The effects of incubation manipulation on prolactin secretion in Adélie penguins (Pygoscelis adeliae)

Although numerous studies on various avian taxa correlate the secretion of the peptide hormone prolactin to parental behavior, the pattern of secretion of prolactin varies widely across species. These differences correlate with the type and amount of care that is given, the mode of development of the young, and the environment in which the birds breed. External cues (eggs and chicks) may promote or maintain the secretion of prolactin. The pattern of prolactin secretion may also be under the control of an internal cycle of timed events associated with the reproductive cycle. One way to gain insights into the relative importance of these factors in the secretion of prolactin is to manipulate the incubation period of birds. We performed such an experiment on free-living Adélie penguins (Pygoscelis adeliae), an offshore feeding seabird with biparental care of semi-altricial young which breeds in the harsh environment of Antarctica. We also measured prolactin levels in male Adélie penguins that lost their eggs during incubation. The usual decline of prolactin at around 50 days after egg-laying was not seen in the experimental birds with lengthened incubation periods, suggesting that the stimulus from young chicks may maintain high levels of prolactin secretion past the point of normal decline. However, these birds left their chicks in créches when the chicks were significantly younger than créching chicks in the other treatment nests. This may be an effect of an internal timed cycle of prolactin. Prolactin levels were significantly lower in males that lost their eggs than in males that were raising chicks at the same sample date, again indicating that the behavioral act of incubating or brooding may be necessary to maintain maximally elevated levels of prolactin. The prolactin levels in the failed Adélie penguins, however, were still relatively high, almost 10-fold above baseline non-incubating prolactin levels. Our results support the hypothesis that the control of the rhythm of prolactin secretion is primarily controlled by an internal timed cycle, but may be modified by external cues.

Name thesis:degree_name

Master of Science

Level thesis:degree_level

Masters

Discipline thesis:degree_discipline

Ecology and Evolutionary Biology

Year dc:date.issued

1997

Author dc:creator

• Ross, Lori Lea

Advisor dc:contributor.advisor

• Vleck, Carol M.

Language dc:language.iso

en

DOI

https://doi.org/10.31274/td-20250603-301

OAI identifier oai:identifier

oai:dr.lib.iastate.edu:20.500.12876/erLKX0nv