Michael Tedengren

Ecosystem perspectives on management of disease in shrimp pond farming

This paper reviews and discusses, from an ecological perspective, the causes behind the development and spreading of pathogens in shrimp aquaculture. The risk of disease in shrimp farming often inc ...

Protein expression signatures identified in Mytilus edulis exposed to PCBs, copper and salinity stress.

Applied to environmental toxicology, proteome analysis may be used to isolate chemical-specific protein expression signatures (PES). In this project specific PES were isolated in mussels, Mytilus edulis, from the Baltic Sea subjected in the laboratory to treatment with copper (70 ppb), Aroclor 1248 (1 ppb), and to lowered salinity. Four mussels in each treatment group were acclimated in the laboratory for 24 h before beginning the 7-day exposure. Whole body tissue was homogenized and separated using two-dimensional gel electrophoresis. The protein gels were scanned to TIFF files and compared using MELANIE II 2D gel analysis software (BioRad). Protein expression signatures including proteins induced and repressed by exposure were isolated for each treatment group. The specificity of PES due to environmental changes shows promise in bioindication, toxicity testing and in helping identify possible toxicity mechanisms.

Phenotypical improvement of morphological defences in the mussel Mytilus edulis induced by exposure to the predator Asterias rubens

Blue mussels, Mytilus edulis, were cultured in field enclosures in close vicinity of, and in absence of its predator, the starfish Asterias rubens. After four weeks, the morphology differed, such that predator-exposed mussels were significantly smaller in outer size (shell length, height and width), but had significantly larger posterior adductor muscle, thicker shell, and more meat per shell volume. These morphological changes suggested an improvement of the defences, which was confirmed in a predation assay where starfish needed significantly longer time to open predator-exposed mussels. The adaptive value was also demonstrated by a significantly larger survival of predator-exposed mussels in an assay where starfish foraged on a mixed population of exposed and control mussels. The experiment shows that predator-induced morphological plasticity exists in M. edulis. Such phenotypic plasticity may explain some of the morphological variation that is found in the field.

Predator‐induced changes in byssal attachment, aggregation and migration in the blue mussel, Mytilus edulis

Blue mussels, Mytilus edulis, were exposed to the water‐borne scent of predators, either to the starfish Asterias rubens, or the shore crab Carcinus maenas, in laboratory experiments. Predator‐exposed mussels developed a stronger byssal attachment compared to that of unexposed mussels, which was significant after about, 24 h, and twice as strong after four days. The byssal attachment response was variable. In the short term (<10h), predator scents could inhibit byssus production in those experimental batches where unexposed mussels had a high rate of byssus production. Predator‐exposed mussels also formed larger aggregates, migrated less, and sought structural refuges more often. Experiments showed that these traits gave significant protection against predation from both crabs and starfish.

Comparative study of the physiology and its probable effect on size in Blue Mussels (Mytilus Edulis L.) from the North Sea and the Northern Baltic Proper

Abstract It is a well-known fact that the Baltic Sea blue mussels are very abundant but do not grow as large and fast as Mytilus edulis from the North Sea. This is often attributed to physiological differences due to the decline in salinities, although the mechanisms behind this are not yet fully understood. In order to elucidate this, the metabolism of mussels from the northern Baltic proper (Asko) and the North Sea (Tjarno) was compared in the laboratory at ambient salinities of about 6.5 and 28.8 ‰, respectively, together with the magnitude of response to acute changes in the salinity. At 13°C and ambient salinities, respiration was higher for North Sea mussels in a non-reproductive stage, while after spawning respiration was higher for Baltic mussels. NH4-N excretion was always about two times higher for Baltic than for North Sea mussels at ambient salinities, and very sensitive to changes in salinity due to changes in the metabolism of free amino acids. While lowered salinities increased excretion, t...

Heavy metal uptake, physiological response and survival of the blue mussel (Mytilus edulis) from marine and brackish waters in relation to the induction of heat-shock protein 70

Earlier studies demonstrate that blue mussels (Mytilus edulis) from the Baltic population are more sensitive, in terms of physiological response and survival when exposed to toxic substances, compared to mussels from a more marine environment. The question whether this can be explained by environmental factors or genetic differences in the ability to synthesise a common stress-inducible protein (HSP 70) was addressed in two experiments. In the first experiment mussels from the North and Baltic Seas were acclimatised to an intermediate salinity of 15‰ S in the laboratory. The physiological performance was studied when the heavy metal cadmium was added and accumulated by the animals during a one week exposure. Tissue concentration was measured and related to physiological response. The level of expression of HSP 70 was analysed by densitometry on Western blots. North Sea mussels rapidly induced high levels and multiple forms of HSP 70, reached a comparatively low tissue concentration of cadmium, and showed only a minor physiological response and low mortality rates. Baltic Sea mussels had low levels of HSP 70, induced at slow rate, reached higher tissue concentrations of cadmium, and showed a more pronounced physiological response and higher mortality rates. High levels of stress proteins and a rapid induction corresponded well with physiological fitness, and the mussels from the North Sea thus seem to have a more efficient detoxification system, probably including stress-inducible proteins. In the second experiment, juvenile mussels from the Baltic population were acclimatised for a month to North Sea conditions in a field transplant. The mussels were then exposed to low-dose copper in the laboratory and the accumulation, physiological response and synthesis of stress inducible proteins were assessed. The results indicate that the physiological differences described between the populations are to a large extent explained by environmental factors. However, some differences can still he observed between the populations, e.g., a lower rate of induction of a major stress protein in Baltic than in North Sea mussels. It can thus be suggested that a reduced ability to stress protein induction, in their natural low saline habitat, might be a contributing factor to the higher pollution sensitivity earlier demonstrated for Baltic blue mussels.

