Early developmental stages of fish are particularly sensitive to water pollution. Heavy metals may affect various developmental processes during the embryonic period, which results in a reduction of offspring quantity and quality. Waterborne metals may accumulate in the gonads of spawners and adversely affect gamete production and viability, or exert direct toxic influence upon developing embryos. The egg shell does not fully protect the embryo against metal penetration, particularly during the swelling phase; thus, metals may accumulate in the egg. The results depend on metal concentration and range from developmental disturbances to death of the embryo. Metals disturb various processes of fish embryonic development and affect the development rate. Early stages just after fertilization are particularly sensitive to metal intoxication, when most disturbances and the highest embryonic mortality occur. Waterborne metals also promote developmental anomalies during organogenesis, including body malformations. Heavy metals often induce a delay in the hatching process, premature hatching, deformations and death of newly hatched larvae. All these disturbances result in reduced numbers and poor quality of the larvae, which show small body size, high frequency of malformations and reduced viability.

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The effects of Cd and Cu on embryos and larvae of the ide Leuciscus idus were evaluated. The ide is an European cyprinid fish, natural populations of which tend to decrease. The ide is also used as a bioindicator organism to evaluate water quality. However, sensitivity of ide early developmental stages to heavy metal intoxication is not known. Fish were exposed to Cd or Cu (100 μg/L) during embryonic, larval or both developmental periods. Survival of the embryos, time of hatching, size and quality of newly hatched larvae were evaluated at the end of embryonic period. Correctly developed larvae from the control and Cd or Cu-exposed groups were transferred to clean water, Cd or Cu solutions (100 μg/L) immediately after hatching. Larval development was observed, and the larvae were photographed. Time of yolk sac resorption, onset of active feeding and swim bladder inflation were evaluated, and the measurements were done on body and swim bladder size. The results showed that exposure of embryos to Cd and Cu significantly reduced embryonic survival and increased frequency of body malformations and death in newly hatched larvae and delayed hatching. Exposure to Cd and Cu during larval period reduced larval survival, growth and delayed development (yolk utilization, beginning of active feeding and swim bladder inflation). Cadmium was more toxic to the ide embryos and larvae than copper. Exposures to metals during embryonic period alone caused adverse impact on larval performance even when larval development took place in clean water. However, exposure of embryos to Cu reduced toxic impact of metal on larvae in continuous Cu exposure compared to the non-preexposed fish, but no such an effect occurred in case of Cd exposure. The results show that even a short-term exposure to Cd or Cu during early development of ide may adversely affect recruitment of this species. Among the measured endpoints, quality of newly hatched larvae (frequency of body malformations and larvae dead immediately after hatching) and swim bladder size were the most sensitive to intoxication with both metals. Embryos were more sensitive to Cu intoxication than larvae, while in case of Cd, sensitivity of both stages was similar.

The aim of the present study was to evaluate bioaccumulation of metals in various tissues of the freshwater fish Cyprinus carpio L. exposed to cadmium and copper (a xenobiotic and a microelement). The fish were subjected to short-term (3 h, Cd-S and Cu-S) or long-term (4 weeks, Cd-L and Cu-L) exposures to 100 % 96hLC50 or 10 % 96hLC50, respectively. Blood, gill, liver, head and trunk kidney were isolated weekly from 5 fish of each group for 4 weeks (post-short-term exposure and during long-term exposure). Atomic absorption spectrophotometry technique was applied to measure concentrations of metals (Cd and Cu) in fish tissues. Initial concentrations of copper in fish tissues were higher than levels of cadmium. Cadmium and copper levels increased in all tissues of metal-exposed fish. After short-term exposures (at higher concentration) and during long-term exposures (at lower concentration), similar changes in metal concentrations were observed. The values of accumulation factor (ratio of final to initial metal concentration) were higher for cadmium as compared to copper. Comparison of metal levels and accumulation factors in various tissues revealed that cadmium and copper showed very high affinity to head kidney of common carp (higher than to other tissues), but accumulation factors for cadmium in trunk, head kidney and liver were much higher than for copper. The concentrations of copper in organs of Cu-exposed fish increased only slightly and quickly returned to the control level, which shows that fish organism easily buffered metal level. On the other hand, concentrations of cadmium considerably increased and remained elevated for a long time which suggests that activation of mechanisms of sequestration and elimination of cadmium required more time.

