Caterpillar Death: an Example of Niche Construction

Last Wednesday I attended a seminar by Dr. Steven Hamblin, a behavioral ecologist that uses economic approaches, who is currently delving into viral niche construction. The terms niche construction refer to any type of process by which an organism changes or manipulates their environment. There are many of examples of this all around us.

As humans we often change our environments to suit our wants and needs. We may build elaborate houses or relocate to be closer to different careers or environments. Other great examples are the birds and the bees. Birds are fantastic examples of nest-building, but also many species are migratory and will travel incredibly long distances for a better climate. Bees are also nest-builders which can vary from very small to incredibly large nests that easily help them to fit into many types of environments. In my opinion, spiders have the largest variety of methods to witch they manipulate their environment with

spectacular webs and traps. I once ran into a long string from an orb spider web in Namibia that was so thick and strong I thought it was string. Even string-like webs are perfect examples of how even the type of construction material is a part of how an organism manipulates the environment.

Hamblin did not of course discuss any of these examples, but the significantly smaller and less discussed example of niche construction: viruses. Currently he has been looking at Baculoviridae which is a type of virus that dramatically changes their host. This virus infects caterpillars and modifies them both behaviorally and internally.

The infected caterpillar becomes awakened and suddenly compelled to move to the very top of it’s tree to wait and die, then the virus liquefies the caterpillar into a goo,

and so ends the life of the caterpillar. The fact that the virus kills its poor unsuspecting host isn’t surprising, but Hamblin investigated why they manipulate their host so dramatically. 

The possible answers are quite fascinating. Hamblin used fancy mathematical models and diagrams to assist in finding the effects of these two traits and their relationship with the virus genetics. These Baculoviridae that cause the dramatic caterpillar death have two specific traits called zombie and gooey which also are related to three specific genes, so basically it is in the virus genetics to create this effect. Hamblins findings also demonstrate that this process is for the viruses own benefit. Although it would seem beneficial for

viruses to grow extremely fast, this can cause death too quickly to the host, some mutated viruses and other errors. Additionally the virus wants to be placed somewhere so it can easily find a new host. The result is an optimal growth rate for the virus in a location that allows it to be easily transmitted leading to a zombie-like and gooey caterpillar.

Niche construction is an interesting concept, but I am certainly intrigued by gaining further knowledge in viral niche construction. For example, why don’t all viruses kill their host? I would think there would be more benefits for a virus to live without having to make so many dramatic changes.

Here are some related articles worth reading:

http://ww.explorelifeonearth.org/cursos/dayetalnicheconstruction.pdf

http://lalandlab.st-andrews.ac.uk/niche/Ecology.html

Creanza, N., Fogarty, L., & Feldman, M. W. (2012). Models of Cultural Niche Construction with Selection and Assortative Mating. PLoS ONE, 7(8), e42744. doi:10.1371/journal.pone.0042744
Harrison, N. M., & Whitehouse, M. J. (2011). Mixed-species flocks: an example of niche construction? Animal Behaviour, 81(4), 675–682. doi:10.1016/j.anbehav.2011.01.013
Okano, K., Vanarsdall, A. L., Mikhailov, V. S., & Rohrmann, G. F. (2006). Conserved molecular systems of the Baculoviridae. Virology, 344(1), 77–87. doi:10.1016/j.virol.2005.09.019
At this point in time I am also disovering other great science blogs, here are some links to websites or blogs I like so far:
http://www.pandasthumb.org/  – a wide variety of short topics and ideas
http://scienceblog.com/  – this has many different scientific topics you can choose from
http://drsophiayin.com/blog  – thoughts from an animal behaviourist
http://www.biology-blog.com/  – mostly biology related blog topics
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