Energy balance of juvenile <Emphasis Type="Italic">Cyprinus carpio</Emphasis> after a short-term exposure to sublethal water-borne cadmium

Stress in fish can be assessed by means of a bioenergetic approach, based on the evaluation of changes in their physiological parameters. The objective of this study was to determine the impact of sublethal water-borne cadmium (Cd) on the energetic balance of juvenile Cyprinus carpio under laboratory conditions after a short-term exposure. Fish were exposed to a concentration of Cd (0.15 mg Cd l⁻¹) for 2 weeks. This concentration is environmentally realistic since it is usually found, even at higher values, in heavily polluted periurban water bodies of Argentina. No mortality was recorded among the animals used in the experiments. Food intake, food assimilation and assimilation efficiency, fecal production, liver glycogen content, oxygen consumption, oxygen extraction efficiency, specific metabolic rate, ammonia excretion and ammonia quotient (AQ), condition factor, and liver somatic index were determined. The overall balance was expressed as the scope for growth (SFG). The morphological indices and the liver glycogen content of Cd-exposed fish showed no significant differences when compared to those of controls. There was a significant decrease in the food intake, fecal production, and food assimilation rates as well as in AQ; the SFG exhibited a highly significant decrease. The remaining parameters (assimilation efficiency, oxygen consumption, oxygen extraction efficiency, specific metabolic rate, and ammonia excretion) increased after the exposure to Cd. We concluded that the sub-chronic exposure of Cyprinus carpio to a sublethal concentration of Cd causes important alterations in the energy-related homeostasis of fish. Most of the responses are indicative of physiological adaptations to compensate an increased energy requirement due to the impairments caused by the metal.     

Aluminum-induced oxidative stress in lymphocytes of common carp (<Emphasis Type="Italic">Cyprinus carpio</Emphasis>)

Several studies of fish have shown that aluminum may induce hypoxia, hypercapnia, metabolic acidosis, and respiratory failure. In lymphocytes, morphologic abnormalities and reduced immune activity have been observed. Nevertheless, there is little data on oxidative stress and such data are essential in order to identify its mechanism of action. The common carp Cyprinus carpio, an omnivorous fish commonly used in commercial aquaculture, has been proposed as a test organism in toxicologic assays due to its economic importance and wide geographic distribution. The aim of this work was to evaluate Al-induced oxidative stress in lymphocytes of the common carp C. carpio. Specimens were exposed to three different concentrations of Al (0.05, 120, and 239 mg/l) in a static exposure system for 96 h. At the end of the exposure period, blood was collected and lymphocytes were separated. Lipid peroxidation, oxidized protein content and the activity of superoxide dismutase, catalase, and glutathione peroxidase were measured. Results show that the tested Al concentrations modified the activity of antioxidant enzymes and elicited higher levels of lipid peroxidation and oxidized proteins. The degree of damage induced was concentration and tissue dependent.     

Sperm of feral carp <Emphasis Type="Italic">Cyprinus carpio</Emphasis>: optimization of activation solution

The spermatozoa of oviparous fish, such as feral carp (Cyprinus carpio), are immotile in the presence of semen plasma or isotonic solutions, and to obtain good motility, they must be diluted with suitable medium. The objective of this study was to identify the best activating solution for feral carp sperm. Sperm motilities were compared in the new activating solution (a): (50 mM NaCl, 30 mM KCl, 30 mM Tris, pH = 8.5) and activating solution (b): (50 mM NaCl, 40 mM KCl, 30 mM Tris, pH = 8.5) based on effect of pH with everyone of Na⁺ and K⁺ ions versus four other activating solutions Billard’s saline solution, Poupard’s saline solution, distilled water and hatchery water that is routinely used for extending carp semen. Our results showed that maximum total motility period and percentage of motile sperm were seen in selected saline solution (a). The present study describes an activating solution that prolongs feral carp sperm motility.     

