Birth Defects

Discussion in 'General Reptile Discussion' started by Nero Egernia, Jun 27, 2016.

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  1. Nero Egernia

    Nero Egernia Subscriber Subscriber

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    What is everyone's experiences with birth defects in reptiles? How does it happen? Is it a genetic issue or perhaps something to do with the environment during incubation? If a lizard or snake were born with kinked or curly tails would it effect the reptile's health and life, and would it be passed on during breeding?
     
    Last edited: Jun 27, 2016
  2. pythoninfinite

    pythoninfinite Subscriber Subscriber

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    If it's congenital, it's genetic...

    J
     
  3. Nero Egernia

    Nero Egernia Subscriber Subscriber

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    Thanks for pointing that out. I should have said birth defects. :facepalm:
     
  4. Waterrat

    Waterrat Almost Legendary

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    Not so Jamie, congenital defects can also be the result of a compromised embryonic development, it's not necessarily genetic.

    Sorry mate. :)

     
  5. pythoninfinite

    pythoninfinite Subscriber Subscriber

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    Oh OK Michael, I must say I was under the impression that a congenital defect meant that it had been passed on from parents. I actually know so little of gene theory (or fact:)) that I generally avoid getting into discussions about this stuff... I loved biology when I was at school, but all that Mendelian theory went right over my head! Trust me to get it wrong!

    Jamie
     
  6. Pauls_Pythons

    Pauls_Pythons Power Seller Power Seller

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    Congenital disorder, also known as congenital disease, birth defect or anomaly, is a condition existing at or before birth regardless of cause. Of these diseases, those characterized by structural deformities are termed "congenital anomalies" and involve defects in a developing fetus.
     
  7. Bluetongue1

    Bluetongue1 APS Veteran APS Veteran

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    First of all, let’s assume that it is only the tail involved. A kinked or curly tail in a lizard that uses its limbs for locomotion is likely to have minimal effect on it, if at all. With a snake, depending on the degree of kinking and whether or not there are malformed muscles involved, it may well impede its locomotion. In captivity, this would not be an issue, whereas in the wild it would be.

    There is the possibility that the kinked tail is indicative of a more widespread problem.

    It could be caused by an environmental influence, in which case it would not be passed on. For example, it may have resulted from insufficient calcium being available to the developing embryo, which would mean that it is odds on there is general skeletal weakness and quite probably other deformities that are not evident from the outside.

    If the cause is genetic, then it may be passed on. For example, the animal may be genetically deficient in its ability to utilise calcium. In this case the same probabilities of widespread problems mentioned in the previous paragraph would also apply.

    If you have an otherwise healthy animal with a kinked tail, odds are it was environmentally produced and is unlikely to be genetic and to be passed on.
     
  8. Nero Egernia

    Nero Egernia Subscriber Subscriber

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    Thank you for the information. I may have an opportunity to acquire some baby lizards with kinky tails and they were born that way. Both parents however, appear to look fine. They all appear to be healthy. I'm not phased by a minor defect but I'm concerned about possible health problems down the track.
     
  9. Bluetongue1

    Bluetongue1 APS Veteran APS Veteran

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    Irrespective of whether the origin is genetic or not, if the lizards are otherwise 100% healthy and active, then you are looking at a localised skeletal deformity in the tails that is not going to change as they grow older.

    If the parents have had young before but without the kinked tails, it is not likely to be genetic.
     
  10. GBWhite

    GBWhite Well-Known Member

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    Ho Oshkii,

    Personally I doubt if it has anything to do with calcium deficiency during incubation or indicative of a more widespread problem.

    Recessive genes that carry defects such as kinked tails may be carried by the parents but not displayed. The origin of multiple lizards being born with defects such as kinked tails is usually a result of continuous and persistent inbreeding between parents and offspring that carry these recessive genes which results in the defect occurring in more and more of the offspring.

    There is no way to safeguard against this as the presence of the recessive bad gene can't be detected in the line until it's too late.

    There is no reason that the lizards should not live a full and healthy life but, for the above reason it is advisable not to include any of these offspring in a breeding program as the gene is never lost from the line.

    Hope this helps.

    Cheers,

    George.
     
  11. Nero Egernia

    Nero Egernia Subscriber Subscriber

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    It was the first clutch so no way to tell as far as I'm aware. Apparently they hatched late, and after were taken to the vet where it was declared that there was nothing wrong with them. Thanks for the information, it's certainly given me a bit to stew over. I've been trying to read up on it, and some sources say it has no effects in breeding while others say it does.
     
