Module 4 |
Topics covered in this module:
Queen maintains dominance by drugging the food of the female bees, keeping them sterile. The "drug" is known as queen substance. It functions to supresses the development of the other female bees' ovaries.
As the colony grows very large, the queen cannot produce enough queen substance to maintain sterility in all the other female bees. So, some of the other females begin to become reproductively active. The hive is unstable in this condition--there can only be one queen. The hive prepares to swarm so that it can be divided into two smaller colonies each with its own queen. Some foraging bees begin to look for a new hive site. Meanwhile back at the hive, other bees prepare several new queen cells for the development of the new queens. The old queen communicates with these developing queens by auditory signals--she "quacks" at them. The most mature developing queen responds to the "quack" with a "toot" = QUEEN PIPING. When a suitable new hive site has been found the old queen and a swarm of sterile females and some male drones take off to go to the new hive site. In the old hive the new queen emerges from her cell and kills the other developing queens.
The above information was taken from the text, "Biology" by Peter H. Raven & George B. Johnson. 1989. Times Mirror/Mosby College Publishing.
Did you know that the waggle dance of the bees is not actually "watched" by other bees? The hive is completely dark inside so the bees couldn't possibly watch the dance. Instead they "feel" the dance. They follow the dancing bee in a tight little congo line, tracing her exact path. They also touch her frequently. It is in this way that the forager bees get the distance and the direction to the food source from the waggle dance.
There are lots of excellent web sites on the Internet that have beautiful descriptions and pictures of bee waggle dances and other interesting bee behaviors. I have spent some time searching for the best ones and I have linked to them below. Instead of me writing out this same information, I suggest you visit these links to review honeybee communication and hive functions.
New scientific article published about how the type of comb that the bee does its dance on determines the success that that bee has in recruiting other foragers to that site. THIS LINK WILL OPEN IN ANOTHER BROWSER WINDOW WHICH MAY APPEAR BEHIND THIS WINDOW.
An introduction to honeybees and their waggle dance. Excellent review of honeybees with pictures!
HEY, THIS PAGE CONTAINS LOADS OF REFERENCES FOR ARTICLES WRITTEN ABOUT BEES AND THEIR DANCES!! HINT, HINT FOR HOMEWORK #4. THIS LINK WILL OPEN IN ANOTHER BROWSER WINDOW WHICH MAY APPEAR BEHIND THIS WINDOW.
See what a bee sees. Compare how well compound eyes see the world versus the human eye. THIS LINK WILL OPEN IN ANOTHER BROWSER WINDOW WHICH MAY APPEAR BEHIND THIS WINDOW.
Short article written about honeybees communication abilities (waggle dance) and their ability to learn. Excellent discussion of learning in simple organisms. THIS LINK WILL OPEN IN ANOTHER BROWSER WINDOW WHICH MAY APPEAR BEHIND THIS WINDOW.
Lecture Outline that matches one Dr. Case gave you nearly perfectly. This one contains very useful information and wonderful pictures of bee waggle dances and colonial life. THIS LINK WILL OPEN IN ANOTHER BROWSER WINDOW WHICH MAY APPEAR BEHIND THIS WINDOW.
Another lecture outline of a university lecture given on honeybee communication, etc. THIS LINK WILL OPEN IN ANOTHER BROWSER WINDOW WHICH MAY APPEAR BEHIND THIS WINDOW.
It is extremely important that you read Chapter 6 very very carefully. Diagram the connections that the text describes as you read about it. Read it several times. It's full of complex info, but your understanding of this info is crucial.
More to come about the crayfish (and the startle response), but here's a nice picture to get you oriented. In particular, note the underlined labels, Dr. Case has used these terms in describing various experiments so you should know them.
Before we get into the Crayfish alarm response, a few words about muscles in general:
Principle 1 Remember the knee-jerk response from your intro bio classes? Opposable muscle groups, the quad, which extends the leg, and the hamstring, which flexes (bends) the leg, work to move the leg in opposite directions. When one muscle is activated the other is always relaxed because of inhibition. The sensory axon of one inhibits the motor axon of the opposing muscle cell to ensure they don’t both contract at the same time.
