# how nutritious are FF larvae?



## Rain_Frog (Apr 27, 2004)

What data proves the arguments that "FF larvae are high in fat?" 

And, how do we know that our frogs are digesting the larvae? Sometimes I see dead larvae in frogs' stools. I do not know if they are exoskeletons or undigested remains. Ed K. said that many frogs have difficulty digesting them.


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## Jer (Feb 9, 2008)

FF larvae are fattier(if fattier is even a word) than fruit flies, but they are not high in fat. Well I guess that depends on your view of what is high and what is not. I would say that FF larvae have a moderate fat content.

I have always used this as a general guideline.
http://www.nagonline.net/Technical%20Pa ... DIFIED.pdf

Exoskeletons of any type of invertebrate are made of chitin, which is indigestible, just as cellulose is indigestible to us. This provides roughage in the diet, which is a good thing.


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## JWerner (Feb 17, 2004)

I regularly larval feed in the fall, winter and spring. While I have no specific data, I can easily say that clutch sizes and frequency of laying after larval feeding does increase. I do see a relationship.


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## Ed (Sep 19, 2004)

Jer said:


> FF larvae are fattier(if fattier is even a word) than fruit flies, but they are not high in fat. Well I guess that depends on your view of what is high and what is not. I would say that FF larvae have a moderate fat content..


If you compare the %ether extract to other inverts you would see that the larva have a fat content of about 29% (DMB) while the adults are only 12% so ff larva are about 2.4 times more fatty than the adults ffs but are less fatty than wax worms... 



Jer said:


> Exoskeletons of any type of invertebrate are made of chitin, which is indigestible, just as cellulose is indigestible to us. This provides roughage in the diet, which is a good thing.


I have to disagree with this statement different insectivores have different abilities to digest the chitin (up to 85% in sea gulls) and there is some recent data that indicates that a lot more nitrogen is available than was previously thought (I have the reference somewhere around here..) 

Ed


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## Jer (Feb 9, 2008)

Ed said:


> If you compare the %ether extract to other inverts you would see that the larva have a fat content of about 29% (DMB) while the adults are only 12% so ff larva are about 2.4 times more fatty than the adults ffs but are less fatty than wax worms...


You got it homie. I said that the larvae were fattier than the adults. Look at the EE for those with a high fat content such as mealworm larvae, and waxworm larvae. That is why I said that I think FF larvae have a moderate fat content. Of course this discussion is of no merit unless we define what is high and what is not. 



Ed said:


> I have to disagree with this statement different insectivores have different abilities to digest the chitin (up to 85% in sea gulls) and there is some recent data that indicates that a lot more nitrogen is available than was previously thought (I have the reference somewhere around here..)Ed


No need to reference that. I can verify that as correct, but we aren't talking about seagulls. I was talking about in general. Of course their are exceptions to every rule which you have graciously stated. It's no big secret that chitin is highly indigestible by a far greater majority of vertebrates than it is digestible, with frogs being on the majority side.


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## Ed (Sep 19, 2004)

Jer said:


> No need to reference that. I can verify that as correct, but we aren't talking about seagulls. I was talking about in general. Of course their are exceptions to every rule which you have graciously stated. It's no big secret that chitin is highly indigestible by a far greater majority of vertebrates than it is digestible, with frogs being on the majority side.


Was there a study on the inability of insectiverous frogs to digest chitin?

Ed


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## Jer (Feb 9, 2008)

Ed said:


> Was there a study on the inability of insectiverous frogs to digest chitin?Ed


Likely lots. I will search for at least one to link.

I was more basing this on a combination of my personal observations and common sense.

From The Journal Of Exotic Pet Medicine, Volume 15, Issue 4, October 2006, Pages 255-263
*"There is no evidence that amphibians produce enzymes to digest chitin, cellulose, or keratin."*
http://www.sciencedirect.com/science?_o ... ad6f1c4308
I don't know if this link will work for you. I am connected to the internet through the University of Saskatchewan.

