It’s Twins! Two Embryos in One Anolis sagrei Egg

For the last several months, I’ve been collecting eggs from 36 female Anolis sagrei from Gainesville, FL. This is for a project on linking the movement patterns and mating patterns of brown anoles. To be able to assess which males have mated with each of these females, I’ll be sequencing the DNA from the mothers, their offspring, and potential fathers, and then trying to figure out which males have fathered each female’s offspring. All this is to say that what I want from the eggs I’ve been collecting is the offspring’s DNA. To this end, I’ve been dissecting out embryos from eggs about ten days after laying, and storing the tissue for future genetic work.

So far, the females have laid over 300 eggs, and dissecting embryos out of them has gotten a little monotonous. So I didn’t pay any special attention to an egg that looked perhaps a bit bigger than normal. I was shocked, though, when two seemingly healthy embryos popped out of it!

Two embryos from a single brown anole egg

Two embryos from a single brown anole egg

My initial excitement waned when I realised that twins are not that rare in humans, but returned when two anole breeding experts (AA correspondents Thom Sanger and Anthony Geneva) said that they haven’t seen anything quite like this before. In Thom’s words, “I’ve only found two [twins] in over a decade of dissecting eggs, both were conjoined and inviable. I think you have something special.”

Have any of you seen anything like this before?


6 thoughts on “It’s Twins! Two Embryos in One Anolis sagrei Egg

  1. It WAS twins!!!
    I know you’re a scientist, but after spending a summer photographing baby anoles as they appeared in my yard, and being able to watch what wondrous little creatures they are, the fact of you destroying 300 eggs and becoming blase’ about it, seems… very brutal. It just makes me sad that “science” is still so inhumane.

  2. Over the past six years or so we have come across a handful of conjoined twins. As I recall one set only had a small bridge of connecting tissue. I’ve never seen two well formed and separate embryos within one egg.

  3. Anolis sagrei is an invasive introduced exotic species in FL. Using them up for research is just fine with me, and I have dedicated my long career to conservation. Just don’t do it yourselves: too many people….

  4. This is great news to see! I am a PhD student in Dr. Daniel Warner’s Lab at Auburn University (previously at University of Alabama at Birmingham). I just finished my masters on the adaptive significance of phenotypic plasticity in the Brown Anole lizard with respect to incubation moisture (more about my project can be found in an earlier post). As a part of my project, I was incubating A. sagrei eggs in very wet and very dry conditions and measuring the change in mass of the eggs over time. I had one egg that was initially comparable in size to any of the other ~2000 eggs incubated, but about half way through incubation the egg was nearly twice the size (in mass) of the others at the same stage. At the end of the incubation, I found two hatchlings had hatched from this egg! We incubated the eggs in individual jars with plastic wrap held over the top with a rubber band, thus the two hatchlings that were found in the jar had to have come from a single egg. As part of the project, these hatchlings were released onto my experimental islands in Florida, but I do have tissue samples from each of them. I was incubating eggs in -30 kPa soil which is much wetter than the common incubation moisture and our lab thinks this extra water available for incubation may have allowed these twins to fully develop. This work is about to be published, but we found significant differences in phenotype as a product of incubation moisture. Additionally, to add to your research of the prevalence of this, our lab has incubated many eggs over the years and never has seen another set of twins! Awesome find! Would be interested in being apart of exploring the prevalence of twins in A. sagrei and everyone’s thoughts on the subject.

    1. Fascinating! The moisture may well explain it. I haven’t been keeping strict tabs on how moist the incubation substrate is, but after a few earlier eggs started drying out, I’ve been keeping the vermiculite quite wet.

  5. We have incubated ~600-700 Sceloporus eggs over the last two years and have not seen this. Will certainly report any occurrence though… Very cool stuff!

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