# egg feeders: the ultimate Q



## james67 (Jun 28, 2008)

so as long as obligate egg feeders have been around (in the hobby), we have been attempting to use egg substitutes, with little to no success. i'd like to start this thread as a discussion that could potentially lead to some new advancements.

i'll start with a question; has a gas-liquid chromatographic analysis ever been done on an egg from an obligate egg feeder who routinely produces viable offspring, and could this possibly lead to a "synthetic" replica which could be used as a food source?

james


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## markbudde (Jan 4, 2008)

That experiment would be very difficult to do. There will obviously be a ton of things in the egg, and in the best case scenario, the is a single nutrient which is required. In order to do this, you need some reference frame, which you can do a bioassay with. As far as I can tell, the only bioassay we know of is whether or not the frogs survive, which takes several months per experiment. You would also need a large supply of feeder eggs to experiment with.

I think the best way (or at least, the most robust way) to approach the experiment would be this...
1) Establish a synthetic medium which gives good results. People have tried a lot of things, use whichever is easiest and allows the tads to progress/survive the longest. This would be something like chicken yolk mixed with vitamins.
2) Get a good supply of feeder eggs. Mix these in with the synthetic diet to determine how available the missing nutrient is. Hopefully you could dilute the feeder eggs quite a bit and they would still retain their magic.
3) Once you have established that it is possible to feed a mostly synthetic diet, you need to isolate the nutrient. To do this, you perform a number of extractions on feeder eggs, and see which fraction it stay with. Examples would be things such as, does it dissolve in organic solvents, can it be dialyzed away, can it be centrifuged out...
4) Once you know which fractions have the activity, analyze the active fractions by chromatography/MS and see what is present in all of the active fractions, but absent in the inactive fractions. Hopefully it is a single, cheap, molecule.


The alternative, of course, is to keep adding more and more things to the synthetic media and see if anything helps. This isn't necessarily an easily solvable problem, but no progress will ever be made unless people keep experimenting. If I had egg feeders, I know that I would be experimenting on a lot of tads. 

What is known about which species eggs work? Can you raise a pumilio with imis as parents?


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## james67 (Jun 28, 2008)

i know that there has been attempts at feeding auratus eggs both whole and with the outer layers removed however, if i remember correctly, the froglets were not viable or had developmental issues.

james


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## Ed (Sep 19, 2004)

One of the confounding problems would be hypovitaminosis of retinol in the parents as this directly affects development as well as survivial post metamorphosis.. 

With respect to amphibian eggs, there are differences in not only the number of membranes but the integrity of the membranes (for example, if you do it gently, you can hand pick, using your fingers cynops eggs out of java moss and have them develop normally, but attempting to seperate many anuran eggs from their egg mass with your fingers isn't going to work well). Some of the earliest attempts to do this utilized leopard frog eggs and this didn't work well as the tadpoles had problems consuming the eggs. There have been a number of later trials with egg substitutions including utilizing Cynops eggs (as a small number tend to be laid daily for long periods of time) but this required the membranes to be removed from the yolk (under a steromicroscope) and all of these trials have had varied amounts of success. 

Other keepers have tried using surrogete parental rearing with good success within and between some species. To date, I am only aware of some people utilizing species within the same genus.. I haven't heard any discussion of cross genera fostering. 

Ed


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## markbudde (Jan 4, 2008)

If somebody had an unlimited source of pumilio eggs (I know that some are quite productive) it could be a really cool project for members to try a number of different things to artificially raise them. Ship them out to different participants, and everyone tries a different variable and reports on the success/failures. For instance, perhaps vitamin A isn't a confounder, but is in fact one of the major problems with artificial diets? I guess it gets back to the initial question, has anyone ever looked at the vitamin content of oophaga eggs? Has anyone supplemented artificial eggs with vitamin A?


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## Ed (Sep 19, 2004)

Hi Mark,

I've been researching this along with carotenoid metabolism in amphibians, and anurans in particular... There are analysis out there of anuran eggs (sorry no, Dendrobatids) which show that at least before the eggs are deposited, they do not contain any vitamin A in the form of retinol.. Now anecdotal evidence has shown that supplementing with vitamin A in the form of retinyl palmitate (based on a paper that showed disrupting vitamin A metabolism in a Eleuthrodactylid) has been shown to resolve problems with embryo development and spindly leg in Dendrobatids. 

There is also evidence that tadpoles may normally utilize a different isomer of retinol than the adults do that is derived either from converting the retinoid that results from beta carotene or from a xanthophyll precursor... 

Ed


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