Histopathological alterations observed in the liver of Poecilia vivipara (Cyprinodontiformes: Poeciliidae) as a tool for the environmental quality assessment of the Cachoeira River, BA

Histopathological alterations in liver have been widely used as a tool in studies for monitoring environmental quality. To evaluate the environmental quality in the Cachoeira river, five spots were monitored between the municipal districts of Itapé and Ilhéus, using liver histological analysis. The species chosen for analysis was Poecilia vivipara due to the fact that it is one of the most abundant in the sampling. The routine technique of inclusion and impregnation in paraffin was used, and the cuts were stained with Hematoxylin and Eosin (H & E). Histopathological alterations in the liver were evaluated semi-quantitatively and based on the severity of the lesions. The results of the histopathological alteration frequency together with the average taken from the Histopathological Alteration Index from points 1 (Vila de Itapé) and 2 (Fazenda Santa Amélia) showed that in this area the environment is more threatened because of some stressor agent, possibly contaminants that seem to be acting in the environment and endangering the health of fish. The statistic results demonstrated that there were no significant differences among points 1, 2 and 4, which means they are very similar to one another, and are ecologically endangered

Mating and aggressive behaviour of Brachyrhaphis olomina (Cyprinodontiformes: Poeciliidae)

Despite the increasing interest in the use of intro-mittent male genitalia and coercive mating behaviour in poeciliids, detailed studies of the mating behaviour of most species in this family are lacking. We describe here the mating and aggressive behaviours of Brachyrhaphis olomina, and correlate them with the condition of the female’s ovum and embryos (immature, mature and pregnant). B. olomina performed a wide range of aggressive (sidle spread, tail beating, coordinate) and mating behaviours (approximation, touch, lateral display, touch-lateral display). Some behaviours (e.g. tail beating) are shared with other poeciliids, but two sexual behaviours (touch and lateral display) and one aggressive (coordinate) behaviour may be unique to B. olomina and were not reported in a previous study. Differences in male behaviour when paired with a female with mature ovum (more mating displays, no agonistic movements) suggest that males detect the female’s reproductive condition from some distance. The distinctive nature of mating behaviour in B. olomina highlights the importance of studying different spe-cies to have a better understanding of the evolution of mating and aggressive behaviours in poeciliids. Digital video images related to the article are available at http://www.momo-p.com/showdetail-e.php?movieid=momo170720bo01a, http://www.momo-p.com/showdetail-e.php?movieid=momo170720bo02a and http://www.momo-p.com/showdetail-e.php?movieid=momo170720bo03a.UCR::Vicerrectoría de Docencia::Ciencias Básicas::Facultad de Ciencias::Escuela de Biologí

Fragmentation of a Neotropical migratory fish population by a century-old dam

Loss of connectivity in impounded rivers is among the impacts imposed by dams, and mitigation measures such as fish passages might not accomplish their purpose of reestablishing an efficient bi-directional gene flow in the fish populations affected. As a consequence, fish populations remain fragmented, and a new interpopulational structure may develop, with increased risk of reduced genetic diversity and stochastic extinction. In order to evaluate the effects of the Gavio Peixoto Dam, which was constructed almost a century ago on the Jacar,-Gua double dagger u River in the Upper Parana River basin, Brazil, a comparative morphometric study was undertaken on the populations of the Neotropical migratory characid fish Salminus hilarii living up- and downstream of this dam. Population dynamics, spatial segregation, and habitat use by different age classes were monitored for 2 years. We found that segregation caused by the dam and long periods with no efficient connection by fish passages have led to fragmentation and interpopulational structuring of S. hilarii, as revealed by canonical variable analysis of morphometric features. The fish populations occupying the up- and downstream sections have succeeded in performing short-distance reproductive migrations in the main river and tributaries, have found suitable habitats for completing their life cycle, and have been able to maintain distinct small-sized populations so far