Food cues and gonadal development in neotropical spotted antbirds (Hylophylax naevioides) |
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Authors: | Sara OBrien and Michaela Hau |
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Institution: | (1) School of Integrative Biology, University of Illinois, Champaign/Urbana, IL, USA;(2) Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ, USA;(3) Department of Zoology, University of Washington, Box 351800, Seattle, WA 98195-1800, USA |
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Abstract: | Most temperate-zone birds live in environments with a regular seasonality, and primarily use the long-term changes in photoperiod
as a cue to initiate gonadal development in anticipation of the breeding season. Short-term cues such as food and temperature
are later used to fine-tune the rate of gonadal development to local conditions. Many tropical habitats are seasonal, but
the timing of the seasons (e.g., rainy season) can vary considerably between years. We hypothesize that to time breeding in
environments with seasonal variability, tropical birds respond to both long-term and short-term environmental cues to initiate
gonadal growth. We tested the effectiveness of photoperiod and food cues for the initiation of gonad growth in captive male
spotted antbirds (Hylophylax n. naevioides) from Panama. A ‘control’ group was maintained on the short natural photoperiod of 12 h light and 12 h dark (LD 12:12) and
adequate food. A ‘food-stimulated’ group was also held on LD 12:12 but received an increase in food quantity and quality.
A ‘photo+food-stimulated’ group experienced an increase in daylength by 1 h (LD 13:11, the maximal photoperiod in Panama)
and an increase in food quantity and quality. Within 3 weeks testis sizes of ‘food-stimulated’ birds increased significantly,
suggesting that food cues alone can initiate gonad development. As expected from the previous experiment, testis sizes of
‘photo+food-stimulated’ birds, but not ‘control’ birds, also increased. We suggest that the capability to respond to both
food and photoperiodic cues allows animal the flexibility to adjust reproductive activity to variable environmental conditions
each year. Future work should elucidate whether food provides nutritional or non-nutritional cues, and the neurophysiological
mechanisms by which food stimulates reproductive activity. |
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Keywords: | Food cues Environmental seasonality Reproduction Tropical bird Photoperiod |
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