Erik Baatrup

Silver nanoparticles and silver nitrate cause respiratory stress in Eurasian perch (Perca fluviatilis)

Silver nanoparticles are utilised in an increasing amount of products, and discharge to the aquatic environment is inevitable. Fish gills are in direct contact with the ambient water, making them potential exposed and vulnerable to suspended silver nanoparticles. The present study investigates the effect of silver nanoparticles (average 81 nm) on the oxygen consumption (M(O2)) in Eurasian perch (Perca fluviatilis), expressed by the basal metabolic rate (BMR) and the critical oxygen tension (P(crit)) below which the fish can no longer maintain aerobic metabolism. For comparison, the impact of silver nitrate (AgNO(3)), was examined as well. Perch were exposed to nominal concentrations of 63, 129 and 300 microg L(-1) silver nanoparticles and 39 and 386 microg L(-1) AgNO(3), respectively, plus controls which were not exposed to silver. M(O2) measured by automated intermittent closed respirometry. After one day acclimatization in the respirometer, the pre-exposure BMR was determined together with P(crit). Hereafter, nanoparticles or silver nitrate were added to the test tank and BMR and P(crit) were measured again the following day. The results demonstrate that nanosilver had no impact on the BMR, whereas exposure to 386 microg L(-1) AgNO(3) resulted in a significant raise in BMR. P(crit) was increased approximately 50% after exposure to 300 microg L(-1) nanosilver plus 31% and 48% by 39 microg L(-1)and 386 microg L(-1) silver nitrate, respectively. These findings reveal that exposure to nanosilver results in impairment of the tolerance to hypoxia. Possibly, nanosilver affects the gills externally, reducing the diffusion conductance which then leads to internal hypoxia during low water oxygen tensions (P(O2)).

In Vivo Toxicity of Silver Nanoparticles and Silver Ions in Zebrafish (Danio rerio)

The influence of water chemistry on characterised polyvinyl pyrrolidone- (PVP-) coated silver nanoparticles (81 nm) was investigated. NaCl solution series of 100–800 mg L−1 lead to initial and temporal increase in nanoparticles size, but agglomeration was limited. pH variation (5–8) had only minor influence on the hydrodynamic particle size. Acute toxicity of nanosivler to zebrafish (Danio rerio) was investigated in a 48-hour static renewal study and compared with the toxicity of silver ions (AgNO3). The nanosilver and silver ion 48-hour median lethal concentration (LC50) values were 84 μg L−1 and 25 μg L−1, respectively. To investigate exposure-related stress, the fish behaviour was observed visually after 0, 3, 6, 12, 24, 27, 30, and 48 hours of both nanosilver and ionic silver treatments. These observations revealed increased rate of operculum movement and surface respiration after nanosilver exposure, suggesting respiratory toxicity. The present study demonstrates that silver nanoparticles are lethal to zebrafish.

Structural and functional effects of heavy metals on the nervous system, including sense organs, of fish

1. Today, fish in the environment are inevitably exposed to chemical pollution. Although most hazardous substances are present at concentrations far below the lethal level, they may still cause serious damage to the life processes of these animals. 2. Fish depend on an intact nervous system, including their sense organs, for mediating relevant behaviour such as food search, predator recognition, communication and orientation. 3. Unfortunately, the nervous system is most vulnerable and injuries to its elements may dramatically change the behaviour and consequently the survival of fish. 4. Heavy metals are well known pollutants in the aquatic environment. Their interaction with relevant chemical stimuli may interfere with the communication between fish and environment. 5. The affinity for a number of ligands and macromolecules makes heavy metals most potent neurotoxins. 6. The present Mini-Review highlights some aspects of how trace concentrations of mercury, copper and lead affect the integrity of the fish nervous system; structurally, physiologically and biochemically.

