IP Teaching Resources

Appendix I. Course Syllabus

Insect Physiology

University of California, Riverside

January 5, 1996

1. Introduction to insects.

The Class Insecta compared to closely related arthropods.

Comparative phylogeny. There remain hundreds of thousands of undescribed and undiscovered species of insects in the world. Despite this, all of the principles of insect physiology were developed from detailed studies of relatively few insects. The choice of experimental animal often amounts to convenience driven by local circumstances with a good deal of pure luck thrown in.

The scientific names of some of the more common insects used in physiological studies are: Thermobia domestica; Mantis religiosa, Periplaneta americana; Acheta domesticus, Locusta migratoria, Schistocerca gregaria; Carausius morosus; Myzus persicae, Oncopeltus fasciatus, Rhodnius prolixus; Tenebrio molitor; Apis mellifera; Aedes aegypti, Sarcophaga bullata, Culex pipiens, Drosophila melanogaster, Musca domestica; Bombyx mori, Danaus plexippus, Hyalophora cecropia, Manduca sexta, Pectinophora gossypiella.

Common names of insects: firebrat, praying mantis, cockroach, cricket, grasshopper, locust, stick insect, aphid or plant lice, milkweed bug, kissing bug, yellow mealworm, honey bee, mosquito, black blowfly, vinegar fly, housefly, silkworm, monarch butterfly, giant silk moth, tobacco hornworm, and pink bollworm.

Primitive versus advanced insects can be separated into ametabola (firebrats), hemimetabola (praying mantises, cockroaches, locusts, aphids, bugs) and holometabola (mealworm, honey bees, flies, moths). Endopterygota and exopterygota also describe and separate the hemi- and holometabola. The theory of the pupal stage will be described in class.

Some other terms: univoltine, cladistics, phylum.

Friday laboratory/demonstration.

The first lab session will be spent with computer familiarization and obtaining accounts for class members. Appropriate insects will then be searched from the Entomology Department database and described. Principles described in lecture will be reinforced with visual demonstrations, and media presentations covering the diversity of insects.

2. Integument.

The cuticle, physical description. The formation of the cuticle. Growth of insects necessitating molting. The molt. Apolysis. The physiology of molting. Molting fluid. The mode of action of benzoylureas as insecticides. The chemistry of chitin. The tanning process. Plasticization of the cuticle. Eclosion. Eclosion hormone. Ecdysis. Resilin protein, properties. The growth of cuticle. The deposition of cuticle. Waterproofing properties of integument.

3. Hormones.

This and the following two lectures cover the discovery of insect hormones. Brain hormone, structure and function. Molting hormone, structure and function. Juvenile hormone, structure and function.

4. Hormones, lecture two.

The second lab/demonstration session will involve a review of the major insect hormones and endocrine glands, a demonstration of endocrine glands under a microscope, then ligature of larvae insects by the class members to demonstrate the head critical stage, and treatment of insects with juvenile hormone analogs. The results of these experiments will be read the following week.

Friday laboratory/demonstration.

The second lab will have a variety of preparations of insect endocrine tissues to view in dissecting microscope including the prothoracic gland and corpora cardiaca/allata complex. Then insects will be treated with juvenile hormone analogs, and set aside; ecdysone analogs and set aside; benzoylureas and set aside. Then a number of insect larvae will be ligatured to demonstrate the head critical stage and set aside. These treated insects will all be “read” the following week. Video tape the ligature procedure for archiving in the computer.

5. Hormones, lecture three.

6. Hormones, related subjects.

The Banana experiment. The paper factor. Bursicon. Plasticization of cuticle. Juvenile hormone mimics and antijuvenoids. Ecdysone mimics as insecticides. The physiology of eclosion. hormone levels and titres during molting and development.

Friday laboratory/demonstration.

The ligatured and topically treated insects from the previous week will be evaluated and scored for effects of hormone analogs. Intermediate stages of development will be discussed in the treated insects. Video tape all of these results for future classes along with a dialog of the results.

