Maternally derived yolk testosterone enhances the development of the hatching muscle in the red-winged blackbird Agelaius phoeniceus.
نویسندگان
چکیده
Hatching asynchrony in avian species often leads to the formation of a size hierarchy that places last-hatched nestlings at a significant disadvantage. The hatching muscle (musculus complexus) is responsible for breaking the shell during hatching and for dorsal flexion of the neck during begging. An increase in its strength in last-hatched nestlings could mitigate the effects of hatching asynchrony by reducing the time required for hatching or enhancing the effectiveness of begging for parentally delivered food or both. We have previously found that yolk testosterone concentration increases with laying order in the red-winged blackbird Agelaius phoeniceus. In this study, we investigated the hypothesis that yolk testosterone has anabolic effects on the development of the complexus, thereby influencing competition among asynchronously hatched nestlings. We found that both yolk testosterone concentration and relative complexus mass (complexus mass/nestling body mass) increased with laying order and that these two variables were positively correlated in both newly hatched nestlings and in two-day-old broods. Moreover, direct injections of testosterone into egg yolks resulted in an increase in relative complexus mass, while injections of flutamide, a testosterone antagonist, resulted in a decrease in relative complexus mass. Neither yolk testosterone concentration nor relative complexus mass differed between male and female nestlings.
منابع مشابه
Egg yolk layers vary in the concentration of steroid hormones in two avian species.
Maternally derived steroid hormones are known to be present in the yolks of avian eggs; however, the physiological mechanisms involved in their deposition remain largely unexplored. Investigations of steroid production by avian follicles have demonstrated temporal differences in the concentrations of progesterone, 17beta-estradiol, and testosterone during yolk formation. Because yolk is deposit...
متن کاملGeneralizability of Artificial Neural Network Models in Ecological Applications: Predicting Nest Occurrence and Breeding Success of the Red-winged Blackbird Agelaius phoeniceus
17 Separate artificial neural network (ANN) models were developed from data in 18 two geographical regions and years apart for a marsh-nesting bird, the red-winged 19 blackbird Agelaius phoeniceus. Each model was independently tested on the spatially and 20 temporally distinct data from the other region to determine how generalizable it was. The 21 first model was developed to predict occurrenc...
متن کاملPredators on Red-winged Blackbird nests in eastern North Dakota
Predation has consistently been identified as the most common cause of nest failure for Redwinged Blackbirds (Agelaius phoeniceus). During May and June, 2000 and 2001, we used infrared-triggered camera systems to identify potential nest predators on artificially relocated Red-winged Blackbird nests in eastern North Dakota. For some of the species observed, these observations represent the first...
متن کاملWest Nile virus antibody prevalence in red-winged blackbirds (Agelaius phoeniceus) from North Dakota, USA (2003-2004).
This study was designed to explore the role that red-winged blackbirds (Agelaius phoeniceus) may have played in disseminating West Nile virus (WNV) across the United States. Using enzyme-linked immunosorbent assays designed to detect WNV antibodies in avian species we were able to determine the WNV antibody prevalence in a cohort of red-winged blackbirds in central North Dakota in 2003 and 2004...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید
ثبت ناماگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید
ورودعنوان ژورنال:
- Proceedings. Biological sciences
دوره 267 1456 شماره
صفحات -
تاریخ انتشار 2000