Exciting times! I will again be working with monarch butterflies, the most iconic of all North American butterflies. We are interested in how this long-distance migrant copes with infection by the protozoan parasite Ophryocystis elektroscirrha. This parasite is host-specific and infects monarch caterpillars. Once the infected individual reaches the adult stage, the parasite releases spores that will infect a next generation of monarchs. Studies by Sonia Altizer, Jaap de Roode and colleagues have shown that infection reduces lifespan and reproductive output in monarchs. Infected individuals also have lower flight capacity, which in the case of a long-distance migrant with a declining population size, is not good news.
We are studying the mechanistic underpinnings of reduced flight capacity in infected monarchs. We are measuring metabolic rates at two levels: at the whole-animal and at the mitochondrial level. This should give us a pretty good understanding of what contributes to poor flight capacity.
We just picked up a set of pupae from the lab of Jaap de Roode at Emory University. The next step was to weigh all pupae and glue them to the lids of their individual cups where they will develop into adult butterflies. That’s what I call a royal welcome!
Monarch pupae are some of the most amazing creations of nature. Look at that pleasant blueish green colour and voluptuous shape! And what’s up with those gold ornaments? Turns out they’re not actually gold, but a combination of a structural colour and carotenoid pigments. Nobody really knows why all milkweed butterflies (family Danainae) have metallic-looking patches, though.
Pupae look dormant, but amazing things happen inside them. The entire animal and its tissues are being restructured and reshaped. I went ahead and measured the metabolism of a couple of pupae. There’s a lot of metabolic activity going on!
Previous work on Glanville fritillary butterflies showed that the metabolic activity of pupae was at its highest around midday, and like ectotherms do, they were more active in higher temperatures. The metabolic rate of a pupa however did not predict the resting or flight metabolic rate of the same individual when it had emerged as an adult butterfly.
Some individuals had brought a souvenir from their earlier life as a caterpillar. This is the crumpled larval skin that was left behind in the final moult.
We’re expecting the first adults to emerge this weekend. Stay tuned!
All photos by Ryan Weaver.