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The objective of the study was to determine the rate of growth and cytotoxicity of mycelium of fungus-like organisms Saprolegnia parasitica on media with variable form of available carbon and nitrogen (Sabouraud Dextrose Agar (SDA), Malt Extract Agar (MEA), Potato Dextrose Agar (PDA), Czapek-Dox Agar (CDA)) in magnetic field of 1, 5 and 10 mT. The growth rate of S. parasitica in magnetic field was most varied on SDA medium: the mycelium growth was the slowest in the field of 5 mT compared to the remaining experimental variants and to the control. On MEA and PDA media the growth rate did not vary among the tested field values and the control. The kind of medium and magnetic field had an effect on cytotoxicity of S. parasitica -- on SDA medium the mycelium cytotoxicity was reduced to the greatest extent in magnetic field of 5 mT. The phenomenon can be used to increase the effectiveness of stocking material production. [ABSTRACT FROM AUTHOR]

Effects of water salinity (3.0-9.0 PSU) on the duration and outcome of embryogenesis in the lesser sandeel ( Ammodytes tobianus (L.) as well as on survival, size, and malformation rate of the newly hatched larvae were followed, based on observations involving equipment consisting of a microscope and still and digital cameras. The images obtained and measurements of egg and larval dimensions were analyzed using the NIS elements Br. computer software package. The lowest salinity tested (3.0 PSU), similar to that in the inshore Baltic Sea waters native for the species studied, produced a lower fertilization rate and resulted in extended embryogenesis, reduced embryo survival, changes in the hatch size, and increased larval malformation rate. The high-end salinity (7.5-9.0 PSU), higher than that prevailing in the species's spawning grounds in the Baltic Sea, resulted - similarly to the low-end salinity - in disturbed development and growth of the embryos. [ABSTRACT FROM AUTHOR]

Effects of total suspended solids in riverine water on embryonic development and larval survival, size, and malformation rate in pike (Esox luciusL.) were studied. Total suspended solids in concentrations even below 25 mg · dm[sup -3] (the generally accepted threshold level) were found to inhibit fish embryogenesis by affecting fertilisation (% fertilisation: untreated, filtered riverine water and tap water: 75; 91; 85, respectively), perivitelline space formation (perivitelline space %: untreated, filtered riverine water and tap water: 29.77; 33.07; 29.68, respectively), organogenesis, and hatching (in riverine water - hatching began at 95 D° and terminated at 140 D°; in filtered riverine water - hatching began at 110 D° and terminated at 150 D°). The total suspended solids were also found to affect the larval size: the larvae hatched in water containing suspended 0particulates were smaller than those hatched in clean water (larvae hatched from eggs incubated in riverine water total length 9.34mm, filtered water - 9.82 mm); the larval malformation rate was higher in the suspended solids-rich water (% malformed larvae - 9.0) than in clean water (% malformed larvae 7.0). [ABSTRACT FROM AUTHOR]

The purpose of this study was to characterize in detail the reproductive strategy, course of embryogenesis, and development of larvae in three species of fishes of the genus Cichlasoma : the green terror ( Andinoacara rivulatus ), the red discus ( Symphysodon discus ), and the jaguar cichlid ( Parachromis managuensis ). Eggs for the study were obtained from five pairs of each species (300 eggs from each female) and incubated at 26 °C. The developing eggs were observed under a microscope (Carl Zeiss Stereo Discovery. V12 and Nikon 2000SE software (NIS-Elements F 4.30.01 64-bit) from fertilization to larval hatching until complete yolk-sac resorption. The largest average number of eggs per female was found in the jaguar cichlid (x¯ = 2991 eggs), a smaller average number of eggs was shown in the green terror (x¯ = 922 eggs), and the red discus showed the smallest average number of eggs (x¯ = 300 eggs). There were significant differences in the sizes of the eggs of the studied species: jaguar cichlid eggs were the smallest (1.060 ± 0.05 mm 3 ), red discus eggs were larger (1.070 ± 0.07 mm 3 ), and green terror eggs were the largest (1.365 ± 0.16 mm 3 ). The embryogenesis time in the red discus was 2132 °H (82 Hpf), in the green terror it was 2158 °H (83 Hpf), and the longest in the jaguar cichlid was 2470 °H (87 Hpf). At the end of embryogenesis, the average size of the larvae after hatching was measured (red discus x¯ = 4.346 mm, green terror x¯ = 5.203 mm, and jaguar cichlid x¯ = 5.301 mm) and the time of yolk-sac resorption from the moment of hatching to the transition from endogenous to exogenous feeding was determined (jaguar cichlid 5 days, green terror 6 days, and red discus 3 days). The results of this study may contribute to the development of reproductive biotechnology for the studied fishes that could be used in aquaculture and, thus, help protect them in their natural habitats.

High mortality is among the most serious problems and challenges in the ornamental fish trade. Examination of the discus Symphysodon aequifasciatus from ornamental fish hatchery revealed infestation with the monogenean Sciadicleithrum variabilum. Gill infestation with this monogenean induced serious damage to the gill lamellae, including clavate lamellae, vascular congestion in the peripheral blood vessels, lamellar blood sinus dilation, and other structural anomalies. Light and transmission electron microscopy showed that in all infested hosts the interlamellar cell mass (ILCM) completely filled the interlamellar space. The monogenean-associated damage combined with the ILCM led to severe impairment of respiratory efficiency of the gill. Anti-parasitic treatment was applied during breeding (hatchery), which was followed by almost complete regression of the ILCM seen in the fish. A single point of ILCM hyperplasia was observed in only one specimen at the site of parasite attachment to the gill filament. The ILCM covering the gill lamellae protected the discus against infestation with this monogenean, but considerable reduction in the gaseous exchange surface and serious damage to the gill lamellae contributed to the increased mortality of the fish in the hatchery, which reached 90%.