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Sword play. In a slow-moving tropical river deep in the canyons of Mexico’s Sierra Madre, a female swordtail catches sight of an ultraviolet flash, signaling that a male swordtail is swimming nearby. Their dance of courtship begins. Gil Rosenthal, a CAS assistant biology professor in BU’s Marine Program (BUMP), studies such private visual communications — private because other species of fish, most notably the main predator of the swordtail, the Mexican tetra, are unable to see the ultraviolet light that shines in stripes running along the flanks of the swordtail. Rosenthal’s research suggests that such communication plays an important role in the evolutionary development of new species.

Often the traits that make a member of a species attractive to a mate, such as bright colors, conspicuous markings, or large size, also make it more noticeable and therefore more vulnerable to predators. But attributes visible only to prospective mates and not to predators confer an evolutionary advantage that makes the males more likely to survive, mate, and pass on such attributes to their offspring.

To test the ultraviolet markings as a means of private visual communication, Rosenthal and colleagues at the University of Texas, Austin, studied swordtail populations in two geographically diverse species: one in an area with a high density of predatory tetras, the other in an area with fewer predators. The researchers found that swordtails in the area with numerous tetras were more likely to have ultraviolet ornamentation than those in the safer area. They also confirmed that the predators were not attracted by the ultraviolet ornamentation and established the role of the markings in sexual signaling by showing that they were more prevalent among males (the signalers) than females (the receivers).

The work is an important part of Rosenthal’s overall research, which focuses on the evolution of the mechanisms animals use to communicate and on how animals choose their mates. It was published in the May 2003 issue of the Proceedings of the Royal Society of London.

Caution: baby on board. Thalidomide, a medication frequently prescribed outside the United States in the late 1950s and early 1960s to alleviate nausea in pregnant women, caused thousands of children to be born with devastating birth defects and led to a heightened concern about the effects of prescription drugs on the fetus. However, there has not been similar concern about the effects of over-the-counter drugs on fetal development, says Allen Mitchell, a MED professor and director of the Slone Epidemiology Center, in an article in the New England Journal of Medicine entitled “Systematic Identification of Drugs That Cause Birth Defects — A New Opportunity.”

For more than 25 years, Mitchell and his Slone colleagues have been studying the connections between medication use and birth defects. A recent study, for example, describes a possible link between two common medications — aspirin and pseudoephedrine (commonly sold as Sudafed) — with a rare gastrointestinal defect requiring surgical repair immediately after birth. They have also associated certain cardiac defects with the use of trimethoprim, an antibacterial often found in drugs prescribed for urinary tract infection.

According to Mitchell, currently available over-the-counter medications are unlikely to pose the kinds of risks associated with thalidomide. If they did cause birth defects, it would be infrequently. But because they are consumed so widely, they may in fact present a greater overall public health danger than the high-risk medications that receive medical and public attention. Studies by the group reveal that over-the-counter drug use during pregnancy is common and has been increasing — both in the number of people using them and the amount used — over time.

“Though a number of individual research programs have been established to generate and test selected hypotheses . . .” Mitchell writes, “these programs have not had the mission or the resources for the systematic and routine study of the risks and safety either of drugs newly introduced to the market or of those most commonly used in pregnancy.”

He urges the Food and Drug Administration to establish such a program, funded with proceeds from the Prescription Drug User Fee Act, first passed by Congress in 1992, which authorizes that fees collected from the pharmaceutical industry be used to enhance the drug-review process. “We can and must develop an efficient, comprehensive, ongoing system,” he writes, “that will identify and quantify the risk of birth defects posed by the large number of prescription and over-the-counter medications that are available now and that will be available in the future.”

The article was published in the December 25, 2003, issue of the New England Journal of Medicine.

"Research Briefs" is written by Joan Schwartz in the Office of the Provost. To read more about BU research, visit


15 May 2003
Boston University
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