Assessment of the individual and mixture toxicity of cadmium, copper and oxytetracycline, on the embryo-larval development of the sea urchin Paracentrotus lividus

Florfenicol induces malformations of embryos and causes altered lipid profile, oxidative damage, neurotoxicity, and histological effects on gonads of adult sea urchin, Paracentrotus lividus

The frequent occurrence of antibiotics in the aquatic environment has engendered negative impacts on non-target organisms. The effects of the veterinary antibiotic florfenicol (FLO) during the embryo-larval development of the sea urchin, Paracentrotus lividus was assessed using four increasing concentrations (1, 2, 5 and 10 mg/L). Furthermore, FLO toxicity to adults was investigated through the analysis of oxidative damage, histopathological alterations, lipid metabolism and acetylcholinesterase activity following an exposure period of 96 h. FLO induced embryotoxicity with estimated EC50 values of 5.75, 7.56 and 3.29 mg/L after 12 h, 24 h and 48 h, respectively. It generated oxidative stress assessed as lipid peroxidation in gonads despite the increased antioxidant activity of catalase (CAT). Neurotoxicity was also evident since the AChE activity significantly decreased. Moreover, FLO affected the lipid metabolism by increasing saturated fatty acid (SFA) and monounsaturated fatty acid proportions (MUFA), except in the group exposed to 5 mg/L. The increase in polyunsaturated fatty acid (PUFA) levels and docosahexaenoic acid (DHA, C22:6n-3) proportions were noted with all FLO concentrations. Eicosapentaenoic acid (EPA, C20:5n-3) decreased, while arachidonic acid (ARA, C20:4n-6) increased in sea urchins exposed to 5 and 10 mg/L FLO. Histopathological alterations of gonadal tissues represent an additional confirmation about the toxicity of this antibiotic that might decrease the reproductive performance of this species. Nevertheless, even if reproduction of sea urchins would be partially successful, the embryotoxicity would compromise the normal development of the embryos with consequences on the population.

A broad-taxa approach as an important concept in ecotoxicological studies and pollution monitoring

Aquatic invertebrates play a pivotal role in (eco)toxicological assessments because they offer ethical, cost-effective and repeatable testing options. Additionally, their significance in the food chain and their ability to represent diverse aquatic ecosystems make them valuable subjects for (eco)toxicological studies. To ensure consistency and comparability across studies, international (eco)toxicology guidelines have been used to establish standardised methods and protocols for data collection, analysis and interpretation. However, the current standardised protocols primarily focus on a limited number of aquatic invertebrate species, mainly from Arthropoda, Mollusca and Annelida. These protocols are suitable for basic toxicity screening, effectively assessing the immediate and severe effects of toxic substances on organisms. For more comprehensive and ecologically relevant assessments, particularly those addressing long-term effects and ecosystem-wide impacts, we recommended the use of a broader diversity of species, since the present choice of taxa exacerbates the limited scope of basic ecotoxicological studies. This review provides a comprehensive overview of (eco)toxicological studies, focusing on major aquatic invertebrate taxa and how they are used to assess the impact of chemicals in diverse aquatic environments. The present work supports the use of a broad-taxa approach in basic environmental assessments, as it better represents the natural populations inhabiting various ecosystems. Advances in omics and other biochemical and computational techniques make the broad-taxa approach more feasible, enabling mechanistic studies on non-model organisms. By combining these approaches with in vitro techniques together with the broad-taxa approach, researchers can gain insights into less-explored impacts of pollution, such as changes in population diversity, the development of tolerance and transgenerational inheritance of pollution responses, the impact on organism phenotypic plasticity, biological invasion outcomes, social behaviour changes, metabolome changes, regeneration phenomena, disease susceptibility and tissue pathologies. This review also emphasises the need for harmonised data-reporting standards and minimum annotation checklists to ensure that research results are findable, accessible, interoperable and reusable (FAIR), maximising the use and reusability of data. The ultimate goal is to encourage integrated and holistic problem-focused collaboration between diverse scientific disciplines, international standardisation organisations and decision-making bodies, with a focus on transdisciplinary knowledge co-production for the One-Health approach.

