The aim of this report is to describe the hippocampal formation of two
migratory birds, Calidris pusilla and Actitis macularia, that leave the cold regions of
the Canadian Tundra, escaping the winter, towards the coast of South America and
the Caribbean Islands where they remain until winter ends returning to the Northern
hemisphere. We intend to describe the qualitative and quantitative morphological
organization of the hippocampal formation, using cytoarchitetonics with cresyl violet
and immunostaining for neurons and microglia, followed by stereological estimates
of the total number of cells identified with selective markers. We intend as well to
compare the three-dimensional morphology of hippocampal microglia of these
species with those of the dentate gyrus of Wistar rats and Capuchin monkey. The
shorebirds used in the characterization were captured in Canela Island, Bragança
City, State of Pará, Brazil (0°47'21.95"S and 46°43'7.34"W), as well as in Canada,
in the Bay of Fundy, near Johnson's Mills, New Brunswick (45° 50' 19.3" N 64°
31' 5.39" W).
The hippocampal formation limits definition was performed employing Nissl
staining and immunostaining for NeuN. For the objects of interest definition of
stereological estimates and three-dimensional reconstructions we used
immunostaining with anti NeuN for neurons and anti-IBA-1 for microglia respectively.
The stereological results revealed similar number of neurons in both species
whereas the number of microglia in Actitis macularia was 37% higher than in Calidris
pusilla. Furthermore, it was found that the hipocampal formation average volume in
Actitis macularia was 38% higher than that found in Calidris pusilla. Comparative
studies of the microglial morphology with mammals (Rattus novergicus and Cebus
apella) revealed significant morphological differences that indicate microglia in birds
shows on average lower complexity (smaller fractal dimension), smaller tree
volumes and areas and thinner branches than rat and monkey microglia.
|
