Variability in the Dynamics of Mortality and Immobility Responses of Freshwater Arthropods Exposed to Chlorpyrifos

Abstract

The species sensitivity distribution (SSD) concept is an important probabilistic tool for environmental risk assessment (ERA) and accounts for differences in species sensitivity to different chemicals. The SSD model assumes that the sensitivity of the species included is randomly distributed. If this assumption is violated, indicator values, such as the 50% hazardous concentration, can potentially change dramatically. Fundamental research, however, has discovered and described specific mechanisms and factors influencing toxicity and sensitivity for several model species and chemical combinations. Further knowledge on how these mechanisms and factors relate to toxicologic standard end points would be beneficial for ERA. For instance, little is known about how the processes of toxicity relate to the dynamics of standard toxicity end points and how these may vary across species. In this article, we discuss the relevance of immobilization and mortality as end points for effects of the organophosphate insecticide chlorpyrifos on 14 freshwater arthropods in the context of ERA. For this, we compared the differences in response dynamics during 96 h of exposure with the two end points across species using dose response models and SSDs. The investigated freshwater arthropods vary less in their immobility than in their mortality response. However, differences in observed immobility and mortality were surprisingly large for some species even after 96 h of exposure. As expected immobility was consistently the more sensitive end point and less variable across the tested species and may therefore be considered as the relevant end point for population of SSDs and ERA, although an immobile animal may still potentially recover. This is even more relevant because an immobile animal is unlikely to survive for long periods under field conditions. This and other such considerations relevant to the decision-making process for a particular end point are discussed.

Effects of insecticides on aquatic ecosystems in Bangladesh

“…The aquatic contamination by pesticides used in agriculture may constitute potential (eco)toxicological risks to non-target aquatic organisms of different trophic levels in a food chain i.e. primary producers (Daam et al, 2008a;Malev et al, 2012;Liu et al, 2013;Kumar et al, 2014), invertebrates (Maltby et al, 2005;Palma et al, 2009;Rubach et al, 2011;Roessink et al, 2013;Van den Brink et al, 2016), and fish (Tillitt et al, 2010;Marimuthu et al, 2013;Manjunatha and Philip, 2016;, when exceeding the threshold levels.…”

“…and Diaptomus sp. were determined using log-logistic regression as programmed in the software GenStat 11 th (VSN International Ltd., Oxford, UK) according to Rubach et al (2011). …”

“…The LC10 and LC50 values of the toxicity experiment were calculated by means of log-logistic regression using the software GenStat 11 th (VSN International Ltd., Oxford, UK) according to Rubach et al (2011). To evaluate the toxic effects of different chlorpyrifos concentrations in embryo and larvae and hatching rate, we computed a one-way analysis of variance (ANOVA) by using the Duncan's multiple comparison with SPSS (version 20; SPSS Inc., Chicago, IL) at 5% significant level.…”

“…Chlorpyrifos shows a high toxicity to non-target aquatic organisms including vertebrates (Kienle et al, 2009;Bernabò et al, 2011;Xing et al, 2012;Jin et al, 2015) and invertebrates (Daam et al, 2008;Palma et al, 2009;Rubach et al, 2011Rubach et al, , 2012. Like other groups of vertebrates, fish embryos and larvae are also considered to be the most sensitive stages in the life cycle and sensitive to low levels of environmental pollutants (Marimuthu et al, 2013).…”

“…The release of this insecticide into the aquatic environment may have potential toxic effects on non-target aquatic organisms like invertebrates (Maltby et al, 2005;Daam et al, 2008;Palma et al, 2008;Rubach et al, 2011;, and vertebrates (Maltby et al, 2005;Oruç, 2010;Bernabò et al, 2011;Manjunatha and Philip, 2016;. Among vertebrates, fish is often used as suitable bio-indicator, because of their wide distribution in aquatic environment, long lifespan, free swimming, ability to respond against environmental xenobiotics, and importance as a food source for human beings (Gupta et al, 2009;Narra et al, 2011;Correia et al, 2017).…”