Recent expansion of Northeast Atlantic and Mediterranean populations of <Emphasis Type="Italic">Melicertus</Emphasis> (<Emphasis Type="Italic">Penaeus</Emphasis>) <Emphasis Type="Italic">kerathurus</Emphasis> (Crustacea: Decapoda)

We analysed the genetic diversity of Melicertus kerathurus (Penaeidae), a commercially valuable penaeid shrimp that is distributed in the Mediterranean Sea and eastern Atlantic Ocean. We examined the polymorphism of a 494 bp DNA segment of the mitochondrial COI region in 173 individuals, sampled in nine Mediterranean and two Atlantic samples, covering the whole range of the species from the tropical waters of the Gulf of Guinea to the eastern part of the Mediterranean Sea. The mean nucleotide and haplotype diversities were π = 0.00275 and h = 0.718, respectively, for the global data set, with the highest values occurring in the African samples and the lowest in the Adriatic Sea. A clear sample differentiation was found (F _st = 0.194), but this did not reflect a geographical pattern and there were only faint traces of an Atlantic–Mediterranean subdivision. Mismatch analysis and a high significant negative value of Tajima’s D suggested that M. kerathurus is not at mutation drift-equilibrium, but underwent a recent expansion after a period of low effective sample size. A postglacial recolonisation of the Mediterranean from an Atlantic refuge could be hypothesised based on these data.     

Response of <Emphasis Type="Italic">Cyprinus carpio</Emphasis> to copper exposure: alterations in reduced glutathione,catalase and proteins electrophoretic patterns

This study was conducted to characterize the alterations in reduced glutathione (GSH) level, catalase (CAT) activity and proteins electrophoretic patterns in response to sublethal copper (Cu) exposure in Cyprinus carpio and to determine whether these responses are related to Cu accumulation in gills, chosen as target tissue. Fish were exposed to 0.1 and 1.0 mg/l Cu for 10 and 20 days. There were increasing level of Cu in the gill with increasing concentrations of metal in the exposure medium, and with increasing duration of exposure. GSH level and CAT activity increased in fish exposed to 1.0 mg/l Cu for both exposure periods, while no change was detected at the lower Cu concentration. Electrophoretic patterns of gill proteins by sodium dodecyl sulphate gel electrophoresis (SDS–PAGE) consist of 25-, 26-, 30-, 44- and 48-kDA medium molecular weight proteins (MMP) for five bands and 64-, 72-, 90- and 101-kDA high molecular weight proteins (HMP) for four bands in both control and treatment groups. The levels of 25-, 26- and 30-kDA MMP and 72- and 90-kDA HMP increased in response to Cu exposure. The present study demonstrated that Cu caused stress in fish gills and an acclimation with induction of GSH, CAT, MMP and HMP, which were important in the protection against metal damage, was observed.     

Relationship between biological characteristics of eggs and female brood stocks of Persian sturgeon <Emphasis Type="Italic">Acipenser</Emphasis><Emphasis Type="Italic">persicus</Emphasis>: a comparison with other fish species

We have determined a number of biological characteristics of the Persian sturgeon egg (including diameter, surface-to-volume ratio, yolk sphere and perivitelline space) and of female brood stocks (including age, length, weight, condition and absolute fecundity) in 420 specimens of the migratory population of Acipenser persicus in Gorgan bay of Iran from 2001 to 2004. In the hydrated egg, the average egg diameter, yolk diameter, surface-to-volume ratio and yolk sphere-to-perivitelline space ratio values were: 3.64 ± 0.17 mm, 3.26 ± 0.25 mm, 1.65 ± 0.08 and 0.75 ± 0.01, respectively. In this chondrostean species, the egg surface and volume were found to increase with increasing egg diameter, but the egg surface-to-volume ratio decreased. In Persian sturgeon, the surface-to-volume ratio and yolk sphere-to-perivitelline space ratio is very high; therefore, the metabolic rate is low and female spawning occurs in low-temperature waters. The statistical Pearson correlation between egg diameter relative to a number of brood stock characteristics, including fork length (r = 0.059), weight (r = 0.140), age (r = 0.081) and absolute fecundity (r = 0.095), were not significantly different (P > 0.05). An extensive comparison of these results with data published on other fish species is presented and discussed.     

