We found that vitamin C is an essential nutrient for an Amazonian ornamental fish, the oscar (Astronotus ocellatus). This was demonstrated by the absence of L-gulonolactone oxidase activity, the enzyme responsible for the biosynthesis of vitamin C, in liver or kidney of oscars and by a feeding trial in which oscars without vitamin C dietary supplementation developed clinical deficiency signs. F...

Glycoconjugates involved in many functions are produced by cell types. This study aimed to investigate the glycoconjugate expression Oscar fish (Astronotus ocellatus) gills using five horseradish peroxidase-conjugated lectins. revealed that gill epithelial cells react with Canavalia ensiformis agglutinin (Con A) and Arachis hypogaea (PNA). Strong reaction Con A was seen of primary lamellae. Epi...

We investigated chemical cues among groups of zebrafish (Danio rerio) when communicating information about the risk of predation. We found that visual cues of the predator (tiger Oscar, Astronotus ocellatus) did not increase whole-body cortisol levels in groups of zebrafish but that water conditioned by these (donor) zebrafish stressed (target) conspecifics, thereby increasing whole-body cortis...

The efficacy of [3-H]proline radioautography for tracing retinal ganglion cell projections to the optic tectum of the jewel fish, Hemichromis bimaculatus, has been compared with that of degeneration techniques. There was good agreement between the various methods. Retinal projections to the optic tectum of two other teleosts, the oscar, Astronotus ocellatus, and the goldfish, Carrasius auratus,...