Tortoise Pedigree

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Tortuga_terrestre

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Can someone please clarify this question for me... Well besides loving tortoises, I also share a passion for working line german shepherds. Before a sire and a dam are bred, their is careful planning. You have to look at both parents pedigree (Titles, Health: For Example-Hip Dysplayia and elbows ect and of course most importantly the shepherds drive to work) Obviously tortoises are not competing nor serving as police K-9's. But when tortoises are bred, Are breeders taking into consideration if the 2 animals are genetically compatible? Are the offsprings of 2 random possibly related or not related animals going to contribute to its species? In the German Shepherd breed, There is alot of genetic defects and health problems because of reckless breeding. Thank You
 

Yvonne G

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No, this is not a consideration with tortoises (besides the obvious afflictions) because tortoises have not gone through years and years of human intervention. More than likely, the tortoise you see today is exactly like the tortoise seen in the desert 200 years ago.
 

Tortuga_terrestre

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Thank You, I would say your right about most species of tortoises. But what about the over bred Sulcata Tortoise.You can purchase a sulcata for $45 online, Pet Stores purchase these awesome tortoises for wholesale. There is definitely an over breeding of this species.
 

Tom

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In an animal as basic as a reptile, it will take more generations to start seeing genetic anomalies than it would in a mammal. In roaches, it is estimated by people much better educated than me that it would take 33 years of inbreeding, starting with one male and one female, before you would see any genetic problems. Add one and it expands to 99 years. I've had one roach colony that started in 1992 with three individuals. There have literally been millions over that 18 year span and they are as healthy, normal and virile as they were on day 1.

Having said all of that, I ponder this question occasionally. "Personalities" and other genetic traits are definitely passed on in captive bred exotics. This was always very apparent with the apes. You could tell instantaneously whose offspring were whose. There is relatively so little captive breeding that goes on, in comparison to dogs, that I think people are generally happy just to get two of anything together and breeding successfully.

On the sulcata question, there were a lot of them imported from the wild in the past and so the captive breeding population has a pretty deep gene pool. Also, because so many people are breeding them it is easy enough to get unrelated individuals for breeding, if that is ones intention.

On the question about overbreeding, I don't agree that they are overbred. The supply meets the demand and sales continue to be high even after 20 years of widespread captive breeding. I live on the West Coast where the market is supposedly flooded and you reportedly can't give them away, yet they sell in pet stores for $150 and the guys at the reptile shows out here won't drop below $50-$60, because they know darn well they will sell them all at a higher price. If they were overbred, people would be giving them away and selling them as cheaply as possible. If you consider the tens of thousands that are sold every year, relatively few end up in rescues.
 

snake_girl85

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Very interesting video! Thanks for sharing! There is definitely a connection between physical appearance and other genetic factors in some animals, with a specific color or other physical attribute in a male signaling fitness to a female. It is possible that certain colors are associated with higher testosterone levels, and when you breed for "tameness" (theoretically lower testosterone levels), more color patterns emerge.

I'm not sure that this exact same principle is occurring in captive reptiles, as breeders generally aren't selecting for tameness. A python breeder is much more likely to breed a phenotypically unique, but aggressive, individual than they are to breed a "normal" animal merely because of its mellow personality. Interesting side note: some keepers have claimed that certain color variations of the infamously aggressive white lipped python are more "tame" than others, and the aggression appears to be breeding out of them as more captive generations are being produced.

