytis cinerea (53%) Aspergillus niger (65%), Fusarium graminearum (25%), and Fusarium oxysporum (34%). Our results highlight the importance of the bacterial expression system with oxidative cytosol in producing promising biopesticides that can be applied for post-harvest processing and crop protection.

Effect of Aluminum Concentration in Water on Its Toxicity and Bioaccumulation in Zooplankton (Chaoborus and Chironomus) and Carp (Cyprinus carpio L.) Roe

An attempt to evaluate aluminum toxicity to living organisms was undertaken in the study. A laboratory experiment was conducted to determine aluminum bioaccumulation and toxicity in Chironomus and Chaoborus larvae and in Cyprinus carpio L. roe depending on aluminum concentration in water reflecting natural chemical composition. Water was examined for temperature, pH, electrical conductivity, dissolved oxygen, color, nitrate nitrogen, nitrite nitrogen, sulfates by spectrophotometric method; total hardness and chlorides by titration method; and calcium, magnesium, sodium by flame atomic absorption spectrometry, total aluminum by electrothermal atomic absorption spectrometry. Determination of aluminum levels in water, roe, and zooplankton was carried out after mineralization using electrothermal atomic absorption spectrometry. Aluminum bioaccumulation factor in roe was determined with respect to concentration in water. Moreover, acute toxicity (LC50) was calculated. In the roe experiment, aluminum concentration in water at the end of the experiment was 0.0635-0.1283 mgAl∙dm-3. The lowest values were noted for the control sample and the highest for water with 0.03 mgAl∙dm-3 aluminum content. The final aluminum level in roe was, like in water, the highest in roe treated with 0.03 mgAl∙dm-3 (18.95 mgAl∙kg-1), and the lowest in roe treated with 3.00 mgAl∙dm-3 (6.96 mgAl∙kg-1). Aluminum bioaccumulation in roe was the strongest in the control. Survival rate ranged from 2.00 to 97.00%, which shows higher sensitivity of roe to aluminum concentration. LC50 value for Chaoborus was 0.6464 mgAl⋅dm-3, and for Chironomus 0.2076 mgAl⋅dm-3 indicating that Chironomus is more sensitive to aluminum toxic effects. Concentration of 3.0 mgAl∙dm-3 caused the highest mortality. Aluminum in both species at each concentration reached the highest levels after one day (24 h), 254.58 mg⋅kg-1 for Chaoborus and 3107 mg⋅kg-1 for Chironomus. After another day, aluminum levels decreased. This demonstrated the differential accumulation of aluminum depending on the species, which predisposes Chironomus as a better indicator organism. This type of research is important from the point of view of aquaculture, which is a targeted activity with a high degree of economic importance, but is also important for aquatic organisms living in natural conditions. Fish reproduction takes place in both types of waters, so all these reservoirs regardless of their source of destination should be inspected.

The Effect of Copper and Copper Oxide Nanoparticles on Rainbow Trout (Oncorhynchus mykiss W.) Spermatozoa Motility after Incubation with Contaminants

The study aimed to analyse the effect of copper nanoparticles of similar particle size of Cu and CuO and copper ions (CuSO4) on the motility parameters of rainbow trout spermatozoa after long-term exposure and compare its harmful effect. Nanoproducts of Cu and CuO (Cu NPs, CuO NPs) of primary particle size around 50 nm and ionic solution of CuSO4 were used for the study. Suspension of concentrations 0, 1, 5, 10, 25, and 50 mg Cu·L−1 of Cu NPs, CuO NPs, and CuSO4 was dissolved in an artificial seminal plasma. Milt was mixed with the prepared solution and stored in a fridge, at 6 °C, for 96 h. At the defined incubation time, spermatozoa were activated for movement, and six motility parameters were evaluated using an automated system (CASA). Increasing concentrations of Cu NPs, CuO NPs, and CuSO4 in an incubation medium in parallel decreased the percentage of motile sperm (MOT). The effect of Cu NPs and ionic copper on MOT was more deleterious than that of CuO NPs. Copper products slightly increased the velocity (VCL) compared to the control, particularly up to 24 h of storage. Linearity (LIN) was improved by three tested products, particularly CuO NPs. Generally, the motility duration was prolonged when the sperm was incubated with copper products compared to the control. Nanoproducts made from different compounds of the same elements of similar particle size have a different effect on cells. Cu NPs were more harmful than CuO NPs. The effect of Cu NPs was similar to an ionic form of CuSO4. When incubated, the copper nanoproducts and ionic form exert a slightly positive effect on spermatozoa velocity, linearity, and motility duration, particularly up to 24 h of storage.

