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Whats the sexual organ tatia use? Can the name be used for guppies, and all other live bearers as well?

The term "gonopodium" (frequently applied to livebearers) has also been used for auchenipterids.

Thanks that was bugging me. I didn't realize all auchenipterids were internal breeders as well. Or would that include specific genus?

As the gonopodium Poecilia males have, is not homologous with the organ Auchenipterids have, the name gonopodium should not be used.

Goodeia fishes (a family closely related to Poecilia) have a different strategy of internal fertilisation, using another organ. Nobody uses gomnopodium for this organ.

Perhaps the Auchenipterid organ is nameless, but one should not raise confusion by stating untrue things - a relation between both families

Bas Pels wrote:Perhaps the Auchenipterid organ is nameless, but one should not raise confusion by stating untrue things - a relation between both families

I fail to see where that relation was made.
The genital pore of Auchenipterids is indeed nameless afaik - at least I couldn't find a term in many books - but I see no harm in using the term gonopodium, for that's what it is: an organ for internal fertilization.

If a part of an animal has a name, say a leg, and a part of another animal is called a leg too, that implies a homology between both parts.

This homology means their common ancestor had this part already.

Poecilids developed their gonopodium after their ancestor split from the catfishes, and thus no catfish has a gonopodium (or a penis for instance)

Bedides, trhe Poecilid goniopodium consists of highly developed fin spines. They do no longer have any function related to swimming, and can mouve in any direction - willfully

Most organs for internal fertilisation are not made from fins. However, I can not say anything in relation to Auchenipterids

So what you're saying is that while we may be using the word gonopodium to describe the external sexual organ it is infact only correct for guppy, while the catfish that internally fertalize have developed an external fertalizing organ it would not be considered to be the same name. I don't think that warrants an immediate withdrawel of the name in the describing the sexual organ. Or at least until someone gives it another name.

I did find some information on wikipedia on the subject of sexual organs...


"In many species of fish, fins have been modified to allow internal fertilization.
A gonopodium is a modified anal fin in males of certain species of live-bearing fish in the families Anablepidae and Poeciliidae. It is movable and used to impregnate females during mating. The male`s anal fin?s 3rd, 4th and 5th rays are formed into a tube like structure in which the sperm of the fish is ejected. In some species, the gonopodium may be as much as 50% of the total body length. Occasionally the fin is too long to be used, as in the "lyretail" breeds of Xiphophorus helleri. Hormone treated females may develop gonopodia. These are useless for breeding. One finds similar organs having the same characteristics in other types of fish, for example the andropodium in the Hemirhamphodon or in the Goodeidae."

I am with Bas Pels on this.
Gonopodium is best left as a term reserved for the Poeciladae.

However, until a specifc terminology is developed and adopted it doesn't do any harm to use the term in quotation marks or other device to indicate that the terminology may not be specifically correct or known.

Got to call the organ something perhaps just the "organ", since most people would still get the idea trying to be conveyed.