SYNAPSIS IN SUPERNUMERARY CHROMOSOMES OF PROCHILODUS-LINEATUS (TELEOSTEI, PROCHILODONTIDAE)

Meiotic analysis performed on a sample of 10 specimens of Prochilodus lineatus revealed continuous filaments of different sizes stained by A gNO3, corresponding to the bivalent of the normal complement. Small su pernumerary chromosomes were observed as isolated and well stained bod ies, scattered among the other elements. Synaptonemal complex studies have shown that the beginning of chromosome pairing process in P. line atus usually occurs from the telomeres to the pericentromeric region. At the end of the pachytene 27 bivalents are perfectly paired and the small supernumerary chromosomes of this species are seen as bivalents, trivalents, or tetravalents. The central region of these small chromo somes show a trick staining when they formed bivalents or tetravalents . This portion seems to correspond to the pericentromeric region of th e regular chromosomes with the heterochromatic characteristic of B chr omosomes.