Chap.03 Proximate factors 鄭先祐 (Ayo) 教授 國立台南大學 環境與生態學院 生態科學與技術學系 環境生態研究所 + 生態旅遊研究所

Proximate factors 1.Ultimate and proximate perspectives 2.Hormones and proximate causation 3.Neurobiological underpinnings of behavior 4.Molecular genetics and animal behavior 5.Development and animal behavior 6.Foraging in Honeybees: an integrated proximate analysis 7.Interview with Dr. Geoggrey Hill

Significant natural variation exists in house finch coloration.

Artificially brightened (top left to top right photo) or lightened (bottom left to bottom right photo) the plumage coloration of male house finches.

Hill examined how brightening and lightening plumage coloration affected a suite of variables in male house finches. There were 40 males in the brightened condition, 20 males in the same control, and 40 males in the lightened condition.

Hormones and Proximate causation  introduction  Endocrine system (Fig. 3.7)  Neuro-hormones  兩個案例： 1.The long-term effects of in-utero exposure to hormones 2.Stress hormones and spatial memory in rats

Hormones can affect input systems (sensory systems like those for smell, sight, or hearing), central nervous system function (processing), and output systems.

1.The long-term effects of in-utero exposure to hormones

When male Mongolian gerbils were castrated, they spent more time with pups than did “sham” castrated males that had undergone a similar operation but were not actually castrated.

2. Stress hormones and spatial memory in rats

The swimming path of the control rat was consistently near the target (T), indicating that its memory for the location of the platform was not impaired, while the swimming path of the rat that was shocked thirty minutes before being put in the water maze was random, indicating that its memory for the location of the platform was impaired by the shock.

(A) Rats that receive a shock thirty minutes before their trial in the water maze spend less time near the platform (target) than did rats in the other three groups.

Corticosterone levels  Only rats in Group 1 (the group with decreased ability to find the area of the platform) had higher levels of corticosterone, suggesting an important memory inhibiting role for this hormone.  Injected rats with a drug called methrapone, rats did not show impaired memory compared to control one.  Methrapone, inhibits the production of corticosterone by blocking certain cheical reactions in the adrenal glands, where corticosterone is produced.

Neurobiological underpinnings of behavior

Neurobiology and learning in voles

Meadow voles  Males showed superior spatial learning abilities.  From a neuroethological perspective, we can 1.Examine the neural substrate underlying the differences in male and female spatial learning abilities 2.Examine how components of the nervous system change as a function of a spatial learning experience.

Male meadow voles spent more time near the platform in water maze trials than did female meadow voles.

In meadow voles, males have more dentritic spines in both the frontal and the parietal cortex of the brain than do females.

Neural plasticity  The rats went through the spatial learning trails would have more dendritic spines than the control animals.  This is a good example of neural pasticity.  The ability of neurons to undergo change as a function of experience.

Vocalizations in plainfin midshipman fish (A) The two smaller fish on the ends are type II sneaker males (who do not sing), while the fish that is second from the left is a “singing” type I parental male.

Sleep and predation in Mallard ducks  Sleeping individuals are more susceptible to being attacked by predators.  Sleeping with one eye open and one eye shut.  This type of sleep was first recorded in chickens and is best examined in mallard ducks.  Birds are capable of putting one hemisphere of the brain – the hemisphere active during – into what is called slow-wave sleep.

Slow-wave sleep  “slow-wave” refers to the frequency of the brain waves that investigators record using a device called an electroencephalogram (EEG).  This slow-wave state allows quick responses to predators, but it does not interfere with the sleeping half of the bird’s brain until danger is present.  EEG recordings indicate that the part of the brain controlling the open eye during unihemispheric sleep showed the low frequency range characteristic of slow-wave sleep, while the other half showed EEG patterns that were similar to those of true sleep.

In some aquatic mammals, like the fur seal, unihemispheric sleep is thought to allow individuals to swim to the surface and breathe during sleep.

4. Molecular genetics 1)Ultraviolet vision in birds A wide array of animals, including fish, amphibians, reptiles, birds, insects, and mammals. (Table 3.3) In mammals, is used in the context of mating, foraging, hunting, and social signaling. UV vision in zebra finches. 2)Song acquisition in birds  The zebra finch has become a model system to illustrate the relationship between gene expression and birdsong.  Habituation

A single amino acid change  Zebra finches are able to see in UV, and via a single amino acid change (C84S), the researchers were able to transform the ultraviolet pigment– the substance that allows the birds to see in UV– into a violet pigment that doesn’t allow for UV vision.  Using sections of DNA that were very similar to those found in the finch, the researchers were able to generate ultraviolet pigments from violet pigments.  One change in amino acid, and pigeons and chickens were able to see in UV.

Song acquisition in birds  The FOXP2 gene in brain regions is associated with both song perception in birds and language acquisition in humans.  Zebra finch, a model system, to illustrate the relationship between gene expression and birdsong.  Neostriatum in the forebrain,  A gene called zenk, increased after the birds heard zebra finch songs, and that was associated with an increase in the number of neurons in the neostratum (Fig.3.30)

(A)Induction of zenk mRNA in the forebrain of a male zebra finch that has been exposed to zebra finch song for forty-five minutes. (B) same area in male who was not exposed to song.

if a zebra finch is played the same song repeatedly, all of the strong responses begin to decrease, and slowly return to their baseline levels. (habituation).

5. Development  Early development and its effect on parental behavior in the oldfield mouse.  Mice in the Brookfield Zoo.  IF = inexperienced female  EF = experienced female  The broods of EF survived with a higher probability than those of IF, in part due to the superior nest-building behavior displayed by EF. (Fig. 3.32)

Development, Temperature, and ovipositing behavior in wasps

Foraging in honeybee  Mushroom bodies, at the front brain  Both the mushroom bodies and the hippocampus are often associated with spatial navigation.  Mushroom bodies play a central role in spatial navigation and foraging behavior in honeybee. (Fig. 3.35)  Mushroom bodies were larger in foragers than in bees that remained in a colony (Fig.3.36)

Mushroom bodies – shown in light blue– are clusters of neurons located at the front of the bee brain. The yellow denoted the optic lobes of the bee brain.

Genes, mRNA and honeybee foraging  When compared to younger bees that remained at the hive, per mRNA in the brain was significantly greater in older individuals that foraged for food. (Fig. 3.37)  Both of the amount of manganese and the amount of mRNA in the head were high in pollen foragers and nectar foragers, and low in nurses. (Fig. 3.38)

Hormones  Four groups  One is allatectomized bees, remove the corpus allatum, the gland that produces JH, juvenile hormone.(Fig. 3.39)  One went through a similar surgical procedure but did not have their corpus allatum removed.  One, anesthetized only.  One is control.  Results:  Allatectomized bees began foraging significantly later.

Hormone: octopamine  Octopamine, neurohormone, has been linked to increased foraging activity in honeybees.  Octopamine modulates learning and memory in honeybee, and also affects their visual, olfactory, and gustatory senses.  Increase flight activity related to foraging

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