Bilateral Gender Bender

Image credit here.

Gender

Typically animals are either male or female. Most species have their gender determined when they are conceived. Two gametes, sex cells, are fused together when this happens. One cell comes from the mother and one from the father. In humans the sex cells can be either X or Y.  Females are XX and males are XY. Sex is determined by the father as he can donate the Y and the mother can only give an X.

In other species gender is determined by the mother. These creatures have ZZ and ZW sex cells. The mother can give a Z or W and the father can only give a Z.

We think of gender determination in these simple terms, XX for female and XY for male. Yet nature likes to screw with our classification systems. Although uncommon, organisms of some species have been found that display characteristics of both males and females.

One side completely male. The other side completely female. Right down the middle.

Gynandromorphs

Some male and female butterflies
have very different markings.
Image credit here.

Scientists aren’t quite sure what causes this phenomenon but several hypotheses have been presented. They call these organisms gynandromorphs. Gyn refers to female, andro refers to to male, and morph refers to structure. Literally half female and half male form.

There have only been a few species found that display this strange condition. It occurs in birds, crustaceans, butterflies, and other insects. However it could exist in other animals. Butterflies and birds that display gynandromorphism are easily recognized as males and females often have different colorations. It would be difficult to tell in species where males and female look very similar.

Image credit here.

Sad Little Bird

Many cardinals with this condition have been seen. Bird researchers, Brian Peer and Robert Motz of Western Illinois University, watched one particular little she-male for months. During the whole period, it was observed that s/he did not sing or interact with other cardinals. It made no attempt to court either male or female birds and stayed by itself.

Although they are remarkably beautiful, these creatures live a life of solitude.

How it Happens

Image credit here.

Scientists aren’t exactly sure what causes gynandromorphy. However, in a study on chickens conducted by researchers lead by Dr. Michael Clinton of the University of Edinburgh,, birds displaying the anomaly were found to have normal female and male cells on the corresponding sections of their bodies.

A female and male bird seemed to have been perfectly fused down the middle. Yay chimera!

Their hypothesis? When the birds were conceived, they were fertilized by two sperm. After fertilization the cell split and used genetic material from one sperm on one side and genetic material from the other on the other side.

Other scientists believe gynandromorphy could be caused by things like two embryos fusing in the womb or genetic errors occurred in the early stages of development. 

In ZW sex determined animals, after cells divide they are assigned a certain task and continue doing that task. They are fixed, according to the Dalton State University website, whereas in humans cells can develop to fill the needs of the body. They're "flexible."

Image credit here.

When ZW organisms are conceived, as with all creatures, the cells being splitting. However, the two resulting cells from the first division determine the left and right sides of the body. Scientists believe that if one of these cells experienced a genetic mutation in their sex chromosomes it could result in gynandromorphy.

The organisms display male and female characteristics. Sometimes their genitalia is not split. Although, most of the time they have half and half of both genitalia. As the birds could tell you “life sucks with half a penis.”

A gynandromorph is different from a hermaphrodite, an organism with both male and female sex organs. In gynandromorphs the whole body displays half male and half female. These creatures are usually infertile. Hermaphrodites have both organs with are fully functional. Banana slugs are one such species.

Bilateral

Image credit here.

Creatures that are split perfectly down the middle with a male and female half are referred to as bilateral gynandromorphs. However, smaller sections of animals have been found to have similar characteristics. A whole bird may be female and have a small patch of male cells.

Can it Occur in Humans?

Only animals with the ZW gender system seem to be affected by gynandromorphy and the condition is very rare. So even if your future baby has a genetic defect it's safe from living the life of a half male, half female hybrid. At least as far as scientists know…

Thanks for reading! If you want more information, check out this or this.