Frontiers in Neuroanatomy (Jan 2018)

Hippocampal Astrocytes in Migrating and Wintering Semipalmated Sandpiper Calidris pusilla

  • Dario Carvalho-Paulo,
  • Nara G. de Morais Magalhães,
  • Diego de Almeida Miranda,
  • Daniel G. Diniz,
  • Ediely P. Henrique,
  • Isis A. M. Moraes,
  • Patrick D. C. Pereira,
  • Mauro A. D. de Melo,
  • Camila M. de Lima,
  • Marcus A. de Oliveira,
  • Cristovam Guerreiro-Diniz,
  • David F. Sherry,
  • David F. Sherry,
  • Cristovam W. P. Diniz

DOI
https://doi.org/10.3389/fnana.2017.00126
Journal volume & issue
Vol. 11

Abstract

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Seasonal migratory birds return to the same breeding and wintering grounds year after year, and migratory long-distance shorebirds are good examples of this. These tasks require learning and long-term spatial memory abilities that are integrated into a navigational system for repeatedly locating breeding, wintering, and stopover sites. Previous investigations focused on the neurobiological basis of hippocampal plasticity and numerical estimates of hippocampal neurogenesis in birds but only a few studies investigated potential contributions of glial cells to hippocampal-dependent tasks related to migration. Here we hypothesized that the astrocytes of migrating and wintering birds may exhibit significant morphological and numerical differences connected to the long-distance flight. We used as a model the semipalmated sandpiper Calidris pusilla, that migrates from northern Canada and Alaska to South America. Before the transatlantic non-stop long-distance component of their flight, the birds make a stopover at the Bay of Fundy in Canada. To test our hypothesis, we estimated total numbers and compared the three-dimensional (3-D) morphological features of adult C. pusilla astrocytes captured in the Bay of Fundy (n = 249 cells) with those from birds captured in the coastal region of Bragança, Brazil, during the wintering period (n = 250 cells). Optical fractionator was used to estimate the number of astrocytes and for 3-D reconstructions we used hierarchical cluster analysis. Both morphological phenotypes showed reduced morphological complexity after the long-distance non-stop flight, but the reduction in complexity was much greater in Type I than in Type II astrocytes. Coherently, we also found a significant reduction in the total number of astrocytes after the transatlantic flight. Taken together these findings suggest that the long-distance non-stop flight altered significantly the astrocytes population and that morphologically distinct astrocytes may play different physiological roles during migration.

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