Killifish Egg Incubation

Every one uses a different technique to incubate their killifish eggs. You will have to experiment to find the way that works best for you. I will begin with annual egg incubation as it the simplest. An in depth look at non-annual egg incubation will follow.

ANNUAL EGG INCUBATION

Collection of the peat and the drying of it have been dealt with in my Notho Information Sheet and will not be discussed here. Another good source of information is Brian Watters’ Introduction to Nothobranchius which can be found on the AKA website.

Once you have collected and dried the peat the next critical step is incubation. Some people invest in various incubators but I just use a small box and store it in a warm place where the temperature doesn’t fall below 10°C. Fortunately for me that is a cupboard. A friend simply stores the eggs under his aquarium hoods in ice cream tubs with great results. Cooler temperatures don’t bother some Notho and Cynolebias species but a rapid shift from warm to cold will kill the eggs!

Most notho eggs will do well between 22 and 24°C. Some Cynolebias will require higher or lower temperatures. Certain species from Southern Africa such as orthonotus and rachovii benefit from a cooler incubation period followed by a gradual warming as in their natural habitat. As with any part of the hobby extremes in temperature must be avoided.

The major factors regulating annual egg incubation period are temperature and oxygen supply. I have read of people pumping humidified air through bags of eggs and getting rachovii eggs to hatch in a fraction of the normal time. People in Singapore (where the average temperature is 30°C) get N. rachovii hatches in only 2 months and eggersi in 4 weeks.  It is important to monitor egg develop on at least a monthly basis if you intend to get viable hatches from your eggs. It is also a good idea to never wet all the peat at once but only portions so as to gauge the proper incubation time to avoid belly-sliders.

What follows is a brief description of a method to accelerate egg development taken off the AKA killitalk email list

From: "azkillie" <azkillie@quixnet.net>
To: "AKA Killie Talk" <KillieTalk@aka.org>
Subject: Accelerated incubation times
Date sent: Fri, 1 Sep 2000 23:47:43 -0700
Send reply to: killietalk@aka.org

Bay Area Killifish Association members remember the late Howard Gibbs. Howard would hatch out annuals in weeks instead of months and then grow them to phenomenal sizes in a short time. His results were incredible.

Howard invented a technique to accelerate the incubation process. I have seen some articles on this years ago, either in the BAKA Newsletter or JAKA (or both). Essentially, Howard strung his bags of eggs in peat to a overhead line in his fishroom. This increased the temperature by being higher up. The second thing Howard did was to connect all of the bags to an air pump. This increased the oxygen level in the bags. Finally, he ran the airline through beakers of water to keep the peat from drying out. As I said earlier, the results were incredible.

I have never tried this personally.

It is crucial to check the dampness of the peat regularly to ensure that it is not too dry and to see if the eggs have eyed up. Some eggs can rest in the peat for years while other such as N. foerschi and korthausae don’t last long after their due date.

To stretch out the incubation times of nothos allow the peat to turn anoxic before collecting it. As a consequnce the eggs can go into an extended diapause for many additional months with out much eggs loss. Incubation at cooler temperature also help slow the incubation. As an example of how long incubation can last read this extract from the AKA killitalk email list by Dr. Brian Watters. The eggs were incubated at 25-26°C.

From: "Brian R. Watters" <bwatters@sk.sympatico.ca
To: "AKA KillieTalk" <killietalk@aka.org>
Subject: N. orthonotus - incubation trivia
Date sent: Sun, 24 Oct 1999 15:53:18 -0600
Send reply to: killietalk@aka.org

I thought that some subscribers interested in annual killifish might find the following information interesting:

I wet some peat of various species of Nothos this weekend, among them N. orthonotus MW 91/8 (one of three populations of this species that Harry Woodsford and I collected in southern Malawi in 1991). I always inspect the peat carefully for eggs before I wet it and in doing so I found a good number of both eyed and clear eggs in the oldest spawning of this population that I had in my incubator. The spawning was 3 years, 5 months and 2 weeks old ! The next oldest, at 3 years 4 months had even more eggs, both clear (undeveloped) and eyed. I got an excellent hatch from these with perfectly healthy fry.

I regularly hatch various populations of N. orthonotus, N. furzeri, N. rachovii, N. sp. Hoba, N. sp. Liwonde, etc. after incubation periods of 1-2 years but the MW 91/8 case beats my own previous record which was for N. rachovii KNP Black. About a year ago I hatched a large batch of fry of this species from a spawning that was 3 years, 3 months and 2 weeks old - and there were clear, undeveloped eggs in that one too.