Effect of age on the mercury sensitivity of zebrafish (Danio rerio) sperm

The effect of age on the sensitivity of zebrafish sperm against mercury exposure was investigated in the present study. Although results of the use of sperm from mature individuals for toxicity tests have been published, there is no information about the exact age of the fish in some cases, which can affect the results. During the experiments, pooled sperm was stripped from males of 7, 12, or 18 months of age, divided into 5 sub-groups, diluted with different concentrations of Hg (0, 0.5, 1, 2.5, and 5 mg/L Hg), and incubated for 240 min. The motility parameters of sperm (progressive motility (%), curvilinear velocity (VCL)) were measured by a computer-assisted sperm analysis system, at 30, 120, and 240 min of exposure. Regarding the age, significant differences were found in PMOT (p = 0.0267) as well as in VCL (p = 0.0004) among the three different age groups. The different concentrations of Hg also caused significant differences. The most significant differences in PMOT were between the 7- and 18-month-old groups; these differences were observed at 0.5, 1 and 2.5 mg/L Hg at 30 min, at 0.5 and 1 mg/L at 120 min, as well as at 0.5 mg/L at 240 min. In VCL the most significant differences were found between the 7- and 12-month-old groups; significant differences were found at each tested concentration at 30 min as well as at 0.5 and 2.5 mg/L at 240 min. According to the results, the age of zebrafish negatively influences the sensitivity of its sperm. This may concern not only toxicology tests but many techniques in fish breeding where the sperm is treated before use (cryopreservation, pressure shock, etc.).

Investigation of Fertilizing Capacity of Zebrafish (Danio rerio) Sperm Exposed to Heavy Metals

The objective of our study was to investigate the effects of heavy metals on the fertilizing capacity of exposed zebrafish sperm, on embryonic survival, and on occurrence of embryonic deformities following fertilization with exposed sperm. It is important to test heavy metals because they are well-known pollutants. Sperm of externally fertilizing species can get in contact with pollutants found in aquatic environment. Zebrafish sperm, despite its advantages, has seldom been used in in vitro toxicological studies and no reports are available regarding the fertilizing capacity of exposed sperm. Zebrafish sperm was stripped and exposed to concentrations of the tested heavy metals (Zn²⁺, Cd²⁺, Cr³⁺, Cu²⁺, Ni²⁺, Hg²⁺, As³⁺) for 30 or 120 minutes. Calculated half-maximal effective concentration (EC₅₀) values do not differ significantly from those calculated for motility for any of the tested heavy metals, which means fertilization rate can indicate the toxicity of the given substance following exposure of sperm. Thus, its application as in vitro toxicological end point is reasonable. The survival of embryos and embryonic development have not been affected by the exposure of spermatozoa, which means all alterations in spermatozoa caused by heavy metals have been expressed before 24 hours post fertilization.

Life-time exposure to waterborne copper IV: Sperm quality parameters are negatively affected in the killifish Poecilia vivipara

In previous studies, we have shown that copper (Cu) is significantly accumulated in various tissues of killifish Poecilia vivipara following chronic exposure. Also, we showed that chronic metal exposure disrupted energy production and growth in this species. In the present study, we aimed to evaluate if chronic exposure to this metal could also affect reproductive parameters of P. vivipara males (sperm quality). In order to test that, newborn (<24 h-old) fish were exposed to two concentrations of waterborne Cu (5 and 9 μg/L) for 345 days. After exposure, fish were euthanized and the testes were collected for sperm analysis. We could observe that exposed animals had reduced sperm motility and period of motility. Also, the sperm of exposed fish had reduced plasma membrane integrity, mitochondrial functionality and DNA integrity when compared to sperm of control animals. It is suggested that the well-known association of Cu with elevated oxidative damage, endocrine disruption and energetic disturbance are involved with the observed outcomes. The results obtained in the present study show that chronic exposure to environmentally relevant concentrations of waterborne Cu caused reductions in all parameters used to evaluate sperm quality. Therefore, it is concluded that life-time exposure to this metal may disrupt fish reproduction and negatively affect the maintenance of its populations.

