Linking Molecular and Population Stress Responses in Daphnia magna exposed to cadmium

Abstract

DNA microarrays can be used to measure environmental stress responses. If they are to be predictive of environmental impact, we need to determine if altered gene expression translates into negative impacts on individuals and populations. A large cDNA microarray (14000 spots) was created to measure molecular stress responses to cadmium in Daphnia magna,the mostwidely used aquatic indicator species, and relate responses to population growth rate (pgr). We used the array to detect differences in the transcription of genes in juvenile D. magna (24 h old) after 24 h exposure to a control and three cadmium concentrations (6, 20, and 37 microg Cd2+ L(-1)). Stress responses at the population level were estimated following a further 8 days exposure. Pgr was approximately linear negative with increasing cadmium concentration over this range. The microarray profile of gene expression in response to acute cadmium exposure begins to provide an overview of the molecular responses of D. magna, especially in relation to growth and development. Of the responding genes, 29% were involved with metabolism including carbohydrate, fat and peptide metabolism, and energy production, 31% were involved with transcription/translation, while 40% of responding genes were associated with cellular processes like growth and moulting, ion transport, and general stress responses (which included oxidative stress). Our production and application of a large Daphnia magna microarray has shown that measured gene responses can be logically linked to the impact of a toxicant such as cadmium on somatic growth and development, and consequently pgr.

Natural dissolved humic substances increase the lifespan and promote transgenerational resistance to salt stress in the cladoceran Moina macrocopa

“…Increasing salinity, as well as the concentrations of heavy metals or other pollutants, decreases lifespan and somatic and population growth rates and may delay the sexual maturity in these organisms (Connon et al 2008;Teschner 1995). At least some stressors, when present at non-lethal levels, may also lead to a switch from asexual reproduction, the sexual production of resting eggs in cladocerans, as a means to insure the persistence of the population in the environment (Gyllstrom and Hansson 2004).…”

It’s All in the Genes: How Genotype Can Impact Upon Response to Contaminant Exposure and the Implications for Biomonitoring in Aquatic Systems

“…Maes et al, 2005;Matson et al, 2006); and 4. genome-wide changes in genetic diversity (e.g. Armendariz et al, 2004;Connon et al, 2008;Poynton et al, 2008; for reviews on evolutionary toxicology, see : Bickham, 2011;Theodorakis & Wirgin, 2002;van Straalen & Timmermans, 2002).…”

Toxicogenomics Applied to Ecological Risk Assessment

“…Other fish species examined in ecotoxicogenomic studies include common carp (Cyprinus carpio; e.g., Moens et al, 2006), goldfish (Carassius auratus; e.g., Martyniuk et al, 2006), the coral reef fish Pomacentrus moluccensis (Kassahn et al, 2007), largemouth bass (Micropterus salmoides; e.g., Garcia-Reyero et al, 2008), European flounder (Platichthys flesus; e.g., Williams et al, 2006), three-spined stickleback (Gasterosteus aculeatus; e.g., Geohegan et al, 2008), and Gobiocypris rarus (Wei et al, 2008). As a common test organism, the aquatic invertebrate, Daphnia magna, has also been used in a number of ecotoxicology-oriented transcriptomics studies (Heckmann et al, 2006;Poynton et al, 2007;Watanabe et al, 2007;Connon et al, 2008). To date, fish, particularly zebrafish and fathead minnow, and Daphnia magna, appear to be the most common model organisms for ecotoxicogenomics studies employing DNA microarrays.…”

“…For example, a number of studies have examined transcriptional responses to heavy metals, including copper, cadmium, zinc, arsenic, mercury, and chromium (Hook et al, 2006;Jamers et al, 2006;Klaper et al, 2006;Lam et al, 2006;Williams et al, 2006;Poynton et al, 2007;Watanabe et al, 2007;Bundy et al, 2008;Connon et al, 2008). Endocrine disrupting chemicals have also received considerable attention Helbing et al, 2007a;Benninghoff and Williams, 2008;Hoffmann et al, 2008;Kausch et al, 2008;Leon et al, 2008;Villeneuve et al, 2008).…”

“…For example, both Carney et al (2006) and Andreasen et al (2006; anchored mechanistic transcriptomic studies of developmental effects of TCDD in fish to histological and/or morphological measurements. Transcriptomic results for Daphnia magna were anchored to embryo abnormalities and carapax length in one study (Soetaert et al, 2007) and population growth rates in another (Connon et al, 2008). Gene expression changes in earthworms exposed to ordnance chemicals were related to survival, growth, and reproduction (Gong et al, 2008).…”