With that said, there's no doubt in my mind that there are amphibians that are capable of digesting chitin, just none of which are currently known by science.


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## Jer (Feb 9, 2008)

Im not here to argue or prove anyone wrong on the forums. Ive been told that my writing style reeks of arrogance and is arguamentative in nature. This is totally incorrect. It's very hard to read expression through words across the internet, and I hope that you and everyone else realizes that I am not here to be arrogant and obnoxious. I AM HERE TO LEARN AND MAKE FRIENDS WITH THOSE THAT KNOW SO MUCH MORE THAN I DO. I just wanted to make that clear.


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## JWerner (Feb 17, 2004)

I have seen both undigested larva, which seem to remain whole and I have seen only exoskeletons left in the feces


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## sports_doc (Nov 15, 2004)

Sometimes if I eat too much corn on the cob... :shock: 

I just couldn't resist.

Jon, and others. Have you used larvae to fatten frogs that stay chronically lean? [despite clean fecals] and do the effects last? I am not in the habit of feeding larvae but I am giving it a try lately on pums, some leaner tincs, and my terribilis to see if egg hatch success improves.

S


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## Jer (Feb 9, 2008)

Your makin me hungry.


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## Ed (Sep 19, 2004)

Jer said:


> Ed said:
> 
> 
> > Was there a study on the inability of insectiverous frogs to digest chitin?Ed
> ...


Interesting.... however its incorrect... (see http://ci.nii.ac.jp/naid/110003372739/en/) 


and the more we look the more we are discovering chitinases in other mammals (see http://www.jhc.org/cgi/reprint/50/8/1081.pdf) such as humans, mice and cows.... 

The more we look the more we discover them.. 

Ed


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## Jer (Feb 9, 2008)

Don't tell me it is incorrect. Tell Dr. Catherine A. Hadfield and Dr. Leigh A. Clayton DVM whom I quoted. I for some reason am more willing to believe them and their study than you telling me it is incorrect. I mean how else do you explain the presence of chitinous exoskeletons from all sorts of feeder insect in the feces of many species of amphibians if you say that they cant digest chitin?

Your study simply points out that one species of toad produces a protein that functions like a chitinase, which I find fascinating, it does not however state that all amphibians are capable of digesting chitin. As I have already stated, "there is no doubt in my mind that there are amphibians out there that are capable of digesting chitin". Thanks for that.


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## JWerner (Feb 17, 2004)

Any diet studies out there focusing of toad species from arid areas? IMO that is where you would begin.


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## Rain_Frog (Apr 27, 2004)

> Sometimes if I eat too much corn on the cob...


Same here, plus peas. :lol:


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## Jer (Feb 9, 2008)

Any other studies, Im interested to read them.


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## Ed (Sep 19, 2004)

Jer said:


> Don't tell me it is incorrect. Tell Dr. Catherine A. Hadfield and Dr. Leigh A. Clayton DVM whom I quoted. I for some reason am more willing to believe them and their study than you telling me it is incorrect. I mean how else do you explain the presence of chitinous exoskeletons from all sorts of feeder insect in the feces of many species of amphibians if you say that they cant digest chitin?.


You quoted them to prove your point (and they quoted a much older reference (Duellman and Trueb 1994). I don't have to correct them... I simply need to point it out to you that they are incorrect because they are referencing older material... 


The presence of chitin in the feces is easy to explain. There have been studies in other vertebrates showing that chitin digestion ranges from about 12% to 85 % in insectivores. For there to be no chitin present in the fecal material would require a greater percent digestion of the chitin than has been currently found. 
Flip it around, if the frogs could not digest any of the chitin then why are they not passing totally whole insects? Unlike mammals and birds there are no mechanisms to masticate the food arthropods.....(for circumstancial evidence see http://content.karger.com/ProdukteDB/pr ... elNr=70646 ) 




Jer said:


> Your study simply points out that one species of toad produces a protein that functions like a chitinase, which I find fascinating, it does not however state that all amphibians are capable of digesting chitin. As I have already stated, "there is no doubt in my mind that there are amphibians out there that are capable of digesting chitin". Thanks for that.