Sperm quality in fish: Determinants and affecting factors

Fish sperm quality assessment is helpful for optimizing production and for monitoring the environmental state. Sperm can be monitored relatively easy and, to date, various analyses have been applied and proven to be helpful in this task. Among them, sperm motility parameters such as sperm speed are one of the main performance traits during assisted fish reproduction. Apart from motility the sperm concentration, volume, and seminal plasma pH and osmolality are also frequently evaluated and are the main sperm quality indicators measured in fish sperm. However, other parameters also determine sperm fertilization potential. Recent knowledge reveals several additional parameters of high importance for sperm function. Among them are DNA integration, membrane stability, mitochondria status and enzymatic activity. Measuring all these parameters in fish sperm provides complex knowledge regarding male fertility and helps to improve broodstock maintenance protocols as well as gamete handling and fertilization processes. This review focuses on the presentation of the sperm quality measures for freshwater and marine species of the fish and provides information regarding recent methods of sperm quality evaluation.

Exposure of male tilapia (Oreochromis niloticus) to copper by intraperitoneal injection: DNA damage and larval impairment

The present work aimed to assess the genotoxic effects of intraperitoneally injected copper in males of O. niloticus, and to investigate its association with eventual changes in the quality of the gametes and in the generation of offspring abnormalities. Thus, to evaluate DNA damage, the alkaline comet assay was performed in sperm and blood; sperm parameters were analyzed to determine the quality of the gametes, and the incidence of morphological abnormalities of larvae, originated from eggs fertilized by males exposed to copper, was used as a measure of reproductive impairment. Male fish were exposed to three doses (1 mg/kg, 2 mg/kg, 4 mg/kg) of copper sulfate via intraperitoneal injection and observed after 96 h of exposure. We found that the quality of gametes was not affected by copper, as indicated by the lack of differences in sperm parameters between the exposed and the control groups. Nonetheless, copper induced an increase in sperm DNA damage at all tested doses. Taking into consideration the total number of abnormalities, larvae presented a higher proportion of morphological abnormalities at all the tested doses. Considering the morphological abnormalities separately, the 2 mg/kg and 4 mg/kg groups presented significantly higher frequencies of arrested development and spinal abnormalities than the control group. This work suggests that intraperitoneally injected copper is an inductor of DNA breakage in germ cells of O. niloticus males. Copper induces the formation of larval morphological abnormalities, causing reproductive impairment to this species. The fact that copper did not induce alterations on sperm parameters indicates that the parental genotoxic effects are inheritable to the offspring.

In vitro toxicology test system based on common carp (Cyprinus carpio) sperm analysis

The effect of heavy metals on the motility parameters of common carp sperm was investigated. In vitro test systems are widespread in ecotoxicology, and fish sperm can be a suitable model. For this reason, studies had been carried out in this topic; however, the published methods are not standard in several aspects (donor species, measured endpoint, etc.). In this study, a previously published toxicology-aimed sperm analysis protocol was tested to examine the effect of heavy metals (arsenic, cadmium, chromium, copper, mercury, nickel, zinc,) on common carp sperm. According to our results, PMOT is the most sensitive of the investigated parameters: dose-response was observed in case of each metal at low concentrations, already after 30 min of exposure. VCL was less sensitive: lower effects were observed at the same concentrations compared to PMOT. Among the examined parameters, LIN was the least affected: a dose-response was observed only in case of arsenic and mercury. The same sensitivity of motility parameters was observed on zebrafish sperm previously. Moreover, we found that PMOT, VCL, and LIN of common carp sperm were affected at the same concentrations as it had been observed in zebrafish, when the identical analytical protocol was applied. The only exception was As³⁺, where common carp sperm proved to be more sensitive: lower concentrations already reduced its motility parameters. Consequently, PMOT of common carp sperm is an accurate and fast bioindicator of aquatic pollution.

