A toxicity test was developed to examine the effects of heavy metal contaminants on the early life stages of the marine polychaete. We have studied the effects of metals on fertilization and early development of marine polychaete Hydroides elegans. These heavy metals have often been found in polluted ground and water near industrial discharges, and have therefore been detected from time to time in the food chain. They have been reported to alter various reproduction functions in various animals including marine populations. The toxic effect of mercury, cadmium, lead, nickel and zinc on sperm viability, fertilization, embryogenesis and larvae of H. elegans was examined. We observed that the rate of fertilization decreased when the sperm was incubated with heavy metals. Treatment of eggs with each metal did not prevent fertilization, but delayed or blocked the first mitotic divisions, and altered early embryonic development. All these effects were observed at relatively high concentrations. However, bio-accumulation in sediments and aquatic organisms have been reported. Polychaete eggs may then be in contact with very high concentrations of these heavy metals in areas where these metals are not handled or stocked properly, and then develop into abnormal embryos. In addition to bivalves and sea-urchins, polychaete embryos can provide biological criteria for seawater quality standards taking into account the sensitivity of the invertebrates and their contribution in detection of harmful chemicals with no marked effect on the species. Our results indicate that the early development of H. elegans is highly sensitive to heavy metals and this polychaete can be routinely employed as a test organism for ecotoxicity bioassays in tropical and subtropical regions.
"For the past 15 years, early life stages (ELSs) have been the subject of numerous studies aimed at assessing the toxicity of chemicals, especially in aquatic environments (Gomot, 1998; Gopalakrishnan et al., 2008; Ismail and Yusof, 2011). Because the embryonic phase is an essential step in the life cycle and thus a key element of population dynamics (Laskowski, 1997; Caswell, 2000), it is relevant to focus on this life stage. "
[Show abstract][Hide abstract] ABSTRACT: This study aims to determine various parameters that allow the evaluation of the toxicity of chemicals to embryos of the ubiquitous land snail Cantareus aspersus. For this purpose, we investigated morphological and physiological endpoints in control embryos and in embryos exposed to a solution of 6 mg Cd/L (CdCl2) in a liquid phase bioassay: size at days 3, 6 and 10, heart rate at 7 days, delay in hatching, states of development of non-hatched eggs after 17 days and the fresh mass of newly hatched embryos. The kinetics of Cd accumulation in eggs and DNA fragmentation were also measured. The first detectable sign of adverse effects appeared after 7 days of development, when the heart rate decreased in Cd-exposed embryos compared with the control. After 10 days of exposure, Cd-exposed hatchlings exhibited a lower fresh mass than control individuals. The majority (75 percent) of non-hatched embryos at 17 days was dead and presented signs of disaggregation or malformations. The hatching of Cd-exposed eggs was delayed 4 days, and DNA fragmentation was later detected after 20 days of Cd exposure. The measurement of Cd in the eggs showed that concentrations are relatively stable during the exposure period from 3 days (20–27 µg Cd/g DW) to the end of exposure. The present study completes the range of endpoints that can be used to study the effects of contaminants and provides new parameters that are readily measured throughout the embryonic development of a terrestrial mollusk.
"Cd, at high concentrations, can be lethal to aquatic invertebrates (Holdway et al., 2001; Burger, 2008; Gopalakrishnan et al., 2008; Mebane et al., 2012), whereas, at sub-lethal concentrations, various negative effects on animal behaviour, biochemical activities and reproductive capability have been reported (Kaspler, 1999; Pruski and Dixon, 2002; Medesani et al., 2004; Riddell et al., 2005; Gopalakrishnan et al., 2008; Geffard et al., 2010; Ivanina et al., 2010). Development is also negatively affected by the presence of Cd (Ramachandran et al., 1997; Gorski and Nugegoda, 2006; Gopalakrishnan et al., 2008; Mao et al., 2012). In fish, at sublethal doses, Cd causes malformations of the vertebral axis (Sassi et al., 2010), alterations of haematological parameters and stress hormone levels (Mekkawy et al., 2011; Garcia-Santos et al., 2013; Zhang et al., 2013), modifications in the plasma ionic concentrations due to the inhibition of ionic transport (Verbost et al., 1988; Reid and McDonald, 1988; Alsop and Wood, 2011), hyperglycaemia and increase of cortisol levels (Lin et al., 2011), as well as reduced oxygen exchange at the branchial level (Gill et al., 1988; Pierron et al., 2007). "
[Show abstract][Hide abstract] ABSTRACT: In order to get insights into the effects of cadmium (Cd) on cell morphology and functions, we exposed haemocytes of the colonial ascidian Botryllus schlosseri to sub-lethal concentrations of CdCl2. Results indicate that Cd hampers haemocyte spreading and phagocytosis in a dose-dependent way, through the alteration of the actin cytoskeleton. In addition, the metal decreases the stability of the internal membranes, as revealed by the Neutral Red assay. The fraction of cells showing positivity for the lysosomal enzyme acid phosphatase is also reduced in the presence of Cd, whereas the number of cells responsive to the Annexin-V assay and showing chromatin condensation increases, suggesting a metal-dependent induction of apoptosis in exposed cells. As Cd is a known cause of oxidative stress, the decrease in the percentage of cells positive to the assay for superoxide anion, observed at low Cd concentrations, is indicative of the synthesis of metal-chelating molecules, such as metallothioneins, whereas, the increase at high Cd concentrations suggests a depletion of the cell reducing redox potential.
Comparative Biochemistry and Physiology Part C Toxicology & Pharmacology 04/2013; 158(1). DOI:10.1016/j.cbpc.2013.04.003 · 2.30 Impact Factor
"temper - ature change or the presence of environmental pollutants ( Forbes et al . , 2010 ; His et al . , 1999 ) . A wide range of contaminants have been shown to affect fertilisation success in marine invertebrates but there are relatively few studies on polychaetes , with most focussing on the impacts of heavy metals such as cadmium and copper ( Gopalakrishnan et al . , 2008 ; Watson et al . , 2008a ; Zheng et al . , 2010 ) . Assays on fertilisation are quick and convenient"
[Show abstract][Hide abstract] ABSTRACT: In the last 15 years the diversity of pollutants and routes of impact have increased. However, the polychaete families, species and endpoints investigated have remained fairly constant. Reproductive outputs are more ecologically relevant than adult physiological or biochemical changes. Nevertheless, there remains a paucity of data on the reproductive responses of the popular species to pollutants which limits our ability to understand the true ecological impacts of such contaminants on natural populations. We highlight the current knowledge gaps in our understanding of the impacts of pollutants on the 'model' species' reproductive biology and therefore the potential ecological impacts of such contaminants on their natural populations, and the potential benefits of a wider use of polychaete reproductive endpoints for ecotoxicological assessments. The following priority areas are suggested for inclusion in the polychaete ecotoxicology toolbox: 1. Include reproductive endpoints as assessments of ecotoxicology for the traditional 'model' species and those that have different reproductive traits to ensure broad ecological relevance. 2. Nereids and Arenicola marina should be used to investigate the interaction of pollutants with the endocrine/environmental control of reproduction. 3. Polychaetes are ideal for addressing the under representation of male eco-toxicity effects. 4. Emerging pollutants should be assessed with reproductive endpoints together with the traditional biomarkers. 5. Effects of pollutants on larval behaviour need to be explored considering the limited but equivocal results so far.
Marine environmental research 08/2011; 75:10-22. DOI:10.1016/j.marenvres.2011.08.002 · 2.76 Impact Factor
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