CARDENOLIDES AND CATERPILLARS: the effects of cardenolides on the longevity of monarch butterflies, Danaus plexippus, infected with the protozoan parasite Ophyrocystis elektroscirrha. Open Access

Huang, Junjian (2010)

Permanent URL: https://etd.library.emory.edu/concern/etds/xk81jk808?locale=en
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Abstract

CARDENOLIDES AND CATERPILLARS: the effects of cardenolides on the longevity of monarch butterflies, Danaus plexippus, infected with the protozoan parasite Ophyrocystis elektroscirrha. By Junjian Huang

Cardenolides are secondary metabolites synthesized by milkweed plants. The functions of secondary metabolites are not fully understood but there have been studies that suggest milkweed plants use cardenolides as a form of protection from generalist herbivores. Monarch larvae are specialist herbivores that feed only on milkweeds and the larvae are able to sequester these toxic compounds into their bodies, which protects them from predation. In addition to anti-predator properties, it has been hypothesized that these cardenolides may possess antiparasitic properties as well. The focus of these three experiments is to study the role of cardenolides in the host-parasite system of monarch butterflies, Danaus plexippus, and its parasite, Oprhyocystis elektroscirrha. We found that latex from A. curassavica, which contains a wide range and high concentration of cardenolides, reduced the parasite load of infected monarchs; however, the cardenolides digitoxin and ouabain did not show significant effects of reducing parasite load in infected monarchs. This result suggests that cardenolides may be involved since they are the only organically active compounds discovered thus far in milkweeds. However, further tests are necessary before we can draw any definite conclusions regarding the anti-parasitic properties of cardenolides.

Table of Contents

1. Introduction ------------------------------------------------------ 1

Figure 1--------------------------------------------------------------1

1.1 Monarch Butterflies------------------------------------------------3

Figure 2--------------------------------------------------------------3 1.2 The Parasite------------------------------------------------------4

Figure 3--------------------------------------------------------------5

1.3 The Monarch-Host Plant System-----------------------------------6

Figure 4--------------------------------------------------------------7

Figure 5 --------------------------------------------------------------7 2. Materials and Methods --------------------------------------------9

2.1 Cardenolides and Latex-------------------------------------------- 9

2.2 Leaf Discs-------------------------------------------------------- 9

2.3 Parasite Spore---------------------------------------------------- 9

2.4 Spore Deposition------------------------------------------------- 9

2.5 Caterpillar Rearing----------------------------------------------- 9

2.6 Pupal Scoring---------------------------------------------------- 10

2.7 Vortexing-------------------------------------------------------- 11

2.8 Digitoxin and Ouabain Experiment ----------------------------------11

Table 1---------------------------------------------------------------12

2.9 Natural Cardenolide Experiment--------------------------------- 12

Table 2---------------------------------------------------------------13

2.10 Latex Experiment---------------------------------------------- 13

Table 3 --------------------------------------------------------------14 3. Results -----------------------------------------------------------16 3.1 Digitoxin and Ouabain Experiment -------------------------------16

Figure 6--------------------------------------------------------------16

Figure 7--------------------------------------------------------------17

Figure 8--------------------------------------------------------------17

3.2 Natural Cardenolide Experiment--------------------------------- 18

3.3 Latex Experiment------------------------------------------------ 19

Figure 9--------------------------------------------------------------19

Figure 10-------------------------------------------------------------19

Figure 11-------------------------------------------------------------20

4. Discussion --------------------------------------------------------21 5. Conclusion --------------------------------------------------------23 6. References--------------------------------------------------------25


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