STUDY QUESTIONS        EXAM III

(Answers give below)

Butterflies are holometabolous insects that have a caterpillar larva and which spin a cocoon for pupation.  Many butterflies have well developed biological clocks and exhibit circadian rhythms for activity.  In some species, caterpillars that develop late in the season can enter diapause and overwinter.  Butterflies can be infected with several types of bacteria and also can be infected by a species of parasitoid, which lays its egg inside the body cavity of the butterfly.  Assess the following statements.

a.  Butterflies possess eruciform larvae and exarate pupae.

 b. During pupal development, adult structures arise from the embryonic blastoderm.

 c. Butterflies bees are amonotelic. 

 d. The elimination of nitrogenous wastes involves active transport in both the malpighian tubules and the rectal glands.

 e. During diapause the caterpillars would use passive suction ventilation (if you think this is true, explain how it works).

 f.  The presence of a parasitoid egg would stimulate nodule formation, in which plasmatocytes would produce agglutinin and phenyloxidases.

g.  Sex determination in butterflies is chromosomal: females are XX; males are XY.

 h. Butterflies exhibit haplodiploidy, which refers to the process of  metamorphosis, in which imaginal discs are activated by JH to produce adult structures.

 i.  The biological clock of the butterfly involves three genes.  The per gene produces PER protein, which accumulates in the cells of the fat bodies and activates two other genes:  (1) the fap gene, which produces HCO3- which inhibits the per gene, and (2) the tim gene, which produces DBT protein which stimulates PER production.

 j. When foraging for nectar on a hot sunny day, the butterfly would begin to suffer water loss.  It will therefore produce protolin hormone, which will decrease the rate of uptake of Na+ and K+ ions by the rectal glands.

 k. When contracting a bacterial infection, the bacteria can stimulate non-inducible immune responses in which pheyloxidases activate a cascade of reactions resulting in the production of melanin, which kills bacterial cells.

l.  Female butterflies would possess panoistic ovaries, in which yolk would be taken up and desposited in the forming ova by speical cells called nephrocytes contained in the the germarium of the testicular follicle, and egg RNA would be supplied by the apical cell of the vitellarium of the ovariole.

2.  Assess the following statements about insect hormones:

a.  EDNH is produced by the fat bodies of female mosquitoes after taking up a blood meal, and it stimulates the primed ovary to release JH, which stimulates the prothroacic gland to produce vitellin.

b.  JH and ecdysone are involved in molting and development during larval growth and in egg formation and yolk production during reproduction in adult insects.  (Whether you think this statement if true or false, explain precisely how JH and ecdysone operate)

c.  The per gene produces the hormone, ecdysiotropin, which activates the dbt gene and the tim gene, which are responsible for the insect biological clock.

d.  Proctolin, diuretic hormone and antidiuretic hormone are involved in maintaining homeostasis in insects (whether true or false, explain what each hormone does)

ANSWERS

1.  a.  False:  caterpillars are referred to as eruciform larvae, but butterflies have coarctate pupae (with a cocoon),  Exarate pupae are without a cacoon. 

    b.  False:  during pupal develpment, adult structures arise from imaginal discs in holometabolous development.  The blastoderm is the first layer of cells that forms around the periphery of the egg and gives rise to the germ band (embryo) and serosa.

    c.  False:  butterflies are uricotelic (produce uric acid).  Only some aquatic insects excrete amonia and are amonotelic.

    d.  True:  Malpighian tubules use active transport to move K+ and Na+ ions into tubules and water (with dissolved solutes) follows passively.  Rectal glands use active transport to pump K+ and Na+ back into hemolymph and water follows passively.

    e.  True:  spiracular valves would remain closed but not sealed, and would "flutter".  Oxygen would be removed from trachea due to metabolism, and CO2 would move into trachea at a slower rate because much remains dissolved in hemolymph as HCO3-.  As a result, a negative pressure forms in trachea which causes a constant suction of air into the spiracles (which is why the valves flutter).  Periodically, when CO2 level in trachea reaches a threshold concentration, spiracles open wide briefly and there is an outrushing of CO2.  In this manner, water vapor is loss is minimized, because most of the time air is being sucked into the trachea which prevents outflow of water vapor and loss of water vapor can occur only during the brief periods when spiracles burst open to release CO2.

    f.  Falase:  would stimulate encapsulation, in which granulocytes degranulate, which attracts more granulocytes and also plasmatocytes, which attach to egg and eventually cover it (encapsulate it).  Agglutinin and phenyloxidases are components of the non-inducible immune response, which is noncellular (not produced by plasmatocytes or granulocytes).

    g.  False:  sex determination is chromosomal, but in Leps. XX is male and XY is female (don't ask me why).

    h.  False:  Leps. do not exhibit haplodiploidy, which is a method of sex determination found in Hymenoptera and aphids.  Is based on partenogenesis, in which fertilized (diploid) eggs are female and unfertilized (haploid) eggs develop parthenogenetically into males.  In honeybees, a haplodiploid species, there is a single sex determining locus with 20+ alleles.  Individuals that are heterozygous at the locus become female; those homozygous or hemizygous at the locus become males.  It is possible to get a diploid drone, if both the queen and drone carry the same allele at the locus.  However, these individuals die in the early larval stages, because workers eat them.

    i.  False:  does involve 3 genes, but not in manner indicated.  per gene produced PER protein, which affects general activity levels of insects.  PER increases in concentration in cells of optic lobes.  When concentration of PER hits a threshold level, it activates two other genes:  dbt (not fap) gene produces an enzyme (not HCO3-) that degrades PER (does not inhibit per gene); tim gene produces TIM protein (not DBT protein) which binds with PER and the TIM+PER complex inhibits the per gene (negative feedback loops).  The end result is that the concentration of PER waxes and wanes on a 24 hour cycle, forming the basis of circadian rhythms.

    j.  False:  water loss would stimulate release of antidiuretic hormone, which would increase uptake of ions by rectal glands and thus the reabsorption of water (and result in less water being excreted).  Proctolin increases rate of movement of material through rectum and out of anus, and thus increases amount of water eliminated from body.

    k.  True:  the process described makes up the noninducible component of the noncellular immune response of insects.

    l.  False:  most holometabolous insects (including Leps.) have polytrophic ovarioles; panoistic ovarioles are found in more primitive insects.  In butterfly, yolk would be taken up by a combination of follicular epithelial cells and trophocytes contained within the follicle with the ovum.  Nephrocytes are individual cells suspended in the hemolymph that help maintain blood homeostasis and females do not possess testicular follicles; they have ovarioles.  Egg RNA in polytrophic ovarioles is supplied by the trophocytes contained within the follicles, not by the apical cell, which is found in the germarium of the testicular follicle (not vitelarium of ovariole) and nourishes spermatogonia.

2.  a.  False:  EDNH is released from pars intercerebralis in response to blood meal.  It causes primed ovary to release ecdysone, which stimulates primed fat body (not prothoracic gland) to produce vitellin.  JH from corpora allata primes ovaries and fat bodies.

    b.  True, JH and ecdysone are involved in both of these processess (see your notes for details).

    c.  False, per gene does not produce a hormone, produces PER protein, which activates dbt and tim, which contribute to biological clock of insects.  Ecdysiotropin is produced by pars intercerebralis and initiates the molting process.

    d.  True:  proctolin increases rate of movement through rectum and results in voiding of more water.  Diuretic hormone decreases active transport of ions by rectal glands, so less water is reabsorbed and more is voided.  Antidiuretic hormone increases rate of active transport by rectal glands so that more water is reabsorbed and less is voided.