Male zebrafish (Danio rerio) courtship behaviour resists the feminising effects of 17α-ethinyloestradiol-morphological sexual characteristics do not

The reproductive success of most fish depends partly on their ability to perform correct courtship behaviour. Alteration of this behaviour due to xenooestrogens can potentially affect the reproductive output and consequently population dynamics. In this lifetime study, zebrafish (Danio rerio) were exposed to environmentally realistic (0.05, 0.50 and 5.00 ng L(-1)) nominal concentrations of 17alpha-ethinyloestradiol (EE2) in a flow-through system for 4 months, from egg until sexual maturity. At 0.05 ng EE2L(-1), the secondary sexual characteristics of the males were significantly feminised with development of urogenital papillae and change in body colour. At 0.50 ng EE2L(-1), the sex ratio was altered from 69% males in the control groups to 59% males. The courtship behaviour of the male zebrafish was not affected by these two lower EE2 concentrations. Only at the highest concentration of 5.00 ng EE2L(-1), where only 5% of the group developed into males, was a change in behaviour recorded, and these few males were unable to induce spawning. Accordingly, the courtship behaviour of zebrafish is more resistant to oestrogenic exposure than secondary sexual characteristics and gonad development. This study provides the first quantitative measure of zebrafish courtship behaviour.

17α-Ethinylestradiol Reduces the Competitive Reproductive Fitness of the Male Guppy (Poecilia reticulata)

Abstract Whether endocrine disruption in an individual male is actually translated into reduced reproductive success in a natural competitive environment is extremely difficult to predict. Here, we have used paternity analysis to provide new information on the ability of an endocrine disruptor to deleteriously affect male guppy reproductive fitness by including the effect of intermale competition. Groups of male guppies were exposed to 10.5, 44.4, or 112 ng/L of the synthetic estrogen 17α-ethinylestradiol (EE2) from birth to adulthood. Subsequently, an exposed male competed against an unexposed male for the opportunity to fertilize a receptive female. The successful males siring the majority of the offspring in each brood were then identified using microsatellites in genetic paternity analysis. Only the highest dose of EE2 produced harmful effects with a significantly female-biased sex ratio, significant reductions in male sperm count, testis weight, body coloration and courtship behavior, and a significant increase in body size. These feminizing effects were translated into a highly significant reduction in fertility, where only 1 of the 17 exposed males sired offspring in competition with unexposed males. The evidence suggests that EE2-treated males have reduced reproductive fitness compared with untreated males, possibly the result of EE2 effects on multiple fitness traits. To our knowledge, this is the first study providing evidence of endocrine disruption at the population level that has included the ecologically highly relevant effect of sexual competition on male reproductive fitness.

Histochemical demonstration of two mercury pools in trout tissues: Mercury in kidney and liver after mercuric chloride exposure

Juvenile rainbow trout (Salmo gairdneri) were exposed to 100 ppb mercury (as HgCl2) in the water for 14 days. Concentrations of mercury in water and fish organs were monitored using radiolabeled mercury. Tissues from kidney and liver were fixed, and sections were developed by autometallography, a method whereby accumulations of mercury sulfides and/or mercury selenides are silver amplified. In the kidney, mercury was found within lysosomes and extracellularly in the basal lamina of proximal tubules. In the liver, mercury was found within lysosomes of the hepatocytes. Additional groups of mercury-exposed trout were subjected to selenium (as Na2SeO3), administered intraperitoneally 2 hr before fixation. Following this treatment, additional mercury could be visualized in the kidney circulatory system, including glomeruli, and in the nucleus and endoplasmic reticulum of liver cells. It is suggested that the mercury visualized prior to selenium treatment represents inorganic mercury, while additional mercury visualized after selenium administration represents an organic form.

The Effects of Vinclozolin, an Anti-Androgenic Fungicide, on Male Guppy Secondary Sex Characters and Reproductive Success

Abstract Despite the enormous volume of research concerning the various effects of chemicals with endocrine-disrupting properties in fish, there is still very little evidence that endocrine disruption can adversely affect individual fertility and, hence, pose problems for the population. In the present study, guppies (Poecilia reticulata) were fed with the anti-androgenic fungicide vinclozolin at concentrations ranging from 1.8 to 180 mg/kg from 8–14 wk of age. Male sperm count and the intensity of his sexual display behavior were significantly reduced in treatment groups, which was in line with the results of previous studies. Here, we show further that these impairments translate into reduced fertility, measured as the size of the females first clutch. Also, this reduced fertility was correlated to the male sperm count, but not to the intensity of the male sexual display. Finally, by crossing exposed with unexposed animals, we show that the adverse effect of vinclozolin on reproduction is mediated through the male alone.