Albinism, hypomelanism, etc... can occur in the wild, and they do more often than you would think. These traits are usually recessive, and also cause a wild animal to stick out like a sore thumb to predators. The atypical appearance can also signal a propensity to mutate or lack of genetic fitness to potential mates, causing them to be rejected. That is why these mutations almost always go extinct in the wild. When you remove natural selection, and breed animals out of a relatively "shallow" gene pool, these traits are much more likely to surface and survive in a captive, artificial population. Some snake species are now even producing "scaleless" varieties ( which I strongly disagree with but that's another story)

That being said, I believe that popularly bred reptiles, perhaps not specifically tortoises, are already genetically different than their wild counterparts - at least in terms of appearance. Aside from the obvious "morphs," even the "normals" of some species look much different than the average wildcaught individual. My passion is Brazilian rainbow boas (hoping to breed them someday soon), and when I see obviously wildcaught specimens in zoos, they look positively drab compared to what the "average" boa looks like in the pet industry. Duller colors, and fairly tiny and dull "crescents" along the side of the animal. Some breeders have selected for larger, brighter crescents, and while it is not a definite morph that is either turned "on" or "off," the genetics of the captive population have definitely been altered from the wild type.

As far as tortoises go, I think that they are still fairly similar to wild tortoises, mainly because most species don't have as isolated of a captive population. There are still many wildcaught specimens being added to the mix and eventually bred. This will probably continue to occur since tortoises are such slow growing animals and some may consider imports more cost effective than breeding (which is why pet shops that cannot sell turtles under 4 inches always seem to have WC animals... Who is going to breed red eared sliders and care for them for 4 years before selling them for 10 bucks?). Once more and more morphs become available, it will not only take pressure off the wild populations, but it will further isolate the captive populations, and more likely allow for genetic drift.

(lol, sorry for the longwinded response... Recently graduated Biology major who just finished watching an 8 hour miniseries on Charles Darwin... ;))
 

egyptiandan

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The answer to your question is yes and no. :p Most hobbyists keep track of their own animals, but not everyone else's. Zoos though have species survival plans (SSP) for endangered species. The plan keeps track of who is related to who to maximise the genetic diversity of the species in captivity. Hobbyists can participate in a SSP.

Danny
 

Tortuga_terrestre

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wow, thank you for that very educational response. Since we are talking about genetics and breeding practices; here is a very intresting article I read. I hope you guys find it as intresting as I did. Now this was forwarded to me by a friend of mine;who breeds german shepherds for government agencies and the military.


The difference between linebreeding and outcrossing.


Linebreeding for stock and outcross for performance.



*_Linebreeding _*

Linebreeding can increase the possibility of expression of undesirable, as well as, desirable genetic characteristics. This is why it is very important to know and understand the strengths and weaknesses of dogs before making a lot of breeding decisions. Linebreeding/inbreeding "locks in" characteristics by limiting the possible genes that the pups carry. With inbreeding & close line breeding you normally can not expect to produce anything better than what you start with (the parents).

You are breeding a much smaller subset of the GSD gene pool. And you end up with dogs that have a greater chance of being homozygous for many traits (carry two copies of the same gene, rather than one each of the range of posiblities for THAT gene).

Equally as important if you are line breeding, you also increase the chances that problem genes will be expressed in the puppies. In long lines of strictly line bred animals there is an increase in the chances for genes to mutate and be expressed.

Often in lines that are extensively linebred (nine or more generations), there tends to become a decrease in the quality of the line, due to the lack of genetic material to draw from. This is known as inbreeding depression, and can result in decreased fertility. This is part of the reason why very close breedings are discouraged (brother to sister, father to daughter, mother to son). These close breedings can and have been used to strengthen a trait, but they are almost always followed with an outcross.

Line breeding is also useful in the bringing out of recessive genes. It increases the chances that you will have both genes be recessive in an offspring if the line is bred closely. Close line breeding can become a crap shoot because you may end up with something you don't want and then have to go more aggressively for outcrossing to get rid of the trait.

*_Outcrossing_*

With outcrossing you have the chance to produce something better than the parents. The phenomenon of "Hybrid vigor" occurs when the puppies are better than the average of the parents.

So, when you outcross, you are expanding the gene pool again. There are two main results :-

ONE: You cross two lines that have been bred for most of the same traits and you get very similar traits, but possibly improve on a trait your line is weak on. For example, if your line has floppy ears and you outcross to a very similar line, but one with good ears, you will keep the same "type", but have some pups with better ears than your line has been producing.

