Chapter 3 Hormones And Neurobiology Proximate and Ultimate
Chapter 3: Hormones And Neurobiology • Proximate and Ultimate Perspectives • Hormones and Proximate Causation • Neurobiology and Behavior
• Proximate and Ultimate Perspectives • • Proximate: here and now Ultimate: then, now and why House Finches (Geoff Hill, Auburn University) • Plumage coloration • Sexual dimorphism • Males are brightly colored • Females are not
• Proximate Question: • What causes males to be more brightly colored ? • Ultimate Question: • Why does this dimorphism persist over evolutionary time?
• Proximate Question: • What causes males to be more brightly colored ? Carotenoids cause the coloration. Over 600 compounds Xanthophylls (contain oxygen) Carotenes (no oxygen) Carotenoids absorb green to violet wavelengths seen as yellow, orange, or red Animals do not synthesize these compounds (two exceptions spider mites and aphids) They are acquired in the diet.
• Proximate Question: • What causes males to be more brightly colored ? So male House Finches must eat more carotenoids than females. Across populations, differential availability of carotenoid in food seems to explain the variation. 1. Females fed high carotenoid diets were more colorful than females fed low carotenoid diets. 2. In populations where there higher carotenoid levels in the diet, females tend to be more colorful. Within populations, males seems to forage differently from females. 1. Males actively seek and eat high carotenoid food, females will eat almost any diet. 2. Males have more colorful plumage directly related to their foraging activity.
• Proximate Question: • What causes males to be more brightly colored ? This just in… Matthew B. Toomey, Ricardo J. Lopes, Pedro M. Araújo, James D. Johnson, Małgorzata A. Gazda, Sandra Afonso, Paulo G. Mota, Rebecca E. Koch, Geoffrey E. Hill, Joseph C. Corbo, and Miguel Carneiro High-density lipoprotein receptor SCARB 1 is required for carotenoid coloration in birds PNAS 2017 : 1700751114 v 1 -201700751 The gene SCARB 1 regulates the uptake of carotenoids in the gut of birds! Lopes, R. L. , J. D. Johnson, M. B. B Toomey, S. M. Ferreira, J. Melo-Ferreira, L. Andersson, G. E. Hill*, J. C. Corbo*, and M. C. Carneiro*. 2016. The redness gene in birds. Current Biology
• Proximate Question: • What causes males to be more brightly colored ? and Lopes, R. L. , J. D. Johnson, M. B. B Toomey, S. M. Ferreira, J. Melo-Ferreira, L. Andersson, G. E. Hill, J. C. Corbo*, and M. C. Carneiro. 2016. The redness gene in birds. Current Biology There is an enzyme (ketolase) that allows birds to convert yellow dietary carotenoids to red carotenoids used for ornamental feather coloration. (This ketolase is a cytochrome P 450)
• Ultimate Question: • Why does this dimorphism persist over evolutionary time? • • Why do males search for high carotenoid foods? What are the benefits to the males how do this? Hill’s color manipulation studies in House Finches (1990 through 1993)
Using hair dye and bleach he altered male plumage coloration (Hill, 1991)
The males were released into the population and the number of mate pairings and time to pairing were measured. 100% of brightened males were paired in 12 days (Hill, 1991)
More “ultimate” questions: Why do females prefer (choose) the more colorful males? Disease resistance and parasite load (Hamilton and Zuk, 1982; Hill and farmer, 2005)
More “ultimate” questions: Why do females prefer (choose) the more colorful males? More colorful males make better fathers. Parental investment increased in more colorful males. (Hill, 1991) and… More colorful males tend to be better foragers and this leads to higher survivorship. And this trait appears to be heritable.
Hormones and Proximate Causation
Effects of Ecotourism on stress in Magellanic Penguins
Many bird species breed during the spring and early summer, and changes in day length are an excellent cue for seasonal change. As day length changes, it affects circulating levels of testosterone (T). Increases in T increase the probability that males are aggressive toward one another (to gain access to females), guard their mates, build nests, and defend their broods. (From B. Walker et al. , 2005)
How the endocrine system integrates sensory input and output
Effects of circulating testosterone during development Intrauterine position in mice
Long-term effects of intrauterine position In Mongolian Gerbils 1. 2 M males had significantly higher lifetime testosterone levels than 2 F males 2. 2 M males sired more pups than 2 F males 3. 2 M males were more aggressive than 2 F males 4. 2 M males mounted faster, ejaculated sooner 5. 2 F males spent more time with offspring
Oxytocin and Vasopressin
Hormones and Honeybee Foraging Proximate questions
In bees, hormones regulate development and determine foraging behavior 1. 2. Juvenile hormone determines shift to foraging Octopamine increases foraging
Neurobiology How nerves work
Vocalization in Plainfin Midshipman
Proximate Functions of Sleep Behavior
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