Effects of fluoride and aluminum on expressions of StAR and P450scc of related steroidogenesis in guinea pigs' testis

A lot of studies have shown that fluoride and aluminum have toxic effect on male reproductive system, but the mechanism of which and the interaction between fluoride and aluminum is still unknown. This study investigated the effects of fluoride (NaF) or/and aluminum (AlCl3) on serum testosterone level, gene and protein expression levels of Steroidogenic Acute Regulatory Protein (StAR) and Cytochrome P450 cholesterol side chain cleavage enzyme (P450scc) in the testes of guinea pigs. Fifty-two guinea pigs were divided randomly into four groups (Control, HiF, HiAl and HiF + HiAl). Fluoride (150 mg NaF/L) or/and aluminum (300 mg AlCl3/L) were orally administrated to male guinea pigs for 13 weeks. The results showed that F and Al reduced number and elevated abnormal ratio of sperm. Meanwhile, the concentrations of serum testosterone in all experimental groups were decreased. P450scc protein expression was significantly reduced in all treatment groups, and StAR expression was decreased remarkably in HiF group and HiF + HiAl group. The levels of StAR mRNA in three groups were reduced by 53.9%, 21.4% and 33.4%, respectively, while the expressions of P450scc mRNA were reduced by 67.8%, 17.0% and 47.8%. Therefore, we concluded that F induced the reduction in testosterone and sperm amount, and thus in lower fertility, which might occur as a consequence of depressed StAR and P450scc mRNA expression. There were no synergistic effects between F and Al, instead, Al weakened the toxicity of F to some extents. The results indicated that Al had antagonism effects on F.

The sperm motility pattern in ecotoxicological tests. The CRYO-Ecotest as a case study

Changes in environmental stressors inevitably lead to an increasing need for innovative and more flexible monitoring tools. The aim of this work has been the characterization of the motility pattern of the cryopreserved sea bream semen after exposure to a dumpsite leachate sample, for the identification of the best representative parameters to be used as endpoints in an ecotoxicological bioassay. Sperm motility has been evaluated either by visual and by computer-assisted analysis; parameters concerning motility on activation and those describing it in the times after activation (duration parameters) have been assessed, discerning them in terms of sensitivity, reliability and methodology of assessment by means of multivariate analyses. The EC50 values of the evaluated endpoints ranged between 2.3 and 4.5ml/L, except for the total motile percentage (aTM, 7.0ml/L), which proved to be the less sensitive among all the tested parameters. According to the multivariate analyses, a difference in sensitivity among "activation" endpoints in respect of "duration" ones can be inferred; on the contrary, endpoints seem to be equally informative either describing total motile sperm or the rapid sub-population, as well as the assessment methodology seems to be not discriminating. In conclusion, the CRYO-Ecotest is a multi-endpoint bioassay that can be considered a promising innovative ecotoxicological tool, characterized by a high plasticity, as its endpoints can be easy tailored each time according to the different needs of the environmental quality assessment programs.

Heterologous expression, purification and biochemical characterization of endochitinase ChiA74 from Bacillus thuringiensis

ChiA74 is a secreted endochitinase produced by Bacillus thuringiensis. Previously we have partially characterized the physical parameters that affect enzymatic activity of ChiA74 in crude preparations of bacterial secretomes. In the present study, we cloned the chiA74 open reading frame (ORF) lacking the 5' sequence coding for its secretion signal peptide (chiA74Δsp) into a cold shock expression vector (pColdI) for production of the enzyme in Escherichia coli BL21-Rosetta 2. As a result, the N-terminal end of ChiA74Δsp ORF was fused to an artificial sequence of 28 amino acid, including a 6× histidine tag for purification of recombinant 6×His tagged-ChiA74Δsp (rChiA74, ∼74kDa). Along with a protein of ∼74kDa, we co-purified its ∼55kDa processed form which was confirmed by Western blot analysis. Optimal endochitinase activity of purified rChiA74 occurred at pH 7 and 40°C. Most divalent cations (e.g. Ba(+2), Ca(+2), Mn(+2), Mg(+2), Zn(+2) and Cu(+2)) at concentration of 10mM reduced chitinase activity by ∼30%, and Hg(+2) (10mM) drastically inhibited ChiA74 activity by ∼75-100%. The Vmax, Km and kcat for rChiA74 were 0.11±0.01nmol/min, 2.15μM±0.45 and 3.81s(-1), respectively, using 4-MU-GlcNAc3 as substrate. Using purified rChiA74 and colloidal chitin as substrate, chitin-derived oligosaccharides with degree of polymerization of 2 and 1 were detected.