Principle 2 When a muscle is stretched it responds by contracting. Some of you might be familiar with this concept in the heart. It is called the Starling mechanism. This is the basis for how asynchronous flight muscles work in insects.
Remember one entire muscle (in any animal) is composed of lots of intrafusal and extrafusal fibers all interconnected to one another.
The tail (abdomen) of the crayfish works just like the human leg, it has extensor muscles to extend the tail and flexor muscles to bend the tail. Note: in crayfish only the extensor muscles have stretch receptors. Stretch receptors sense the stretch of the intrafusal fibers and are also called muscle receptors.
Crayfish with tail extended
Crayfish with tail flexed
Below are some homework questions on Crayfish that last year's class was given. I didn't give these to you because Dr. Case didn't cover many of these topics in as much detail this year. But, if you would like to test your knowledge, see how you do answering these questions after you study your lecture notes.
Crayfish Male to Male Antagonistic Interactions
Some more homework questions from last year. To help you test your knowledge gained from lecture.
1. A scientist is studying two male crayfish, Bob and Jim. Bob has had several fights (=agonistic encounters) with other male crayfish and, poor Bob, he’s lost all of them. Bob seems doomed to a life of submission. Because of this past lack of success he’ll probably just back down during the next agonistic encounter. Jim has had better luck; he has had five agonistic encounters and has won four out of five. Jim’s feeling pretty good about his dominance, except when that one male is around that he lost to; Jim is the big dog in town.
(b) If Bob is given a high does shot of 5-HT and sent back into the ring with Jim, what would you predict to happen?
(c) What does Bob’s future hold?
(d) One day the scientist gets mixed up as to which one is Bob and which is Jim. The scientist decides she can just measure levels released in the of each crayfish to determine which crayfish is dominant now, namely identify .
Caenorhabditis elegans, the model nematode
The amphid's function and location in C.elegans illustrates what generalized evolutionary step in the formation of increasingly complex nervous systems? (one word answer) .
Why is the amphid located at the anterior end of the nematode?
List 3 reasons a researcher might want to work with Caenorhabditis elegans as a research subject.
Drosophila: the genetic key to understanding memory
Below are some homework questions on Drosophila that last year's class was given. I didn't give these to you because Dr. Case didn't cover many of these topics in as much detail this year. But, if you would like to test your knowledge, see how you do answering these questions after you study your lecture notes.
To elucidate mechanisms of learning and memory, Seymour Benzer, in the 1970s, performed elegant genetic studies of Drosophila. He created many different mutant fruit flies by performing point mutations on portions of the fly’s DNA. He would observe resulting morphological changes or learning behavior changes caused by the mutation. From this he could deduce that a given gene is involved in learning process "X". And, with further analysis he could state that learning process "X" must involve cellular mechanism "Y".
Point mutations are single base changes made to DNA. There are three types of point mutations that vary in their deleterious effects on the final protein. These include substitution of one base for another (resulting in only one amino acid in many being affected in final protein); deletion, where one base is removed (resulting in a reading frameshift which alters all the amino acids that are coded from that point on); and additions, where one base is added to the gene (resulting in a reading frameshift which alters all the amino acids that are coded from that point on). The two that result in reading frameshifts are much more serious in their effects than substitutions.
A quick review of the basic dogma of molecular biology:
Fruit fly mutants are given simple names denoting either the observed changes in morphology resulting (apparently) from the genetic mutation or from the observed effects on learning.
The Drosophila shown below is a mutant named, "bithorax" because the genetic mutation performed caused this fly to abnormally develop two thoraxes (instead of one), thus resulting in two sets of wings (instead of the normal or "wild-type" one pair of wings).
2. Complete this table of Benzer’s Drosophila mutants and what he and his colleagues learned from them.
Following the example, add two more of Benzer’s mutants you heard about in lecture.
| Name of Mutant | Gene mutated (if known) |
Observable result of mutation | Wild-type (Normal) Behavior / Morphology |
| ex. "dunce" | protein which acts as a receptor to receive odors (chemicals) & transduce the signal across the membrane | have no memory for odors. no behavior induced by odors the fly has been previously trained with. | You can train wild-type Drosophila to respond a certain way when they are exposed to a certain odor. They have the ability to remember this odor for several hours. |
Learning and Memory Formation: mechanisms of
Don't worry about the details and the unfamiliar terms in the following description, but I just wanted to give you a feel for the main theory behind mechanisms of memory formation and learning in humans right now. "Retrograde-signalling molecules" that turn on protein synthesis in upstream cells is the upshot of the theory. I strongly suggest you read the short article on learning in a mollusc that is linked below the colored figure below.
