The characins are a large group of freshwater fishes found in South and Central America and Africa. They are characterized by the Weberian Apparatus (the linkage of bones between the swimbladder and the inner ear) that allows them to hear high frequency sounds.
The science of genetics is concerned with the way in which characteristics pass from one generation to the next. The characteristics of all living organisms, including fish, are contained in the genes, which are carried on rodlike structures called chromosomes, present within the nucleus of every living cell in the body.
Despite their reputation for being difficult, it is possible to keep some killifishes in a community aquarium, and here three species spring readily to mind: Aplocheilus lineatus (Sparkling panchax) Pachypanchax playfairi (Playfair’s panchax), and Oryzias latipes (rice fish or medaka). These are surfacedwelling species, so they make a useful addition to the aquarium in that they occupy an area of the tank that is usually ignored when buying fishes.
