What's agamous?

[Viktor Jarikov]

For instance the tilapia are agamous, I read. Then I look up the definition.

FishBase: "(English) Not involving the fusion of male and female gametes in reproduction."

Then a few more definitions... Gamete is a mature haploid (having half) male or female germ cell (sperm or egg) which is able to unite with another of the opposite sex in sexual reproduction to form a zygote (diploid cell having full set of chromosomes).

Then I read for tilapia: (FishBase too) "...eggs are deposited in single clutches and are taken into the females mouth as soon as they are fertilized"...

And I understand that I don't understand.

Can anyone explain please?

[Shane]

Wow great question! If I understand correctly, it means the eggs may be fertilized by more than one male.
-Shane

[bekateen]

Hi Viktor,

I'm not familiar with that term, but I believe it refers to a form of artificial parthenogenesis. In other words, the eggs are activated to develop without needing to be fertilized by sperm first. As you can imagine, the developing eggs might be lacking the normal complement of chromosomes observed in fertilized eggs of normally reproducing fishes, so the offspring would be different from those of a sexually producing line of the "same" species.

I'm not aware of any parthenogenic Tilapia, but I've heard of fish farming methods which induce development in unfertilized eggs, so maybe it's an artificial technique.

Cheers, Eric

[Silurus]

Agamy means that males and females do not form lasting bonds, i.e. they do not mate for life.

[bekateen]

Agamy means that males and females do not form lasting bonds, i.e. they do not mate for life.

Interesting. It must have a very different usage in plants.

Thanks HH.
Eric

[Viktor Jarikov]

Thank you all.

I understand the monogamy, polygamy, and agamy angle. However, FishBase seems to keep talking about the cellular reproductive biology, not "fish morals" if I may

I tend to think Silurus is right but then the FishBase use of the word is confusing at least...

Agamous seems the same as agamic:
https://www.collinsdictionary.com/us/di ... sh/agamous
simply points to
https://www.collinsdictionary.com/us/di ... ish/agamic
agamic
in American English
(əˈgæmɪk )
ADJECTIVE Biology
1. asexual; having no sexual union
2. able to develop without fertilization by the male; parthenogenetic

...

FishBase: https://www.fishbase.in/glossary/Glossary.php?q=agamous
As I quoted before:
Definition of Term
agamous
(English) Not involving the fusion of male and female gametes in reproduction. (See also: agamic)

...

Here comes agamic by FishBase: https://www.fishbase.in/Glossary/Glossa ... amic&sc=is
Definition of Term
agamic
(English) Without gametes. Used by complex organisms in which all individuals reproduce asexually. (See also: agamete, agamogony, agamont)

...

agamete by FishBase: https://www.fishbase.in/Glossary/Glossa ... mete&sc=is
agamete
(English) A mature reproductive cell which does not fuse with another to form a zygote. (See also: agamic, agamogony, agamont)

...

https://www.fishbase.in/Glossary/Glossa ... gony&sc=is
Definition of Term
agamogony
(English) Asexual reproduction by development of a new individual from a single cell, following binary or multiple fission, or budding. (See also: agamete, agamic)

...

agamont by FishBase: https://www.fishbase.in/Glossary/Glossa ... mont&sc=is
Definition of Term
agamont
(English) The asexual individual or generation producing agametes. (See also: agamete, agamic, agamogony)

[Viktor Jarikov]

An example of where it is coming from: section Biology, third line from the bottom
https://www.fishbase.se/summary/Oreochromis-aureus.html

[Jools]

New one on me too, always something to learn, great start to 2021!

Jools

[Bas Pels]

If I read `Ovophilic, agamous` I would assume both words to refer to reproductive behaviour.

Now it does complicate that agamous also has a meaning in cell biology, but here it must refer to pair bonding, as Siluris wrote.

Apart from that, fish base writes about normal situations in nature. And any aseksual reproduction this fish may be capable of, is not natural, only possible in a laboratory. So this explanation cannot be the right one.

Still, I did not know this word, as most of us didn´t

[Viktor Jarikov]

Thank you much all.

Yeah, I am pretty sure Silurus's right. Not only he almost always is (for which we love him) but it makes more sense too in this case as asexual reproduction has nothing to do with tilapia in nature anyway.

ENGLISH LESSON: Agamous = unfaithful in reproductive sense.

[Jools]

Now onto how you pronounce it. I'm guessing agamous like atypical?

Jools

[Bas Pels]

I would expect so, as the a in agamous will have the same meaning as the a in atypical. That is, anti. Or just `not´.

Woud you pronounce the mous part similar to mouse . the rodent?

[Viktor Jarikov]

Collins dictionary I linked above says: (ˈægəməs ) stresses the first sound.

No "mouse" but more like "mess" haha...

Now mind you this is all about the asexual reproduction.

It is not a given, I imagine, that it is pronounced the same when used in the "no long term pairing" meaning.

[Bas Pels]

The correct English pronouncation is not always predictable from the spelling, but I never heard the same spelling has different pronouncations depending on the meaning. You put me in uncharted waters, Victor.

[TwoTankAmin]

Good old Google to the rescue.

Go here and click on the little speaker icon next to the word https://www.thefreedictionary.com/agamous

Or maybe when a person scared by rodents sees a tiny one of them run across the floor, they jump onto something while screaming "Agamous!"

[Narelle]

I'm late to the discussion, but I wouldn't be so quick to assume that asexual reproduction couldn't be happening in nature. I recall from my ichthyology course a couple years ago that wild Amazon mollies reproduce asexually - the females mate with males from other livebearer species whose sperm pierce the egg and initiate development, but don't contribute any genes. The same process that Bekateen described above.

Perhaps this has been found to occur in tilapia? I'm not very familiar with them, but now I'm curious to look into it more.

Edit: Because this is such a major aquaculture species, results so far are turning up lots of artificial gynogenesis. If it does ever occur in nature, those results are being buried in the searches I'm using. I'm not sure if I'm curious enough to dig through this many aquaculture studies just in case actual evidence of natural gynogenesis is here somewhere. I suspect it doesn't occur in nature, but I'll see if I can find my notes from the class and perhaps will try to get a hold of my ichthyology professor, who studies African cichlids and may know more.

[Bas Pels]

Where many cichlids are rather insensitive towards crossbreeding, this species Oreochromis mossambicus produces with the related O niloticus infertile offspring.

Now this is a huge advantage, fertile Oreochromis start breeding at 6 cm or smaller, and infertile ones just grow, untill cought and eaten. Furter, anyone excaping cannot produce a disaster.

But I would not expect such a species to reproduce virginal. The amazon molly does (it is named not afer the river, but after the mythological Amazon people) but I would assume it took some adaptation.