Behavioural and histochemical changes induced by osmotic stress in Poecilia reticulata Peters (pisces, cyprinodontidae)

1. 1. Behavioural activities and histochemical changes of mucopolysaccharides, ATPase and respiratory enzymes in the gill epithelium of freshwater fish Poecilia reticulata Peters were examined at different times after 100% sea-water exposure. 2. 2. Acute stress was observed in the first 6 hr, with behavioural and histochemical changes. 3. 3. Up to 6 hr reduction in reaction activities of succinic-dehydrogenase, cytochrome-oxidase, ATPase and mucopolysaccharides was observed. 4. 4. After the first 6 hr a strong increase in ATPase and respiratory enzymes levels was observed until they reached levels similar to the controls at 7 days. Mueopolysaccharide reactions were gradually reduced and disappeared completely at 7 days. 5. 5. Behavioural adaptations changed in the same time and behavioural activity appeared normal at 24 hr. 6. 6. A correlation between the adaptive flexibility of P. reticulata and morphological and physiological characters is hypothesized.