• Hello guest! Are you an Apistogramma enthusiast? If so we invite you to join our community and see what it has to offer. Our site is specifically designed for you and it's a great place for Apisto enthusiasts to meet online. Once you join you'll be able to post messages, upload pictures of your fish and tanks and have a great time with other Apisto enthusiasts. Sign up today!

Apistogramma mendezi sex ratio

Ruki

Member
5 Year Member
At our polish forum about Apisto we are talking about sex ratio of Apistogramma mendezi.
We are searching for the best water conditions to have 50:50 sex ratio of offsprings(having more females than males is too good, 1:1 will satisfy us :biggrin:).

In one of case:
1+1 A. mendezi F1
4,5 PH, hardness nearly 0, T=26C, water in tea colour
2 spawns, around 100 small Apistogramma, survival rate around 80%
From this all fishes around 85% were 100% males, the rest were hard to identify, probably sneaker males. No 100% female.

Second case
A. mendezi WF
4,5 PH, hardness nearly 0, T=22C
2 spawns(from two different pairs), around 100 small Apistogramma, survival rate around 80%
From this all fishes around 70% were males, 30% of females.

Anyone tries to do some research in this matter? Maybe water with pH around 5-5.5 and T around 22-24*C will be the best? But will the spawns be successful?
 

dw1305

Well-Known Member
5 Year Member
Hi all,
I think that all the scientific papers indicate that sex differentiation in Apistogramma sp. is temperature dependent, and acts on the fry before they are 30 days old.

This follows your example, cooler conditions lead to females and warmer males.
I'm a little surprised by the quoted water temperatures, they seem very low.
But I would expect the temperature that produced 1:1 sex ratio to be nearer the 26 - 28oC range.

cheers Darrel
 

Ruki

Member
5 Year Member
But I would expect the temperature that produced 1:1 sex ratio to be nearer the 26 - 28oC range.

cheers Darrel
Hi Darrel,
but in first case T was 26*C and friend hasn't got any female.
In second, probably thanks to so much cold water second friend got 30 percent of females.
So, mathematicaly, water should have around 18*C to have 1:1 sex ratio, but it's imposibble to have Apistogramma in so much cold water for long time.
I think, that probably pH should be lower, maybe around 3.5-4.0? And then, what temperature?
 

dw1305

Well-Known Member
5 Year Member
Hi all,
I think, that probably pH should be lower, maybe around 3.5-4.0? And then, what temperature?
Hi Lukasz, that is the question. There isn't much in the scientific literature, best reference is probably - "Temperature-Dependent Sex Determination in Fish Revisited: Prevalence, a Single Sex Ratio Response Pattern, and Possible Effects of Climate Change". I can access this, but I'm not sure whether it is public access, or we have access at the university (I am at work). <http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0002837>.

"TSD has been claimed in 59 different species (33 of them of the genus Apistogramma, F. Cichlidae, and all included in the same study) ...... Fish with TSD have readily been grouped according to three patterns of sex ratio response to environmental temperature

1, more males at high temperature;
2, more males at low temperature; and
3 more males at extreme (high and low) temperatures.

However, a critical examination of sex ratio produced in response to temperature in fish has never been carried out.... The 33 species of the genus Apistogramma follow pattern 1...
. "

The tabulated data doesn't include A. mendezi, or give a pH, but it does give percentage male at different temperatures for a range of species.
The reference is "Römer U, Beisenherz W (1996) Environmental determination of sex in Apistogramma (Cichlidae) and two other freshwater fishes (Teleostei). J Fish Biol 48: 714-725."

So if Uwe is about? he might be able to tell us more?

For A. agassizi 23oC = 60% m(ale) 26oC = 60%m 290C = 81% m.
and most of the other 32 species listed have similar temperature ranges.

cheers Darrel
 

Mike Wise

Moderator
Staff member
5 Year Member
pH also has some effect on sex ratios. It really depends on the species. For A. mendezi, I would try pH 5-5,5 @ 24ºC. You should get a higher ratio of females. A. mendezi isn't an extreme blackwater species.
 

Ruki

Member
5 Year Member
@Darell
Thanks for interesting link. Today was exhausting day so I don't have any strength to read something so difficult. :eek: I only looked on it but tomorrow I'll read it.

@Mike
You said something interesting. In first case, friend was talking about no spawns when pH was above 5.5(eggs didn't hatch, fry died if pH rose). :confused:
 

dw1305

Well-Known Member
5 Year Member
Hi all,
Lukasz, do you know if your friend has access to a TDS or conductivity meter?
It maybe that the water has a high TDS (salts content) even though the pH is low.

cheers Darrel
 

blueblue

Active Member
5 Year Member
i bred quite a lot of mendezi, with
temperature ranging from 20C to 30+C...
however, i never face the issue of having 80% male!
In all temperature ranges, male's ratio is never over 50%...
of course, both my case and your case are not under scientifically
controlled environment and temperature could vary. Plus, the survival rate
plays a trick. Since female is usually smaller and might be weaker
during the fry stage... would it be the case that the female of your
case simply fail to compete and grow large?

According to the literature, low temperature should increase
the ratio of female...
 

Mike Wise

Moderator
Staff member
5 Year Member
@Mike
You said something interesting. In first case, friend was talking about no spawns when pH was above 5.5(eggs didn't hatch, fry died if pH rose). :confused:
Yes, that is the reason for a pH below 5,5, but above 5,0. Breed them like A. bitaeniata. Many breeders think that bacteria & fungi are less likely to infect the eggs at this pH range, yet the pH is not so low that it affects the sex ratio. If you can keep the aquarium perfectly sterile, it might be possible to hatch eggs at a higher pH. Many extreme blackwater species have been bred in this manner. If, however, you raise the pH too high, then there is a possibility that you will get 80% females!:tongue:
 

Ruki

Member
5 Year Member
Thanks for replies!
I knew that I can rely on you. :biggrin:

If only my pair will breed I'll tell you. :rolleyes:
 

ButtNekkid

Active Member
Sorry to resurrect an old thread but i was just wondering about A. Baenschi.
For some reason all of the fry are female. This has oocured on all spawns in my main tank. Temperature about 26C

I don´t have a PH reading but conductivity is a somewhat steady 100µS. Any ideas?

There are just 2 males. Original wild one and a male that was born in the quarantine phase.
 

Mike Wise

Moderator
Staff member
5 Year Member
Are you are positive that all of the females are females, and some not sneaker males? You can test this by removing the positive males and see if more males develop among the females. If this doesn't work, then raise the temperature slightly. Also note that pH is a factor in sex determination, but not as important as temperature. Lower pH values tend to increase the number of male offspring in a minor way.
 
Top