EFFECT, DISTRIBUTION, AND PREVALENCE OF GLUGEA STEPHANI (MICROSPORA) IN WINTER FLOUNDER (PLEURONECTES AMERICANUS) LIVING NEAR TWO PULP AND PAPER MILLS IN NEWFOUNDLAND

Effects of Loma morhua (Microsporidia) infection on the cardiorespiratory performance of Atlantic cod Gadus morhua (L)

The microsporidian Loma morhua infects Atlantic cod (Gadus morhua) in the wild and in culture and results in the formation of xenomas within the gill filaments, heart and spleen. Given the importance of the two former organs to metabolic capacity and thermal tolerance, the cardiorespiratory performance of cod with a naturally acquired infection of Loma was measured during an acute temperature increase (2 °C h(-1)) from 10 °C to the fish's critical thermal maximum (CT(Max)). In addition, oxygen consumption and swimming performance were measured during two successive critical swimming speed (U(crit)) tests at 10 °C. While Loma infection had a negative impact on cod cardiac function at warm temperatures, and on metabolic capacity in both the CT(Max) and U(crit) tests (i.e. a reduction of 30-40%), it appears that the Atlantic cod can largely compensate for these Loma-induced cardiorespiratory limitations. For example, (i) CT(Max) (21.0 ± 0.3 °C) and U(crit) (~1.75 BL s(-1)) were very comparable to those reported in previous studies using uninfected fish from the same founder population; and (ii) our data suggest that tissue oxygen extraction, and potentially the capacity for anaerobic metabolism, is enhanced in fish infected with this microsporidian.

Host-parasite interactions in some fish species

Host-parasite interactions are complex, compounded by factors that are capable of shifting the balance in either direction. The host's age, behaviour, immunological status, and environmental change can affect the association that is beneficial to the host whereas evasion of the host's immune response favours the parasite. In fish, some infections that induce mortality are age and temperature dependent. Environmental change, especially habitat degradation by anthropogenic pollutants and oceanographic alterations induced by climatic, can influence parasitic-host interaction. The outcome of these associations will hinge on susceptibility and resistance.

Long-term exposure of European flounder (Platichthys flesus) to the flame-retardants tetrabromobisphenol A (TBBPA) and hexabromocyclododecane (HBCD)

Tetrabromobisphenol A (TBBPA) and hexabromocyclododecane (HBCD) are widely used flame retardants that have increasingly been found as contaminants in the aquatic environment. In the present study, European flounder (Platichthys flesus) were chronically exposed to TBBPA; (105 days) and HBCD (78 days), in a wide range including environmentally relevant concentrations. TBBPA was administered via the water, whereas HBCD was administered in food and sediment, or in sediment alone. Chemical analysis of muscle showed an average increase in internal concentrations of approximately two orders of magnitude for both compounds tested. Animals exposed to HBCD via sediment alone (8000 microg/g total organic carbon, TOC) showed a proportional increase of alpha-HBCD in muscle compared to animals exposed via food and sediment. In both studies, exposure to the test compounds did not affect general health and toxicity parameters (behavior, survival, growth rate, relative liver and gonad weight). Hepatic microsomal enzyme activities (TBBPA: EROD; HBCD: EROD, PROD, and BROD) were not induced by any of the tested chemicals. Aromatase activity in male gonads showed a mild increase with rising TBBPA levels. There were no morphological and immunohistochemical indications for increased production of the yolk precursor protein vitellogenin (VTG) in animals exposed to TBBPA and HBCD; immunochemical analysis of plasma VTG levels showed no dose response in animals exposed to TBBPA. In animals exposed to TBBPA, levels of the thyroid hormone thyroxin (T(4)) increased with internal concentrations of the test compound, possibly indicating competition of TBBPA for plasma protein binding. Triiodothyronin (T(3)) levels were not affected and histology showed no signs of altered thyroid gland activity. Other organs investigated (liver, gills, kidney, skin, and gonads) revealed no histological changes related to TBBPA or HBCD exposure. Overall, the present results indicate limited endocrine effects of these widely used flame retardants in a test species representative of European estuaries at environmentally relevant exposure levels and at internal levels up to 4300 ng TBBPA/g wet weight, and 446 microg HBCD/g lipid weight in flounder muscle.

Assessment of stress-related bioindicators in winter flounder (Pleuronectes americanus) exposed to discharges from a pulp and paper mill in Newfoundland: a 5-year field study

This study assessed the effects of discharges from a sulphite-bleaching paper mill on winter flounder (Pleuronectes americanus) sampled each spring over a 5-year period in St. George's Bay, Newfoundland, prior to foraging activity. The fish were captured by SCUBA divers near the mill and at a reference site 10 km up current. Several bioindicators were used to assess fish health. Larger and older flounder exhibiting gross and microscopic tissue lesions, lower condition factor, and elevated hepatosomatic index but lower gonadosomatic index that was associated with delayed development, were observed in samples caught near the mill compared to those at the reference site. Additionally, fish examined near the mill were infested with an ectoparasite, Cryptocotyle lingua, that causes black spot disease but harbored fewer numbers of a digene, Steringophorus furciger, in the digestive tract than samples taken at the reference site. These results suggest that abnormal size distribution, interruption of growth, high prevalence of lesions, lower condition factor, enlarged liver, delayed gonadal development, and differences in parasitic levels were indicative of stress in winter flounder caused by discharges from the mill compared to samples from a reference site. There was no evidence of a population decline in the inlet because of annual recruitment possibly from St. George's Bay into which it opens.

Description of an ultrathin multiwire proportional chamber-based detector and application to the characterization of theSpraguea lophii(Microspora) two-dimensional genome fingerprint

Multiwire proportional chamber is a useful technology to build detectors that supersede the lack of interactivity of autoradiography in molecular biology experiments. Some drawbacks still limited the diffusion of existing instruments in biological laboratories. The major competitors are storage phosphor imaging systems. The simplified description of a radio-chromato-imager prototype (RCI) based on an original ultrathin multiwire proportional chamber is presented. It combines the advantage of the different existing technologies to present competitive properties in terms of efficiency, spatial resolution, robustness, manipulation easiness and production cost. Application of the RCI detector to molecular biology was performed by the analysis of karyotype and restriction display two-dimensional pulsed-field gel electrophoresis (KARD 2-D PFGE) data which are used to describe small eukaryotic genome structures. The comparative analysis with autoradiography was performed with the PDQuest software on Spraguea lophii (Microspora) genome fingerprints. The spot detection procedure applied to the different images leads to a similar conclusion considering the genome structure of S. lophii which appeared to be composed of 15 chromosomes for 13 karyotypic bands (200-880 kbp).