Genetic Diversity in Cultures/Colonies

[Thomas]

Inbreeding has obvious adverse effects in mammals and other, more "complex", animals, and many say the same is true for arthropods and other invertebrates. If this is the case, is it best to keep multiple separate colonies of the same species and periodically switch out specimens between them to keep the inbreeding to a minimum? Would this keep the colony going for a longer amount of time, or does it really not matter so much.

I haven't really found any information regarding this and I'd really like to hear some opinions.

[platymeris]

It's an interesting question, I've been wondering about it as well. In some Phasmid (stick insect) species there is evidence that inbreeding by hobbyists has led to stock with reduced vigour eg Extatosoma tiaratum. I don't know if the same has been seen in roaches. Then again, when one considers that captive chinchillas today were supposedly derived from just 12 animals..

[rockpython]

My guess is that it would eventually turn bad... It may take a ton of generations, like with the cheetah, all cheetahs have genetic issues now... They are surviving but are permanently crippled. Roaches being the survivors they are, would probably weather the storm well, but I think it'd catch up sooner or later.

[Alex]

This is a really complex topic....I honestly do not know if we can use vertebrates in this discussion but here I go.

The roaches we have in captivity are heavily inbread so much so it's rather disturbing. Just for fun does anyone know when was the last time Dubia have been imported into the US? And we're they distributed to the roach breeders?

In nature if there is a animal with a genetic weakness either physical or mental, it would be disposed of as food for another or just death from no support. And whatever they had dies with them and they don't contribute to the wild gene pool. It's upsetting but painfully true.

In captivity we try our hardest to keep our captives alive and support them ALL to exist and breed in doing so they may carry the defective gene, it's very obvious in dogs, cats, and horses but happens with spider ball pythons "head shaking" HCll strain mice are highly susceptible to diseases, much more so than other strains.

I guess what we could do is be more more like Mother Nature and not allow the roaches with weak traits to procreate and make them a hereditary defect.

Now I have a couple questions: Do animals that come from island populations or isolated ranges suffer from hereditary defects? And are the simandoa the US just received screwed?

[Thomas]

I was reading a scientific article entitled Desiccation resistance among clones in the invading parthenogenetic cockroach, Pycnoscelus surinamensis: A search for the general-purpose genotype from 1995, and I coincidentally found some information regarding this topic.

"Our design does not allow us to estimate variance components in the sexual species. Instead, we are simply asking what desiccation tolerances a sample of adult sexual females and males exhibits compared to their parthenogenetic descendents. Although this culture of P. in&us has been maintained for approximately 50 generations in the lab, it still exhibits variability in body color and protein loci (Parker et al., 1977, unpubl. data) and, more importantly, shows no general inbreeding depression, having maintained high fecundity and fast development at 30” C (Parker, 1984; Niklasson and Parker, 1994)."

[thesavageprojects]

I wanted to touch on the rats, and mice for that matter. There are a ton of lab strains maintained in culture because they have defects. For exple strains can be ordered that have an increased incidence of cancer for cancer therapy research. (Albinos are handy for easily seeing blood and sores)

This topic illustrates the importance of culling and/or isolating roaches that are questionable. Luckily even in captivity animals with defects my not thrive and be out competed or rendered sterile from said defect. While it is possible that any one of our roach cultures my become corrupt. There isn't much of a need to keep multiple cultures of the same sp. since most species are readily available from other blatticulturists. One of the bonuses of this forum existing.

[Nicolas Rousseaux]

hi

we were talking about that a few weeks ago with a friend. We've noticed the same things in our colonies: a little colony tend to fail after a few generations, they stop breeding, and they need to get some new roaches to reproduce again.

In a big colony, it seems that this problem doesn't exist. The colony survive for years and years, with no blood addition.

[Keith]

In feeder colonies nobody can accurately keep track of how long each individual lives and what they die from, or lineage of each roach, ex if parents had any abnormal traits, just because there's too many roaches in an unnatural environment. Take dubia, it's said wild males fly, but have you ever seen a captive dubia fly, probably not, same as lifespan how long do wild dubia live, nobody knows.

We base what is normal and healthy on what we know from captive individuals.

If wild male dubia fly and ours don't we already negatively altered the species, clearly genetics did take over as captive individuals have no reason to fly. Finding gynandromorph and small individuals are common in large colonies, but these both are abnormal genetic traits size should be consistent and roaches that are half male half female, or winged females clearly isn't normal.

Then lifespan, usually large colonies always have dead roaches, but if they have everything they need and are healthy they shouldn't be dying.

I keep my dubia in a natural environment, I bred my own selectively (no inbreeding) and each generation added new individuals so no parents and children mated. I give them great food variety and decaying wood and leaves like they would eat in the wild. I can tell you what traits each parent had and what offspring got what trait.

I keep only the males and have them live over 2 years, I assume large colonies never see them live this long. I rarely found small individuals, all of mine were large and healthy like parents, and the one or two I did find acted differently and were more willing to try and take flight. I only had one odd death in a nymph, otherwise all offspring survived to adulthood and were normal and healthy.

To prove my case, I "adopted" and "bred" dubia, some from someone else's colony, and some from mine, both at same time. Males from another colony put in my natural tank did well but died about 6 months later even with the best of care. Males from my colony the same age are still alive. Nymphs I raised from my colony had perfect health. Nymphs from other colonies males did well when bred with my females I raised, so it appears genetic diversity and good environment fixes and health problems or inbreeding.

[Alex]

I agree and disagree with that Nicolas. I have had some species go with just 2 individuals and become a established colony. On the other hand I had started with 10 animals and they had a group and went a few generations and then just all mature a really slow down in breeding.

[Nicolas Rousseaux]

Alex, I think I haven't explained what I meant really well. Actually, I think that a big colony, when it's established, with thousands specimens, doesn't seem to suffer from inbreeding, and small groups, whan we always keep, for every generation, a same small amount of roaches, tend to stop reproducing. But you're totally right when you say that a colony can establish with a really few roaches to start it!

Keith, in my view, inbreeding is not tho only, and probably not the main reason to get small roaches, gynandromorph and so on. It happen with loads of other insects, such as phasmids, wich may be parthenogenetic. Sometime something fail within the egg, something during maturation, and sometimes just uncommon genetics.

All those kinds of weirds individuals can be found in nature, but they often die quickly, they haven't the good adaptations. But if the weird caracteristic is an advantage, then, it can reproduce, and yes, the babies can get that difference, that's just evolution.

As you said, in captivity, roaches have no reason to die quickly, so the strange individuals live even if they should have been eaten in natura. Their caracteristic may be kept in colonies, due to their reproduction!

[Thomas]

Thank you all for the thoughtful responses. This topic is pretty complicated. I, personally, like to feed off individuals who aren't "good" specimens (small hissers, "thin" or lethargic dubia, etc.) and try to introduce new specimens into other cultures when it comes to smaller colonies I have going. For instance, I'm thinking of setting up a third colony of G. lurida (I have one with producing normals and one with a couple of yellows who have yet to reproduce) to ensure myself a little more diversity so I can move individuals around when I feel the need.

This is why I love my P. surinamensis; they clone themselves, so I don't have to worry so much about any of these problems arising in their population