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  • Lesser snow goose  (1)
  • Lipogenic enzymes  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Fitness consequences of egg-size variation in the lesser snow goose (1993)
    Springer
    Oecologia 96 (1993), S. 331-338 
    Details
    ISSN: 1432-1939
    Keywords: Egg size ; Fitness consequences ; Offspring survival ; Selection ; Lesser snow goose
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We investigated the relationship between eggsize variation and (a) egg hatching success, (b) chick survival to fledging and recruitment, and (c) adult female survival, over 12 years in the lesser snow goose (Anser caerulescens caerulescens). By comparing the means and variances of egg size for successful and unsuccessful eggs, our aim was to assess the relative fitness of eggs of different sizes and to determine the type of selection operating on egg size in this species. As both egg size and reproductive success vary with age in the lesser snow goose we controlled for the effects of female age. Egg-size variation is very marked in this population, varying by up to 52% for eggs hatching successfully. However, there was no relationship between egg size and post-hatching survival of goslings to fledging or recruitment, either within or between broods, pooling across years. Egg size varied significantly between successful and unsuccessful clutches in only 2 of 33 individual year comparisons. First-laid eggs surviving to onset of incubation, and eggs hatching successfully, were on average larger than unsuccessful eggs, but this was probably due to the confounding effects of female age-specific and sequence-specific egg survival. Variance of egg size differed significantly between successful and unsuccessful eggs in only 3 of 24, and 0 of 21, individual year comparisons for pre- and post-hatching survival respectively. We therefore found little evidence for a relationship between egg-size variation and offspring fitness, or for strong directional, normalising or diversifying selection operating on egg size, in the lesser snow goose. In addition, there was only weak support for the hypothesis that egg-size variation is maintained by temporal variation in selection pressure (sensu Ankney and Bisset 1973). It is likely that egg-size variation represents the pleiotropic expression of alleles affecting more general physiological or metabolic processes. While this does not rule out the existence of alleles with more direct effects on egg size we suggest that their contribution to heritable egg size is small.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00317502
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Modulation of lipogenic enzymes, fatty acid synthase and Δ9-desaturase, in relation to migration in the western sandpiper (Calidris mauri) (2000)
    Springer
    Journal of comparative physiology 170 (2000), S. 169-174 
    Details
    ISSN: 1432-136X
    Keywords: Key words Migration ; Lipogenesis ; Lipogenic enzymes ; Intraspecific variation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Long-distance migration in birds is characterized physiologically by periods of rapid fattening and lipogenesis, and increased desaturation of fatty acids stored in adipose tissue. We investigated seasonal, age- and sex-related differences in activities of two lipogenic enzymes, fatty acid synthase and Δ9-desaturase, in relation to migration in the small, Arctic-nesting western sandpiper (Calidris mauri). Migration, and associated lipogenesis and fattening, involved marked upregulation of these enzymes in this species. However, this increase in enzyme activity was only seen in actively migrating birds during spring migration, when fatty acid synthase and Δ9-desaturase levels increased by 53% and 113%, respectively, compared to non-migrating birds. There was no change in fatty acid synthase enzyme activity during the premigration period, even though body mass of adult birds increased significantly during this period. Similarly, there was no increase in Δ9-desaturase activity during premigration, despite the fact that birds increase the proportion of monounsaturated fatty acids in their fat stores at this time. We suggest that upregulation of lipogenic enzymes is required to support high rates of mass gain (0.4 g day−1) during short (1–4 day) periods at stop-over sites. However, slower rates of mass gain (0.09 g day−1) over several weeks prior to migration can be achieved without any increase in tissue-specific enzyme activity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003600050272
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    Paper (German National Licenses)
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