Bioengineering professor featured on "Sex in the Wild," a new PBS series on animal reproduction

How fast is dolphin sperm? This question is addressed in a new episode of “Sex in the Wild,” a multipart PBS documentary that aired on Aug. 6. The episode on dolphins and whales features UC San Diego bioengineering professor Michael Berns. Sex in the Wild is studying animal reproduction in “vivid detail.” A PBS film crew spent a day in the Berns lab last spring to examine orangutan and dolphin sperm that had been imaged and “trapped” in Berns’ pioneering laser tweezers. You can watch the complete episode on PBS.com.

Professor Michael Berns (left) tests the speed of dolphin sperm with veterinary scientist Mark Evans (right) on an episode of PBS' new documentary series "Sex in the Wild" that aired on Aug. 6.

In research published in 2007, researchers in the Berns lab, including then-grad student Jaclyn Nascimento, used the sperm-trapping technology to find evidence that supports the theory that speed and force matters in reproductive competition among primates who are highly promiscuous such as chimpanzees and rhesus macaques. 

The technology relies on the momentum inherent in laser light: when the path of laser light bends as it passes through a small transparent object such as a cell, some of the light’s momentum is transferred to the cell, effectively holding, or trapping it. The stronger the laser, the more firmly the cell is held. After a cell is trapped, the light intensity is reduced in a precise manner. Such a timed decay in laser power allows a trapped sperm cell to escape at the point at which its swimming force exceeds the trapping force. The adjustable laser tweezers and sperm-tracking software allowed the team led by Berns and his Nascimento to precisely and accurately measure swimming force and speed of hundreds of individual sperm cells from males of the four primate species: gorillas, humans, chimpanzees and rhesus macaques. 

Their research attracted the attention of the “Sex in the Wild” producers who were eager to see how the technology works and what it could tell us about orangutan and dolphin sperm.  Referring to the dolphin sperm, “It’s a lot faster than most of the species we looked at,” said Berns during the segment. They also demonstrated that salt water kills dolphin sperm instantly.

Berns is also a professor of biomedical engineering and founder of the Beckman Laser Institute at UC Irvine. He is currently on full time sabbatical at UC San Diego.