Impact of environmental and genetic factors on the scale shape of zebrafish, Danio rerio (Hamilton 1822): A geometric morphometric study

Intraspecific morphological variability may reflect either genetic divergence among groups of individuals or response of individuals to environmental circumstances within the frame of phenotypic plasticity. Several studies were able to discriminate wild fish populations based on their scale shape. Here we examine whether the variations in the scale shape in fish populations could be related to genetic or environmental factors, or to both of them. In the first experiment, two inbred lines of zebrafish Danio rerio (Hamilton 1822) reared under identical environmental conditions were compared. Secondly, to find out what effect environmental factors might have, offsprings were divided into two groups and reared on different diets for 12 weeks. Potential recovery of scales from an environmental effect was also assessed. Experimental groups could successfully be distinguished according to the shape of scales in both experiments, and the results showed that both genetic and environmental factors may notably influence scale shape. It was concluded that scale shape analysis might be used as an explanatory tool to detect potential variability of environmental influences impacting genetically homogeneous groups of fish. However, due to its sensitivity to environmental heterogeneity, the applicability of this technique in identifying intraspecific stock membership of fish could be limited

Effects of water level fluctuation on reproduction and spawning habitats of fish species in Lake Balaton

In 2004, the types of shoreline were estimated on Lake Balaton, such as rip-rap covered, reedy, concrete or grit. Exact area of a specific face of a rock in the rip-rap covered parts can be determined by digital image analysis. Wetted rocky area of the shore was estimated as a function of water level in 10 cm steps of level changes. Taking into account the reproduction characteristics of the studied fish species (Cyprinidae) the potential substrates for spawning are dominantly the shallow zones near the shoreline. The lake becomes substrate deficient when the water level decreases to -50 cm. This may cause problems in the reproduction of species of bream, so it would be very important to open River Zala and the Kis-Balaton reconstructed wetland for spawning fish. The reproduction area can not sustain the spawn-taking of fish (i.e.: carp, catfish, asp) even when the water level is normal

Sensitivity of three unionid glochidia to elevated levels of copper, zinc and lead

In this study glochidia as most sensitive life-stage of bivalves were used to evaluate the toxicity of copper, zinc and lead. Sensitivity of three species, Anodonta anatina, Pseudanodonta complanata and Unio tumiduswere compared to copper and zinc, based on 24 and 48 h LC50s. The copper 24 h LC50 showed the lowest value (26.8 μg·L-1) for Unio tumidus glochidia. After 48 h exposure, close LC50 values, 18.9 and 19.0 μg·L-1, were recorded for A. anatina and U. tumidus glochidia, respectively. U. tumidus glochidia exhibited the highest sensitivity to zinc (48 h LC50 = 134.2 μg·L-1) followed by P. complanata (48 h LC50 = 201.6 μg·L-1) and A. anatina (48 h LC50 = 233.5 μg·L-1). Toxicity of lead to P. complanata glochidia was estimated, 24 and 48 h LC50s of lead to 374.6 and 260.8 μg·L-1, respectively. No observed effect concentrations (NOECs) for the tested metals exhibited species differences. All NOECs exceeded environmental quality standards (EQS), therefore these species are at risk only in such European freshwaters which have extreme concentration of these metals. Synergistic effect was reported for the combinations of Cu + Zn and Cu + Pb, additive effect was reported for Zn + Pb

Sensitivity of three unionid glochidia to elevated levels of copper, zinc and lead

In this study glochidia as most sensitive life-stage of bivalves were used to evaluate the toxicity of copper, zinc and lead. Sensitivity of three species, Anodonta anatina, Pseudanodonta complanata and Unio tumiduswere compared to copper and zinc, based on 24 and 48 h LC50s. The copper 24 h LC50 showed the lowest value (26.8 μg·L-1) for Unio tumidus glochidia. After 48 h exposure, close LC50 values, 18.9 and 19.0 μg·L-1, were recorded for A. anatina and U. tumidus glochidia, respectively. U. tumidus glochidia exhibited the highest sensitivity to zinc (48 h LC50 = 134.2 μg·L-1) followed by P. complanata (48 h LC50 = 201.6 μg·L-1) and A. anatina (48 h LC50 = 233.5 μg·L-1). Toxicity of lead to P. complanata glochidia was estimated, 24 and 48 h LC50s of lead to 374.6 and 260.8 μg·L-1, respectively. No observed effect concentrations (NOECs) for the tested metals exhibited species differences. All NOECs exceeded environmental quality standards (EQS), therefore these species are at risk only in such European freshwaters which have extreme concentration of these metals. Synergistic effect was reported for the combinations of Cu + Zn and Cu + Pb, additive effect was reported for Zn + Pb