Biological gender isn’t necessarily an either-or situation for Mother Nature. Some species have both female and male organs that work at the same time. Others switch from female to male or vice versa depending on their needs or the environment.
The reasons for this erratic movement are numerous: Some are natural processes that allow a species to reproduce more freely, whereas others aren’t so natural, and are frequently triggered by rising global temperatures. Here are seven critters that provide an interesting look at the many stages of gender transition.
7. Bearded Dragons
In the egg, the adorable bearded dragons do a gender reversal. Male bearded dragons frequently reverse course to become female when temperatures rise during egg incubation, according to studies. However, it is not a full change. They are genetically male, but they act and breed like females. Furthermore, non-binary lizards lay twice as many eggs as traditional females. Gender reversal in male bearded dragons is increasing, most likely as a result of rising global temperatures.
These brightly colored harem dwellers are protogynous, meaning they start out as females but can transform into males when needed. This usually occurs when the harem’s male leader takes on too many females, causing the largest female to transform into a male hawkfish and flee with half of the harem. Hawkfish can switch back and forth, unlike most other sequential hermaphrodites that make the changeover and stay with it.
The split can be seen across the entire body of some species, such as butterflies. Some Lycaeides butterflies have a rare disorder known as gynandromorphism, which causes male and female features to be placed haphazardly or bilaterally, with one side being male and the other equally female. Crustaceans, insects, birds, and, probably most notably, butterflies all have gynandromorphism. This unusual occurrence occurs in about one out of every 10,000 butterflies.
Researchers have been observing frogs changing gender spontaneously in the lab for years; now they have conducted the same investigation in the wild. Their findings show that gender transition in green frog populations, complete with fully functional reproductive organs, is very common. While previous research suggested that gender reversal in frogs was caused by pollution introduced by humans, new research from the same team reveals that the transition is a natural occurrence in amphibians.
3. Copperhead Snakes
Some female snakes, such as copperheads, are capable of virgin birth, or parthenogenesis, which means that they fertilize their own eggs without the help of a male gender partner. While not strictly a reversal, this is the ability to perform both genders’ reproductive activities at the same time – without being a hermaphrodite. A unique cell called a polar body that is created with an egg sometimes functions like sperm to “fertilize” it in facultative parthenogenesis.
2. Green Sea Turtles
Green sea turtle embryos, like bearded dragons, are temperature sensitive. More females are born when the sand where eggs are placed is warmer. Females may choose mates in milder locations so that reproduction can continue, according to the study. Sea turtle populations, which are already endangered, might suffer a dramatic drop if too many females are unable to find a partner.
Clownfish are sequential hermaphrodites, meaning they are born in one gender but can transition to the other if necessary. They are bright orange with three white bands. Clownfish live in groups of only two members, a giant male, and a female, who are both gender mature. If the breeding pair’s female dies, her male mate changes into a female and chooses the next largest male in the group to be her replacement spouse.