Development of a Lymnaea stagnalis embryo bioassay for chemicals hazard assessment

The validation of high-throughput toxicity tests with invertebrate species is a key priority to improve hazard assessment of new chemicals and increase the available test guidelines with organisms from a representative set of taxa. This work aimed to contribute to the validation of an embryo test with the freshwater gastropod Lymnaea stagnalis, which has been identified by Organization for Economic Co-operation and Development (OECD) as a potential invertebrate test model, and provide the basis for such an endeavor. Recently, a L. stagnalis reproductive test was standardized by the OECD. However, to encompass the entire life cycle, it is crucial to addresses embryogenic development - a phase highly susceptible to various anthropogenic chemicals, which is covered in the proposed methodology. The approach used in the present study is in line with the OECD guidelines and other published studies, namely the Detailed Review Paper (DRP) on Mollusks life-cycle toxicity testing. Here, the assay quality criteria such as basal mortality and abnormality rates, development, growth and hatching rates, the appropriated testing media, and the optimal assay duration were investigated. Cadmium was chosen as the positive test substance, due to the available data and the verified model sensitivity to this compound, namely in the OECD reproductive test validation process. The obtained data demonstrate that L. stagnalis embryogenesis using the developed methodology is highly sensitive to cadmium. High concentration-response correlation was observed using this reference compound, the EC10 and EC50 for growth are 13.57 and 21.84 μg/L, respectively, after 168 h of exposure. The development EC's 10 and 50 were 15.75 and 38.66 μg/L, respectively, after 240 h. This demonstrates the model sensitivity to this compound when compared with other embryo test models, as well as the model sensitivity during the embryogenesis, if compared with the adult stage. Further, given the determined sensitivity parameters, and incubation times, the test can be performed at 240 h as over 95 % of the control embryos were hatched and no further significant changes in the exposure groups were determined. Overall, the findings of the present study demonstrate that the embryo test with L. stagnalis has potential to high-throughput testing and the model has a high sensitivity to cadmium during this life cycle period. The background data provide by this study will be essential to foster the future standardization of this assay.

Assessment of sediment porewater toxicity in Biscayne National Park with sea urchin (Lytechinus variegatus) embryos

The sea urchin embryo development toxicity test was used to investigate toxicity of the benthic substrate in Biscayne National Park (BISC). Twenty-five sites were selected based upon a high potential for anthropogenic stressor input (e. g., hydrocarbons, personal care products, nutrients, etc.) or proximity to coral reef habitats. We found that sediment interstitial water (porewater) was toxic to urchin embryos at 22 of 25 sites. Healthy sites included two coral reefs (Anniversary Reef and Marker 14 Reef) and Turkey Point Channel. Discrete areas of BISC have highly toxic sediments and the presence of sediment contaminants could negatively impact reproduction, growth and population density of benthic invertebrates, such as corals. Results of the sea urchin embryo development toxicity test can be used as a baseline assessment for monitoring improvements or degradation in ecosystem health and could be a valuable tool to investigate the suitability of degraded habitats for future reef restoration. Since the last comprehensive environmental assessment of BISC was performed in 1999, further investigation into the sources of toxicity at BISC is needed.

Stress response to trace elements mixture of different embryo-larval stages of Paracentrotus lividus

This study investigated for the first time the oxidative biomarkers responses in all larval stages of sea urchin. The contamination effects were reproduced by using contaminated seawater to concentrations measured in the area adjacent to an old asbestos mine at factors of 5 and 10. The results suggested that the concentrations were not sufficiently high to induce a major oxidative stress. The biometric differences make this method a more sensitive approach for assessing the effects on sea urchin larvae. Measurements of specific activities of antioxidant enzymes at each stage suggested a high capacity of the larvae to respond to oxidative stress. This normal activity of the organism must be considered in future research. This work also highlighted the importance of spawners provenance in ecotoxicological studies. These data are essential to better understand the stress responses of sea urchin larvae and provide baseline information for later environmental assessment research.

