Mirror, mirror, …

… but not on the wall.

This image hurts my brain.  A lot.

Bembidion kuprianovi #3, male genitalia, right side

Bembidion kuprianovi #3,
voucher DNA3307, Alaska.
male genitalia, right side

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:

On the left, specimen DNA3307 (right side). On the right, specimen DNA3743 (left side).

On the left, specimen DNA3307 (right side). On the right, specimen DNA3743 (left side).

And here is a view of their undersides:

Ventral view. On the left, specimen DNA3307. On the right, specimen DNA3743.

Ventral view. On the left, specimen DNA3307. On the right, specimen DNA3743.

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.

Badister

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.]

This entry was posted in Morphological Techniques, Revising Bembidiina and tagged , . Bookmark the permalink.

8 Responses to Mirror, mirror, …

  1. Cool! Wow! So in 30 years this is the only time you’ve ever seen this?

  2. Martin Donabauer says:

    I observed the same in two Trechus (Carabidae: Trechini) in NE Turkey as well. Two populations had a few male individuals with mirrored aedeagi among others with normal ones.
    I studied approx. 20.000 individuals of Trechus during the past 20 years but never detected something similar. Likely I overlooked it. In future I will have a closer look ….

  3. James Bergdahl says:

    Regarding mirrored median lobes – that is totally bizarre. It will be interesting to see if, now that you have reported the phenomena, more people will be able to provide other examples. I have not closely examined that many median lobes in my Pacific Northwest Bembidion collection; however I have extracted and pointed many hundreds of median lobes of Pterostichus (Pseudoferonina), from all of the nine described species, and have never encountered this type of extreme ‘variation’ event.

    Many of my years spent in graduate school was closely associated with marine biologists who worked on larval ecology and development. I would suspect that “mirrored mutants” are not that uncommon in animals with asymmetric structures, and there are certainly many of them. One very strange example that comes to mind (since I used to fish halibut commercially) is that eyes of flatfish go thru a migration during early development so that they are both on the same side of the mature fish. Although I have never seen it myself, every now and then individuals are found that are exceptions to the norm and the eyes are on the “‘wrong side” – the individual is therefore a “mirrored mutant”.

    For some inspiration on how perhaps such bizarreties can occur, I recommend reading: Sean B. Carroll, 2005. Endless Forms Most Beautiful: The New Science of Evo Devo and the Making of the Animal Kingdom. W.W. Norton, New York, NY.

    I would guess there is a gene, or suite of genes, that trigger the development of asymmetry in a structure in some way, and some non-lethal mutations to the switch may modulate a reversed fate of the structure from right to left handed, or visa versa.

    It will be interesting to see how closely related the DNA from those two B. kuprianovi specimen is. If one subscribes to sophisticated lock-and-key genitalia evolution in carabids, I suppose there is a very chance that mirrored median lobes could represent a rare opportunity for an isolating mechanism between populations, one that could act fairly rapidly when a successful population is founded my a wrong-handed mutant. There is the chance that it is much more common that presently recognized since so few carabidologists closely examine median lobes.

    More than 70 years ago Phil Darlington proposed that there may be polymorphism in median lobes within carabid-beetle populations, much like the flight wings of some species. Of course, polymorphism in median lobes would throw a huge wrench into taxonomy based on their morphology! The mirrored median lobes you report is a example of this, so unless these two specimens are different species, you appear to have confirmed Darlington’s suspicion (hypothesis). My next paper on Pseudoferonina briefly reviews variation in median lobe morphology among these closely related Pterostichus species and mentions the implications of Darlington’s proposal.

    Regarding B. kuprianovi – over many years of intensively sampling carabid communities along streams, especially small forested streams, I would say this “species” is one of the most widespread carabid in the Pacific Northwest. (The most common and widespread is probably Bembidion iridescens). Interestingly, over many years of searching, I was unable to document B. kuprianovi on any of the San Juan and Gulf islands, even the largest ones, although it is very easy to find along small creeks descending hillsides on the adjacent mainland. One factor is that many islands have watersheds that are too small to provide opportunities for the development of anything but the tiniest riparian zones. There is however a depauperate small-streamside carabid community on the larger islands in the Archipelago despite these limited habitat opportunities. Notice how Lindroth (1963: 269) indicates B. kuprianovi in British Columbia is: “Generally distributed on the mainland; not seen from the islands.” Similarly Bousquet (2012) does not indicate any records of the species from the the Queen Charlotte Islands, nor Vancouver Island. I have intensively sampled carabids throughout Vancouver Island, and actually have specimens from a number of widely distributed sites, but for some reason it is rarely encounter there.

    Lindroth (1963:269) indicates the species has “Wings full”. Although B. kuprianovi may usually be long-winged, is general absence from nearshore islands despite a huge mainland source population indicates the species’ dispersal power appears to be limited.

    Happy holidays,
    James Bergdahl
    Spokane, WA, USA

  4. The DNA from those two specimens of B. kuprianovi are identical in the several genes I have sequenced. I believe they are the same species.
    A number of carabidologists have reported in emails to me seeing the same phenomenon, so it does happen in other carabids. Most carabidologists who do revisionary work regularly look at median lobes, and so in the thousands upon thousands that have been examined it has popped up now and again.

  5. Pingback: Carabid beetle males and their twisted genital orientation | pterostichini

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