A gynandromorph is an organism that contains both male and female characteristics. The term gynandromorph, from Greek "gyne" female and "andro" male, is mainly used in the field of entomology - the scientific study of insects.
These characteristics can be seen in the butterfly below where both male and female characteristics can be seen physically because of the sexual dimorphism butterflies display. Cases of gynandromorphism have also been reported in crustaceans, especially lobsters, sometimes crabs and even in birds. A clear example in birds is the gynandromorphic zebra finch. These birds have lateralised brain structures in the face of a common steroid signal, providing strong evidence for for a non-hormonal primary sex mechanism regulating brain differentiation.
A gynandromorph can have bilateral asymmetry, one side female and one side male (as seen below) or they can be mosiac, a case in which the two sexes are not so clearly defined.
Bilateral asymmetry arises very early in development, typically when the organism has between 8 and 64 cells, later the gynandromorph is mosiac.
The cause of this mutation is typically, but not always, an event in mitosis during early development. While the organism is only a few cells large, one of the dividing cells does not split its sex chromosomes typically. This leads to one of the two cells having sex chromosomes that cause male development and the other cell having chromosomes that cause female development.
For example, an XY cell undergoing mitosis duplicates its chromosomes, becoming XXYY. Usually this cell would divide into two XY cells, but in rare occasions the cell may divide into an X cell and an XYY cell. If this happens early in development, then a large portion of the cells are X and a large portion are XYY, Since X and XYY dictate different sexes, the organism has tissue that is male and tissue that is female.
In his autobiography, Speak, Memory, the writer and lepidopterist Vladimir Nabokov describes a gynandromorph butterfly, male on one side, female on the other that he caught in his youth on his family's Russian estate.
Gynandromporphic butterflies such as this are unfortunately non-viable - note the kink in the abdomen (half male, half female) of this specimen.
In my 8 years as a professional entomologist at Stratford Upon Avon Butterfly Farm I have still not been fortunate enough to witness a gynandromorphic specimen in the flesh this perhaps testifies to the extreme rarity of this bizarre mutation. About a month ago we sent about 500 south American pupae to the Vannes Butterfly Farm in France and a few days ago we received these photographs from them of a superb gyandromorphic Queen Swallowtail Papilio androgeus.
How I wish this individual had emerged with us as we've had only four gyandromorphic specimens successfully develop in the last thirty years as they are an extremely rare, nonviable mutation.
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