7. Neurosecretion and "other" neurohormones.

The difference between ordinary lipophilic hormones, and neurohormones. Proctolin, diuretic hormone, allatostatin, egg development hormone, pheromone biosynthesizing neurohormone hormone, pupariation neurohormones, other neurohormones. Octopamine and neuromodulators.

8. The insect nervous system.

Overall anatomy. Ventral nerve cord. Peripheral vs. central nervous system. The Autonomic nervous system. Ganglionic organization. The perineurium. The neural lamella. The neuropile. The neuron and its axon. The motor neuron. The interneuron. The sensory neuron. The nervous impulse. The ionic basis of the nervous impulse. Tetrodotoxin, mode of action. The mode of action of DDT.

9. Vision.

Fast and slow eyes. The ERG. apposition, superposition and neural superposition eyes, examples of each. Color vision. The color spectrum. uv light detection. The plane of polarized light. visual acuity. simple eyes. Function of ocelli. Function of stemmatae. Extra-ocular light sensitivity, and possible functions.

Friday laboratory/demonstration.

Examination of the different insect eyes with dissection microscope. Ask Mike Adams if he has any cobalt fills to show, or slides. Ask Mike if he has any fluorescent nerves from Dushan Zitnan’s work to show. Microscope demonstrations of insect nervous system. American cockroach ventral nerve cord with hyperneural muscle and median nerves, and lateral cardiac nerve cord. Students will be asked to find and draw the nerves shown. Set up to take pictures with the Nikon camera apparatus (or take computer pictures with our video camera/television set-up). Use these results to form permanent computer records. Update or replace them every year as preparations improve.

See if we can make some visuals of the Nick Strausfeld fly brain book, or the protocerebral ganglion papers in JIP. See if Leo has some slides of his autoradiography work.

10. Mid-term exam.

11. Mechanoreception.

The trichoid hair. Campaniform sensillae. Scolopidia and chordotonal organs. Johnston's organ. Subgenual organs. Tympanal organs. Detection of bat sonar and behavior.

12. Chemoreception.

The chemoreceptor, some structures. gustatory receptors. The labellar hair. the tarsal chemoreceptor. The palps. Olfaction. Pheromones and sexual attraction. Control of pheromone biosynthesis and control of pheromone perception.

Friday laboratory/demonstration.

Ask mike to set up a locust leg preparation (or get some legs ourselves). Have the students make the same preparations. Take notes of how many preparations actually work, and the rate of rhythmic contraction. Video tape everything. Mount some starved adult flies or moths, and present the sugar to the tarsi on a filter paper to get the sugar response. Or use both flies and moths. Make sure to have a control with no sugar, or with a substance causing an aversion response.

Find a film of the moth bat cry avoidance reaction. Record cricket singing and look at the pattern on a sonogram. This might require an oscilloscope display and photograph.

13. The synapse and synaptic transmission.

The neuromuscular junction, anatomy and function. Neurotransmitters. Postsynaptic potentials. Fast and slow motor units. Inhibitory motor neurons. The motor unit. Neuromodulators and examples. The DUM neurons and the firefly light organs.

14. The central synapse.

The cholinergic synapse. Acetylcholine. The cercal-giant synapse. The Deutocerebrum and antennal nerves, anatomy and function. Glomeruli.

15. Insect muscles.

The structure of insect muscles, examples. Fast and slow units again in terms of muscle anatomy. Synchronous flight. Asynchronous flight and fibrillar flight muscles. The locust jump, structure and function of the grasshopper extensor tibia muscle during the jump. The cricket song and fixed action patterns. Reflex postural tonus and the function of peripheral inhibition.

Friday laboratory/demonstration.

Asynchronous flight. This is going to take some preparation and practice. Video tape preparations ahead of time if the preparations don’t work. (Tom has some old films of flies flying. Set up a demonstration dissection of the cercal-giant synapse. Find some visuals of the giant axons/neurons. Stain some fresh nerve/muscle preparations.

16. The circulatory system.

The hemolymph, composition of. Hemocytes, function of. Structure and function of pumps and septae. Neurogenic versus myogenic hearts. Nervous versus hormonal control of heartbeat, evidence. Tidal flow of hemolymph.

