Eric Gismondi

Influence of gender and season on reduced glutathione concentration and energy reserves of Gammarus roeseli

As biomarkers are known to be influenced by biotic and abiotic factors (e.g. gender, temperature), we investigated over a one-year long sampling period, the influence of season and gender on reduced glutathione concentrations and its synthesis in the crustacean amphipod Gammarus roeseli. At the same time, we assessed energy reserves and malondialdehyde levels as toxic biomarker. Results have shown that, in both genders, reduced glutathione concentrations were inversely correlated to water temperature, and higher in females than in males whatever the season. Total lipid and glycogen contents were higher in females than in males, allowing females to have enough energy to assume the reproductive period and maintain high GSH concentrations for detoxification processes. Conversely, females have lower cell damages than males. These differences between genders could induce differential sensitivity in a contamination context, and thus affect the population. Females could resist better than males in contaminated environments, especially in spring when reduced glutathione concentration is the highest.

Behavioural and physiological responses of Gammarus fossarum (Crustacea Amphipoda) exposed to silver

The study aims at investigating the effects of silver (Ag), a re-emerging contaminant, on physiological and behavioural responses in Gammarus fossarum. In a first experiment, G. fossarum Ag LC50s were evaluated during 96 h under semi-static mode of exposure. Juveniles appeared to be more sensitive to Ag (LC5096h: 1.01 μg L(-1)) than ovigerous females (LC5096h: 1.9 μg L(-1)) and adult males (LC5096h: 2.2 μg L(-1)). In a second experiment, the physiological (osmo-/ionoregulation; antioxidant enzymes; lipid peroxidation (LPO)) and behavioural (locomotor activity and ventilation) responses of male G. fossarum exposed to Ag (0, 0.5, 1, 2, and 4 μg L(-1)) were investigated. The mortality and Ag bioconcentration of gammarids exposed to Ag were significantly higher than controls. Concerning physiological responses, a 48 h-exposure to Ag had no impact on catalase activity but led to a significant decrease of haemolymph osmolality and [Na(+)]. On the contrary, LPO, Se-GPx and Na(+)/K(+)-ATPase activity were significantly increased. Behavioural responses, such as locomotor and ventilatory activities, were also significantly reduced in Ag exposed gammarids. After 96 h-exposure, especially to 0.5 μg Ag L(-1), most responses (ventilation, locomotor activity, haemolymph osmolality and [Na(+)]) were even more pronounced and haemolymph [Cl(-)] was significantly decreased but, contrary to observations after 48 h-exposure, Na(+)/K(+)-ATPase activity was significantly reduced. Our results demonstrate the drastic effects of realistic [Ag] concentration (0.5 μg Ag L(-1)) on an ubiquitous and functionally important freshwater invertebrate (implied in detritus breakdown), but also strongly suggest an energetic reallocation to the detriment of locomotor activity and in favour of maintenance functions (i.e., osmoregulation and detoxification). These results highlight the risk represented by Ag and the need to perform integrated studies (at different scales, from individual to ecosystem).

Effects of Sublethal Cadmium Exposure on Antipredator Behavioural and Antitoxic Responses in the Invasive Amphipod Dikerogammarus villosus

Amphipods are recognised as an important component of freshwater ecosystems and are frequently used as an ecotoxicological test species. Despite this double interest, there is still a lack of information concerning toxic impacts on ecologically relevant behaviours. The present study investigated the influence of cadmium (Cd), a non-essential heavy metal, on both antipredator behaviours and antitoxic responses in the invasive amphipod Dikerogammarus villosus under laboratory conditions. Amphipod behaviour (i.e. refuge use, aggregation with conspecifics, exploration and mobility) was recorded following a 4-min test-exposure to 500 µg Cd/L with or without a 24-h Cd pre-exposure and in the presence or absence of a high perceived risk of predation (i.e. water scented by fish predators and injured conspecifics). Following behavioural tests, malondialdehyde (MDA) levels, a biomarker for toxic effect, and energy reserves (i.e. lipid and glycogen contents) were assessed. Cd exposures induced (1) cell damage reflected by high MDA levels, (2) erratic behaviour quantified by decreasing refuge use and exploration, and increasing mobility, and (3) a depletion in energy reserves. No significant differences were observed between 4-min test-exposed and 24-h pre-exposed individuals. Gammarids exposed to Cd had a disturbed perception of the alarm stimuli, reflected by increased time spent outside of refuges and higher mobility compared to gammarids exposed to unpolluted water. Our results suggest that Cd exposure rapidly disrupts the normal behavioural responses of gammarids to alarm substances and alters predator-avoidance strategies, which could have potential impacts on aquatic communities.

Effect of Multiple Parasitic Infections on the Tolerance to Pollutant Contamination

The horizontally-transmitted acanthocephalan parasite Polymorphus minutus and the vertically-transmitted microsporidian parasite Dictyocoela roeselum have both been shown to influence on the antitoxic responses of mono-infected Gammarus roeseli exposed to cadmium. The present study investigates the effect of this co-infection on the antitoxic defence responses of naturally infected females exposed to cadmium stress. Our results revealed that, depending on the cadmium dose, bi-infection induced only slight, significant increased cell damage in G. roeseli as compared to non-infection. In addition, the antitoxic defence pattern of cadmium-exposed bi-infected hosts was similar to the pattern of cadmium-exposed D. roeselum-infected hosts. Reduced glutathione concentrations, carotenoid levels and γ-glutamylcystein ligase activity decreased, while metallothionein concentrations increased. This similar pattern indicates that host physiology can be controlled to some extent by microsporidia under stress conditions. It supports the hypothesis of a disruption of acanthocephalan effects in the presence of microsporidia. However, the global negative effects of bi-infection on host condition should be tested on more biological models, since competition between parasites depends on life history trade-off.

