# Tinctorius tadpole development



## Parinari (Aug 20, 2020)

I have 3 tinctorius nominate French Guiana tadpoles that have still not developed legs after 4 months or have only just got very small back legs. Is this a normal length of time for development? If not, why might it have been so slow and how much longer should I wait before, sadly, giving up on them?


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## Tijl (Feb 28, 2019)

These will probably never develop into a (healthy) frog.


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## Socratic Monologue (Apr 7, 2018)

Any speculation on what causes this?

Here's a relevant thread, the most comprehensive discussion of it I've found here:

https://www.dendroboard.com/forum/general-discussion/9612-non-morphing-tads.html


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## Tijl (Feb 28, 2019)

It's a grow hormonen issue. I used to know what it's called, but I forget.. 😄


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## Encyclia (Aug 23, 2013)

Welcome, Parinari!

I am pretty sure that when I first started breeding frogs that I delayed the development of some of my tads by not feeding them enough. I have been a lot more diligent since then in my feeding and my results have improved a lot. You might try feeding a bit more and give them time. It seems like I have had some tads that have stuck around way past when they should have morphed and they still developed. If they have popped rear legs at all, I would give them some time to see if they legs get bigger.

Mark


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## Encyclia (Aug 23, 2013)

Socratic Monologue said:


> Any speculation on what causes this?
> 
> Here's a relevant thread, the most comprehensive discussion of it I've found here:
> 
> https://www.dendroboard.com/forum/general-discussion/9612-non-morphing-tads.html


I went back and read SM's linked thread and that was fascinating. Notice how long ago this thread was made, though. Do you think that things have changed (especially nutritionally) so much since then that what was said is no longer relevant? It is pretty rare that anyone has problems with Spindly Leg Syndrome anymore, mostly because of much better supplementation options available now. Pure speculation, though.

The other thing that makes me skeptical that this is a hormonal perma-tad situation is that there are 3 of these tads. Are these together in the same container? If not, I find it pretty unlikely that the exact same situation is impacting all 3 tads. It could be something genetic, I suppose, but it's not as likely. If they are co-housed then the homone theory is more likely because they are all sharing the same water. I co-house Terribs and Pepperi and both have some very odd rhythms of tad morphing that make me suspect there is something going on that suppresses all but one or a few of the tads from morphing simultaneously (which is counter to the strategy that I believe some other taxa use to have all of their tads morph simultaneously to avoid depredation). Finally, I have never read anything about multiple perma-tads spontaneously arising. The stories I have read start with "I have this one tad..." 

Tijl, you could be correct, I just don't know enough to verify. Regardless, I still like the idea of giving the little fellas some more time, just in case.

Mark


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## Socratic Monologue (Apr 7, 2018)

Google Scholar, as usual, seems a rabbit hole of great studies. A quick scan turns up no straightforward answers, though. 

Here's a study on Xenopus that fail to metamorph, and the researchers basically can't figure it out:

https://scholar.google.com/scholar_...gCg&scisig=AAGBfm0j3Wvo3tNX89YRynMS8lx8b2QxXg


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## Fahad (Aug 25, 2019)

To complicate matters, I've experienced this recently.

First time P. terribilis parents. 40 tadpoles have made it into the water since their first clutch on May 7th.

Tadpoles from first and third clutches respectively have all produced all four of their limbs between August 18th and 20th and are leaving the water sporadically, development looks good so far. 

All other tadpoles appear to be doing well and growing quickly *except* ...

*First Clutch:* 1 tadpole has an unusual speckled appearance, halted growth and development weeks ago (no sign of limbs), is still swimming and presumably eating but a little hard to tell with this one. Its siblings are about to leave the water.

*Second Clutch:* 1 tadpole presented same as the first, but this one was even smaller and expired around August 16th, having originally hit the water on May 26th.

I expect the first non-metamorph still swimming to die off at some point.

While their size was different, both have/had a very streamlined, tapered shape relative to the more bulbous look of a normal tadpole, with the same weird speckling. I haven't come across much in the way of specifics on this topic yet outside of a few things already mentioned here, and have up to now chalked it up to congenital defects weeding them out rather than external factors.

I raise them individually, and presumably the parents' nutrition, tadpole nutrition, and water quality are all within acceptable parameters given that I'm _*so far*_ seeing proper limb development and active, growing tadpoles as far as their three dozen or so siblings go.