Application of the Paracentrotus lividus sea-urchin embryo-larval bioassay to the marine pollution biomonitoring program in the Tunisian coast

The pollution of the marine environment by treated and untreated effluents has increased due to human activities. Monitoring the marine ecosystem is nowadays a global concern. In this work, we evaluated the effect of contaminated and uncontaminated seawater, from different Tunisian coastal areas, on the fertilization, gastrulation, and embryo-larval development events of sea urchins (Paracentrotus lividus). The station of Salakta (SA) is considered as a control station, while the stations of Hamdoun Wadi (HW), Port of Monastir (PM), Karaia Monastir (KM), Teboulba (TE), and Khniss Lagoon (KL) are considered to be contaminated stations. The analysis of seawater physicochemical characteristics showed that levels of the total suspended matter (TSM), chemical oxygen demand (COD), biochemical oxygen demand (BOD), total organic carbon (TOC), and nitrate (NO^3-) were lower in the seawater of the reference site Salakta (SA) when compared to those of the contaminated seawater sites. In addition, a very strong variation in the levels of trace metals in seawaters sampled in the studied sites was noted. In fact, the highest concentrations of Pb and Cu were observed in Hamdoun Wadi (HW), port of Monastir (PM), and Karaia Monastir (KM), while the highest concentration of Zn was noted in the Teboulba lagoon (TE) and Khniss (LK). Alterations in physicochemical characteristics as well as elevated trace metal levels in the studied seawater samples were correlated with reduced fertility rate, gastrulation rate, and the frequency of normal sea urchin larvae. The total absence of normal sea urchin pluteus larvae in the sea waters of heavily polluted sites proves the great sensitivity of the larval frequency to mixed pollution. This work recommends the utility of urchin fertilization and gastrulation rates and normal pluteus larval frequencies as useful bioassays to monitor the exposure of marine ecosystems to mixed pollution.

Early-stage anomalies in the sea urchin (Paracentrotus lividus) as bioindicators of multiple stressors in the marine environment: Overview and future perspectives

The morphological anomalies of the early development stages of the sea urchin Paracentrotus lividus, caused by exposure to environmental stressors, are used as biomarker in ecotoxicological and ecological investigations. Here, we reviewed the available literature and classified the embryo and larval anomalies identified so far, to highlight potential commonalities or differences related to the biological action of the different stressors and their ecological impact. Morphological anomalies are influenced by a) the developmental stage of exposure to stressors; b) the intensity of the stress; c) the intra- and inter-cellular mechanisms affected by the exposure to environmental agents. The classification and analysis of embryo and larvae anomalies, either observed by the authors of this review and reported in literature, indicate that sea urchin abnormalities, caused by exposure to different stressors, can be very similar among them and classified into 18 main types, which can occur individually or mixed. All anomalies can be used to calculate an Index of Contaminant Impact to assess the impact of multiple stressors and to identify relationships between morphological anomalies and compromised biological mechanisms. This approach could be useful for a first screening of the presence of potential stressors impairing the growth and development of the early life stages of marine organisms, thus providing a relevant advancement for in future monitoring activities devoted to assess the health status in coastal marine ecosystems.

Adverse effects of oxytetracycline and enrofloxacin on the fertility of Saanen bucks

This study aimed to determine the adverse effects of oxytetracycline and enrofloxacin application on the fertility of Saanen bucks. For this purpose, twenty-four bucks were divided into three groups. Group I (control group) received only 5 ml of 0.9% NaCl for 7 days, group II was given a single dose of 20 mg/kg oxytetracycline and group III was given at a dose of 2.5 mg/kg per day for 7 days intramuscularly. Serum and semen samples were collected from the bucks at post-treatment 1, 3, 5, 7, and 9 days and examined spermatological parameters (quantity, motility, density, abnormal sperm ratio, and live-dead sperm ratio), serum testosterone levels (with ELISA) and sperm DNA parameters (with Comet assay). The results showed no change in sperm volume, abnormal sperm rate, and dead-live sperm ratio in group II and III following oxytetracycline and enrofloxacin administration. However, a decrease in sperm density, sperm motility, mass activity, and testosterone levels, and an increase in sperm DNA damage were detected. These spermatological parameters (density, motility, mass activity) and testosterone levels were less decreased and sperm DNA damage was less increased in group II than group III. The greater damage in group III may be attributed to the longer duration of enrofloxacin administration compared to oxytetracycline and the effect of enrofloxacin on DNA. The results obtained from this study suggest that usage of oxytetracycline and especially enrofloxacin should be restricted and antibiotics with fewer side effects on sperm should be preferred in Saanen bucks during the reproduction period.

