… but not on the wall.
This image hurts my brain. A lot.
I suspect that other folks who study Bembidion have sore brains as they look at this, too. Why?
The reason that image is just so confusing can be seen by putting that specimen side by side with another specimen of the same species from the same locality:
And here is a view of their undersides:
Specimen DNA3307 has perfect, mirror-image genitalia!
That is a specimen that had undergone DNA extraction before the bizarre genitalia were observed. My grad student John had extracted DNA from the abdomen, and I then pulled the male genitalia out to prepare a permanent mount. I pulled it out from the ring sclerite, not noticing anything was amiss. Then… then I just got confused. Something felt dreadfully wrong, but I couldn’t figure out what it was. I have been doing this for over 30 years and I suddenly felt lost. It was as if I woke up in the morning, and found the bathroom in my house on the wrong side of the hallway, and all its contents reversed. I felt as if I had amnesia, and couldn’t continue the dissection. Then, slowly, I realized that what was wrong. Even though I know now that this beetle simply has mirror-image genitalia, it still disturbs me.
Alas, because the abdomen had undergone DNA extraction, we can’t see how the accessory glands were shaped (they are not bilaterally symmetrical), to see if they were mirrored as well. And, because I didn’t notice what was wrong until after I pulled the genitalia out of the abdomen, we can’t tell how the genitalia were oriented in the abdomen. (I will check the mandibles, which are typically asymmetrical, to see if they might be reversed.) The good news is that we have DNA of the beetle, and perhaps someday a genomic study might reveal something interesting there.
In the meantime, the very fact that the genitalia could develop so perfectly in this mirrored fashion surely tells us something important about beetle development. Alas, I do not know it might be, as that is not my field. Any developmental biologists out there?
I am reminded of the ground-beetle tribe Licinini, some of whose members (e.g., Badister) have snail-cracking, asymmetrical mandibles. Here’s the head of a Badister, showing the modified right mandible, with a notch and a bump.
Asymmetrical mandible are standard in carabids, but normally not as dramatically as in Badister. But simple asymmetry is not why I mention Badister. More importantly, some species of Badister having mirror-image mandibles relative to other species.
While the consequences of having reversed mandibles might not be so drastic (in fact, perhaps they are beneficial in a world with dextral and sinistral snails), the consequences of having mirrored genitalia likely are. Perhaps, though, females can be mirrored, too. One wonders if there was a mirror-image female along the Chatanika River in Alaska in 2008 that lost, because of my swift aspirator, her only compatible mate.
[Oh, by the way, the reason that this species is called “Bembidion kuprianovi #3″ in the first figure caption is that B. kuprianovi, as understood in the literature, is clearly at least two species, and likely three. This is the third of those species.]