MORPHOMETRICAL AND TOPOLOGICAL STUDY OF CARDINAL NEON BRAIN, Paracheirodon axelrodi (CHARACIFORMS: CHARACIDAE)

This work identified and described external and internal brain anatomy of Paracheirodon axelrodi (Schultz, 1956, Characiformes: Characidae). 28 individuals were sacrificed using bioethical protocols for research animal use. Heads were stored in 4% formaldehyde. The brains were later removed and dissected for anatomical description and digital image capture. In addition, length and area of some brain lobes (olfactory bulbs, telencephalic hemispheres, optic lobes and cerebellum) were obtained and an ANOVA was carried out to determine if statistical differences in size existed between these structures. For brain internal topology a protocol was followed for the preparations of paraffin sections and Nissl staining was performed. The brain of P. axelrodi exhibited several lobes in agreement with the general teleost brain pattern. However, as special characteristics, olfactory bulbs were sesil, the cerebellum was intermediate in size, and no facial lobes were observed. In the morphometrical analysis, for both length and area, highly significant differences were observed between the evaluated structures (p < 0.001), with optic lobes being the larger structures, suggesting a mayor role of vision. Internal topology of P. axelrodi brains was similar to other teleosts in terms of main nuclei location.