  12. Waterrat

    Waterrat Almost Legendary

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    Hi George,

    are there any data / statistics re- the incidence of spinal / tail kinking in hatchlings as opposed to live-born juveniles?
    As you know, GTPs are prone to spinal kinks, but emerald boas are not, in fact, it's unknown in ETBs. This suggests that the kinks (at least in GTPs) are most likely the result of compromised embryonic development during artificial egg incubation. Would the same apply to lizards?

    Cheers
    Michael
     
  13. GBWhite

    GBWhite Well-Known Member

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    Hi Michael,

    Personally, I'm not aware of any data/statistics regarding the incident of tail kinks in hatchling GTP's v live born ETB's.

    However, from what I have read on the subject it appears that tail kinking does occur in ETB's and that it is suspected to occur as a result of rough handling. Which would suggest to me that it may not necessarily be a result of compromised embryonic development during artificial incubation in GTP's. I also note that to my knowledge there is no data to confirm it one way or another.

    I also remember reading (I believe it was one of your articles on Health Issues with GTP's) that it is also thought that tail kinking may be related to a lack of dietary calcium during the early growth stages of hatchlings due to a poor unnatural diet of pinky mice.

    I've also read that other breeders suggest that it is a result of probing to determine gender before the snakes are a year old.

    I suppose that it might also be worth considering that from what I've read it appears that tail kinking in GTP's has been observed in wild specimens, and as such it may be that hatchlings born with this affliction in captivity could be
    a result of the continuous inbreeding of parents and off spring of stock animals originally taken from the wild that unknowingly maintain a naturally occurring bad recessive gene.

    Alternatively it may even be a result that the prehensile tails of both GTP's and ETB's are susceptible to being damaged.

    It is an interesting topic of discussion and I suppose we won't really know the actual cause until someone decides to take it by the horns and look into it.

    I can only presume that if it is proven that it is related to artificial egg incubation in GTP's that it would be highly probable the same would apply to lizards.

    Cheers Michael and all the best.

    George.
     
  14. Allan

    Allan Subscriber Subscriber

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    A bit off the subject re. the genetics......
    A bit over a year ago, I sold a healthy GTP hatchling with no deformities. The same hatchling was returned a month later with three bad kinks. In fact, so bad that I was at one stage considering euthanizing it. However the little thing was feisty and what it ate came out the other way with a little help, so I decided to give it a chance.
    I built a small outdoor enclosure and put it on a diet of adult mouse heads moulded in to a size that it could swallow. Hoping that sun and the extra burst of calcium would be beneficial. 12 months later and two of the kinks are gone and the third barely visible, it is now a very healthy snake. I don't know how the kinks appeared, I can only assume improper handling, but it doesn't seem like kinks appear until after the first 6 months.
     
  15. Waterrat

    Waterrat Almost Legendary

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    Hi George,

    I was merely thinking oviparous v viviparous when it comes to the incidence of spinal deformities. I agree with your points, I certainly believe that rough handling and early probing / popping can cause damage but I am not convinced it's the underlying cause of the problem, nor is inbreeding. I bred GTPs from unrelated parents for years, never probed them till after OCC and never handled them roughly - yet, I still had some kinked individuals that popped up randomly.

    Harlin Wall, one of the most respected US breeder and herpetologist wrote this:
    "I do not believe that kinking in GTP is caused by compromised embryonic development during artificial incubation. Rather it seems to be a case of ligaments/connective tissue that is/are only loosely attached in the vertebrae of juveniles. Similar to how a young human's joints and ligaments are not fully developed until a later stage of their growth. While they are young these connections are very delicate. As they mature the ligaments strengthen and solidify. Interestingly Corallus species do not have these same issues. While I would NEVER consider popping a GTP at any age...they are safe to probe at either 1 year of growth or at the 100 grams size/weight. Emeralds (and other Corallus species) on the other hand can easily be popped or probed without fear of negative effects shortly after parturition. Of course any method of determination of gender is only as good as the skill level and experience of the person wielding the probe or attempting to exvert hemipenes. "

    I tend to lean towards lack of calcium and also exposure to natural UV (as oppose to artificial UV) as being the culprit. If I get a clutch or two this season, I am geared up to inject pinkies with calcium syrup (as recommended by reptile vets) and also expose them to natural UV. It's going to be tricky and tedious but worth experimenting.

    Interesting topic indeed, thanks for your thoughtful input.

    Michael
     
  16. Bluetongue1

    Bluetongue1 APS Veteran APS Veteran

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    In talking to a highly experienced reptile vet, he feels it is likely an environmental issue with the eggs.