The performance of larvae and juveniles of the crucian carp, Carassius carassius, held at temperatures of 22, 25, 28 and 31°C was evaluated in terms of growth, survival and, only in juveniles, haematological indices. The best growth in both larvae and juveniles was recorded at 28°C (relative growth rate (RGR) of 27.52% and 3.50%/day, respectively). The highest final survival rates were found at temperatures of 25–28°C, exceeding 99% in larvae and equal to 100% in juveniles. Haematopoietic activity and leucocyte count were significantly disturbed at temperatures of 28 and 31°C. These temperatures were stressing to the juveniles, as shown by the lymphopaenia and neutrophilia found in their peripheral blood and haematopoietic kidney. Thus, the optimum temperature for growth of larval and juvenile crucian carp is close to 28°C. However, stress indicators found at this temperature in juvenile fish strongly suggest that the most favourable temperature range for long‐term rearing is below 28°C and near to 25°C.

Hematological, biochemical and hematopoietic effects of therapeutic doses of two antibiotics, oxytetracycline (OTC) and gentamicin (GEN), in clinically healthy common carp juveniles were studied. The fish were divided into four groups: controls 1 and 2 (untreated or injected with 0.6% NaCl solution), and two groups treated with antibiotics (orally with 75 mg/kg OTC four times every two days or injected with a single dose (4 mg/kg) of GEN dissolved in 0.6% NaCl). Blood and head kidneys were sampled from all fish 3 days post-treatments for hematological, biochemical and hematopoietic tissue analyses. No major alterations in the values of hematological and serum biochemical parameters occurred following administration of OTC or GEN. Glucose concentrations were significantly lower in both groups of fish subjected to injections (Control 2 and GEN), while the oxidative metabolic activity of phagocytes increased in the antibiotic-treated groups (significantly in OTC). More alterations were observed in hematopoietic tissue. Immunocytochemical analysis revealed that G caused a significant increase in the rate of cell proliferation (PCNA-positive cells) and an increase in the frequency of apoptotic cells (caspase-positive). The frequency of lymphoid lineage decreased, which was related to a decrease in the abundance of mature lymphocytes in GEN-treated fish. Percentages of neutrophilic lineage were significantly elevated in OTC and GEN groups compared to controls. The obtained results showed no considerable hematotoxicity or hepatotoxicity of therapeutic doses of OTC and GEN to carp.

Ługowska K., Sarnowski P. 2011. Heads or tails-fish hatching. Acta Ichthyol. Piscat. 41 (1): 13-17.Background. Hatching is a process in which the embryo emerges from the egg by breaking the protective egg shell. Our preliminary observations indicate that hatching duration and time-distribution may vary among and within the fish species, and that some embryos fail to hatch or hatch incompletely, probably due to the "incorrect" hatching way. So the aim of this study was a detailed description of hatching of three fish species: common carp, barbel, and rainbow trout. Materials and methods. Three species of fish: common carp, Cyprinus carpio; barbel, Barbus barbus; and rainbow trout, Oncorhynchus mykiss; were examined for their hatching modes. The mode and the time of hatching of each larva were noted. Newly hatched larvae were counted and examined. The malformations were classified. Observations of embryos and larvae were done using the stereoscopic microscope Nikon connected to the computer with the MultiScan 8.4 image analysis system; the hatching embryos and larvae were photographed. Results. Three modes of hatching were observed, two of them similar in all three fish species. Some fish started hatching tail first from the egg shell, others head first or-specifically for barbel-yolk sac first. The data obtained in the present study showed that tail hatching was the most successful in all fish species, and shown by most good quality larvae. The majority of tail-hatched larvae developed normally and were viable, and only some of them were deformed and showed slight morphological defects, mainly single vertebral malformations that in most cases were negligible. Head hatching was the precarious in carp, and in all fish species less common and successful comparing to the tail hatching. Conclusion. The hatching mode could be used as another good parameter for estimation of quality of eggs and larvae.

Hexavalent chromium ( Cr(VI) ) has carcinogenic, nephrotoxic, hepatotoxic, and neurotoxic effects. Exposure to Cr(VI) can also lead to hematological alterations and blood biochemical changes. The literature on Cr(VI) toxicity concerns mostly adult forms of vertebrates. In this study, an attempt was made to determine the effect on the developing chicken embryo of Cr(VI) in ovo administration. It was observed that chromium affected the hatchability of chicks in a dose-dependent manner. At a dose from 25 to 250 μg per egg, Cr(VI) resulted in a statistically significant reduction of hatchability. Chromium administrated at lower doses (1.56 and 2.5 μg per egg) caused a statistically insignificant increase of hatchability. However, chromium at a level of LD 50 (15.6 μg per egg) or 1/10 LD 50 (1.56 per egg) did not cause major changes in hematological parameters or plasma biochemical indices in newly hatched chicks. The same doses did not lead to any histopathological changes in the liver.