Acanthocephalan parasites: help or burden in gammarid amphipods exposed to cadmium?

We investigated the influence of the acanthocephalan parasite Polymorphus minutus on the mortality of its intermediate host, Gammarus roeseli, exposed to cadmium, by the measure of LC50–96h values as well as the bioaccumulation of cadmium both in the host and in its parasite. LC50 results revealed that infected G. roeseli males died less under cadmium stress than uninfected ones; while the converse has been observed in females. Cadmium resistance of infected males could be explained by a weaker bioconcentration factor (BCF) than in females. The lower BCF in infected individuals was closely related with an uptake of cadmium by P. minutus in its host. Nevertheless, although infected females had both weaker BCF and cadmium concentration in their body, the presence of P. minutus did not induce lower mortality than uninfected females. On the contrary, their sensitivity to cadmium was increased by the presence of P. minutus. We discuss the hypothesis that differences of mortality between uninfected and infected gammarids could be explained by a difference of cadmium bioconcentration in host, and by the cadmium bioaccumulation in the parasite. Indeed, results suggested that P. minutus could help G. roeseli to face with stress, what contributed to keep the host alive and favour the parasite transmission.

Biochemical and morphological responses in Chironomus riparius (Diptera, Chironomidae) larvae exposed to lead-spiked sediment.

The aim of the present study was to assess the potential use of biochemical markers and mentum deformities as indicators of long-term exposure to lead (Pb) in Chironomus riparius larvae. To do this, the authors measured 3 biochemical markers (i.e., malondialdehyde level, metallothionein concentration, and energy reserve content) as well as larval growth and mentum deformities after 16-d exposure to sediment containing Pb. The concentrations studied ranged from 3.5 mg/kg to 505.5 mg/kg dry weight. Despite the bioaccumulation of Pb in C. riparius bodies, frequencies of both mentum deformities and the dry weight were not significantly different between the control and stressed groups. On the contrary, Pb exposure caused a significant increase of both malondialdehyde level and metallothionein concentration. The increase of body Pb concentrations did not significantly modify body copper and zinc concentrations. Moreover, we observed a decrease of total lipid content and an increase of glycogen content as a function of a dose-response relationship, while no variation in protein concentrations was observed. Despite the adverse effects observed at the biochemical level, larval development was not affected. These results suggested that measurements of malondialdehyde level, metallothionein concentration, and energy reserve content can be used as relevant biomarkers of long-term sublethal exposure to Pb in C. riparius larvae.

Do male and female gammarids defend themselves differently during chemical stress

To investigate xenobiotic impacts on organism physiology, several studies involve biomarker assessment. However, most studies do not take into account the toxic effect on both males and females. Here, we have investigated the influence of gender on the detoxification response (reduced glutathione, metallothionein, γ-glutamylcystein ligase and carotenoid), energy reserves (protein, lipids and glycogen) and biomarker of toxic effects (malondialdehyde) in Gammarus roeseli exposed to cadmium. A principal component analysis revealed that G. roeseli males and females were differently impacted by cadmium. We observed lower malondialdehyde levels in females than in males, whatever the condition tested (i.e. control, 2 and 8 μg CdL(-1)), although the pattern of responses of control and exposures to 2 or 8 μgL(-1) was the same for both genders. Results could be linked to apparently more effective detoxification displayed by females than by males. Protein concentrations were unchanged in both genders, lipids contents were always significantly decreased and glycogen contents decreased only in females. This study supports the importance of taking into account the gender in ecotoxicological studies to have an overview of xenobiotics effects on a population.

Polymorphus Minutus Affects Antitoxic Responses of Gammarus Roeseli Exposed to Cadmium

The acanthocephalan parasite Polymorphus minutus is a manipulator of its intermediate host Gammarus roeseli, which favours its transmission to the final host, a water bird. In contaminated environments, G. roeseli have to cope with two stresses, i.e. P. minutus infection and pollutants. As P. minutus survival relies on its hosts survival, we investigated the influence of P. minutus on the antitoxic defence capacities and the energy reserves of G. roeseli females after cadmium exposure. In parallel, malondialdehyde, a toxic effect biomarker, was measured in G. roeseli females and in P. minutus. The results revealed that infected females displayed higher cell damage than uninfected ones, despite an apparent increase in reduced glutathione and metallothionein production. In fact, the increase of these antitoxic systems could be counterbalanced by carotenoid intake by the parasite, so that the overall defence system seemed less efficient in infected females than in uninfected ones. In addition, we demonstrated that cadmium induced cell damage in P. minutus, probably linked with cadmium accumulation in the parasite. Altogether, we observed a paradoxical pattern of responses suggesting that P. minutus increases cadmium toxicity in G. roeseli females although (i) it tends to increase several host antitoxic defence capacities and (ii) it bears part of the pollutant, as reflected by cell damage in the parasite.