Variability of heat shock proteins and glutathione S-transferase in gill and digestive gland of blue mussel, Mytilus edulis

Glutathione S-transferase (GST) and heat shock proteins (hsps) 40, 60, 70 and 90 were determined by immunoblotting using actin as an internal control in Mytilus edulis from one station outside (site1) and three stations within (sites 2-4) Cork Harbour, Ireland. Comparisons were made between gill and digestive gland and between sites. Gill shows generally higher hsp 60, 70 and 90 while digestive gland has higher hsp 40. Site 1 showed higher gill hsps 40 and 70 than sites 2-4 while gill GST was higher in sites 3 and 4 than 1 and 2. Comparison with sites in the North Sea (site 5: outside Tjärnö in The Koster archipelago in the Skagerack) and Baltic Sea (site 6: Askö island) also revealed lower hsps 40 and 70 in site 6 (low salinity) than site 5 (high salinity) although hsps 60, 70 and 90 were detectable in digestive gland unlike sites 1-4. Previously, only hsp 70 had been studied at these sites [Mar. Environ. Res. 39. (1995), 181]. At the mRNA level, gill hsp 70 is 80-fold higher at Tjärnö than Askö. These data suggest that, while salinity may slightly decrease hsp 40 and 70, both hsp 70 and GST are selectively up-regulated by approx. 10- and 3-fold, respectively, at Tjärnö compared to the other sites which we attribute to exposure to more widely fluctuating pollution levels.

Heat pretreatment increases cadmium resistance and HSP 70 levels in Baltic Sea mussels

The focus of this thesis is the early detection of stress in the environment. It has been proposed that studies on the cellular level would detect stress reactions earlier in time compared to common physiological methods. In a series of experiments we investigated how different stress factors, both natural and introduced by man, affect levels of stress proteins. One- and two-dimensional gels were used to determine individual proteins and families of proteins. The two-dimensional gels were also used in a proteomic approach, were the presence and absence of proteins after treatment was observed, and the protein expression signatures (PES) were identified. Baltic Mytilus edulis was used in all experiments and it is evident that earlier observed differences in physiological rates and pollution sensitivity, compared to marine mussels, is also manifested as lower concentrations of stress proteins after exposure to copper and cadmium. When the Baltic mussels were allowed to acclimate for one month the difference decreased, suggesting an environmentally induced difference (paper I). Pre-exposure to heat before exposure to either a second heat-shock or cadmium was found to enhance the levels of HSP70 and thus tolerance, significantly (paper II). Exposure to a mixture of stress factors (PCB, copper and lowered salinity) revealed synergistic, additive and antagonistic effects in induction of 6 different stress proteins. When analyzing a large number of proteins it was shown that it is possible to identify PES with this technique, and we hypothesize that it could be possible to separate responses to mixtures of stress factors (Papers III and IV). Different techniques were also applied to analyze the protein expression pattern when mussels were exposed to PAH- and PCB-fractions extracted from Baltic Sea sediments. In this experiment the protein assays were accompanied by physiological measurements. All methods indicated stressed conditions, but the variation between individual mussels within treatments was smaller in terms of protein response than for physiological parameters (paper V). It is concluded that measuring the induction of stress proteins is a reliable way to detect stressful conditions. Proteins visualized on a one dimensional gel give a “gross” picture of an organism’s condition. The major challenge is to identify the origin and severity of the elucidated stress response. Further mapping of two-dimensional gels suggested that protein patterns are specific to type and level of stress. A most important future step is to establish links between sub-cellular protein response to well known physiological effects. This should include long term experiments where altered protein expression signatures are linked to life history characteristics like survival, growth and reproductive success.

Comparative stress response to diesel oil and salinity changes of the blue mussel, Mytilus edulis from the baltic and north seas

Abstract Due to the lower salinity, Baltic Mytilus edulis are dwarfed compared to North Sea mussels. The relative sensitivity to pollution of the two populations has been much debated. We have compared the stress response of Mytilus edulis from the Baltic and North Seas to addition of diesel oil in combination with salinity changes. Respiration and NH4-N excretion were found to change synergistically with lowered salinity in Baltic mussels but not in North Sea mussels. Stress effects were generally aggravated by simultaneous lowering of salinity and counteracted by salinity increases. A more pronounced lowering of O/N-ratios of Baltic mussels at ambient salinities indicates that these are more sensitive to additional stress of oil pollution that is superimposed on the already existing salinity stress.

Effects of the multiple stressors copper and reduced salinity on the metabolism of the hermatypic coral Porites lutea

This study investigates the physiological responses in the hermatypic coral Porites lutea when exposed to a combination of reduced salinity (from ambient 30 psu to 20 psu) and two concentrations of copper (CuS04), 10 microg 1(-1) and 30 microg 1(-1). Corals were exposed for 14 h and changes in metabolism in terms of primary production rate per chlorophyll a and respiration per surface area (cm2) were used as measures of stress. The results showed no significant changes in respiration rate in any of the treatments compared with controls, or between treatments. The primary production rate, however, displayed a more complex pattern. Corals exposed to reduced salinity, 30 microg 1(-1) copper, and the combination of the two stressors significantly reduced the production rate, whereas corals exposed to 10 microg 1(-1) only, remained unaffected. However, adding 10 microg 1(-1) copper to reduced salinity did not affect the production rate thus indicating an antagonistic effect.