TWO: If you breed to a line that has been breeding for a different set of traits than your line, you will get a huge variation in the trait that the pups express. You are, in essence, doubling the possibilities for the traits of the pups. You will probably end up with some great dogs and some horrible dogs, but neither type will tend to be "prepotent", which means "tends to reproduce like itself", because they will tend to be heterozygous, having two different genes, rather than two copies of the SAME possible gene, or homozygous.

If you want to suppress the expression of some unwanted gene, you outcross. If you want to eliminate a trait, inbreed to bring it to the surface and then remove the affected dogs from the gene pool. The outcrossing works short-term but allows the recessives to spread thru the genepool without anyone knowing who carries it. This makes it more likely that it will become a widespread problem in the breed. With the inbreeding, you see these undesirable traits within a few generations and can quickly weed them out. However, when you go back to an outside line, you run the risk of bringing these recessives back into your line.

If you only outcross after outcross etc., and you only use excellent examples for breeding, your going to be able to find some excellent puppies in these litters. The problem is that the line loses it's seperate identity quickly and hybrid vigor decreases with each outcross.

*_Linebreeding & Outcrossing : In Respect to Both _*

Linebreeding is what provides for the outcrossing that equals hybrid vigor.

Line Breeding and outcrossing go hand-in-hand. One's not much good without the other. Too much emphasis in either direction will produce poor results.

With inbreeding or with outcrossing you can surface the undesireable recessive traits. But unless both parents carry the recessive, it may not reveal in the offspring, and some (about 25%) of the pups produced by carriers bred to non-carriers will also be carriers.

One way to test an animal for a recessive is to breed it to a known carrier and see if any of the puppies produced have the characteristic. The test breeding can be either an outcross or inbreeding, it's irrelevant.

Taken from the Dr. Denny Article on the "Principles of Genetics" part 1

/"Hybrid vigor has occurred when the performance of the offspring is different from that of the average of their parents. The actual mechanism of hybrid vigor is not well understood, however, matings can be made to increase the beneficial effects of hybrid vigor. Mating of animals which are not alike in their pedigree or that are not related are those which will generally exhibit higher levels of hybrid vigor. Closely related animals do not exhibit high levels of heterosis.

Crossbreeding in plants and animals is done to take advantage of both hybrid vigor and complimentarity. Complimentarity is the term used to describe the "combining" of desirable traits from two breeds or lines that are not related. Hybrid vigor is also maximized when animals are mated that have little or no genetic history in common."

/The best way to maximize Hybrid Vigor is to cross two separate, unrelated linebred lines. Breeders would benefit to keep their lines as seperate as possible from other lines, to ensure that more lines are available for hybrid vigor.

No matter what you do you will be placing pets if you breed. No matter if you linebreed or outcross. The balance is so tricky that you generally only find 10-20% of progeny are really top quality. When you add the problem of restricting your selection to fewer dogs, you will make compromises to stay with in the line. This is how problems tend to creep in. If you are looking at the ability to make the selection from a wider variety of animals and select the best from that pool you will see improvement.

*_In Summary_*

Line breeding has been a major problem driving the decline of many breeds. That does not mean that outcrossing alone becomes a sound breeding theory! It is not a question of line breeding or outcrossing. It' a question of how to obtain predictability, by taking advantage of both. Whether you are trying to get rid of a nasty disease, or you are just trying to put some good litters on the ground, no matter the goal, a breeder won't make any progress without taking advantage of predictability.
 

Yvonne G

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We do have different folks who keep stud books on various types of tortoise, but it would be up to the individual keeper to pay attention to the blood lines and breed or not. And not every species of tortoise is represented. Plus, each stud book is only as good as the information that is sent to the keeper of the book. I have a copy of the Manouria stud book, and I DID send in the information about my intergrades many years ago, but little Emmie is now 2 years old, and I've never sent in information about her.
 
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