Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
2800310 | General and Comparative Endocrinology | 2013 | 8 Pages |
Abstract
Yolk androgens in avian eggs play a significant role in embryo and nestling development. However, few studies have examined the differential effect of two of the main yolk androgens, testosterone (T) and androstenedione (A4). Here, we injected eggs of spotless starlings with physiological levels of either T, A4, the combination TÂ +Â A4 or vehicle substance (control), to examine the differential ability of these steroids to influence nestling development. We found that the duration of the embryonic period was increased by T, and less so by A4, but not by the combination TÂ +Â A4. Body condition was reduced in all experimental treatments where A4 was present, particularly so in the combination TÂ +Â A4. Tarsus length was increased in males by A4, and in a lower degree by T, whereas the combination TÂ +Â A4 inhibited growth. However, these differences in tarsus length between groups disappeared at the end of the nestling period. Cell-mediated immune responsiveness was marginally affected by the interaction between treatment and sex. These patterns suggest that in this species, T has a stronger influence during embryo development than A4, whereas during nestling development the capacities of both androgens to influence growth are similar. The combination TÂ +Â A4 showed non-additive effects, suggesting either some kind of inhibition between the two androgens, or else an excessive effect due to a bell-shaped pattern of response. Our results suggest a complex picture of sex and age-dependent effects of T and A4, and underline the necessity of further research in the metabolism and action of egg androgens.
Related Topics
Life Sciences
Biochemistry, Genetics and Molecular Biology
Endocrinology
Authors
Jaime Muriel, Lorenzo Pérez-RodrÃguez, Marisa Puerta, Diego Gil,