Biology 484 – Ethology Chapter 5b – Neurohormones

5.4 Nervous system and digestive system of a blowfly The recurrent nerve is a sensory nerve that receives sensory input from the foregut. As we saw in our video, when this nerve is severed, it will keep the fly from receiving these signals and the blowfly will eat beyond capacity. This is an inhibitory behavioral response that is guided neurally but leads to the release of hormones in the brain that will promote satiety.

5.7 The cricket nervous system If the optic lobe region of the brain is separated from the subesophageal ganglion, the fly will lose its clock rhythm… its ability to maintain a circadian rhythm. A circadian rhythm is an endogenously driven cycle in biochemical, physiological, and/or behavioral processes. Typically close to a 24 hour time frame, circadian rhythms have been observed in plants, animals, and even fungi.

5.8 A master clock may regulate mechanisms controlling circadian rhythms within individuals The master “clock” (the pacemaker) will regulate the response of many other timed rhythms in the body. This pacemaker will in tern be regulated by sensory information it receives.

5.10 Mutations of the per gene affect the circadian rhythms of fruit flies The per gene is a regulatory gene that has been shown to affect circadian rhythms in fruit flies. The bars indicate periods of activity. Notice how each point mutation affects the genes regulation of the “clock” differently.

5.11 Expression of the gene that codes for PK2 in the SCN PK2 is the equivalent of per in mammals. Here we see differences in expression of PK2 dependant upon the hour of the day. LD = 12:12 Light/dark cycle 2DD = two days of darkness 8DD = eight days of darkness

5.12 Circadian control of wheel-running by white rats changes when the rats are injected with PK2 Behaviorally, we see that that infusions of the products of PK2 in the suprachiasmatic nucleus (SCN) alter wheel running behavior. In this instance, the control group shows high activity at night, whereas the PK2 group shows high daytime activity.

5.13 Naked mole-rats lack a circadian rhythm Logically, the naked mole- rat’s lack of rhythm can be understood when we think of it living its entire life underground.

5.14 Circannual rhythm of the golden-mantled ground squirrel Circannual rhythms are produced when the internal biological clock also operates on an annual basis.

5.16 Lunar cycle of banner-tailed kangaroo rats

5.17 A cycle of photosensitivity White-crowned sparrows exhibit a clock mechanism that is highly light sensitive between a specific two hour patch (hours in a 24 hour clock). The read peaks show these sensitivities. When the bird receives light stimulus at those times, testicular growth is seen. Other light cycles failed.

5.18 A hormonal response to light Leutenizing hormone is a pituitary hormone that will stimulate the activity of the gonads. The birds were held in darkness for varying lengths of time, and THEN exposed to an 8 hour period of light. (Upper graph) After the 8 hour exposure, the typical cycling rate in LH was maintained for the five days shown.

5.20 Photoperiod affects testis size in the red crossbill Question to Ponder: How would you explain this seasonal rhythm?

5.21 Regulation of infanticide by male house mice (Part 1) Infanticide can be affected by manipulation of the circadian rhythm.

5.21 Regulation of infanticide by male house mice (Part 2) Fast Day males (those in the teal color) halted the display of infanticidal behavior within 20 days of real time (their perceived days were 22). By contrast, Slow Day males (those in the purple) did not show a decline in infanticde until 25 days of real time (their perceived day 22).

5.22 A hormonal effect on infanticidal behavior in laboratory mice Progesterone surges appear to be the key to inducing infanticide. Males lacking this gene, do not display infanticide. The PRKO mouse is a knockout mouse that lacks the ability to detect its own circulating progesterone.

Measurements: Anogenital Distance Interoccular Distance Body Length Weight Pup Morphology as a Measure of Development

Reproductive Behaviors Reproductive Behaviors in Rats

Reproductive Behaviors - Data Male Reproductive Behaviors: Mounts Intromissions Ejaculations

Reproductive Behaviors - Data Female Reproductive Behavior: Lordosis  Lordosis Score of “0”  Lordosis Score of “1”  Lordosis Score of “2”  Lordosis Score of “3”

Reproductive Behaviors - Results Average Mounts vs. Average Intromissions Percentage of Animals Displaying Sex Behavior Results of Male Reproductive Behavior Tests Following Developmental Exposure to PFOA

5.23 Testosterone and progesterone levels in two categories of male California mice NS Significant

5.24 Testosterone and the control of sexual motivation in male Japanese quail (Part 1)

5.24 Testosterone and the control of sexual motivation in male Japanese quail (Part 2) Therefore…. Even though testosterone is produced by the gonads, the motivation to behave sexually is controlled by estradiol. Estradiol is therefore the hormone that is associated with male sexual motivation. Notice the red line with the aromatase inhibitor.

5.32 Testosterone and territorial behavior (Part 1) Notice how elevated testosterone is associated with territorial behavior.