The dilated, round pupils of a species of suckermouth armoured catfish (Liposarcus pardalis) constrict slowly on illumination (over 35-40 min) to form crescent-shaped apertures. Ray tracing of He-Ne laser beams shows that the lenses of a related species (Pterygoplichthys etentaculus), which also has a crescent-shaped pupil, are well corrected for longitudinal spherical aberration, suggesting th...

Spatial distribution of fish assemblages in Lajes Reservoir, a 30 km2 impoundment in Rio de Janeiro State (Lat. 22 degrees 42'-22 degrees 50'S; Long. 43 degrees 53'-44 degrees 05'W) was assessed to detect patterns of available habitat use by the fish. A standardized monthly sampling program was carried out from January to December 1994 at three zones of the reservoir (upper, near tributary mout...

Lernaea cyprinacea Linnaeus is an ectoparasitic copepod that infects the gills and skin of various freshwater fishes and amphibians tadpoles. It is capable of infecting fish at high levels, with high pathogenicity and mortality, mainly during the summer season. Besides the effects of penetration, haemorrhages and ulcerations are also caused. The objective of this study was to investigate the pr...