The antagonism of aluminum against fluoride-induced oxidative stress and c-Fos overexpression in rat testes

Sodium fluoride (NaF) has been found to interfere with the reproductive system of animals. However, the cellular mechanisms underlying the reproductive toxicity of fluoride are unclear. The present study aims to define a possible mechanism of NaF-induced reproductive toxicity with respect to mineral, oxidative stress and c-Fos expression and the role of aluminum (Al) in intervening the toxic effect of NaF on rat testes. Fifty-six male Wistar rats were treated with normal saline, 1.0, 2.0, and 3.0 mg NaF/kg body weight (bw)/day, and each NaF concentration plus Al ion (0.1 mg Al(3+)/kg bw/day). After 90 days, no significant changes in the contents of Fe and Cu were observed in any of the NaF-treated groups compared with those of the control group. There were, however, significant decreases in the contents of Ca in the 1.0 mg NaF group, Zn in all NaF-treated groups and Mg in the 3.0 mg NaF group. The levels of malondialdehyde (MDA) in the 1.0 mg NaF group and hydrogen peroxide (H2O2) in the 2.0 mg NaF group significantly increased, whereas the activity of nitric oxide synthase (NOS) significantly decreased in the 1.0 mg NaF group. Meanwhile, the protein expression of c-Fos increased significantly in the 1.0 and 2.0 mg NaF groups compared with the control group. Conversely, these changes were partially attenuated in rats simultaneously administered Al. The present study suggested that NaF could decrease the contents of Ca, Fe and Mg and enhance oxidative stress leading to c-Fos overexpression, and some deleterious effects were more prominent at lower NaF intake. Furthermore, Al within the research concentration could minimize reproductive toxicity caused by fluoride.

Involvement of oxidative stress in municipal landfill leachate-induced toxicity in boar sperm

Exposure to leachates generated from an improperly managed hazardous waste dump sites is detrimental to human health and the ecosystem. The present study investigated the effect of Olushosun municipal landfill leachate (OMLL) on sperm characteristics and antioxidant systems in boar sperm cells. The sperm cells were incubated with the leachate at final concentrations of 0, 1, 2, 4 and 8% for 3h at 37 °C. Sperm characteristics were monitored hourly during the incubation period whereas aminotransferases activities and oxidative stress indices were determined after the incubation period. Results revealed a time- and dose-dependent decline in sperm progressive motility from 1h post-treatment with 2, 4 and 8% OMLL whereas decreased sperm viability with elevated abnormalities were observed from 2 h post-treatment with 4 and 8% OMLL when compared with control. Exposure to OMLL caused a significant increase in aminotransferases, catalase and glutathione-S-transferase activities whereas it markedly decreased superoxide dismutase and glutathione peroxidase activities without affecting glutathione level in the treated sperm cells. Co-incubation of sperm with OMLL increased the levels of hydrogen peroxide and malondialdehyde levels. In conclusion, OMLL elicited spermatotoxicity via induction of oxidative stress possibly generated through an enhanced intracellular reactive oxygen species.

Cytotoxic and clastogenic activity of CdCl2 in human lymphocytes from different donors

The sensitivity of human lymphocytes from different donors to CdCl2 using a complex of methods for determination of cytotoxicity and genotoxicity was studied. As endpoints for cytotoxicity the mitotic index (MI) and apoptosis were evaluated. To indicate genotoxicity chromosome aberrations test (CA) was used. The results indicate an individual sensitivity of lymphocytes to CdCl2-induced damage, which is directly depending on the concentration (10(-6), 10(-5), 5×10(-5), 10(-4)mol/l) applied. The assessment of the toxic and genotoxic effect using various endpoints allows more complete risk estimation for organisms exposed to heavy metals. The results have direct practical significance for threat evaluation in humans.

