Scientists at the University of Alabama campus in Birmingham in their study of a tiny (1 millimeter) nematode, C. elegans, a worm which has long been a focus of scientific study for its easily elucidated biological functions, have discovered a fascinating aspect of the worm’s sexual activity. Although most of the worms are hermaphrodites (contain male and female sexual functions) there are males who produce sperm and who mate with the female side of the hermaphrodites. The research demonstrates that the environment causes the worm receiving the sperm to produce chemicals, which hinder or aid the travel of the sperm to the egg and therefore control fertilization of the egg. A female in receipt of environmental information informing “her” that fertilization is not a good “idea,” such as too much crowding or not enough resources, will mate with the male but produce these chemicals. In the words of the authors of the paper, which appeared in the May 16 issue of Science this year and summarizes their findings: “……. female environmental perception can have strong effects on sperm function.” The authors point out that this mechanism of control of the consequences of mating was an early output of evolution and may likely be at work in higher animals, such as infertile human couples for one example.
In the same issue of Science, there is a frightening headline: “Crippling Virus Set to Conquer Western Hemisphere.” The virus, called by the strange name, chikungunya, was discovered to have traveled from its source in East Africa by the same mosquito, Aedes aegypti, that causes Dengue Fever with the virus carried from place to place by tourists from infected areas who are bitten by this mosquito. The spread is thought to have begun with French tourists to La Reunion in the Indian Ocean bringing the virus to other destinations where the tourists are then bitten by Aedes aeqypti at their destination. Investigations of the path of the infection have taken the virus now to the Caribbean and to Brazil where the many tourists attending the World Cup will inevitably spread the virus widely. The virus is known to cause fevers, rashes and painful crippling to joints such as fingers, elbows, toes, ankles and knees, which can sometimes last for years and gives rise to the name of the malady. In the Makonde or Bantu language, kungunyaia, means “that which bends up,” which describes what is observed in someone afflicted. In the absence of a vaccine, not yet available, control of the mosquito is the only certain way to stop the spread of chikungunya. However, Aedes aegypti breed all over the place, flower pots, plastic containers, old tires, any place with a bit of water, and bite people near to where they breed. They are what is called a “local vector of disease.” The Science article quotes Paul Reiter, a medical entomologist at Institut Pasteur in Paris, who based on the local breeding of the biting mosquito concludes: “There is just very little we can do about it. The mosquito wins.” That would be true if we are looking for large-scale control. However, I have some information from my own scientific work that may help. Jeff Singer, a doctoral student in my laboratory in the late 1980s wrote a thesis in which we investigated African folk tales about control of mosquitoes by a species of marigolds. We published the results arising from our collaboration with the president of the American Mosquito Control Association, Don Sutherland, in a paper, which has been widely quoted but not yet put to practical use: The Larvicidal Activity of Tagetes Minuta L. Toward Aedes Aegypti (L); M.M. Green, J.M. Singer, D.J. Sutherland and C.R. Hibben, J. Am. Mosq. Control Assoc., 7 (2), 282 (1991). The research showed that small amounts of the oil of this marigold (which can be obtained by simply steaming the cut up plant) in small amounts of water, such as where the Aedes aegypti breed, will kill the larvae of the mosquito causing chikungunya and dengue. The plant can be easily grown in one’s garden.