I've been seeing dramatic jumps in viability and somewhat less dramatic but noticeable increases in egg and tadpole size in the last three or four clutches, so hopefully the two non-metamorphs are artefacts of the early clutches they were found in, although I suppose that's no guarantee.


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## Fahad (Aug 25, 2019)

Encyclia said:


> [snip]I am pretty sure that when I first started breeding frogs that I delayed the development of some of my tads by not feeding them enough. I have been a lot more diligent since then in my feeding and my results have improved a lot.[snip]


I do tend to feed more frequently now than I did in the beginning, which no doubt accounts for some of the faster growth I'm seeing in the later clutches my terribilis have been producing.


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## macg (Apr 19, 2018)

I haven't had time to read this whole thread or the links, so I apologise if I'm repeating something already known.

Sometimes metamorphosis stunting is a result of thyroid hormone issues due to iodine deficiency. I don't recall the exact mechanism, but I believe it is key in the process of apoptosis (cell death), which is key in metamorphosis. Some cells must die and others must divide.

It has been demonstrated (again no time for sources, sorry) that adding iodine to the tadpole's environment in the event of a deficiency can induce completion of metamorphosis, normally.

This process was described to me by a researcher familiar with xenopus. 

A friend of mine recently recommended this as solution to a friend for a tadpole stuck in metamorphosis, and it worked (so I've heard). 

If you want to give it a try, dip the head of a pin in iodine from the store, and dip that into your tadpole's cup. Simple as that. Shouldn't take much.

Again sorry for the hastiness. Correct anything that's wrong.


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## Parinari (Aug 20, 2020)

Thanks for all your help with this, I will try a little bit longer with increased feeding and potentially iodine and see if this cause metamorphosis. Thank for your help!

Andrew


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## Fahad (Aug 25, 2019)

I'm actually trying that myself with my one non-morphing tadpole.


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## macg (Apr 19, 2018)

Cool I'm very interested to see your results.


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## azandis (Sep 13, 2020)

This is an interesting thread. I studied anuran development for my PhD, so I thought I'd offer some other potential mechanisms.

As mentioned, metamorphosis is driven by a hormonal cascade involving thyroxin. Some of the earliest studies found that destruction of the pituitary gland (which regulates thyroxin production) could prevent metamorphosis entirely. Interestingly, there seems to be a threshold point in development where metamorphosis will continue even if thyroxin production is halted. This makes sense from an ecological perspective because metamorphosis is a dangerous transition for frogs. Locomotion is hindered because they are partly aquatic and partly terrestrial. Their eye morphology shifts for refraction in air rather than water (meaning that they have poor eyesight at metamorphisis), making them easy snacks for predators. Also, the anatomical restructuring of the digestive organs that goes on during metamorphosis leaves them nutritionally vulnerable. As the tadpole's gut and mouthparts transition from herbivorous to carnivorous, they cannot consume new resources--they must rely on stored reserves in fat bodies and calcium stored within the tail. For metamorphosis to halt in mid-transition would lead to starvation.

All of that is to say that tadpoles are engineered to wait until conditions will allow them to fully metamorphose prior to initiating metamorphosis. Two big variables that will preclude the initiation of metamorphosis are inadequate food (amount or quality) to build up reserves and inadequate heat (ectotherm development is closely tied to ambient temperature, so cooler temperature will delay or prevent metamorphosis). So, being sure to feed liberally and keep the temperature warm is important (no surprise there!).

There is another counter-intuitive bit of amphibian biology that can alter metamorphic timing. Amphibians are renowned for developmental plasticity (or the ability to alter the timing of development based on the environment). The most well-studied examples are _Ambystoma tigrinum_ which can completely avoid metamorphosis if aquatic conditions are suitable. And _Scaphiopus couchii_ which will convert to a monstrous cannibal morphotype if conditions are poor (this allows them to eat their sibling competitors and quickly build nutrient stores to escape drying ponds).

So, there may be a case that rearing tadpoles in TOO GOOD of conditions could protract larval development. Metamporphic timing has been shown to speed up in scenarios with higher conspecific density and in decreasing water levels. This has primarily been studied in pond-breeding Ranids, but Dendrobatids breeding in treeholes or broms would encounter the same environmental constraints. So, one option to try might be to housing your tadpoles in communal water (either free-swimming or in individual containers with flow-through) and decrease the water volume a bit each day. This would simulate drying up of the natal breeding pool and may inspire metamorphosis.

Anyway, I thought I'd put some of my dissertation reading to use and share some thoughts!


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