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This is no doubt a simple question.

I was reading about Sterile Insect Technique where sterile males out-compete non-sterile ones to mate with females and thus reduce the population.

My question is - why don't the females just re-mate after they don't reproduce?

I'm assuming that the number of sterile males will be much less than the existing male population.

Is it because my assumption is incorrect and there are more sterile males? Or my assumption is correct and given the life-cycle of the organism, the females have only once chance to mate? Or something else?

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Sterile insects are typically produced by radiation. A sufficient dose is used to cause substantial DNA damage in the gametes of the males. However, this doesn't mean the sperm are completely non-functional.

In fact, it is important that the sperm are functional and simply contain dominant-lethal mutations at a sufficient probability (Robinson, 2005 describes this in detail as well as the dosing strategies to optimize the desired outcome).

The males still mate and fertilize the eggs of the female; it is only later that the eggs will eventually fail to develop, but there is no way for the females to be aware of this (nor much that can be done even if they were - once the eggs are fertilized they cannot be fertilized again).

It is also important to release a sufficient population of sterile males to impact the population. Depending on the species, it may or may not be necessary to completely overwhelm the existing population, but a typical goal seems to be 10-100x the native population. By raising males in laboratory conditions, it may be possible to produce a larger population than would typically survive to mating age in the wild.


References:

Cockburn, A. F., Howells, A. J., & Whitten, M. J. (1984). Recombinant DNA technology and genetic control of pest insects. Biotechnology and genetic engineering reviews, 2(1), 68-99.

Klassen, W., & Curtis, C. F. (2005). History of the sterile insect technique. In Sterile insect technique (pp. 3-36). Springer Netherlands.

Robinson, A. S. (2005). Genetic basis of the sterile insect technique. In Sterile Insect Technique (pp. 95-114). Springer, Dordrecht.

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    $\begingroup$ Finally some quality content. What a relief. +1 $\endgroup$ – AliceD Mar 12 '18 at 22:46
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    $\begingroup$ @AliceD Haha I've been trying where the questions warrant it. Unfortunately it seems most of my answers have gone unnoticed lately, based on the very low total view counts in the 30-40 range even after several days. Just not much of a voting population around lately. $\endgroup$ – Bryan Krause Mar 12 '18 at 22:54
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    $\begingroup$ Good answer, but "In the cases I am aware of, this technique is used with species that only produce one batch of offspring" - the main case I'm familiar with is mosquitoes, where this isn't true. $\endgroup$ – arboviral Mar 13 '18 at 8:57
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    $\begingroup$ @BryanKrause As far as I know females have one receptive period, and normally mating is inhibited once sperm are transferred (hence mate once), but you sometimes get incomplete sperm transfer and therefore multiple mating (cambridge.org/core/journals/bulletin-of-entomological-research/…). Males can mate with several females. $\endgroup$ – arboviral Mar 13 '18 at 16:37
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    $\begingroup$ No worries. I'll leave it removed. I think if anything it distracts from the main point of my answer, which is that these sterilization strategies are predicated on making sterile embryos rather than males completely incapable of mating. $\endgroup$ – Bryan Krause Mar 13 '18 at 16:39

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