So, been a bit of a hectic week. The course in Molecular Ecology I mentioned finished on friday, meaning I spent the days prior to that frantically trying to finish the paper and presentation of the final project. It was on butterflies.

…

Oh alright. Here’s part of the introduction (the only interesting part of the paper, in my opinion):

The mating behaviour and associated pheromones of pierid butterflies, among them the green-veined white butterfly P. napi, have been studied extensively by Andersson et al. (2000, 2003 & 2004). These butterflies are polygamous, with males seeking out and courting females, which may then allow or refuse copulation.

During copulation, the male P. napi transfers a spermatphore to the female’s bursa copulatrix. This packet contains not only sperm, but also nutrients and pheromones, and is quite large – the mass can extend to 23 % of the female’s body weight. Recently mated females hence cannot receive another packet until they have absorbed the old one (Forsberg & Wiklund, 1989). Also, both mating and oviposition must take place during fair weather, which restricts the time a female can spend on both activities. Thus, females should be allocating more time for oviposition than mating when they are recently mated. This is facilitated by an anti-aphrodisiac transferred to the female during mating. The anti-aphrodisiac, methyl salicylate, is synthesised only by males.

When approached by a male, the female adopts a so called “mate-refusal posture”: She spreads her wings and lifts her abdomen. This posture is well suited for spreading pheromones from her abdomen, while at the same time preventing the male from copulating with her. Females initially adopt this posture regardless of whether they are receptive to mating or not. Receptive females will however, after having been courted by the male, lower their abdomen so that copulation may ensue. Males will approach any female, but quickly abandons recently mated and thus unreceptive ones – it appears that males are incapable of forcing females to accept their spermatophores, and hence they have no incentive to court an unreceptive female.

Females who have received methyl salicylate are thus less likely to suffer extended harassment from unwanted suitors, and can spend more time laying eggs. This also benefits the male, as it maximises the amount of his sperm that is used before an eventual remating. This is an interesting example of how sexual selection may sometimes lead to co-operation between sexes, rather than sexual conflict.

Stand back - I’m going to try science.

Thrilling, isn’t it? Our study, conducted over the course of about ten days, was quite simple. Our task was to find out whether males can utilise three different compounds to synthesise the anti-aphrodisiac. In the picture I’m posing with a gas chromatographer coupled to a mass spectrometer, used to identify volatiles emitted by male butterflies.

Oh you wanted to know the results? They could use two of the compounds we tested but not the third. That’s pretty much it.

Yeah, this is not my subject. The other two groups had more fun projects - paternity analysis in arctic foxes and phylogeography of … some other butterflies. They got to work with DNA! I was intensely jealous, but at least now it’s over. (And I got a B on the course. This corresponds to 85-95% correct marks on an exam so I’m quite happy.) Also, the next course I’m taking, which begun yesterday, is Molecular Systematics. So it’s pretty much guaranteed to be fun.

biology, science, pheromones, butterflies