Monarch butterflies medicate diseases in offspring

Jaime Ashton
0707463



New studies have shown exciting new evidence to prove the first trans-generational medication in animals. Biologists at Emory University in Atlanta have discovered that Monarch butterflies, who are infected with the parasite Ophryocystis elektroscirrha (a disease that can be passed down to their offspring), have been found to lay their eggs on anti-parasitic host plants. These plants have been shown to reduce parasite infection in the offspring, and many of the disease symptoms are eliminated.


The parasite enters the insect when it is in its caterpillar form. Spores of the parasite are ingested and are coated on the eggs when the female butterflies lay them. The gut wall of the insect is penetrated and the parasite begins to multiply right away and in large amounts.


Since the butterfly nor the caterpillar cannot cure itself of the parasite it lays its eggs on toxic plants that reduce the parasites growth and disease in its offspring.


The idea of animals using medication on their offspring is quite intriguing and interesting to scientists, since traditionally it was thought that animals only focused on "self-medicating". "Self-medicating" is where the species uses compounds and other materials to try and cure itself or try and prevent diseases before they have even gotten one. This type of self-medicating is one of two, where the other one is called therapeutic self-medication. In this instance the animal uses anti-parasitic substances from already infected species to fight off or kill the pathogen. Therapeutic self-medicating is scarcely found among animals and is still undergoing research. This new finding of animals using medicine to help their offspring is exciting to people in the health field, thinking that maybe one day, the medicines that animals use can one day be manipulated to help fight human pathogens. People believe that since Monarch butterflies are able to do this, that perhaps other sorts of insects are capable and perhaps even some vertebrates.


The biologists experimental design was made up of two predictions: that the larvae do not have the ability at that point in their life to choose to eat the more anti-parasitic plant, and that the adult butterflies will choose to lay their eggs on the anti-parasitic host plants when they are infected. The first prediction was proven correct when the larvae in fact choose to eat both plants with no preference, but parasite burdens were lower in the larvae that ate the higher anti-parasitic host. The Monarch butterflies (some infected, some not) were given the choice of two milkweed species (the host plants). It was found that most of the infected butterflies chose to lay their eggs on the more anti-parasitic plant, A. curassavica, and the non-infected chose the other plant, A. incarnata. The genotypes of the parasites on the butterflies born on A. curassavica were seen to produce less spore loads. The experiment proves prediction number two and then showed that the infected offspring born on the more anti-parasitic plant had reduced effects of the parasite than those born on the other host plant. Also, the infected offspring born on A. curassavica had a longer life span than those born on A. incarnata. Uninfected offspring had a longer life when born on A. incarnata. This experiment also showed the decreased laying abilities of females that were infected with the parasite. Twenty seven out of forty nine infected females did not lay eggs and fourteen out of forty three uninfected didn't. However, the number of eggs laid by able females differed only slightly.


This study proves evidence that animals are learning to cope with diseases and are trying to save their offspring by treating them with medicine of sorts. The results also support the research that kin selection can and usually is crucial in initiating the evolution of behaviours in wild animals. The Monarch butterflies are choosing to help their offspring and try to improve their health, so eventually in future generations the parasite will be somewhat elminated.

Reference

Lefevre, T., Oliver, L., Hunter, M. D., and DeRoode, J. C. (2010, October 6). Ecology letters. In Evidence for trans-generational medication in nature. Retrieved October 12, 2010, from http:ééonlinelibrary.wiley.comédoié10.1111éj.1461-0248.2010.01537.xéfull