    That aside, if it were due to inbreeding and Mendelian genetics, then the chance of any offspring with a double recessive (deleterious) gene, and therefore showing the characteristic, is 25%. So while it is possible to get a higher ratio than this in any given clutch, one would not expect it in a majority of offspring. If it involves more than one gene, than the probability of it being expressed phenotypically is even less. There is also the high likelihood of more than one deleterious gene carried in highly related individuals and so one would also expect multiple abnormal characteristics to show.


    To say that a gene is never lost from the line is not correct. That is what outbreeding seeks to do. It is about utilising the independent assortment of chromosome pairs during meiosis, to separate and ultimately eliminate undesirable alleles/characteristics. Even with a deleterious allele on the same chromosome as that of a desirable trait, crossing-over provides the opportunity to separate the genes onto different chromatids - which are then separated via independent assortment. The difficulty is the number of generations of carefully selected breeding and the number of offspring required to be confident this has been achieved. That is why correctly line-bred animals are expensive. Unfortunately there are those who do not have the understanding, patience and/or resources to do it properly, but say they do so they can charge higher prices under false pretences.
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  17. Nero Egernia

    Nero Egernia Subscriber Subscriber

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    Thanks for the input everyone. This is proving to be very interesting. In my search for information I came across these interesting links in regards to birth defects, inbreeding, and ethics.

    Inbreeding in Captive Reptile Populations

    Birth Defects - Causes and Reactions

    In A Guide to . . . Australian Lizards in Captivity quoted directly from the source under Spinal and Limb Defects it says;

    "These range in severity from major spinal curvatures or twists to missing toes or bent tail tips. Most commonly they are the result of temperature issues, egg trauma or neonatal nutritional deficiencies. The severity of the defect is related to the precise developmental stage at which the insult occurred - if it occurred as the spinal column was developing, the spine may be developmentally abnormal and the limbs normal".

    I also recall reading somewhere (or perhaps it's my imagination as I can't find the source again) that early in the breeding program of albino Olive Pythons there was a high tendency of hatchlings being born with kinky tails and spines. Numerous out crossings over generations soon appeared to have bred out the tail kinks however. Please correct me if I'm wrong here.

    Also, is it possible that for species with longer incubation periods are more prone to birth defects as there's more time and opportunities for the incubation process to go wrong? Is there a way to test if birth defects are genetically related?
     
  18. GBWhite

    GBWhite Well-Known Member

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    Hi Jamie,

    The Mendelian theory really isn't that difficult to understand.

    If your interested I've provided a link that not only explains the theory but also provides links to further discussions.

    I've also provided a link that explains the basics of dominant and recessive alleles.

    http://anthro.palomar.edu/mendel/mendel_1.htm

    http://www.yourgenome.org/facts/what-are-dominant-and-recessive-allele

    Basically, as far as reptiles go. the same principals apply whether you are selectively breeding to produce colour morphs or unknowingly breeding animals that maintain a recessive bad gene.

    I haven't been able to locate anything regarding what Oshkii has alluded to regarding out breeding as a means to address tail / spine kinking in albino Olives but if this is the case then it would be more evidence to suggest (at least in GTP's) that the infliction may be genetic.

    Cheers,

    George.
     
  19. Bluetongue1

    Bluetongue1 APS Veteran APS Veteran

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    The original query was with respect to lizards and I should have qualified the opinion I quoted from the vet, that it was in reference to lizards that hatch from eggs.

    @Oshkii, your reasoning with respect to environmentally induced congenital defects is correct. The longer the time spent incubating, the greater will be the opportunity for environmental influences to manifest themselves. However, there are two things to take into consideration here.

    The first is a general point, applicable to all situations. Probabilities are not good predictors in small samples. They are more accurate the larger the sample size. For example, there is a 50% chance of producing a male vs female baby and the total population demonstrates this, yet there are occasional families that have 6 daughters or 7 sons or the like.

    The second point is that the types and degree of variations of physical influences exercised over a given clutch can vary depending on the incubation set-up and the person involved and what they do.. So some incubation periods may be extremely consistent, irrespective of length, with little or no variation or interference, while others may be the opposite, even for short incubation periods.

    So basically what works as a generalisation, may not apply to a specific sets of data. But that set of data does not invalidate the generalisation. So while what you suggest may not apply in every case, as a general rule it is true.
     
    Last edited: Jul 4, 2016
  20. Nero Egernia

    Nero Egernia Subscriber Subscriber

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    Thanks you for all the information so far. Still not sure whether this particular clutch with the kinky tails is a genetic or environmental defect. Wish things could be easier to figure out.

    In regards to the early process of albino Olive Python breeding I must have been imagining it as I can't find the source.
     
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