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Re: KHV resistance in feral carp

Posted by Fishbreeder on 5/5/2009, 5:53 am, in reply to "Re: KHV resistance in feral carp"
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Diploid, having two complete sets of chromosomes, the usual condition for most organisms that use sexual reproduction. One set from each parent. A normal, diploid fish (or anything else) is viable and reproduces sexually. Triploid, having three sets of chromosomes, usually results in a sterility. Grass carp (Ctenopharyngodon idella) sold in most states are sterile triploids. Triploidy can be induced many ways, but in the case of grass carp it is done at an early stage of cell division in the egg by compressing the egg up to 40,000 psi. It can also be done by heat or cold shock or by the use of chemicals like colchicine. The three sets of chromosomes do not match up and triploids are usually sterile. Tetraploids, (four sets) however, are usually viable. Hybrid, a cross between two different species. Usually, but not always sterile. Hybridization is done a myriad of ways, and sometimes occurs in the wild. Hybrids are normally diploid, but each set of chromosomes (one from each parent) may contain a different number of chromosomes per set and may not "match up" properly during cell division, resulting in sterility. Some hybrids are not sterile and some may be sterile in the F1 generation, unless a member of that generation is backcrossed to one or the other parent species. Examples of hybrids, a mule (horse x donkey), most sterile hybrids are referred to as "mules." A common hybrid in fish is the cross between a green sunfish (Lepomis cyanellis) and bluegill sunfish (Lempomis machrochirus). Sometimes this hybrid sunfish goes by the trade name "Georgia Giant." It is a sterile hybrid unless crossed back to one of the parent species, then the offspring are viable, but with reduced fecundity. F1 (first generation) hybrids many times exhibit hybrid vigor (better growth and health than either parent species). However, F2 (cross between two F1's) hybrids tend to be inferior than either original parent stock or F1 hybrids. Now I gotta go to bed, just loaded a Peterbilt headed for Phoenix with 111,000 "hybrid" (not true hybrids) Florida bass fingerlings. Crosses between sub species and varieties are not true hybrids, as they are the same species, but sometimes these do exhibit hybrid vigor to some extent. A cross between a dachsund and a poodle is not a hybrid, just as a cross between a sanke and a showa is not a hybrid. Brett

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Responses: Re: KHV resistance in feral carp - JR 5/5/2009, 11:45 am « Back to thread

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