Sperm rely on heat to find egg

According to a recent research, sperm move towards an egg using temperature sensors. The site where fertilization occurs is warmer than other sites in the female genital tract and they can sense this temperature difference to find their way to the egg.Researchers from Weizmann Institute, Rehovot, Israel studying the details of rabbit reproduction, found that rabbit sperm wriggle towards warmth. The authors point out that the egg sends out a chemical message, but this can only be sensed when the sperm are relatively close to the egg. Another potential cue for sperm guidance is the ovulation-dependent temperature difference within the female genital tract. To check to see if this was the cue being used by rabbit sperm, the researchers ran a test in the lab. They designed a device that had two dishes connected by a narrow bridge. In one part of the experiment, the temperature in the dishes was kept the same while in a second experiment, the researchers made the temperature in one dish 2 degrees Celsius warmer than the other. They found that the sperm were more likely to move from dish to dish if they were put in the cooler dish and allowed to navigate their way to the warmer one. They also reported that the temperature at the site where eggs would normally be fertilized is approximately 2 degrees Celsius warmer than other spots along the path that sperm must traverse to meet up with an egg. While the results are interesting, they may not apply to human sperm.