Certain glutamate receptors/channels are believed to play a very important role in learning and memory formation via a process called long-term potentiation or ltp. This mechanism involves the production of compounds by the postsynaptic cell that travel to the presynaptic cell and stimulate further neurotransmitter release. These compounds that travel "backwards" are called retrograde-signaling molecules. Generally they are membrane permeable (so they don't need to be exocytosed), as soon as they are produced they seep out of the producing cell and into any other nearby cells. These retrograde-signaling molecules are therefore not packaged in synaptic vesicles. The most studied retrograde compound is nitric oxide or NO.
NOTICE THE IMPORTANCE OF Ca+2!!
In the postsynaptic cell:
The production of NO is indirectly triggered by the influx of Ca+2 that occurs in the postsynaptic cell following the opening of NMDA channels. Second messengers trigger the enzyme (NOS or NO synthetase) that makes NO from Arginine.
In the presynaptic cell:
NO diffuses out of the postsynaptic cell and into the presynaptic neuron that released some neurotransmitter, example, glutamate. Inside the presyanptic cell the NO triggers the enzyme guanylate cyclase to make cGMP from GMP.
This cGMP binds to cGMP sensitive targets, which can result in the opening or closing of ion channels. This leads to the eventual increase in the # of synaptic vesicles that the presynaptic cell can release and an increase in the size of the presynaptic terminal. So that the next series of APs that arrives in the presynaptic terminal will result in a greater # of neurotransmitters being released. The release of NO by the postsynaptic cell facilitates the communication between these two cells. It is by this mechanism that learning and memory formation are thought to occur. Synapses that are used often will become larger and more robust, making them "freeways" of neuronal traffic.
Click here to read a short article about the structural changes to neurons induced by learning in a mollusc.
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Habitutation - the reduction in response over time to a continuous stimulus of continuous strength
There are two types of habitutation
Behavioral
This is seen in Ascaris behavioral response to a continuous steady tapping. When the tapping first begins, the nematode exhibits the behavior of avoiding the area. As the tapping continues, the nematode appears to "ignore" the stimulus and go about its normal behavior. It is becoming habituated to the tapping stimulus.
Cellular
This is seen in Ascaris chemoreceptors. Normally one chemoreceptor can respond to more than one chemical, but if that chemical is encountered at a steady, high concentration, the chemoreceptor's sensitvity to this chemical decreases (AP are fired at a lower and lower frequency from the chemoreceptor neuron) = habituation.
Latency - the delay before a response is noted in an organism to a given stimulus.
Ex. I put my hand on a hot burner and it takes 100 ms before I pull my hand off the burner. The 100 ms is the latency associated with my response to the heat and pain stimuli. This delay is due to the time it takes the sensory signal to travel to the CNS, be processed, a motor impulse sent down the motor nerves, then there is a delay in getting the muscles activated to remove the hand.
The latency associated with an organism's response to a given stimulus is an important piece of information for evaluating the importance the organism gives certain stimuli and the neural mechanisms that are most likely involved in the response to the stimuli. (In inverts, if the latency is very short, the animal is most likely using giant axons, if the latency is long, then the animal is probably using non-giant axons.)
Facilitation -"to make easier". This is seen in nerves when, upon repeated stimulation the response to the stimulus increases. (At a cellular level: increased release of synaptic transmitter from a neuron due to previous synaptic activity.)
An example of this in lecture was the cnidarian, Renilla, or "sea pansy". This organism produces waves of bioluminescence that radiate from the point of physical stimulation. The first few times you poke the animal you get no response or very dim bioluminescence, but after a few more pokes of the same magnitude all of a sudden the animal is producing bright waves of bioluminescence. It appears as if the pathway to stimulate the bioluminescence has been made easier to trigger.