Justin Rhodes has been interested in researching and studying the behavior and habits of clownfish for quite some time. Recently, he captured—in HD—the circle of clownfish life.
Rhodes has several tanks of clownfish in his research lab at the Beckman Institute, where he is a full-time faculty member of the NeuroTech Group. Thanks to an HD camera and perfect timing, Rhodes captured a video of the clownfish mating and then the hatching of the larvae, a feat not many have accomplished.
“The video at this resolution and quality is rare. You can find other similar videos of clownfish sex, but not this quality,” Rhodes said.
In the first part of the video, the female clownfish can be seen depositing eggs onto a rock. The male then swims over the eggs to fertilize them. The fertilized eggs take nine days to mature. During this time, the clownfish painstakingly care for the larvae, though their parental care instincts fade after the babies hatch.
“The parental care is very dramatic,” Rhodes said. “The male spends all his time fanning and caring for the eggs, and when they hatch both parents very aggressively fan and bite at the eggs. The video also shows the female eating one of the larvae as they hatch, which is interesting because it shows that as soon as they hatch they are fair game, and the instinctual nature of the parental care fades away.”
Clownfish only hatch at night, so Rhodes took special measures in order to capture this process.
“In order to simulate nighttime, we turned off the lights, but still captured the video with the help of a red light,” Rhodes said. “Clownfish eggs hatch at night to avoid predation. Their parents protect them when they are eggs, but after they hatch they are very vulnerable. They need to swim up to near the surface where the plankton is.”
The survival rate of the clownfish babies in the lab was quite high compared to those in the wild. The normal survival rate in the wild is very low—less than 1 percent survive. In the aquarium, the researchers can keep close to 90 percent alive.
Rhodes has also been featured in a previous video on clownfish, in which he discussed the interesting phenomenon of clownfish changing their sex if reproductively necessary. To put it into perspective, if the movie producers of Disney’s Finding Nemo had created a biologically accurate movie, the storyline certainly would have been quite different. After Nemo’s mother died, Nemo’s father would have become his mother, and then Nemo would have become the male to complete the pair—an interesting plot twist to be sure.
Rhodes’ current research with the clownfish is to study how this sex change happens by looking at how specific chemicals in the brain regulate the establishment of dominance in males and how these chemicals ultimately change their gonad from a testis to an ovary.