17. The respiratory system.

Tidal flow of hemolymph, the respiratory part. The respiratory structures. Control of spiracles. The respiratory part of the autonomic nervous system. Gas exchange. Diffusion of gases. Respiratory quotients. Carbon dioxide, solubility of. Discontinuous respiration. Respiratory strategies of insects. Aquatic insects and respiratory specializations. Insect hemoglobins.

18. Temperature.

Cold blooded versus warm blooded and modern concepts. Behavioral strategies to keep warm or cool. Temperature control of insect flight muscles, Hernd Heinrich work. Forms of radiation and convection with definitions. Adaptations to extremes of temperature. Antifreeze, the need for and methods of producing. An introduction to heat shock proteins.

Friday laboratory/demonstration.

A combination of heartbeat recording with cricket and cockroach hearts. Thermoregulation demonstration using the Sphinx moth.

19. Nutrition.

20. Water balance.

The need to conserve water. Repeat of cuticle waterproofing. Metabolic water. Active accumulation of water. Absorption of water from the atmosphere. Mode of action of boric acid. Elimination of water during locust flight. Diuretic hormone. Rhodnius water dumping.

20. Nutrition.

Dietary requirements. Essential amino acids. Vitamins. Fats. Carbohydrates. Protein. Insect diets, sources of materials. Plant proteins and fats versus animal proteins and fats. Definitions of fats, fatty acids and wax.

21. Digestion.

The alimentary canal of insects, comparative anatomy and specialized functions. The salivary glands. The midgut, structure and function. Goblet cells and columnar cells. Ion pumps. The major groups of dietary materials such as cellulose and specializations to digest, protein, lipids, carbohydrates. Trehalose and digestion. Fat digestion.

22. Digestion.

Protein digestion. Amino acid turnover. Recycling of ions. Krebs cycle introduction. ATP sources.

23. Excretion.

Main principles of excretion. Retention of water. Excretion of nitrogenous wastes. Chemical properties of ammonia, urea and uric acid. Uric acid equilibrium. Uric acid formation. Bicarbonate ion equilibrium. Aquatic versus terrestrial environments and special needs of each. Storage excretion and examples. "Yellow rain" and other fables.

24. Reproduction.

Overview of insect reproduction including major strategies. Sexual organs, male and female. Accessory glands. Complex reproduction. Sexual reproduction. Sexual behavior. Reproduction of fleas and other parasites. Reproduction in social insects. Ovaries, hormonal control of. Hormonal control of reproduction. Reproduction in mosquitoes. Vitellogenesis, control of.

25. Energetics and metabolism.

Overview and summary. No details of metabolic pathways, but caloric output for various substrates used for energy, and trade-offs for the major fuel types, carbohydrate, lipid or proline. The energetics of insect flight muscle and lack of oxygen debt. Strategies to get airborne and stay there.

26. Diapause.

An adaptation to extremes of environment. The physiology of diapause. Physiological triggers and components modulating diapause.

27. Review or introduce hormonal control of insect behavior, or guest lecturers.

There are usually 29 lecture days in a given spring quarter. With two days used for mid-term exams, that leaves 27 days for lectures.

Email addresses.

The course instructors will have email addresses that are listed on the homepage of the Department. In the blanks provided below, write the appropriate information for all instructors and TAs for future reference.

Instructor 1

Name: ______________________

Office hours: _________________

Email: ______________________

Phone: ______________________

Message: ____________________

Instructor 2

Name: ______________________

Office hours: _________________

Email: ______________________

Phone: ______________________

Message: ____________________

Instructor 3

Name: ______________________

Office hours: _________________

Email: ______________________

Phone: ______________________

Message: ____________________

Bulletin Board:

A class Bulletin Board has been established on the internet at: [_________________] (write the code name in the space provide) during the term when the course is offered. Students may post questions or answers to questions, discussions about the class and answers to questions from the instructors as well as from others who may access the Bulletin Board. Exam hints will be posted as well as other class news.

If participation in the Bulletin Board is required by the class, it will be announced near the start of the quarter.

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