If a queen lays a fertilized egg, it will become a female worker or, potentially, a queen; if she lays an unfertilized egg, it will become a male. Each bee egg develops in one of a pair of small tubes (ovarioles) that make up the queen's ovaries, and once the egg is fully formed, it moves through the oviducts into a tubular passage (the lumen). A lifetime supply of sperm is stored by the queen in a little globular sac (the spermatheca) in her genital tract, and the queen controls the release of the sperm, enabling her to choose to lay an unfertilized egg or one that has been fertilized. When drones are needed in the colony, she will lay some unfertilized eggs. This peculiar system of reproduction is known as haplodiploidy because the drones are haploid, meaning they have half the normal chromosome content, and the queens are diploid - with a full set of chromosomes - like most animals.
But Soochin Cho and colleagues established that it is not quite that simple. In humans, sex is determined by the combination of sex-determining chromosomes derived from both parent's sets of genes (XX for females, XY for males). In the honey bee, specific combinations of different versions (alleles) of a sex-determining gene determine the sex of the offspring. If the bee has two different alleles, the sex-determining gene will be female; if it has only a single version of the gene, it will become a normal, fertile male.
But if the queen has mated with a male who has a version of the sex-determining gene that is identical to hers, the fertilized eggs produced from his sperm that have two identical sex-determining genes will yield sterile male offspring, and these drones will be eaten by females in the colony since they cannot reproduce and therefore serve no purpose. Multiple matings reduce the proportion of sterile males that will be produced because not all mates will have a matching sex-determining gene.
There is no election process to become the new queen: she is not chosen, but presents the best traits among the queens that emerge. Once the old queen has swarmed, the first virgin queen that emerges from her cell is soon ready to take over as the reproductive focus of the colony. She begins signaling her presence with audible vibrations, which sometimes are enough to prevent any other virgin queens from emerging. This queen may also kill other queens in their cells before they can emerge. If another virgin queen manages to emerge, there may be a fight to the death between the queens. The departing queen is guided by a group of as many as ten or twenty thousand worker bees in a primary swarm. If more than one new queen emerges in the old colony and the first to emerge does not kill the others, there may be subsequent smaller "after" swarms, each led by a new queen.
Honey bees cannot mate with other types of bees, like bumblebees or carpenter bees, but all of the breeds of Apis mellifera, the European honey bee, can interbreed. And beekeepers can deliberately produce hybrids to improve disease resistance and honey production and to create more prolific, gentle strains. Some of the advantages in the initial generations of deliberately created hybrids may be lost as subsequent generations crossbreed naturally. Some hybrids may become unacceptably aggressive or may have developmental defects.
Can bees be artificially inseminated? Answer: Artificial insemination of bees, known by beekeepers as instrumental insemination, was first demonstrated in 1927 after over one hundred years of failed attempts using all sorts of imaginative techniques. Beekeepers are always trying to improve their stock by developing bees that are more disease resistant, better honey producers, and more docile. As the natural survival of honey bees becomes more difficult, insemination is being used for research and breeding experiments to try to uncover the causes of the decline. Researchers also use this technique to create colonies with certain characteristics that they are interested in studying.
Collecting a drone's semen may be accomplished by holding him by the head and thorax and stimulating the abdomen. It may be necessary to apply gentle pressure to the tip of the abdomen in order for the endophallus (internal genital tract) to be everted so that the semen can be exposed and collected. If this approach is not successful, the head and thorax of the drone must be crushed and the endophallus forced out by firmer pressure on the abdomen. The queen is placed in a holding tube and anesthetized with carbon dioxide, and the semen is injected into her reproductive tract. It may seem cruel that some drones are killed in the collection process, but since they die soon after mating naturally, their loss does not cause negative consequences to the colony.
Our website is not responsible for the information contained by this article. Articleinput.com is a free articles resource thus practically any visitor can submit an article. However if you notice any copyrighted material, please contact us and we will remove the article(s) in discussion right away.
Note: This article was sent to us by: Nigel Arrison at 08172010
1. Effects on efficacy endpoints
All articles are property of their respective authors. Please read our Privacy Policy!
© 2009 ArticleInput.com.
Partners: Damenmode