Behavioural response of carp (<Emphasis Type="Italic">Cyprinus carpio</Emphasis>, L.) pond stock upon occurrence of hunting great cormorant (<Emphasis Type="Italic">Phalacrocorax carbo sinensis</Emphasis>) flocks

Besides various physiological and biological indices, stress in fish can be expressed directly by changes in their behaviour. Electrofishing point sampling approach based on CPUE (catch per unit effort) was used to evaluate fish density (escapement) into the littoral zones of four Czech ponds as a reaction to the occurrence and hunting activities of great cormorant (Phalacrocorax carbo sinensis) flocks. The behaviour of two-year-old common carp (Cyprinus carpio) before and after cormorant arrival was compared. Significant differences (P < 0.001) in CPUE were recorded in fish density before and after cormorant arrival on all of four ponds under study—Žofinsky: 0.04 ± 0.18 and 22.38 ± 26.87 (mean ± SD), Stary Hospodář: 0.05 ± 0.29 and 25.49 ± 25.45, Žebrákov: 0.16 ± 0.57 and 28.58 ± 24.75 and Travičny: 0.03 ± 0.19 and 17.18 ± 18.20, respectively. The evaluation of fish wounding in the CPUE fish samples proved the proportion of fish injured by cormorant attacks ranging from 3.33 to 18.19% in the ponds under study.     

Use of the freshwater rotifer <Emphasis Type="Italic">Brachionus angularis</Emphasis> as the first food for larvae of the Siamese fighting fish <Emphasis Type="Italic">Betta splendens</Emphasis>

Larvae of the Siamese fighting fish Betta splendens were reared on the mass-cultured small freshwater rotifer Brachionus angularis Laos strain (UTAC-Lao), Paramecia sp., and Artemia as live food sources. Larvae fed live food were found to have a significantly high survival rate (97.5–100%) 18 days after hatch (DAH) in comparison to the control unfed larvae, which died by 12 DAH. Rotifer-fed larvae were found to grow faster than paramecia-fed larvae. The fastest growth rate was observed in larvae fed a combination of rotifer and Artemia, with growth in these larvae increasing by 282% by 18 DAH [total length (TL) 11.3 ± 1.2 mm] relative to body measurements taken 3 DAH. The next fastest growth rate was observed in rotifer-fed larvae, with a 158% increase in growth observed by 18 DAH (TL 7.6 ± 0.5 mm). The paramecia-fed larvae were found to grow by only 54.3% (TL 4.6 ± 0.1 mm) during the same period.     

Biochemical changes and sensory assessment on tissues of carp (<Emphasis Type="Italic">Cyprinus carpio</Emphasis>, Linnaeus 1758) during sale conditions

In this study, some biochemical changes of carp (Cyprinus carpio, Linnaeus 1758) tissues were investigated. Studies have been carried out on carp which have regional economical importance. Storage temperature and time are the most important factors that affect the quality of fish during sales. It was observed that the temperature varied between 9 and 12°C in sale conditions. In addition, we assumed the arrival time of the fish at the fish market to be 0 (zero) h. Biochemical analyses [malondialdehyde (MDA) levels and catalase activity] of carp tissues (muscle, liver, heart, spleen, brain) were carried out on fish which were held for 24 and 48 h, as well as on fresh fish (0 h). In addition, sensory analysis was conducted by a panel consisting of experienced judges of sensory evaluation. Statistically significant (P < 0.05) increases in MDA levels were found in liver, muscle, brain and spleen tissues when comparing the 0- and 24-h groups. But there was no statistically significant (P > 0.05) increase in MDA level in heart tissue of carp after 24 h. There was a statistically significant (P < 0.05) increase in MDA levels in muscle, spleen and heart tissues when comparing the 24- and 48-h groups. In the group examined at 24 h, it was observed that there were statistically significant differences from the 0 h group values (P < 0.05) for catalase (CAT) activity in muscle, brain, spleen and heart tissues. The decreases in CAT activity in liver and spleen tissues were found to be statistically significant (P < 0.05) between the group examined at 24 h compared with the group examined at 48 h. Carp maintained good quality during the selling conditions up to 24 h. This experiment deals with the effects of post-slaughter time and storage temperature on carp tissues. It is concluded that by considering the storage temperature (9–12°C) and storage time (post-slaughter) the product maintained acceptable quality up to 24 h. There was significant deterioration of sensory quality, as a result of changes in chemical constituents.     

