re-wetting peat - how many times and for how long

[erikthur]

When I was into killies in the 80-ies I always gave up after 3 attempts.
Now I am not so sure how to go about it...
I will ask for advice in 3 cases all bought by Aquabid.
In all cases I saw eyed-up eggs before the first wetting.

Nothobranchius melanospilus Tan 98/2. 50+ eggs collected in April. 1st hatching in Aug gave 6 fry (now 3 females). 2nd hatching in Sept gave nothing like the 3rd hatching (this week). I do not see any eggs. I am prepared to give this one up.

Nothobranchius rachovii Beira 98. 50+ eggs collected in April. 1st hatching in Sept gave 4 fry (now 2 females). 2nd hatching (this week) gave nothing after 36 hours. I do see some eyed-up eggs in this peat. This one I should not give up. But how long should I wait until I dry up the peat again.

Austrolebias nigripinnis Villa Soriano F2. 35 eggs collected in May. 1st hatching in Aug gave 1 fry that died. 2nd hatching in Sept gave 2 fry with similar outcome. No fry so far after 36 hours from the 3rd hatching (this week). I do see some eyed-up eggs in this peat too. But I wonder if it is worthwhile to continue re-wetting this peat in the future considering the poor results so far.

So I ask for your advice (or some nice sunshine stories) in these cases.
Is it worthwhile to continue and in that case for how many times.
And for how long shall I let each hatching attempt continue?

[TyroneGenade]

Hi

Personally I don't bother rewetting Notho eggs. I find most don't do provide a second hatch. The only case where I have had good second hatches (and third) is with N. luekei. For most the eggs are simply lost in the damp peat. I think water speeds up their development and then they simply die in the peat. I have had packets with 100s of eggs only yeild a few fry on the 1st hatch and 0 on the next with no eggs visible. This is especially the case with N. eggersi.

My opinion is that one wets a small portion of peat or a defined number of eggs. If you get a high enough ratio of good fry then wet it all. If by force hatching the test eggs (with high O2, peat tea, fresh peat and pressuer) then try it rather than redry the peat.

With SAAs, the odds are the 2nd wettign will give you 3x as much fry as the 1st wetting and the 3rd wetting probably the 2x as much as the 1st. They also last a long time compared to Nothos (except Aphyobranchius that seem tolast at least 6 months and then still have uneyed-up eggs).

tt4n

[killiesmania]

Thank you very much for the info... I will use this info for ordering of eggs....

[stormhawk]

A drier peat previously treated with baking soda to neutralise the acidity of the peat would help in egg storage. Many eggs just simply die off in the peat for no apparent reason.

With Austrolebias the key is cool incubation temperatures. Rough incubation guides as given on the DKG-Cynolebias group website also shows the requirement for incubating Austrolebias at lower temperatures. When wetting it is best to use cool water with oxygen tablets to increase the viability of the hatching fry and also to ensure that the fry do not end up as belly sliders. SAA fry seem to like hatching in cooler temperatures. I found this to be true with several species.

On occasions some eggs seem to be fully developed with the shiny iris but the fry that hatch out are invariably deformed with problems like a curled spine and inability to swim properly. It could have been factors like the shipping temperature that may have "shocked" the embryo into stopping development or that they are past their wetting "period" which may result in the developing embryos consuming their internal organs just to survive in the egg until they are wetted.

I have a bag of eggersi "Rufiji River Camp" TAN 95/7 that are ready to hatch. Will try the standard coolwater+oxygen tablet method that I have used to good effect with my SAAs. Should loads of fry pop out of the peat I will update here accordingly. :wink:

Erik, wet the peat if you have to. A risk is always there so be a little gung-ho and do what you think is necessary.

[nonamethefish]

Aren't the eggs programed to be rewetted done by genes? So discarding them would end up losing this trait to the hobby?

[TyroneGenade]

Yes and no. Genes dictate our limitations and ultimate abilites not how we employ them (see Steven Rose's Lifelines for the full argument). Likewise, the annual fish genes allow for them to enter diapause but this diapause is regulated by the environment. The duration of the diapause is totally upto the environmental conditions. If one takes N. furzeri Gona Re Zhou as example. All the fish currently in the hobby came from a single pair raised by Walter Foersch back in 1973. These fish are very inbred but still show tremendous variation in incubation time. You can have some eggs eye up in 6 weeks and others in 9 months. With the wild red furzeri we have we can have most of the eggs eye up in 3 weeks on peat!

