Sex change is not only present in humans (known as transexuality), but there are some examples of animals that change sex, that is, they are born male or female, and throughout his life, species change to the opposite sex. Do you want to know some of these species? Remember that you can also read a post in this blog about Homosexuality in animals.
TRANSEXUALITY IN ANIMALS
The animal sex change is a fact not very widespread, but is present especially among fish and some mollusks, jellyfishes, crustaceans, echinoderms and worms.
However, in the case of animals, the term used is not transsexuality. The change of sex in the animal kingdom is a particular type of hermaphroditism: sequential hermaphroditism.
This change of sex is usually genetically programmed and it is influenced by the environment in which it develops. However, at birth they have already both sexes, so that sex determination is not given by the genes.
There are different types of sequential hermaphroditism:
- Protandry: when an organisms is born male and changes to female, such as the clownfish (Amphip
- Protogyny: when an organisms is born female and changes to male, such as wrasses.
- Bidirectional sex change: when an organism has both full female and male sexual organs, but act as a male or female during different stages of its life, such as the fish Lythrypnus dalli.
It is clear that this strategy supposes an important benefit in front of other species: in front of extreme conditions, the organisms have the capacity of assuring the future generations by changing their sex.
The clownfish is one of the best known examples of sex change in the animal kingdom. Our friend Nemo, throughout its life will become a female. Clownfishes are all born males, but after a certain age they change sex. They can also change sex in case the female dies, so although Nemo’s mother died, found his mother in his father.
The form of reproduction of these very colourful and known fishes is most curious: in each anemone, cnidarian animals with which they live in symbiosis, lives a harem, consisting of one female (bigger in size than the male), a reproductive male and several non-breeding males.
Si la hembra muere, el macho reproductor se transforma en hembra y el macho no reproductor de mayor tamaño madura sexualmente.
Janthinidae is a group of sea-snails with a unique feature: they use their mucus to produce a bubble raft to float in the ocean. Some of them can produce a bubble per minute.
Well, this family of gastropods is made up of individuals who may change sex. Like the clownfish, organisms are born male and then change to female.
BLUESTREAK CLEANER WRASSE
The bluestreak cleaner wrasse (Labroides dimidiatus) is a fish in which the sex change is triggered by some behavioural patterns.
There is usually a dominant male that keeps a harem of females, but if he dies, the dominant female will assume the position of the male in a few hours, courting other females although the change of sex can be extended for two weeks.
THE COMMON SLIPPER SHELL: WHEN SIZE MATTERS
The common slipper shell (Crepidula fornicata) is a marine snail in which the sex change is produced by the size of the animal. This molluscs are born male but, at a certain size, they become females.
They are very curious snails: they live stacked on the top of other animal, with larger organisms at the bottom. This means that the individual of the base is a female and males are above. Thus, when the female dies, the larger male becomes the female of the group.
It is an exotic species in Spain, which could be living in the whole Galician coast. Anyway, its natural distribution area is North America.
THIS ALSO HAPPENS IN THE MEDITERRANEAN
Until now, we have explained species that live far from the place we life, but the truth is that this behaviour also happens in some Mediterranean species. Some examples are the starlet cushion star (Asterina gibbosa) and the ornate wrasse (Thalassoma pavo).
The ornate wrasse is one of the most colourful fishes in the Mediterranean sea. In that case, they are born females, but according to the sex ratio, they can change to males.
If you are one of those who thing that sex change in human beings is unnatural, you have read some examples of animals that change their sex.
All you need is Biology is a LGTB-friendly blog and we love everbody equally. More love and respect, and less hate!
- Acerca ciencia: Los animales que cambian de sexo
- Alvarado, A (2010). Cambio de sexo en algunas especies animales. Revista Digital Universitaria, Vol. 11, núm. 8
- Catálogo Español de Especies Exóticas Invasoras: Crepidula fornicata
- Darwin Book Cats: Fun Fish Fact: Some fish change sex
- Hickman, Roberts, Larson, l’Anson & Eisenhour (2006). Principios integrales de zoología. Mc Graw Hill (13 ed).
- Tree of life web project: An Exploration of the Clowfish
- National Geographic (2002, abril). A bordo de burbujas.
- Picture cover: Alexander Vasenin, Creative Commons