Physiological responses of over-wintering common carp (<Emphasis Type="Italic">Cyprinus carpio</Emphasis>) to disturbance by Eurasian otter (<Emphasis Type="Italic">Lutra lutra</Emphasis>)

Using a tame animal, the impact of otter (Lutra lutra) disturbance on over-wintering carp (Cyprinus carpio) was monitored in two experiments, 133 and 140 days, respectively, over two consecutive winters (November–April). The level of stress in over-wintering carp exposed to various intensities of disturbance by otters was quantified using biological indicators of stress (cortisol, cortisone, indices of nitrogen, carbohydrate, lipid and mineral metabolism and activity of basic blood plasma enzymes) taken from blood plasma of stocked carp at the end of the winter seasons (when the photoperiod was 12 light:12 dark, respectively, 13L:10D). Moreover, condition (Fulton’s coefficient of condition and fat content in muscles) and mortality rate of that carp were measured after over-wintering and also after the subsequent vegetation period. The analysis of blood and tissue samples of experimental fish showed changes in nitrogen, carbohydrate and mineral metabolism as well as levels of hormones and fat reserves. Higher response to stress in metabolism of carp with lower intensity of disturbance by otter suggests that high level of disturbance can lead to metabolic adaptation of carp to stress. The effect of stress on the mortality rate of carp during the over-wintering is not clear. Nevertheless, the negative effect of stress on survival, condition and growth rate of carp in the subsequent vegetation period was not observed.     

Anti-oxidant status in embryonic,post-hatch and larval stages of Asian seabass (<Emphasis Type="Italic">Lates calcarifer</Emphasis>)

The concentrations of anti-oxidant enzymes such as superoxide dismutase (SOD), catalase (CAT) and selenium-dependent glutathione peroxidase (SeGPx), and low molecular weight free-radical scavengers such as reduced glutathione (GSH) and ascorbic acid (vitamin C) were evaluated during the period from gastrulation (GS) to 25 days post-hatch (dph) in the larvae of Asian Seabass, Lates calcarifer. Oxidative damage due to lipid peroxidation (LPO) was also assessed, by evaluation of the formation of malondialdehyde (MDA). All the three anti-oxidant enzymes, SOD, CAT and GPx, showed high activities during gastrulation, suggesting an increased metabolic rate during the period of embryonic development. Though the SOD activity apparently decreased progressively during 3–20 dph of larval development, the difference was not significant. CAT showed high activity during gastrulation and remained constant up to 3 dph, suggesting an increased need to metabolise hydrogen peroxide (H₂O₂) and organic peroxides. In contrast, SeGPx activity increased progressively from 5 dph to 25 dph during larval development, indicating an increased need to detoxify lipid peroxides. This is evident from the observation of increased lipid peroxidation from 10 dph to 25 dph during larval development. GSH levels were low at gastrulation, indicating increased metabolic rate and formation of lipid radicals during this period, corresponding to the decrease in the level of ascorbic acid, which is consumed for regeneration of GSH.     

