普通蓝蝴蝶(Polyommatus icarus)的雌雄同体。
A rare cardinal appears in Pennsylvania's backyard, much to the excitement of countless birdwatchers.
The bird's plumage is almost parted from the middle – cherry red on one side and a soft mix of yellow and brown on the other – and is an animal known as hermaphroditism.
As much as it may sound like something straight out of science fiction, hermaphroditism is very real – if not entirely common. These animals are unique because they exhibit physical traits of both males and females.
More specifically, this colorful cardinal is bilaterally hermaphroditic, meaning that one side of the body has female secondary sex characteristics while the other side has male characteristics.
While it is sometimes true that the reproductive organs match the physical characteristics of a particular sex – i.e., the ovaries appear on the female side and the testicles on the male side – this is not always the case.
You can also refer to this creature as a "sex mosaic" or a type of male-female chimera.
The word Chimera originated from Greek mythology and refers to creatures that carry two different sets of DNA. Since at least the 1800s, scientists have observed hermaphroditism in nature.
They are especially observable in insect and crustacean populations. Among vertebrates, hermaphroditic birds – known as hemilateral birds among bird lovers – receive the most attention.
But how do these hermaphrodites come to be?
Long-standing scientific theories have focused on the loss of chromosomes in mitosis or cell division phases, which is often described as the process of hermaphroditism in Drosophila.
Although for some species, such as crustaceans, an imbalance of sex-determining hormones has also been shown to affect hermaphroditism. But recent theories have challenged the idea of chromosome loss, especially in the case of hermaphroditic birds like our main friend. In birds, sex chromosomes are designated as Z and W.
In males, the sex chromosomes are 2 Z chromosomes (ZZ), and in females, the sex chromosomes are 1 Z chromosome and 1 W chromosome (ZW). Sometimes, problems during meiosis can cause fertilization of female prokaryotes or egg cells (usually combined with male pronuclei to form eggs fertilized with sperm) with both Z and W chromosomes.
A hermaphroditic bird was born.
Although it is easy to confuse hermaphrodites with bisexuals, there are differences between these two animals.
Bisexual organisms have similar genetic tissue throughout their bodies.
Hermaphroditism, on the other hand, contains genetically diverse tissues that result in some cells in hermaphroditism being female and others being male.
So, animals can be half male and half female, although their rarity makes such sightings a precious pleasure.