Hmm, whats that old adage... walks like a duck, quacks like a duck its a duck... 
protien, enzyme, degrades chitin.... chitinase...... 

Which is why I cited the second study... We are finding more and more chitinases in more and more animals... 

However an inability of an animal to produce chitinase does not mean that it cannot digest chitin.. there are other potential sources of chitinases that are exploited by animals. These chitinases are produced by microbial, protozoal and fungal fauna in the digestive tract or even by the prey species themselves (see the primate insectivore discussion here http://www.biaza.org.uk/resources/libra ... /ARSP4.pdf ) I don't have time to dig out all of the references I have lying around or to track them down on the net but I will go back to my original statement (paraphrased here) that presuming that chitin is indigestiable is very premature.... 

Ed


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## Jer (Feb 9, 2008)

Hey Ed Im not arguing with you, just wanted to make that clear. I know that some animals can digest chitin, whether it be quite well, or very piss poor. An animal with a 12% ability to digest chitin basically is unable to digest chitin. I have seen whole cricket and mealworm exoskeletons in the feces of many frogs, and whole beetle elytra in the feces of pretty much any wild caught toad. The simple fact remains that many animals, including amphibians, either have a very limited ability to digest chitin, or are incapable of doing so, and the pointing out of exceptions (ie. those that can digest chitin) isn't very relevent as I have already acknowledged your claim to fame on this.


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## Ed (Sep 19, 2004)

Jer said:


> Hey Ed Im not arguing with you, just wanted to make that clear. I know that some animals can digest chitin, whether it be quite well, or very piss poor. An animal with a 12% ability to digest chitin basically is unable to digest chitin. I have seen whole cricket and mealworm exoskeletons in the feces of many frogs, and whole beetle elytra in the feces of pretty much any wild caught toad. The simple fact remains that many animals, including amphibians, either have a very limited ability to digest chitin, or are incapable of doing so, and the pointing out of exceptions (ie. those that can digest chitin) isn't very relevent as I have already acknowledged your claim to fame on this.


Hi Jer,

When working out a balanced diet for an animal you have to account for all sources of caloric inputs and sources of protiens and fats otherwise the resulting diet will not be correct. This is why even in species of animals that only breakdown 12% of the chitin stilll have to have it accounted for, it cannot be ignored or written off as indigestiable. 

With respect to the beetle elytra and the meal worms is this an artifact of an inability to digest chitin or due to a lack of mastication of the food item? 
It is well known that the total digestiablilty of chitin is related to how well it is mechanically broken down and given that amphibians unlike mammals and birds cannot masticate thier food items I would expect to see large and or thick pieces of chitin appear visually undigested (http://www3.interscience.wiley.com/cgi- ... 4/ABSTRACT). 
However (I need to find the study (I think it was in Zoo Biology)) the availability of nitrogen in the diet of an insectivore needs to be adjusted (if remember correctly) by a factor of about 6.5 due to the availability of N from the chitin...... 

The old way of thinking was that relatively few vertebrates are able to digest chitin but as we continue to look more and more into this topic we are discovering that we need to reevaluate the whole idea.. for example not too many years ago no one would have thought cattle would produce a chitinase for digestion (see http://www.jhc.org/cgi/content/abstract/50/8/1081) but today we are evaluating other protien (nitrogen) sources in feed because of it....


Ed


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## Ed (Sep 19, 2004)

Back to the idea of the ff larva are fatty.. 
Yes they are considered fatty when looked at the overall diet (as are mealworms).. and compare them to the adults basically when you are evaluating larva keep in mind that they are always going to have a higher fat content than the adults because they have to store lipids to enable them to have sufficient nutritional stores to complete metamorphosis. 

Ed


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