If you consider the specific climatic conditions under which some Notho species have to survive (frequent periods of drought lasting for 2 years or more) it is really not surprising that the eggs can survive for so long.

Another method of incubation annual eggs is by incubating them in water. Most annual eggs will develop perfectly well in water. When the eggs have eyed-up simply put them in a hatching container and add some fresh peat and peat extract to stimulate hatching. The addition of oxygen tablets have also proven very useful (particularly in preventing belly-sliders).

The eggs can be picked from a mop (if the fish have been trained to spawn in mops) and put into water or if the eggs can be picked from peat. The rescue of the eggs from the peat can be accomplished by putting the peat and eggs into a tall jar. Add water and stir. Allow the peat to settle for a moment and then pour off the top layer of water with peat debris. Repeat till all the peat is gone or the eggs can be plainly seen. It is a good idea to allow the eggs to stay in the peat for a week or two so all the infertile eggs can die off and decompose before you attempt water incubation.

Shallow dishes should be used so as to allow for good oxygen exchange. The water should also be changed regularly.

NON-ANNUAL EGG INCUBATION

The classic approach is to pick the eggs from mops or what ever spawning substrate and then put them into a shallow dish with some added acriflavine or methylene blue to prevent fungus. This rarely works for me so instead this is what I do.

I pick the eggs directly from mops every two days and place them into a shallow tub with a layer of peat for a substrate. Added to this are one or two shrimps of what I think is from the genus Cardinia. Every so often, I fish the fry from this container. The shrimp eat all the fungus and dead eggs and the tannis and humic acids from the peat retard the bacteria. Some people can’t do this so this what I suggest instead. Pick the eggs and place them immediately into a half strength solution of Tetra General Tonic. Then pipette the eggs into another shallow tray with this half strength General Tonic. You can collect up to a weeks eggs in this tray. Constantly do water changes on this tub and remove any dead or fungusing eggs.

The shallow tub and bacterially directed antibiotic is crucial and is less likely to affect the eggs than strait acriflavine. The methylene blue in general tonic also helps in that it is an oxygen carrier. The importance of oxygen can not be over expressed as explained by Wright Huntley:

To: killies@mejac.palo-alto.ca.us, AKA mail list <killietalk@aka.org>
Subject: Egg handling (was Re: keep gularis cold?)
From: Wright Huntley <huntley1@home.com>
Date: Tue, 06 Jul 1999 09:26:31 -0700

Apologies for those who get it twice. I'm adding it to the killietalk list as they haven't had any good feuds there for days (since the last BNL thing!). :-)

halbasch@ES.COM wrote:

Richard:

I am surprised by the lack of traffic on this thread. Would you care to elucidate a bit on this evidence? Are we talking about storing the eggs at a cooler temperature or keeping the adult breeding pairs at a cooler temperature.

My suspicion is that he meant the latter. It's also true of *A. jeorgenscheeli* and the diapterons, quite often. Many "equatorial" fish come from high enough altitude that they really do *like* cooler mountain water-- 65-72F.

I find that unless I let the eggs sit for a day or so in a weak anti-fungal solution before I place the eggs on peat I have a very low hatch rate.

I sometimes use antibacterials, like thiazine or analine dyes to inhibit egg damage, typically a very weak combination of methylene blue and acriflavin. I'm curious as to what anti-fungals don't damage the eggs, or why one would use them? My impression is that fungus is the more visible stuff, starting only after an egg has already died and is decaying. [Even products like Jungle's "Fungus Eliminator" contain *no* antifungals as such. Just a couple of antibacterials, salt and a mild tanning agent. Excellent stuff, BTW.]

I have noticed an anomaly that I would like to pass on to the rest of the net for comment. I recently returned from a business trip and so hadn't pulled any eggs from the mops in the gularis tanks. All the mops were full of eggs and of several hundred eggs only 10 or so had fungused over the 2 week time period. Being as the honey-do list was threatening to overwhelm me I placed the eggs directly on to damp peat ( no anti-fungal dip). This peat had been wet, microwaved and cooled only an hour or so earlier. By the following afternoon roughly 30% of the eggs were showing fungus. Any comments from the net gurus!!

