Abstract
For the epic journey of autumn migration, long-distance migratory birds use innate and learned information and follow strict schedules imposed by genetic and epigenetic mechanisms, the details of which remain largely unknown. In addition, bird migration requires integrated action of different multisensory systems for learning and memory, and the hippocampus appears to be the integration center for this task. In previous studies we found that contrasting long-distance migratory flights differentially affected the morphological complexity of two types of hippocampus astrocytes. Recently, a significant association was found between the latitude of the reproductive site and the size of the ADCYAP1 allele in long distance migratory birds. We tested for correlations between astrocyte morphological complexity, migratory distances, and size of the ADCYAP1 allele in three long-distance migrant species of shorebird and one non-migrant. Significant differences among species were found in the number and morphological complexity of the astrocytes, as well as in the size of the microsatellites of the ADCYAP1 gene. We found significant associations between the size of the ADCYAP1 microsatellites, the migratory distances, and the degree of morphological complexity of the astrocytes. We suggest that associations between astrocyte number and morphological complexity, ADCYAP1 microsatellite size, and migratory behavior may be part of the adaptive response to the migratory process of shorebirds.
Highlights
Overall, long-distance navigation includes at least three different phases
The observed relationships between candidate genes CLOCK and adenylate cyclase activating polypeptide 1 (ADCYAP1) and migratory behavior in birds appear to vary across species, previous studies revealed that both loci can be significantly correlated with a variety of distinct phenotypes in long distance migratory birds (Saino et al, 2015; Bazzi et al, 2016b)
In previous studies we demonstrated that contrasting long-distance migratory flights of C. pusilla and C. semipalmatus differentially shape the morphological complexity of two morphotypes of hippocampal astrocytes (Henrique et al, 2020)
Summary
The first involves long distance guidance based on global tracks (Able, 1991; Wiltschko R. and Wiltschko, 2012; Wiltschko W. and Wiltschko, 2012; Wiltschko and Wiltschko, 2019); the second includes the construction of a variety of local gradient maps based on learned information from all available sensory information (Bingman and MacDougall-Shackleton, 2017). In addition to the compass-CLOCK system, learned maps become part of the navigation system (Mouritsen et al, 2016) and include olfactory cues (Gagliardo et al, 2013), landmarks (Mann et al, 2014), celestial tracks (Emlen, 1975), and geomagnetic signals (Dennis et al, 2007). It has been suggested that potential interaction between ADCYAP1, wing morphology and sex predict spring migration arrival in blackcap (Sylvia atricapilla) populations (Mettler et al, 2015) and that both ADCYAP1 and CLOCK gene alleles increase in size with breeding latitude in trans-Saharan migratory birds (Bazzi et al, 2016a,b)
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