Welcome to my project page!
What am I studying? I am studying evolutionary biology and I became interested in banana slugs because I feel that they are good organisms to study sexual conflict between hermaphroditic mating partners.
My banana slugs are just so damn cute! Below I have a mating video and pictures of slug penises. All part of my PhD thesis...
What is sexual conflict? The big picture is that there is often a conflict of interests between mating partners because each individual will differ in how it can maximize it's fitness (ie. how many babies it can make in its lifetime). For example, after a male and female mate, the female may want to mate again because she may benefit from gaining sperm from other males. But, from the point of view of the male that she just mated with, her remating is a very bad thing because that means that she will not fertilize all her eggs with his sperm, but with another male's sperm as well. This is an example of a conflict of interests where the female wants to remate, but the male does not want her to.
This is a mating pair. Because their genital opening in near their head, they line up in the yin-yang position and stay like this for hours.
What happens when there is sexual conflict? Males and females are constantly in an evolutionary arms race where males try to manipulate females into doing what they want them to do (for example, NOT mate with a new male) and females are constantly trying to prevent males from manipulating them. For example, some males form sperm plugs where their semen coagulates into a plug that prevents other male sperm from getting into the female reproductive tract. But, some tricky females will remove this plug and mate again! Partner manipulation tactics, like forming a sperm plug to prevent a female from remating, frequently evolve when there is sexual conflict.
Here are two slugs that are engaging in the premating behavior. They bite and swing their heads and bite and bite and bite... these cute guys get pretty nasty during mating
So why study banana slugs? Well, most of the work that has looked at sexual conflict and partner manipulation has been on animals that have separate sexes. So, they look at conflict between males and females. Simultaneous hermaphrodites, those animals that are both male and female at the same time, are drastically under-represented in this field. But, sexual conflict should exist between hermaphrodites just as it does between separate sexed animals. So why banana slugs? Well, they are hermaphrodites and have a very interesting behavior that I believe is the result of sexual conflict.
Here is a close-up of the biting. The slug on the left is biting the genital opening of the slug on the right.
So what is so interesting about banana slugs!? Well, these slugs are hermaphrodites, which means that they can act as both males and females at the same time. When they mate, they insert their penises into eachother at the same time. The unusual thing (in case you don't find that unusual enough!) is that sometimes, but not always, when they finish mating one slug will chew the penis completely off the other, a process called Apophallation. Sometimes it happens that both slugs engage in chewing so that at the end of the mating encounter, both slugs are penis-less.
This is a slug penis. This particular slug was injected with the peptide hormone APGWamide. This hormone causes erections within minutes. I am using this for several aspects of my research
Does it grow back? Probably the most common question that I get. NO. Past work has suggested that it does not regenerate, at least not within a year. The penis is a very bizarre structure that is very complex. It would be difficult to regenerate it.
Ok, what you have all been waiting for... Click on the tripple x's to download a quicktime video of apophallation. It is a time lapse video that is a little difficult to see the first time around. The slug on the lower left chews the penis off the other one. If you watch it slowly, you can see the penis snap to the owner. ouch!
Quicktime movie: 9.2MB
Strange business and such: After what should have been a fairly normal mating encounter, one slug crawled away and left this slug with its penis erect. It was unable to retract its penis back into its body. After many hours, this slug started to gnaw on its own penis! After a while, it succeeded in completely removing its penis and slurping it down. It then went on to eat and act very normal. It is bizarre and I have yet to wrap my head around what is going on... but, here is the video. It is large, so be prepared for a long download... Quicktime move: really big 79.8MB

This page was last modified on Tuesday, June 1, 2004