Captive bloodlines/apparently inevitable inbreeding

8LegsMomWannabe

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Jul 26, 2014
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I am starting a new thread as I do not want to completely hijack this thread.

To summarize, in response to Poec54's post about how tracing a tarantula's bloodline would be difficult if not impossible since there's so few bloodlines in a given species, sources are rarely revealed by dealers, and there's basically a ton of inbreeding in a given levies.

I brought up DNA testing, though suspected the feasibility would be rather low. Poec pretty much confirmed my suspicions as to the lack of feasibility.

So this leads me to wonder, well, I'm not quite sure how to word this. Obviously, in order for the hobby to remain, we need tarantula breeders to breed tarantulas. But, with inbreeding being pretty much inevitable, will the hobby end up suffering eventually? My (limited) understanding of genetics is that inbreeding magnifies traits in a given bloodline, Good and bad traits.

So, as tarantulas keep being bred, would I be correct in assuming that future generations will likely end up wih genetic problems? Is there just simply no way to minimize inbreeding?

My parents breed, in partnership with another breeder, German Shepherd Dogs. They're able to make sure that they are pairing unrelated dogs. I think my mom once mentioned that occasionally you'll breed two dogs who might have a common ancestor, but it's distant for both dogs and I don't think it happens often. Certainly they don't breed close relatives, definitely not siblings.

But it seems there's next to no way to make sure you're breeding unrelated T's. I think Poec mentioned in the thread I linked to that you can buy a spider Tom one state and another spider from another state with intent to breed them, and have both spiders be half siblings or even full siblings/sacmates.

So I'm left to wonder, is it as likely as it seems like it would be for genetic defects to populate a species' captive population? And if that happens, then what?
 

awiec

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I'm going to tackle this from my prospective as a plant breeder. Thing is, most of the crops you eat are very very refined "bloodlines"(we call them lineages) that usually are 97-100% the same. This is to make sure that all individuals will preform the same, taste the same, look the same etc because farmers and consumers want uniformity. Now when you are proceeding with the process of inbreeding in plants, yes you are going to get some really genetic weaklings BUT they then are excluded from the program. The constant inbreeding will keep on "purging" the bad genes and you end up with your elite individual that you may wish to keep and try to get approved for seed release. You have more flexibility with plants as you can produce large amounts of them, can clone them and even get them to double their chromosomes. Though there are crops that are more tricky to get an inbred uniform line (potatoes are a prime example) so one has to get more creative.


As for tarantulas we don't really know of any prominent genetic issues with them so it's a bit of a crap shoot and we really don't have a choice but to inbreed. Now spiders seem to carry certain similarities to plants as in there are a large amount of offspring and a purging process does happen as well (really you do need a purging process for all breeding programs). As people have observed any of the slower molting ones in the first few in-stars are usually consumed by their siblings and those who cannot molt properly also perish often. Then eventually you have the mature stage, some males just don't load their palps properly, lose their palps in a bad maturing molt or are eaten by the female. The females may always eat the sack as they may perceive something "wrong" with it or they are hungry. There are multiple times where mating has occurred but the eggs are never fertilized. While it would be nice to not breed siblings we have no choice as the hobby is built upon only a few specimens. We can have a diverse genetic program for roseas but no one really wants to breed them.
 

Poec54

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So far in tarantulas there's been nothing conclusive about any drawbacks to inbreeding; they're invertebrates and it may be very different than reptiles or mammals.
 

shawno821

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Sacmates can never breed unless someone goes through a lot of trouble to power feed the female,while trying to keep the male from maturing. I personally don't think inbreeding is going to be a problem for a long time.The German sheperd is far more likely to be inbred than any spider you get.That's why there's so many new cross breeds nowadays,the old,pure bloodlines are all becoming inbred,and it took many decades to come to a head.I think spider breeders are pretty safe for now.Add to that the fact that no one even knows if inbreeding is bad for spiders yet.
 

awiec

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Sacmates can never breed unless someone goes through a lot of trouble to power feed the female,while trying to keep the male from maturing. I personally don't think inbreeding is going to be a problem for a long time.The German sheperd is far more likely to be inbred than any spider you get.That's why there's so many new cross breeds nowadays,the old,pure bloodlines are all becoming inbred,and it took many decades to come to a head.I think spider breeders are pretty safe for now.Add to that the fact that no one even knows if inbreeding is bad for spiders yet.
The spider genome hasn't even been completed yet so we have no idea even what the genetic make up is for them. I believe the rule of thumb is the more complex the animal the more of a chance that a "bad" gene could be hiding, in a smaller genome it's a bit quicker to purge those out. I can't make any assumptions until someone does get a good genome up for them which might take a while.
 

8LegsMomWannabe

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Okay, every interesting. So inbreeding may not cause the same problems in spiders as it would other animals, for a very long time if ever. Am I understanding correctly?

Alice, very interesting about the plant breeding! Is the purging process done strictly by the breeder or does it happen more naturally? I ask because unlike tarantulas who can consume slow molters, eat egg sacs and males, etc., well plants can really cannibalize. So I'm curious as to how the purging process would work? If the breeder has to remove the genetic weaklings from the program, wouldn't it be hard to know before a plant's genes are passed down?

Going back to the dog breeding perspective, one genetic defect that can happen especially in German Shepherds is a condition called degenerative myelopathy which causes progressive paralysis from the hind end up. Well a dog generally won't start showing symptoms of DM until they're older, by which time they may have multiple litters of offspring. Best you can do at that point is no longer breed the affected dog and spay/neuter any of spring you have control over and try to notify owners of offspring you no longer own.

Thankfully nowadays there is a genetic DM test where you can determine if a dog has the gene, and if so, make sure that dog is never bred.

Of course, sometimes you can spot a genetic defect in a dog when it is still a puppy, but DM is just one example of a situation that you have to test for (if there is a test like there is in the DM example), otherwise you can pass a genetic defect down before you know a dog carries the gene.

Are there similar issues with plants?

Granted, tarantulas, dogs, and plants are vastly different so there will be many differences in how genetics affects each. But I would think some similarities are likely to exist.
 

awiec

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Okay, every interesting. So inbreeding may not cause the same problems in spiders as it would other animals, for a very long time if ever. Am I understanding correctly?

Alice, very interesting about the plant breeding! Is the purging process done strictly by the breeder or does it happen more naturally? I ask because unlike tarantulas who can consume slow molters, eat egg sacs and males, etc., well plants can really cannibalize. So I'm curious as to how the purging process would work? If the breeder has to remove the genetic weaklings from the program, wouldn't it be hard to know before a plant's genes are passed down?

Going back to the dog breeding perspective, one genetic defect that can happen especially in German Shepherds is a condition called degenerative myelopathy which causes progressive paralysis from the hind end up. Well a dog generally won't start showing symptoms of DM until they're older, by which time they may have multiple litters of offspring. Best you can do at that point is no longer breed the affected dog and spay/neuter any of spring you have control over and try to notify owners of offspring you no longer own.

Thankfully nowadays there is a genetic DM test where you can determine if a dog has the gene, and if so, make sure that dog is never bred.

Of course, sometimes you can spot a genetic defect in a dog when it is still a puppy, but DM is just one example of a situation that you have to test for (if there is a test like there is in the DM example), otherwise you can pass a genetic defect down before you know a dog carries the gene.

Are there similar issues with plants?

Granted, tarantulas, dogs, and plants are vastly different so there will be many differences in how genetics affects each. But I would think some similarities are likely to exist.
The weak plants are pretty obvious especially when you o field trials and you can do some preliminary genetic marker testing if you know what you're looking for. Weak plants have low yields, grow slow, are weak to disease, don't store well etc and thats easy to pin-point and thats how you purge; those individuals are not allowed to breed. You just take the best of best and use one or two as your parents, you then proceed to self pollinate or do backcrosses (offspring with parent). It takes about 7 generations to get yourself a uniform line IF the plant flowers and produces seed every year, I work with sugar beets which my boss has been working on some of these lines for 17 years because sugar beets are bi-ennial and until recently could not be self pollinated. For tarantulas I think (or hope) a similar outcome will happen, eventually we will have "elite" lines that are healthy because all the weaklings have died off as of right now we haven't seen any issues that happen later in life besides sterility (which obviously fixes that issue of passing). Tarantulas are interesting in that they regenerate everything, kinda like a plant does and they can fix most issues they have, dogs obviously can't, they are stuck with what they get.

From what I've learned from other breeders is that each dog/cat/lama is tested to make sure it has the best traits possible and the rejects are fixed and sent off as companions, so that your breeding program is the best. My parents got a Great Pyrenees who was initially used in a breeding program but the breeders decided that her personality was too stubborn and did not want her to be in their program anymore so she was sold off as a pet. When people get careless with their programs (backyard breeders don't help either) is when you get issues from what I understand (once agin I'm a plant person) so if you were to refine your blood lines further then you wouldn't have issues.
 

8LegsMomWannabe

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I should have proofread my previous post. Awiec became Alice once autocorrect was done with it. Sorry about that Awiec!

Very interesting. What you described about the Great Pyranees is similar to how my parents and the breeder they work with deal with a puppy that ends up with long hair. That's outside the GSD breed standard and thus cannot be shown, so when a dog throws a long coat, that puppy is sold as a pet.

I'm sure you can do that with pretty much any animal or plant you're breeding.

I wonder if, in order to have "elite" tarantula lines, a breeder would have to keep all offspring rather than let slings go all over, until the bloodline is well established, to prevent slings they get from their spiders from being bred until enough generations have passed that the weaklings are weeded out of the bloodline? Easier said than done, I'm sure, since a clutch can produce at least a couple hundred slings, the survivors of which need separate enclosures. But considering you can't exactly spay and neuter a spider, you can't sell those with traits you don't want passed and be guaranteed that spider won't be bred and the traits passed anyway. So it seems you either keep all slings indefinitely to control which get bred and which don't, or sell slings and accept that something might be passed that you hope wouldn't be.

Or is a situation where any tarantula who has genetic traits/weaknesses that would be undesirable to pass, would pretty much be guaranteed to die before maturity or be sterile? In which case you wouldn't have to worry about where your slings go since the chances they'd pass weak genes would be slim to none.
 
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