Molecular Changes in the Brain of the Wintering Calidris pusilla in the Mangroves of the Amazon River Estuary

Migrant birds prepare differently to fly north for breeding in spring and for the flight to lower latitudes during autumn avoiding the cold and food shortages of the north hemisphere's harsh winter. The molecular events associated with these fundamental stages in the life history of migrants include the differential gene expression in different tissues. Semipalmated sandpipers (Calidris pusilla) are Artic breeding shorebirds that migrate to the coast of South America during non-breeding season. Thus, the adaptive molecular changes in the brain of these birds at lower latitudes have not yet been investigated in detail. Here, we searched for differential gene expression in the brain of semipalmated sandpiper, of recent arrived birds (RA) from autumnal migration and that of individuals in the premigratory period (PM) in the spring. All individuals were collected in the tropical coastal of northern Brazil. We generated a De novo neurotranscriptome for C. pusilla individuals and compared gene expression across libraries for neurotranscriptome. To that end we mapped RNA-seq reads to the C. pusilla neurotranscriptome in a total of 4 brain samples each group. A total of 266,414 transcripts were reconstructed that yielded 615 differentially expressed genes in the brain of both groups. The present report revealed a remarkable differential gene expression in the brain of recently arrived and premigratory individuals. It also revealed molecular brain changes associated with the recovering of the 4 to 5 days long-distance uninterrupted flight across Atlantic Ocean and preparation for the long-distance multiple stopover spring migration.