[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

RE: incubation times.

On 8 Aug 2001, at 18:33, Guy Wren wrote:

>  just to emphasize the point I checked some RAC Moz 99/3 and was
>  surprised to find them eyed up at six weeks. This leads me onto a
>  question. The fish 
> hatched but unfortunately were belly sliders - not the worse cases I
> have had but they did not survive. I was interested to read Marc
> Bellemans article where he proposes that eggs will only up in aerobic
> conditions, remaining in Diapause I in anaerobic conditions. Eggs that
> eye up but are not wet then begin to burn up energy resulting in belly
> sliders.

From what I have experianced, with nothos you get belly 
sliders when the eggs are wet too early. Just because 
you see eyes does not mean they are ready to hatch. I 
haev seen this with sp. Caprivi, orthonotus, kafuensis 
and rachovii. The eggs may eye up at 3 months but if you 
wet it then then 90% are belly sliders. Wait longer, say 
6 months, and you get a terrific hatch.
The belly sliders issue has more to do with under 
development than energy being burnt up. Fry in diapause 
III are virtually dead. They almost don't respire and 
their heart doesn't beat. The only things that take them 
out of this coma are light and water (read it up in 
Scheel yourself if you don't believe me).
A wet anaerobic environment stimulates transition to 
diapause 1, and the same stimulates the hatching of the 
fry. The transitions to diapause II and III are more 
mystical.

Bottom line, I feel you wet your RAC eggs too soon. 
Better luck next time. Also, try cooler temps for them.

>  If this supposition is correct it behoves us to check eggs frequently
>  (more than I have tended to do) in order to avoid sliders. 

Most of the Southern (and I would geuss Northern) notho 
species come from some what drier climates (i.e. rain 
isn't as frequent). These fish have typically long and 
often sporadic incubation periods (up to 3 yrs for some 
eggs). Those from central Africa (TAN, S. Kenya, E. 
Uganda) have typically short incubation periods of as 
little as several weeks. These latter ones have to be 
checked more frequently. Their eggs don't have a very 
long shelf life, the embryoes rapidly die off after they 
eye up. I have rarely had belly sliders from 5 month old 
korthausae peat, but while I put 100+ eggs in I only get 
20+ fry... as opposed to getting a near 100% hatch at 
2.5 to 3 months.

> One thing that
> occurs to me is that it is unlikely that any of us store eggs in
> anaerobic conditions so what would account for the long incubation
> timess for some fish that have historically been quoted.

When the peat is under water and the fish are laying 
eggs it is generally anaerobic, this triggers D1 (i.e. 
perfectly clear eggs). As the peat dries in storage, 
more O2 enters the peat and development begines. Then 
comes D2 (murky, dark eggs) or some times it progesses 
to D3 (eyed up eggs). The gap between D2 and D3 is 
multifactorial. There is evidence for temperature, 
moisture, genetics is without doubt a big component, 
light etc... Fish addapted for long droubts have long D1 
and 2 states while those coming from more moist climates 
have short D1 and D2 periods (perhaps even only a few 
days). We don't really know the triggers and mechanisms. 
When the peat is wet again, the environment again turns 
anaerobic and the resting fry are forced from their 
shells. I have tried to hatch orthonotus eggs in water 
away from peat but with no success. Add some peat and 
out they come. The microworm/CO2 method works too but I 
don't suggest it.

As a final word, I don't feel it fair to compare SAA 
incubation habits with those of Nothos. These fish, 
while dealing with the same problem the same way, have 
adapted to different triggers.

On Killinutz, Bob Morenski has an article on nothos. He 
give incubation times at various temps. IT is a very 
good article. I'm sure Tom will be able to give us the 
URL.

Bye

Tyrone Genade
Southern African Killifish Society Coastal & Offshore Coordinator
AKA 08248
tyronegenade at yahoo_com
http://www.geocities.com/tyronegenade

*************************************************************
P450 Lab, Biochemistry Department
University of Stellenbosch, 7602, South Africa
Ph: +27-021-808-5876, fax: +27-021-808-5863
**********************************************************

          In God I trust, 
     but in all others I must have irrefutable proof!
---------------
See http://www.aka.org/AKA/subkillietalk.html to unsubscribe
References: