# Tarantula Inbreeding



## Sathane (Feb 21, 2009)

I've been wondering about this for a while and haven't been able to find any information either way on this.  Searching AB results in a thread in the scorp section but nothing for Ts - so I'll ask here.

Are there any problems associated with inbreeding tarantulas?


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## ph0bia (Feb 21, 2009)

There have actually been none reported. All the problems we associate with inbreeding have yet to be proven with tarantulas. We speculate that it means lack of genetic variation (which makes sense) but plenty of tarantulas inbreed in the wild.

Maybe that's why A.seemanni are renowned for being crazy


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## CRX (Feb 21, 2009)

Yeah, communal T colonies in the wild inbreed ALOT, and it doesn't seem to do any harm.


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## Sathane (Feb 21, 2009)

Thanks for the info.
I can definitely relate on the Seemanni front.  My girl loves to dig up the stones I use for drainage in her enclosure and scatter them around.  She'll arrange these for hours sometimes.
Maybe she's trying to improve her figure...


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## RoachGirlRen (Feb 21, 2009)

The potential effects of inbreeding in tarantulas is not fully known or understood; there is no strong, documented evidence that inbreeding in captivity causes harm, but there is also evidence of behavioral and physiological mechanisms in nature to promote genetic diversity in the wild (depending, of course, on the species). 

There have been some experiments in other arachnids showing potential health effects from intensive inbreeding, so I would not rule out the possibility that _intensive_ inbreeding over _many_ generations could weaken the quality of lines. 

More than the overt problems of deformity we tend to think of, reduced genetic diversity is problematic because it results in a population with similar susceptibilities. What I mean by this is that if every specimn of _Tarantulum hypoteticalis_ in the hobby was bred from just a handful of starter stock, we may end up with very little genetic diversity - which means that if a highly communicable disease that individuals with those genetics are prone to were to break out, it could devastate captive stocks depending on what kind of exposure exchange occurs (much like we see in domesticated crops that, due to being selected for consistency via nearly identical genetics, have the same achilles heels). 

I think in brief, the short and skinny of it is: there is a good case for genetic diversity in any species, so when possible, promoting diversity certainly does no harm and may have merit. However, there is no evidence suggesting that we'll end up with horrible genetic defects from the occasional inbreeding or line-breeding, so one needn't panic about mixing related stocks.

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## Stan Schultz (Jan 7, 2014)

Sathane said:


> I've been wondering about this for a while and haven't been able to find any information either way on this.  Searching AB results in a thread in the scorp section but nothing for Ts - so I'll ask here.
> 
> Are there any problems associated with inbreeding tarantulas?





ph0bia said:


> There have actually been none reported. All the problems we associate with inbreeding have yet to be proven with tarantulas. We speculate that it means lack of genetic variation (which makes sense) but plenty of tarantulas inbreed in the wild. ...


Not entirely true. There are sporadic reports of developmental defects in captive populations of tarantulas, and I have personal knowledge of an instance where a significant number of the offspring of a wild caught _G. rosea_ that produced an eggsac in captivity, developed DKS.

The fact that they haven't been reported or officially ascribed to inbreeding is a red herring. Just because we don't know about it doesn't mean it doesn't exist. And, all evidence from virtually every other organism that man has been breeding in captivity confirms the amplification of defects due to inbreeding. If tarantulas didn't follow the same laws of genetics and evolution that virtually every other organism on the planet does, I'd be absolutely astounded.




CRX said:


> Yeah, communal T colonies in the wild inbreed ALOT, and it doesn't seem to do any harm.





RoachGirlRen said:


> The potential effects of inbreeding in tarantulas is not fully known or understood; there is no strong, documented evidence that inbreeding in captivity causes harm, but there is also evidence of behavioral and physiological mechanisms in nature to promote genetic diversity in the wild (depending, of course, on the species). ...





CRX said:


> Yeah, communal T colonies in the wild inbreed ALOT, and it doesn't seem to do any harm.


There is a huge difference between captive inbreeding and inbreeding in nature. In captivity we try to save each and every one of the little darlings without serious regard to defects. In fact, when we do find a defect, as often as not we think it's cute or desirable and actually try to conserve it. If you need proof, consider for an instant the number of *freshwater angelfish* in your friendly, neighborhood, pet shop with deformed gill covers. Or, *waltzing mice*,  *fainting goats*, the incredible number of *albino creatures* we keep as pets, and the seemingly endless number of breeds of dogs and chickens.

However by contrast, life in the wild is not so benign. Natural selection is a brutal, unforgiving arbiter, and the *99% Rule* reigns supreme. It doesn't matter if an organism does inbreed a lot. If there are any resulting defective offspring, they are quickly culled by natural selection. If one of those offspring even twitches at an inopportune moment, they're dead!

There is a peculiar phenomenon as a corollary to this. It involves a little genetics, so stay with me on this.

Firstly, the majority of creatures on Earth possess genes that come in pairs. One member in each pair is contributed by the father, and one by the mother. A little redundancy is often a good thing. Usually. But, not always.

Secondly, almost all mutations of genes result in deactivating that gene. Obviously such a deactivated gene won't display or influence its owner. It rides along the reproductive highway as a dud.

Thirdly, such silent, deactivated genes are called "recessive." Their normal, active counterparts are call "dominant."

If an individual inherits one recessive gene from one parent and a dominant gene from the other, the probability is that this individual will not display the recessive character associated with that gene. Some pretty intensive testing is required to prove that the defective gene is present. In effect, the other (dominant) gene kicks in to cover the fault and everything looks normal.

When two such "hybrid" (in the genetic sense, not the taxonomic sense) individuals mate there is a probability that some of the offspring will inherit a double dose of the recessive gene, and display the mutated character. (I'm conveniently skipping over the obvious cases where one or both parents are "pure" for the mutated, recessive gene. This posting is already getting too long.)

Now consider a population wherein there exists such a recessive gene. It glides along, generation after generation, hidden in those hybrid individuals, only now and again popping into view in the rare instance described above. Whereupon the organism displaying that character either doesn't develop at all (i.e., the egg doesn't develop, or there's a spontaneous abortion or stillbirth), or it gets weeded out of the population by predation, disease, natural calamities, etc., very quickly. The *99% Rule* in action!

And, a moments thought should strongly suggest that such recessive genes may never entirely leave the population, forever hiding inside the (largely unrecognizable) hybrids.

Now, what happens when some enthusiast acquires several tarantulas of the same species, possibly even from the same colony, and interbreeds them? Now we may see sporadic "mutations" in the captive bred population, but fail to realize that they're just the tip of the iceberg. Or, even fail to realize that they may be a problem at all! "Oh, look. Isn't that cute!"

"So, what can we do about this?" you cry! Well, historically, we'd have to look at a half dozen generations (or more) of accurate breeding records, and even then we might make mistakes. These days, at the beginning of the 21st millennium, we have DNA analysis, if we can just figure out what we're looking for. And can afford to pay for it! And yes, we still might make mistakes.

By doing either or both of these things we may be able to find individuals that are "pure" for the non-mutated gene and establish a breeding population composed entirely of their offspring. Until some buffoon who doesn't understand the problem or the solution but wants to breed tarantulas, corrupts that breed or family line. Whereupon we have to start over again from scratch.

In the interim, our only practical defense is to cull our babies to remove any that might be defective (or "suboptimal") before they have a chance to pass on their genes, and to employ some very basic selective breeding practices with the proposed breeders that we have. But, that's another lecture: Basic Animal Husbandry 101.


Like most things about tarantulas, the questions are simple. The answers are marvelously, sometimes maddeningly, complex!

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## advan (Jan 7, 2014)

Stan Schultz said:


> Not entirely true. There are sporadic reports of developmental defects in captive populations of tarantulas, and I have personal knowledge of an instance where a significant number of the offspring of a wild caught _G. rosea_ that produced an eggsac in captivity, developed DKS.


So your argument for inbreeding defects is from your own account of a fake "syndrome" developing in spiderlings from a WC sac? :?

Please stop using the term DKS(dyskenetic syndrome). Dyskinesia is not a syndrome but a symptom that could be caused by many things(dehydration, infection, chemical exposure, etc).  Unless your version means "Don't Know Syndrome" then, please don't use it, you're just spreading more misinformation that needs to be corrected. 

dyskenetic(dyskinesia)- abnormality in performing voluntary muscle movements

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## Stan Schultz (Jan 8, 2014)

advan said:


> So your argument for inbreeding defects is from your own account of a fake "syndrome" developing in spiderlings from a WC sac? :? ...


No, no, no! From decades of watching all sorts of people (me included) breed all sorts of organisms, and from studying college level texts on biology and a bunch of its sub-branches.



advan said:


> ... Please stop using the term DKS(dyskenetic syndrome). ...


Will not! "*A rose by any other name...*" (*William Shakespeare* in *Romeo and Juliet*.)



advan said:


> ... Dyskinesia is not a syndrome but a symptom ...


Ahhh! But it is a syndrome! See *syndrome*. Also, *symptom*. You've managed to get the definitions of the two terms switched.



advan said:


> ... that could be caused by many things(dehydration, infection, chemical exposure, etc). ...


Thank you for confirming my argument.



advan said:


> ... Unless your version means "Don't Know Syndrome" ...


Now I'm a bit confused. Is this a typo or have you changed your mind and now really do mean "syndrome?" Please clarify. (The highlighting is mine.)



advan said:


> ... you're just spreading more misinformation that needs to be corrected. ...


Wrong! I'm labeling it for exactly what it is, "A group of symptoms that collectively indicate or characterize a disease, psychological disorder, or other abnormal condition." (The highlighting is mine.)



advan said:


> ... dyskenetic(dyskinesia)- abnormality in performing voluntary muscle movements


Among other things. Thank you again for confirming my argument.


Like most things about tarantulas, the questions are simple. The answers are marvelously, sometimes maddeningly, complex!

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## esotericman (Jan 8, 2014)

The ego of having so many years of ignorance is completely staggering.  This is why older college professors, who actually have PhDs stop publishing in peer reviewed journals and switch to text books, which are dated the second they're printed.  They just cannot withstand their peers in science any longer, in this case verbose, and outlinked arguments seem to “win” the argument.  I assume it’s because the neophytes are impressed by long posts and extensive vocabularies.

Firstly, sweeping comments across diverse organisms with different breeding strategies is foolish.  In the IUCN red listed species in genus Poecilotheria which garner a great deal of attention, there has been nothing published regarding measurable inbreeding.  This is an arboreal species which may or may not disseminate as mature males greater than a few hundred meters.  Brachypelma vagans in Florida, has been observed up to two miles from the colony would be a different matter altogether.  It does not require a great depth of biology background to understand species which stay put might just be different than those which do not.  Thus claims that inbreeding effects have been observed are an utter lie as specific species have not been discussed.  It is an opinion and the broader the opinion, the greater the chance the facts will be missed.  You know, the earth is flat, all hobbyists should read a specific text.
A few years ago, there was a nice little article in the BTS Journal where P. murinus were sibling crossed for four generations.  There were no measurable differences in the offspring.  That was published in a well-respected magazine, not a rumor hinted at on a discussion board.  Am I foolish enough to point at that one example and claim inbreeding effects do not occur?  Nope, but at least it is a set of reliable observations.   

This "dirty secret" approach which uses suggestions to “facts” and has an air of “conspiracy theory” deludes those newer to the hobby into arguing for the inclusion of wild caught animals, which increases pressures on those species which are limited by distribution or other ecological factors.  This is asinine because there is no evidence short of opinions that inbreeding effects are detectable.
If I were forced to express an opinion on anything claimed to be an effect of inbreeding, I would simply ask if the species being reported were hybrids or not.  For decades there have been claims that G. rosea eggsacs can give rise to both drab and brightly colored specimens.  In today's age, we now know that "G. rosea" is actually 2-5 species which are imported into the US and Europe by the thousands.  Yet breeding success is quite rare.  As the average hobbyist can differentiate species, then what facts can be garnered from such possible hybridization events?  Very little.  Furthermore, the care and culture of each specimen would need to be exactly the same (you know that funny thing called a control) to compare those which are predicted to be inbred (which I note has not been defined at all) with those which are not (which should be defined).
Thus until someone actually inbreeds, by pick a single species to start with  and keeping all over variables the same, there is no evidence of inbreeding in tarantulas of any species.  

Here are a nice few threads on the topic as well, notice the complete lack of mention of mysterious observations found in this thread. 
http://www.arachnoboards.com/ab/showthread.php?62612-Inbreeding
http://www.reptileforums.co.uk/foru...565-inbreeding-theraphosids-old-chestnut.html 
http://thebts.co.uk/forums/showthread.php?2498-Effects-of-inbreeding
http://thebts.co.uk/forums/showthread.php?3610-Tarantula-inbreeding

B. vagans note the retraction of the assumption deformities were due to inbreeding.  That population came from very few individuals and is at least 17 years old. 
http://edis.ifas.ufl.edu/in562

Google scholar is the poor person’s way to peer reviewed literature.  I see ZERO abstracts on the topic.  I am baffled how peer reviewed literature is trumped by rumors.
http://scholar.google.com/scholar?hl=en&q=theraphosidae+++inbreeding&btnG=&as_sdt=1,28&as_sdtp=

I hope people take the time to read and think and not accept whatever long winded and utterly wrong replies follow this post.  I do not have the time to argue with fools.  The links above already answer any arguments I will not waste time to reiterate.

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## advan (Jan 8, 2014)

Stan Schultz said:


> No, no, no! From decades of watching all sorts of people (me included) breed all sorts of organisms, and from studying college level texts on biology and a bunch of its sub-branches.


Comparing invertebrate to other non-invertebrate in terms of biology and genetics is fatuous. You should know that by now, reading those books and all! 



> Ahhh! But it is a syndrome! See *syndrome*. Also, *symptom*. You've managed to get the definitions of the two terms switched.


 A syndrome must have multiple symptoms, not just one. Using the word "syndrome" is implying that you have a diagnosis. See the issue there? When the cause could be multiple things(like my small list above) and have multiple diagnosis, they can not be all combined into one syndrome.



> Now I'm a bit confused. Is this a typo or have you changed your mind and now really do mean "syndrome?" Please clarify. (The highlighting is mine.)


You don't see what I did there? 



> Wrong! I'm labeling it for exactly what it is, "A group of symptoms that collectively indicate or characterize a disease, psychological disorder, or other abnormal condition." (The highlighting is mine.)


See above, dyskinesia or spastic movements is ONE symptom, not a group. 



> Among other things. Thank you again for confirming my argument.


Nothing was confirmed, good sir. It just seems Tootles has lost his marbles. ;P

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## Spiderguy47 (May 14, 2018)

From what I've read in the past, it seems that there are two instances where inbreeding has little to no effects. 1. When there is a high rate of genetic mutations that constantly mix up the gene pool (example: rabbits). 2. When there is already a lack of genetic diversity (example: possibly tarantulas, but like stated above there is no evidence that proves or disproves this). I think that occasional inbreeding wouldn't have devastating effects, but the only way to know for certain is to conduct expirements involving inbreeding tarantulas over and over again for many generations and I doubt anyone will ever do that. The worst part about trying to answer this question is the fact that "tarantulas" is a very generic term, there are hundreds of tarantula species and it is probably safe to assume that their genes behave differently.

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## Jaromysfuneral (Nov 25, 2020)

I’ve researched, there are physical anomaly cases in tarantulas as well as all animals but we are talking 2/3 in millions.

line breeding is common for high production of visible anomalies (Hypomelanism, axanthic, etc.) and thousands or maybe even millions of good cases have been proven that it can be done well, granted the animals offspring is always subject to care from the owner and husbandry so this is all important before deciding an animal is healthy or not. If you breed an unhealthy animal, it’s bound to have unhealthy offspring.

physical anomalies I have seen were two abdomens or triangle shaped abdomens with two sets of spinarettes, but we are talking about a handful of cases ever spoken of in the millions of spiders that have been bred. It’s about as often of an occurrence as human deformities and isn’t acknowledgeable enough to blame on inbreeding/line breeding.


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