What are Sequential Hermaphrodites?

Mary McMahon
Mary McMahon

Sequential hermaphrodites are organisms which are born with the sex organs of one gender and the capability of changing sexes later in life. Sometimes, sequential hermaphrodites change sex at a predestined time, as part of their development. In other cases, the sex change is an elective process, undertaken in response to environmental or biological triggers.

The clownfish is a sequential hermaphrodite.
The clownfish is a sequential hermaphrodite.

Before delving into the world of sequential hermaphrodites, it may help to know that a hermaphrodite is any organism which has sexual characteristics associated with both genders. This term is primarily used in the scientific community; using “hermaphrodite” in reference to a human with ambiguous sex organs is considered offensive. In addition to sequential hermaphrodites, it is also possible to see simultaneous hermaphrodites, which have active sex organs from both genders at the same time. Humans and many other mammals do not develop hermaphroditic tendencies under normal circumstances.

There are two types of sequential hermaphrodites. Animals which are born male with the ability to become female are said to be exhibiting the trait of protandry. Protogyny, on the other hand, is a trait in which animals are born as females, with the ability to become males later in life. Depending on the species, simultaneous hermaphrodites may change sex only once, or they may be able to flip back and forth between genders several times.

Many simultaneous hermaphrodites are fish, such as the clownfish. Some form harems, in which a single male supervises a school of females. If the male is killed, the dominant female in the harem transitions and takes his place. In such harems, the male is usually responsible for defending the school from invaders and protecting his territory to ensure that his flock does not wander astray or encounter potential dangers.

There are some evolutionary advantages to being a sequential hermaphrodite, or this trait wouldn't exist. The ability to change gender in response to biological or environmental pressures makes sequential hermaphrodites much more flexible, and able to deal with situations in which their populations are depleted. This trait ensures the preservation of the species by promoting biodiversity, as animals can exchange genetic material with each other in a variety of ways. Sequential hermaphrodites are also very interesting for biologists to observe, with numerous studies on their evolution and lifestyle being conducted at various points around the world.

Mary McMahon
Mary McMahon

Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a wiseGEEK researcher and writer. Mary has a liberal arts degree from Goddard College and spends her free time reading, cooking, and exploring the great outdoors.

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Discussion Comments


@Iluviaporos - I can't help but wonder what human life would have been like if we had some kind of sequential hermaphrodite abilities. Would women have been repressed as much as they were in history if it was possible for any woman to be a man and vice versa?

I've read science fiction stories where people can just take a pill and become another gender overnight. It seems like most sequential hermaphrodites in nature do this in response to certain conditions, so it will be interesting to see what happens when one species can do it at a whim.


@bythewell - I'm positive that the gene sequence doesn't change like that. The organisms in question just have the ability to change their external and reproductive characteristics.

And it might not have been a gradual evolution. Hermaphroditic sports are common throughout the animal kingdom, so I don't think it's actually that much of a switch to flip in terms of genetic structure, even if it seems like a big deal to us by the time we've gone through puberty.

In fact I think it's supposed to be something like 1 in 10 or even more people are biologically intersex and I'm not sure that's including the people who identify as a sex other than the one they presented as at birth.

Humans tend to think of gender as being set in stone and completely binary but it's actually not like that anywhere.


I can definitely see how this trait would have evolutionary advantages, but I'm not sure how it would have evolved in the first place. It seems like one of those traits that either exists or doesn't and it doesn't have any advantages if it only exists in partial form. I'm also curious as to whether or not the actual gene sequences of the creature change, so that, for example, it goes from XX to XY when it goes from female to male.

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