Enzymatic biomarkers as indicators of dietary cadmium in gypsy moth caterpillars

Heavy metals damage the structure, chemistry, and function of cells, including enzyme systems inside them. Variation in the profile of biochemical biomarkers in prevalent species should be used for assessing environmental contamination. The present study pays attention to the phosphatases present in the midgut of gypsy moth fourth instar caterpillars, which had been exposed to short- and long-term cadmium intake at 10 and 30 μg Cd/g dry food. Chronic cadmium ingestion significantly inhibited the activity of all examined phosphatases, while only the activity of lysosomal phosphatase was acutely decreased. Total acid phosphatase activity recovered from both long-term cadmium treatments within 3 days. The low index of phenotypic plasticity was connected to high variability of plasticity. Dependence of phosphatase isoforms on genotype and duration of cadmium treatment was determined. We concluded that, with further investigations, profiling of total acid phosphatase activity, as well as the lysosomal fraction can be used as a biomarker for acute sublethal metal toxicity.

Cryopreserved semen in ecotoxicological bioassays: sensitivity and reliability of cryopreserved Sparus aurata spermatozoa

The aim of this study was to evaluate the feasibility of using cryopreserved S. aurata semen in spermiotoxicity tests. Cryopreservation is a biotechnology that can provide viable gametes and embryos on demand, rather than only in the spawning season, thus overcoming a limitation that has hindered the use of some species in ecotoxicological bioassays. Firstly, the sperm motility pattern of cryopreserved semen was evaluated after thawing by means of both visual and computer-assisted analyses. Motility parameters in the cryopreserved semen did not change significantly in the first hour after thawing, meaning that they were maintained for long enough to enable their use in spermiotoxicity tests. In the second phase of the research, bioassays were performed, using cadmium as the reference toxicant, in order to evaluate the sensitivity of cryopreserved S. aurata semen to ecotoxicological contamination. The sensitivity of the sperm motility parameters used as endpoints (motility percentages and velocities) proved to be comparable to what has been recorded for the fresh semen of other aquatic species (LOECs from 0.02 to 0.03 mg L(-1)). The test showed good reliability and was found to be rapid and easy to perform, requiring only a small volume of the sample. Moreover, cryopreserved semen is easy to store and transfer and makes it possible to perform bioassays in different sites or at different times with the same batch of semen. The proposed bioassay is therefore a promising starting point for the development of toxicity tests that are increasingly tailored to the needs of ecotoxicology and environmental quality evaluation strategies.

Water-quality issues in the Niger Delta of Nigeria: a look at heavy metal levels and some physicochemical properties

INTRODUCTION

Water contamination is a notable environmental problem of the Niger Delta, Nigeria. The present work is an improved attempt at a scientific discourse of water-quality issues in the Niger Delta of Nigeria with respect to heavy metal levels in surface water in view of the hitherto dearth of scientific data.

MATERIALS AND METHODS

We have looked at the Fe, Mn, Cu, Cd, Cr, Pb, Ni, Zn (quantified by atomic absorption spectrophotometry) profiles and some physicochemical properties (pH and salinity) of some surface water used by the local population in the mid Niger Delta. Surface water samples were collected from these surface waters in the dry and rainy seasons.

RESULTS

Akiplai wellhead stream and Etebde River had the highest level of iron. In Delta State, high levels of cadmium were found in Ijala creek, Ubeji creek, Jeddo River, and Ekpan River, respectively. High lead levels were seen in Jeddo River, Ekurede-Itsekiri Creek, and Ughelli River. In River State, Tombia River had the highest levels of chromium, lead, and nickel. Ijala creek, Eja-Etan, Ifie-Kporo, Ubeji Creek, Jeddo, Ekpan Rivers, and Ekurede-Itsekiri Creek, all in Delta State, presented highest salinity levels. Orash River, Ughewhe stream, and Egbo stream have a lowest pH of 5.22, 5.32, and 5.53, respectively, while Ifie-Kporo River have a highest pH of 8.18.

CONCLUSION

Most of the metal levels were above US EPA Maximum Contaminant Level MCL indicative of water pollution which may be of public health importance, and we, therefore, recommend water-quality monitoring.