Cytochemical demonstration of mercury deposits in trout liver and kidney following methyl mercury intoxication: differentiation of two mercury pools by selenium

The amount and the ultrastructural distribution of mercury was studied in seven different organs of rainbow trout (Salmo gairdneri) fingerlings following exposure to methyl mercury (MeHg)-contaminated fodder for periods of 2 and 7 weeks. The amounts of mercury retained by the whole fish and the selected organs were determined by measuring the uptake of 203Hg-labeled MeHg. Spleen, liver, and kidney had the highest concentrations after both experimental periods, while the largest relative increases were found in brain, muscle, and kidney. The subcellular distribution of mercury accumulations was demonstrated cytochemically in liver and kidney using the silver enhancement method by which accumulations of mercury-sulfides and/or mercury-selenides are made visible for light and electron microscopy. When sections prepared from the liver and kidney from fish, injected with selenium 2 hr prior to being killed, were compared with those of fish not treated with selenium, two distinct pools of mercury could be demonstrated, the HgS pool, and the HgSe pool. The HgS pool, supposed to represent inorganic mercury, was found exclusively within lysosomes. The increase of this pool from 2 to 7 weeks was most pronounced in the kidney. The HgSe pool, supposed to represent methyl mercury, was shown by the presence of silver deposits at new locations as well as by an increase in the amount of deposits within lysosomes. The new locations included (1) secretory-like vesicles and the bile canaliculi of the liver, suggesting a biliary excretion of this mercury pool; (2) microvilli and endosomes of kidney tubular cells, suggesting a glomerular filtration and subsequent reabsorption; and (3) mitochondria of proximal tubule cells.

Ultrastructural localization of mercury accumulations in the gills, hepatopancreas, midgut, and antennal glands of the brown shrimp, Crangon crangon

Abstract The deposition of mercury was studied in four organs of the brown shrimp, Crangon crangon. The shrimps were exposed to 17 μg/l Hg, as mercuric chloride dissolved in the aquarium water, for 14 days. The temporal accumulation of mercury during the experimental period was monitored in the gills, hepatopancreas, and abdominal muscle, using radiolabelled [230Hg]mercuric chloride. Mercury was initially retained in the gills, but after four days, and for the rest of the experimental period, the highest concentrations were found in the hepatopancreas. Autometallographically silver-enhanced mercury deposits were localized by light and electron microscopy within the gills, hepatopancreas, midgut, and antennal glands. In the gills, accumulations of mercury were observed in the lamellar epithelium and within hemocytes. However, the highest density of mercury deposits was found within the branchial podocytes. In the hepatopancreas, silver-enhanced mercury deposits were predominantly localized to the basal region of the R-cells, but were also observed within F-cells and B-cells. In the midgut, mercury was mainly localized to the basolateral portion of the epithelium and within lysosome-like organelles. Among the studied organs, the antennal glands contained the highest density of silver-enhanced mercury deposits. The podocytes, constituting the epithelium of the antennal colomosac, were extensively loaded, whereas less mercury was localized to the epithelium of the tubular labyrinth. Possible routes of mercury absorption and elimination in C. crangon are discussed.

Silver nanoparticles disrupt olfaction in Crucian carp (Carassius carassius) and Eurasian perch (Perca fluviatilis).

The present study investigates the effect of silver nanoparticles on olfaction in Crucian carp (Carassius carassius) and Eurasian perch (Perca fluviatilis). The electro-olfactogram (EOG) signal was recorded by stimulating the olfactory epithelium with pulses of the odorant L-alanine during the pre-exposure, silver exposure and recovery periods, respectively. The nanosilver suspension concentrations applied were 0.00, 0.45 and 45 μg L⁻¹, respectively. Secondly, to compare the toxicity of silver nanoparticles with silver ions, perch were exposed to ionic silver. During exposure to nanosilver suspension, the olfactory epithelium rapidly hyperpolarized, which was not found after exposure to silver ion solution. Exposure to 0.45 μg L⁻¹ nanosilver suspension led to enhanced EOG responses, whereas exposure to 45 μg L⁻¹ silver nanoparticle suspension and silver ion solution resulted in suppressed EOG signals. The EOG signals partly recovered in silver-free water. The silver nanoparticle olfactory toxicity is believed to be a combination of silver particles and released silver ions.