IDK what any of the "gurus" will have to say, but I have been up, down, back and around on this subject for a long time. Chuck Olson and I have devised any number of bubblers and other devices to attempt to duplicate what trout farmers must do to eliminate egg loss. [Trout eggs are terribly sensitive to dissolved oxygen content, for one thing.] Any touching or just placing eggs into stagnant water seems to induce egg death, more in some species than others. The bacteria level in the water may directly harm eggs, or it may just rob them of oxygen. Dyes help here, but may over-harden the chorion and inhibit hatching if not diluted away quickly. Some obvious truths: Keeping egg water colder increases its ability to dissolve oxygen. Diluting dyes by water change also adds fresh oxygen and stirs the water. [The dye benefit could be *entirely* due to the early water changes!] Eggs left in mops in large containers get a lot of slow free-water circulation, by convection if not because of filtering currents. Some "maybe" truths: Handling causes enough damage to let bacteria get in. "Bubblers," like pilsner glasses with air line to the bottom, keep eggs in boiling suspension and may stop "fungus" cold. [Artemia-hatchery effect.] Sealing peat with eggs can cause enough oxygen deprivation to kill them. [Thinnest plastic bags are much safer. Taped Petrie dishes can be really deadly. BTDTBTTS.] The amount of rinsing, and the final dampening water in peat can be critical. Boiled, cooled and drained peat is usually way too acid for most eggs. Rinsing a lot with hard (i.e, well-buffered) water seems safest at preventing egg burn. [Add baking soda to final rinse, if all you *have* is soft water.] End of "maybe"s and into pure speculation: Eggs attached to plants *seem* to do better than eggs attached to mops. In mops or plants, the eggs usually hang by their sticky thread and don't make much physical contact with anything. That is, they are totally surrounded by the water with minimal flow blockage. Hmmm... Eggs do better in small containers if a sprig of Java moss is added -- I think. [The water certainly stays clearer as the rotifers, etc., eat all the free-swimming bacteria.] Hatch is increased by a few percent if you don't stare at them (but do look for and remove white eggs at frequent water changes). Crossing fingers may help. ;-) One family, in ultra-soft-water country, did very well by hatching Aphyo eggs in Petrie dishes where the water was changed a couple of times a day -- always at least daily. IDK if that's *all* they did, tho. Swapping out mops and *not* picking eggs seems to work better, as does using larger-surface-area hatching containers (sweater boxes rather than shoe boxes, for example). Airstones and plants in the hatching container seem to help, too. OK. That should be enough ammunition to bring the gurus out with flame-throwers lit. (^_^; {Japanese smiley. Same as (^_^), but sweating.] Wright

Date sent: Fri, 06 Oct 2000 08:47:40 -0500
From: "Michael Reid" <mreid@sturgis.k12.mi.us>
To: killietalk@aka.org
Subject: Re: To dry or not to dry eggs?
Send reply to: killietalk@aka.org

Hi Tyrone, we use Sphagnum peat usually from canada, not grtound as fine as the stuff in peat pellets. we microwave it , more to help the absorbtion of water into the peat fibers than to kill microorgansims or whatever. We then take some, squeeze out the excess water, put in a plastic conatainer jsut a thin layer on bottmo, add eggs, put on lid and put away for a period of time. We check eyes with a magnifying glass to help in determing hatching time. Mike

From: "Jay-Scott Moylan" <moylan@emi.net>
To: <killietalk@aka.org>
Subject: Re: To dry or not to dry eggs?
Date sent: Fri, 6 Oct 2000 20:24:38 -0400
Send reply to: killietalk@aka.org

Hi George, My method is super simple. I basically learned it from Earl
Fischer in Ft. Lauderdale. I pull a mop out of a tank and wring it quite dry. It shouldn't drip at all. I put it in a zip-lock sandwich bag, which I roll up to empty of air. It gets a label with species, date pulled, etc. This is stored in a cardboard shoe box. Every day for the rest of the week, I pull out the mop's replacement and pick the eggs, putting them carefully into the center of the bagged mop. After a week, the shoe box, now holding a week's worth of eggs for most of my species, goes into the garage (around 80 degrees generally). The next day the whole processs is repeated. After two weeks in the garage, I just pull out the mops and toss them into plastic shoe boxes with an inch or so of fresh, dechlorinated water (I use Ammo-Lock 2 and store the water in a large bucket for a day or two). Usually, the eggs all hatch in a few hours. I like having the fry hatch together so they grow at a similar speed. This method is working very well for me. Jay

Another method I am trying to is to use a damp sponge in a sealed dark container. The sponge is kept soaked in water or some anti-bacterial mix and the eggs are placed on top of the sponge. This seems to work...

I hope this information was of use. If you have a difference of opinion please email me so it can be included.