Cadmium stress effects indicating marine pollution in different species of sea urchin employed as environmental bioindicators

In recent years, researches about the defense strategies induced by cadmium stress have greatly increased, invading several fields of scientific research. Mechanisms of cadmium-induced toxicity continue to be of interest for researchers given its ubiquitous nature and environmental distribution, where it often plays the role of pollutant for numerous organisms. The presence in the environment of this heavy metal has been constantly increasing because of its large employment in several industrial and agricultural activities. Cadmium does not have any biological role and, since it cannot be degraded by living organisms, it is irreversibly accumulated into cells, interacting with cellular components and molecular targets. Cadmium is one of the most studied heavy metal inductors of stress and a potent modulator of several processes such as apoptosis, autophagy, reactive oxygen species, protein kinase and phosphatase, mitochondrial function, metallothioneins, and heat-shock proteins. Sea urchins (adults, gametes, embryos, and larvae) offer an optimal opportunity to investigate the possible adaptive response of cells exposed to cadmium, since these cells are known to accumulate contaminants. In this review, we will examine several responses to stress induced by cadmium in different sea urchin species, with a focus on Paracentrotus lividus embryos. The sea urchin embryo represents a suitable system, as it is not subjected to legislation on animal welfare and can be easily used for toxicological studies and as a bioindicator of environmental pollution. Recently, it has been included into the guidelines for the use and interpretation of assays to monitor autophagy.

Assessment of individual and mixed toxicity of bromoform, tribromoacetic-acid and 2,4,6 tribromophenol, on the embryo-larval development of Paracentrotus lividus sea urchin

Water chlorination is the most widely used technique to avoid microbial contamination and biofouling. Adding chlorine to bromide-rich waters leads to the rapid oxidation of bromide ions and leads to the formation of brominated disinfection by-products (bromo-DBPs) that exert adverse effects on various biological models. Bromo-DBPs are regularly encountered within industrialized embayments, potentially impacting marine organisms. Of these, bromoform, tribromoacetic acid and tribromophenol are among the most prevalent. In the present study, we tested the potential toxicity and genotoxicity of these disinfection by-products, using sea urchin, Paracentrotus lividus, embryos. We highlighted that tribromophenol showed higher toxicity compared to bromoform and tribromoacetic acid. Furthermore, a synergistic effect was detected when tested in combination. Pluteus cells exposed for 1 h to mixtures of DBPs at several concentrations demonstrated significant DNA damage. Finally, when compared to a non-exposed population, sea urchins living in a bromo-DPB-polluted area produced more resistant progenies, as if they were locally adapted. This hypothesis remains to be tested in order to better understand the obvious impact of complex bromo-DBPs environments on marine wildlife.

Molecular effects of copper on the reproductive system of mytilus galloprovincialis

This study aims to assess the effects induced by 24 hr exposure to a subtoxic copper concentration on the reproductive system (gonads, spermatozoa, and protamine-like [PL] proteins) of Mytilus galloprovincialis. Inductively coupled plasma-mass spectrometry indicated accumulation of this metal in gonads, spermatozoa, and PL proteins of exposed mussels. Further, real-time polymerase chain reaction analyses showed altered expression levels of mt10 and PL proteins genes in spermatozoa and gonads, respectively, of exposed mussels. Protamine-like proteins, which represent the main basic component of sperm chromatin of this organism, showed a higher DNA binding affinity and a different DNA binding mode in exposed mussels. Moreover, an increased amount of NaCl was required for the release from sperm nuclei of PL-III, the main PL protein component. Finally, PL proteins extracted from exposed mussels promoted DNA oxidative damage in the presence of H ₂ O _2. These results demonstrate that the tolerable copper amount could also affect the properties of PL proteins and determine the negative effects on the reproductive system of this organism. These analyses could be useful to develop quick and efficient chromatin-based genotoxicity tests for pollution biomonitoring programs.