I am sure we select for strains based on "idealized" developmental times but I do not think we loose the genes. For example, let us assume there is 1 gene that dictates diapause time. This gene has two forms (alleles): a short diapause (s) and a long diapause (S). Let us also assume that long diapause (S) is partially dominat. We spawn a wild population of fish with both ss, sS and ss fish (genes occur in duplicate in the genome incase you don't know). So we will have eggs with ss, sS and SS. The ss eggs will develop fast (e.g. 2 months), the sS eggs will be developed at 3 months and the SS eggs will develop 4 months. If you wet at 3 months you will preserve both the s and S allele. If you wet at 4 you will get mostly S alleles but still some sS eggs will hatch... maybe even ss eggs. That for inbred fish like furzeri GRZ you still get variation in development suggests that the environment of the eggs is more NB than the genes for determining developmental time.

By rewetting you only hatch the eggs that developed differently and you probably loose very few genes. Small breeding populations are the cause for most allele loss.

In the case of SAAs, the first wetting in the wild is normally a failure. The pools dry before the fry mature. Going back to our model of s and S this means that all the ss fish are lost. With the second wetting you then would get mostly sS fish and perhaps some SS. Over time one would see selection for the sS phenotype and S allele for longer development; and fewer ss eggs being laid because there are fewer ss fish to lay them. But this is not what we see with captive SAAs. You always get early hatching fry and if you rewet you get another batch and if you rewet some months later you get more fry. If you breed with those late fry you again get early hatchers.

On trick to get around this as been to prewet the SAA eggs. You take the peat, run water through it and then redry the peat. 4 weeks later you submerse the eggs and get a massive hatch as now all the eggs are ready. We can manipulate development independant of genotype. The genes are no important in determining diapause length and developmental time. They only allow fish to go into diapause to escape drought conditions. By not rewetting we do not loose these genes.

[erikthur]

By the way. Four of the rachovii eggs has now hatched but none of the nigripinnis. The melanospilus peat is no more.

From the information above I guess I should dry the nigripinnis peat once more. And just let the rachovii eggs now continue sort of undergoing water incubation from now on.

Is that wise?

[erikthur]

And about wetting Notho peat only once - a sunshine story

I bought a peat of N foerschi from Tyrone via aquabid collected in April.
1st hatch in June gave nothing.
2nd hatch in July gave 10 fry -> 2 breeding pairs and surplus males.
3rd hatch yesterday will give a minimum of 10 fresh ones.
How about that?

And the count of rachovii fry is now up to seven.
I will continue hatching that one.

[TyroneGenade]

These are the Nothos I have got fry from 2nd time around:
N. foerschi
N. luekei
N. orthonotus
N. furzeri
N. eggersi Kilimani but! There were about 200 eggs. I got 5 1st time and 7 the 2nd whereafter I saw no more eggs.

Aust. nigripinnis: 1st time a few fry, 2nd time many more!
Simp. whitei: 1st time about 15 fry, 2nd about 50!

SAAs are groomed for multiple wettings, Nothos are not it seems unless their habitats are very susceptible to erratic weather.
N. furzeri, rachovii and orthonotus come from such conditions where pools can fill in a day and be gone in a week. Unless you eggs can stand such conditions you go extinct. N. luekei, janpapi and geminus inhabit shallow tempory flood plains. While they are mainly caught in deeper pools with other Nothos this is late in the season where the plains have dried up (probably very quickly) and they are now serving as lunch for melanopsilus. There eggs are tiny and dessication resistant (small surface area for evaporation) and are able to last at least 6 months (I stopped at 6 months with luekei as I then had enough fish to go on with).

N. eggersi comes from much wetter climates with more sustained rain and longer lasting pools. They have no need for a second hatch and so don't fair so well it seems... Same with korthausae. 100s of eggs, bad first wetting, worse 2nd.

With that said, for different people there will be different results as incubation varies from condition to conditions.

I must confess that I have rarely had the need to rewet peat. I normally get all the fry I need first time round.

[stormhawk]

A sudden snap in temperature or shock can and will cause some eggs to go into diapause. When they suddenly stop developing thats when people start tearing their hair out. When they begin to fungus that also causes some major stress.