Abstract

A gynandromorph is an organism that contains both male and female characteristics. The term "gynandromorph", from Greek "gyne" female, "andro" male, and "morphé" form, is mainly used in entomology. These organisms are notable in butterflies and other insects, where both male and female body parts can be distinguished physically because of sexual dimorphism.

Occurrence in other genera

Gynandromorphism has been observed in numerous animal species, e.g., crustaceans such as lobsters and crabs, many bird species. A clear example in birds involves gynandromorphic zebra finch. These birds have lateralised brain structures in the face of a common steroid signal, providing strong evidence for a non-hormonal primary sex mechanism regulating brain differentiation.

Pattern of distribution of male and female tissues in a single organism

A gynandromorph can have bilateral asymmetry—one side female and one side male. Alternatively, the distribution of male and female tissue can be more haphazard.

Bilateral gynandromorphy arises very early in development, typically when the organism has between 8 and 64 cells. Later stages produce a more random pattern.

Causes of gynandromorphism

The cause of this phenomenon is typically, but not always, an event in mitosis during early development. While the organism contains only a few cells, 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 female and tissue that is male.

A developmental network theory of how gynandromorphs develop from a single cell based on internetwork links between parental allelic chromosomes is given in. The major types of gynandromorphs, bilateral, polar and oblique are computationally modeled. Many other possible gynandromorph combinations are computationally modeled, including predicted morphologies yet to be discovered. The article relates gynandromorph developmental control networks to how species may form. The models are based on a computational model of bilateral symmetry.

Gynandromorphs as a research tool

Gynandromorphs occasionally afford a powerful tool in genetic, developmental, and behavioral analyses. In Drosophila melanogaster, for instance, they provided evidence that male courtship behavior originates in the brain, that males can distinguish conspecific females from males by the scent of the posterior, dorsal, integument of females, that the germ cells originate in the posterior-most region of the blastoderm, and that somatic components of the gonads originate in the mesodermal region of the fourth and fifth abdominal segment.

In popular culture

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 as a youth on his family's Russian estate.