Effects of slaughter methods on physical,biochemical and microbiological quality of rainbow trout <Emphasis Type="Italic">Oncorhynchus mykiss</Emphasis> and mirror carp <Emphasis Type="Italic">Cyprinus carpio</Emphasis> filleted in pre-, in- or post-rigor periods

Rainbow trout Oncorhynchus mykiss and mirror carp Cyprinus carpio were slaughtered by either percussion or asphyxiation. For determination of the physical (texture value) and biochemical quality attributes [pH, lactic acid, total volatile basic nitrogen (TVB-N), and malondialdehyde (MDA) values] of trout and carp, the fish were filleted immediately (within 2 h), 12 h after harvest (pre-rigor), 24 and 36 h after harvest (in-rigor), and finally 48 and 60 h after harvest (post-rigor). For microbiological quality attribute (mesophilic and psychrophilic bacteria count) analyses, the fish were filleted immediately (within 2 h) after harvest (pre-rigor), 24 h after harvest (in-rigor) and 48 and 72 h after harvest (post-rigor). By percussion slaughtering followed by pre-rigor filleting, it was possible to process rainbow trout and mirror carp without inflicting excessive handling stress. Percussion slaughter delayed onset of rigor and the percussion-slaughtered fish exhibited a long pre-rigor period (≈24 h), giving plenty time for pre-rigor processing. Percussion slaughtering and pre-rigor filleting of fish was considered to be superior to the traditional asphyxiation slaughtering with respect to texture, TVB-N and MDA attributes.     

Dietary inclusion of detoxified <Emphasis Type="Italic">Jatropha curcas</Emphasis> kernel meal: effects on growth performance and metabolic efficiency in common carp, <Emphasis Type="Italic">Cyprinus carpio</Emphasis> L.

Jatropha curcas is a multipurpose and drought-resistant shrub or small tree widespread all over the tropics and subtropics. Its seeds are rich in oil, and the Jatropha kernel meal obtained after oil extraction is rich in protein. However, presence of toxic and antinutritional constituents restricts its use in fish feed. Jatropha kernel meal was detoxified. Common carp, Cyprinus carpio, fingerlings (15; av. body mass 10.9 ± 0.65 g) were randomly distributed in three groups with five replicates. A 6-week feeding experiment was conducted in a respirometer system to evaluate the growth performance, nutrient utilisation and energy budget. Fish were fed isonitrogenous diets (38% crude protein): control diet (C _ontrol group) containing fish meal (FM) protein based protein and two other diets replacing 75% FM protein with detoxified Jatropha kernel meal (DJKM, J _atropha group) and soybean meal (SBM, S _oybean group). At the end of the experiment, body mass gain, metabolic growth rate, protein efficiency ratio, protein productive value, energy retention, efficiency of metabolised energy for growth and efficiency of energy retention were determined. These parameters were high and statistically similar for C _ontrol and J _atropha groups and significantly lower (P < 0.05) for S _oybean group. Whereas a reverse trend was observed for energy expenditure per g protein retained in fish body. No significant differences were found in heat released, gross energy uptake, metabolised energy intake, metabolisability, energy expenditure, energy expenditure per g protein fed and apparently unmetabolised energy. Conclusively, common carp–fed plant protein (DJKM and SBM) and FM protein–based diets exhibited equal average metabolic rate.     

The effect of praziquantel applied per os on selected haematological and biochemical indices in common carp (<Emphasis Type="Italic">Cyprinus carpio</Emphasis> L.)

The aim of the study was to assess the effects of the anthelminthic, praziquantel, on the haematological and biochemical indices of the blood of common carp (Cyprinus carpio L.). Fish were divided into six groups: two groups received 30 mg kg⁻¹ body weight (bw) of praziquantel, and two groups were given 50 mg kg⁻¹ bw of praziquantel mixed into the heat-treated amyloid vehicle. Fish in the remaining two groups were given only the amyloid vehicle and were used as controls. Fish were examined either 24 or 96 h after administration. Praziquantel treatment was characterised by a significantly lower erythrocyte count, haemoglobin level, packed cell volume and total protein at both dose levels after 24 h compared with the controls, but these parameters were similar to the control values at 96 h. The activity of alanine aminotransferase (ALT) was significantly higher after 96 h in the treated groups, which could be attributed to slight hepatocyte damage caused by praziquantel. However, the differences between the treated and the control groups were not great, and we presumed that they were reversible.     

Effects of bifenthrin on some haematological,biochemical and histopathological parameters of common carp (<Emphasis Type="Italic">Cyprinus carpio</Emphasis> L.)

