On the weird (and cool) phenomenon of gynandromorphism

My friend sent me an article about a cardinal exhibiting a weird phenotype: half of its plumage was the brilliant red of a male, and half of its plumage was the dull colours of a female (source!).  He mentioned that it might be a cool birding goal and I agreed that seeing a gynandromorph of ANY sort in the wild would be awesome!

(More to the point, photographing a gynandromoprh of any sort!)

You can be sure that if I find one personally, you will be the first to know, dear reader(s).

But I did think it would make a fun post to discuss this weird and cool phenomenon.  I first learned about gynandromorphism in developmental biology in college because studying gynandromorphs can teach us a lot about the early stages of development in multicellular organisms (source!).

Gynandromorphic cardinal

Gynandromorphic cardinal Image: DW Maiden, 2 March 2009.

For example, bilaterally asymmetric gynandromorphs (like the cardinal above) are the result of an event that occurs when the developing embryo is between 8 and 64 cells old.  That’s pretty young!  Usually, this occurs because of a mistake in mitosis where the parent cell (for example an XY cell) yields an X daughter cell and an XXY daughter cell.  The cell with just the X chromosome will exhibit a typically female phenotype, while the XXY cell will exhibit a typically male phenotype.

(This is quite the opposite in birds; female birds have a ZW chromosome set, while male birds have a ZZ chromosome set.)

Now, there is a potential source of confusion here…how are gynandromorphs different from chimeras?  Are gynandromorphs a kind of chimera?

From what I have read, the fundamental difference between a gynandromorph and chimera is how they are formed (and correct me on this is your understanding is otherwise).  Chimeras are formed by the fusion of two developing embryos early in development (according to Wikipedia before the 8 cell stage), while the gynandromorph is a single embryo in which there is a relatively early (for bilateral gynandromorphs between 8 and 64 cells) mitotic error.

A gynandromorphic Rose Gypsy Moth (Lymantria mathura), courtesy of Wikipedia

A gynandromorphic Rose Gypsy Moth (Lymantria mathura), courtesy of Wikipedia

If this is true, it seems quite possible that chimerism will be phenotypically indistinguishable from gynandromorphism, but genetically, it should be obvious.  The gynandromorph will have some cells with one sex chromosome, and some cells with three, while all the cells in the chimera should have the full complement of sex chromosomes.

The moral of this story is don’t trust anyone.*

Gynandromorphic Zebra Finch, Figure 1 from Agate et al 2003

Gynandromorphic Zebra Finch, Figure 1 from Agate et al 2003

*Unless they’ve done a genetic analysis.


3 thoughts on “On the weird (and cool) phenomenon of gynandromorphism

  1. Well, I certainly learn a lot of things I never for a moment imagined from your blog . I wonder if those creatures are as confused as they look? Since behavior is often very different in males and females in the wild, makes you wonder if they exhibit both behaviors, one or the other, or neither, something unique? Determining the answer to that question would probably be hard as there would be such a small sampling available. Still, thanks for introducing me to a concept that is certainly unique in my experience !

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