Christelle Malbrouck

Effects of microcystins on fish

Microcystins (MCs) are hepatotoxic heptapeptides released into water during or on senescence of cyanobacterial blooms. This review details the different effects of the MCs on fish and discusses their potential consequences in aquatic food webs. In early life stages, exposure to MCs causes, in a dose-dependent manner, perturbations to embryonic hatching, decrease in survival and growth rate, as well as histopathological effects (enlarged and opaque yolk sac, small head, curved body and tail, hepatobiliary abnormalities, ultrastructural alterations in hepatocytes, heart rate perturbations). In adults and juveniles, field and experimental studies demonstrated that after ingestion MCs accumulate mainly in liver but can also be found in muscle and viscera. Microcystin exposure has been shown to affect growth rate and osmoregulation, increase liver enzyme activities in the serum and heart rate, modify behavior, and exert histopathological effects in the liver, intestine, kidneys, heart, spleen, or gills, but the degree to which these effects were seen depends on the exposure route. The detoxication pathway of MCs in fish begins with a conjugation reaction to glutathione catalyzed by glutathione S-transferases, and this is comparable to the reaction demonstrated in other organisms, from plants to mammals. It appears that MC concentrations found in nature can potently affect several trophic levels in the aquatic ecosystems, in particular by inducing failure of sensitive stages (e.g., fish fry) to develop and accumulating in the food chains. The need of further quantitative studies on the sublethal effects, accumulation, and fate of MCs in aquatic food chains still remains.

Hepatic accumulation and effects of microcystin-LR on juvenile goldfish Carassius auratus L.

After intraperitoneal injection of microcystin-LR (MC-LR) (125 microg kg(-1) body wt.), the concentration of MC-LR in the liver of juvenile goldfish Carassius auratus (30 g body wt.) was assayed by a modified protein phosphatase inhibition method. A temporary accumulation occurred from 3 to 48 h post-injection, followed by a significant decrease between 48 and 96 h. Under our experimental conditions, contamination by MC-LR did not change ionic homeostasis, as attested by blood osmolality values and gill Na(+)/K(+) ATPase activity. Light microscopy observations revealed lesions and cellular necrosis progression, which was concomitant with an increase in enzyme activity of plasma aspartate aminotransferase (AspAT), alanine aminotransferase (AlaAT) and L-lactate dehydrogenase (LDH) and with a decrease of hepatic glutathione-S-transferase (GST) activity. Structural alterations and enzymatic activity modifications became significant within 24 h post-injection. Recovery of hepatocytes on day 21 after MC-LR injection was evident, together with a decrease in the MC-LR equivalent content of the liver.

The effect of PIT tags on growth and physiology of age-0 cultured Eurasian perch Perca fluviatilis of variable size.

Abstract For many biological reasons, it is often necessary to tag and monitor fish from a very early age. However, tagging can adversely affect fish, especially for high tag to body weight ratios. To determine the minimum size for passive integrated transponders (PIT) tagging in juvenile perch Perca fluviatilis , surgical implantation was evaluated in fish ranging from 1.67 to 10.62 g (55–96 mm FL). The survival, gonadal development, and capacity of tagged perch to store abdominal fat was affected neither by the tagging procedure, tag presence, nor tag to body weight ratio. Four months after tagging, no tag had caused internal damage or had been expelled, despite about 95% of them becoming encapsulated by host tissues. Negative effects from tagging were restricted to slower healing rates, and depressed growth of fish with high tag to body weight ratios during the first post-tagging days, which was compensated for by catch-up growth within less than 2 weeks. Surgical PIT tagging can be confidently applied to perch weighing less than 2 g, but the collection of biological data should be delayed by about 2 weeks after tagging. X-ray photographs revealed variable orientations of tags (95% CI: 26°) and slight (ca. 4°) changes of orientation over time. These discrepancies may affect the probability that the tag is detected by automatic data entry stations, and should be compensated for by using smaller antennas (≤87% of maximal antenna size).