The aim of this study was to assess the effect of bifenthrin on common carp (Cyprinus carpio L.). The 96-h LC50 value of Talstar EC 10 (active substance 100 g l⁻¹ bifenthrin) was found to be 57.5 μg l⁻¹. Examination of haematological and biochemical profiles and histological tissue examination was performed on common carp after 96 h of exposure to Talstar EC 10 (57.5 μg l⁻¹). The experimental group showed significantly higher (P < 0.01) values of plasma glucose, ammonia, aspartate aminotransferase and creatine kinase as well as the relative and absolute monocyte count, compared with the control group. Histological examination revealed teleangioectasiae of secondary gill lamellae and degeneration of hepatocytes. The bifenthrin-based Talstar EC 10 pesticide preparation was classified as a substance strongly toxic for fish.     

Effect of <Emphasis Type="Italic">Cratoxylum formosum</Emphasis> on innate immune response and disease resistance against <Emphasis Type="Italic">Streptococcus agalactiae</Emphasis> in tilapia <Emphasis Type="Italic">Oreochromis niloticus</Emphasis>

The effect of aqueous extract of Cratoxylum formosum on innate immune response and disease resistance in tilapia Oreochromis niloticus was investigated. The fish were fed diets containing 0% (control), 0.5% (diet 1), 1% (diet 2), and 1.5% (diet 3) of C. formosum aqueous extract for 30 days. At the end of the experimental period, parameters of innate immune response including phagocytosis of blood leukocytes, lysozyme activity in plasma, and respiratory bust activity were examined. Feeding the fish with diet 2 and diet 3 for 20 days enhanced phagocytic activity and for 30 days stimulated lysozyme and respiratory burst activities. Diet 1 increased the phagocytic activity at 30 days, but did not affect the other measured parameters. All parameters were not significantly changed (P > 0.05) in the control group throughout the experiment. Following 30 days of feeding, fish were infected with S. agalactiae. The cumulative mortalities of bacterial-infected tilapia that were fed diet 1, diet 2, and diet 3 were 56, 12, and 10%, respectively, compared with 85% in the control group. These results indicate that the aqueous extract of C. formosum may elevate the innate immune response and enhance disease resistance in tilapia.     

Spatial learning-induced <Emphasis Type="Italic">egr</Emphasis>-<Emphasis Type="Italic">1</Emphasis> expression in telencephalon of gold fish <Emphasis Type="Italic">Carassius auratus</Emphasis>

The immediate-early gene (egr-1) expression was used to examine the neuron’s response in telencephalon of goldfish during spatial learning in small space. Fishes were pre-exposed in the experimental apparatus and trained to pick food from the tray in a rectangular-shaped arena. The apparatus was divided into identical compartments comprising three gates to provide different spatial tasks. After the fish learned to pass through the gate one, two more gates were introduced one by one. Fish made more number of attempts and took longer time (P < 0.05) to pass through the first gate than the gate two or three. This active learning induces the expression of egr-1 in telencephalon as established by western blot analysis. Subsequently, the fish learn quickly to cross the similar type of second and third gate and make fewer errors with a corresponding decline in the level of egr-1 expression. As the fish learned to pass through all the three gates, third gate was replaced by modified gate three. Interestingly, the level of egr-1 expression increased again, when the fish exhibit a high exploratory behavior to cross the modified gate three. The present study shows that egr-1 expression is induced in the telencephalon of goldfish while intensively acquiring geometric spatial information to pass through the gates.     

Anesthesia induces stress in Atlantic salmon (<Emphasis Type="Italic">Salmo salar</Emphasis>), Atlantic cod (<Emphasis Type="Italic">Gadus morhua</Emphasis>) and Atlantic halibut (<Emphasis Type="Italic">Hippoglossus hippoglossus</Emphasis>)

