Automated image analysis of Euglena gracilis Klebs (Euglenophyta) for measuring sublethal effects of three model contaminants

Abstract

The short-term impacts of atrazine (herbicide), tributyltin (organometal) and copper on the behaviour of Euglena gracilis Klebs (Euglenophyta) were assessed. First, the ECOTOX automated image analysis system was used, which measured swimming velocity, cell shape, percentage of cells swimming upwards, and randomness of swimming. Next, visual observation by microscopy was used to measure percentage of cell motility and cell shape. Behavioural changes can be used as an indicator of stress in less than 24 h, potentially making them suitable for inclusion in early-warning systems for water quality. Findings indicate that E. gracilis is a very sensitive organism to copper, showing inhibition of motility with visual observation at 0.8 μmol/L within 1 h. The image analysis system was in general less sensitive than visual observation for detecting behavioural changes after incubation in copper. In contrast, after exposure to organic contaminants atrazine and tributyltin, the ECOTOX system detected small changes in the number of cells swimming upwards (antigravitactic behaviour) at higher concentrations.

Euglenoid Flagellates in Ecotoxicological Research: Progress and Perspectives

“…The upward swimming and velocity of E. gracilis were sensitive criteria for herbicide impacts (Pettersson & Ekelund, 2006). ECOTOX analysis provided a rapid estimation of small changes in the number of cells swimming upwards (antigravitactic behavior) at higher concentrations of the organochlorine herbicide, atrazine (Netto et al, 2012). Herbicides target the cytoskeletal components involved in both the elongation and contraction of the E. gracilis cells, resulting in changes in movement behavior (Kawano et al, 2004).…”

“…Herbicides target the cytoskeletal components involved in both the elongation and contraction of the E. gracilis cells, resulting in changes in movement behavior (Kawano et al, 2004). The ECOTOX analysis for herbicide toxicity was more sensitive, as the automated system is capable of detecting changes that cannot be detected through visual observation (Netto et al, 2012). Chlorophyll-a fluorescence and motility parameters of E. gracilis were significantly affected by the carbamate pesticide, carbofuran, and the organophosphorus pesticide malathion (Netto et al, 2012).…”

“…The ECOTOX analysis for herbicide toxicity was more sensitive, as the automated system is capable of detecting changes that cannot be detected through visual observation (Netto et al, 2012). Chlorophyll-a fluorescence and motility parameters of E. gracilis were significantly affected by the carbamate pesticide, carbofuran, and the organophosphorus pesticide malathion (Netto et al, 2012). Since the inhibitory effects of pesticides in short-term were stronger than in long-term experiments, ECOTOX-based movement analysis offers a rapid and sensitive method of acute assessment of pesticides in Euglena.…”

“…Microalgae are highly vulnerable to dissolved and suspended pollutants due to their ubiquitous occurrence, large surface-to-volume ratio, short life cycles, and high sensitivity (Pikula et al, 2019). They are the primary route of entry for a large number of toxic chemicals to the aquatic food web, and any impact on them will subsequently affect the upper trophic levels (Bouldin et al, 2008;Hu et al, 2015;Netto et al, 2012). The contamination of aquatic systems by natural and anthropogenic pollutants is a growing concern worldwide.…”