Stress in response to anesthesia with benzocaine, MS-222, metomidate and isoeugenol was studied in Atlantic salmon (Salmo salar), Atlantic halibut (Hippoglossus hippoglossus), and Atlantic cod (Gadus morhua) with no concomitant stress from handling or confinement in association with anesthesia or sampling. All of the anesthetics tested induced a stress response in all species, displayed by a release of cortisol to the water. MS-222 anesthesia elicited the highest cortisol release rates, reaching maximum levels 0.5 h post-exposure and returning to basal levels after 3–4 h. Benzocaine anesthesia caused a bimodal response where the initial peak in cortisol release rate was followed by a second increase lasting towards the end of the trial (6 h). This bimodality was more profound in Atlantic salmon than in Atlantic halibut and Atlantic cod. Metomidate anesthesia induced the lowest release of cortisol of the agents tested in both Atlantic halibut and Atlantic cod, but resulted in a bimodal response in Atlantic salmon where the initial increase in cortisol release was followed by a larger increase peaking at 2–2.5 h post exposure before returning to basal levels after 5 h. The stress induced in Atlantic salmon by isoeugenol anesthesia resembled that of MS-222, but did not reach the same elevated level. Overall, the cortisol release was most profound in Atlantic salmon followed by Atlantic halibut and Atlantic cod.     

Immunological effects of glucan and <Emphasis Type="Italic">Lactobacillus rhamnosus</Emphasis> GG,a probiotic bacterium,on Nile tilapia <Emphasis Type="Italic">Oreochromis niloticus</Emphasis> intestine with oral <Emphasis Type="Italic">Aeromonas</Emphasis> challenges

The present study histologically examined the effects of glucan-containing and Lactobacillus rhamnosus GG (LGG)-containing diets on intestinal damages inflicted on Nile tilapia by Aeromonas challenges. Tilapia were fed control, glucan, and LGG diets for 2 weeks and were subsequently challenged with Aeromonas. The intestines were then histologically examined at 1, 7, 14, and 21 days post-infection. Mortality following the challenge was lower for the fish fed the glucan and LGG diets. The intestines of these groups also showed increased inflammatory cell infiltration and reduced intestinal damage from Aeromonas. Moreover, inflammatory cell infiltration occurred more rapidly in the glucan-fed than in the LGG-fed fish following the challenge. Before the challenge, the dominant mucous cell was the acid type in all the tests. After the challenge, the main mucus cell type in the proximal intestine of the glucan-fed fish shifted to AB-PAS double-staining cells, while in the LGG-fed fish, it remained the acid type throughout the test period, and the number of double-staining cells was smaller than in the control fish after the challenge. Thus, the different mucous cell and inflammatory cell responses show that glucan and LGG might have different immunostimulative effects, although they both reduced the intestinal damage following Aeromonas challenges.     

Bioaccumulation of cadmium and its biochemical effect on selected tissues of the catfish (<Emphasis Type="Italic">Clarias gariepinus</Emphasis>)

The present study examines the pattern of accumulation of cadmium (Cd) and its biochemical effects on selected tissues of a variety of African catfish (Clarias gariepinus), after exposure to various doses of Cd. The results obtained indicate that at the end of 21 days of exposure, the total tissue organ cadmium concentration followed the pattern kidney > gill > liver > muscle for each of the exposure concentrations. The levels of Cd in these organs were higher than those in ambient water. Moreover, while the rate of uptake of Cd increased with time in the kidney, liver and muscle, it decreased in the gill. Superoxide dismutase (SOD) was significantly elevated only in the kidney of catfish treated with 0.2 and 0.4 ppm of Cd for 7 days compared with the control. Conversely, gill SOD was significantly decreased in the same concentrations of Cd-treated catfish relative to the control. Statistically similar levels of SOD were observed in the liver, brain and muscle with all the treatments after the same duration of treatment. In the fish exposed for 21 days, SOD activity was significantly decreased in the kidney with a corresponding increase in lipid peroxidation (LPO), but it manifested only with the 0.2- and 0.4-ppm Cd treatment relative to the control. In the liver, however, Cd exposure significantly increased SOD in the 0.2- and 0.4-ppm treatments of the same duration. In conclusion, the present study indicates that the accumulation of Cd and its effect on SOD and LPO in C. gariepinus is dependent on concentration, tissue and time