Evolution is a rich and dynamic process. The species reacts to pressure in a variety of ways, most of which decrease to find food, avoiding some other food and attracting a helper. To solve the latter, the animal kingdom is filled with fantastic, strange and charming adjustments. Ostracod bioluminescent security displays may include all three.
Ostrakodes are peculiar animals. These crustaceans do not have more than sesame seeds and have shellfish shells and often lack gill. Like many marine creatures, several ostracodes use bioluminescence to avoid predators and attract members. This last use attracted the attention of UC Santa Barbara's PhD student Nicholai Hensley to better understand the interaction between biochemistry and evolutionary change.
To create your own incoming light display, cypridinide ostracode squeezes a little mucus that is injected with the enzyme and reagent, and then swim away from the glowing orb to re-act. The result is fuzzy ellipse trails, or water-column hanging ceilings. And each of these pulse lengths is a key component of the show performance. Some of them are fast, such as an old fashioned flash, said Hensley, while others are in the water.
In the classic scenario, you expect to find a clear correlation between how long the flash lasts and the responsible enzyme structure, Hensley said. "And it's true for some species, but it doesn't apply to all species."
Instead, Hensley and his colleagues found that the two mechanisms affect the duration of the pulses of light. An animal that uses enzymes with a slower rate of reaction will produce a longer shine, but also a squeezing out of a larger amount of reagents that will release the enzymes for longer. Both of these are different combinations for different species.
"It was one of the amazing results we got from our paper," Hensley said. Team discoveries appear in the Royal Society magazine Processes B.
This discovery was partly related to the animal group Hensley who chose to study. Because ostracode radiates its light, Hensley was able to study chemistry separately from the animal's own behavior. Contrast this with the fireflies in which the reaction takes place in their body. As a result, it is in line with animal behavior control all the time, explained Todd Oakley, Professor of UC Santa Barbara Department of Ecology, Evolution and Marine Biology, and Hensley Advisor and Coauthor. "We can get more chemistry specifics because it's outside the body," he said.
The relationship between the two mechanisms can even affect the future development of different species. For example, if one species tends to move for longer pulses, they can drive up to the maximum enzyme capable. Without the ability to make the enzyme more effective, this species can develop to get more chemicals in the impulse to get a longer flash.
Hensley is currently studying how some enzyme changes affect its ability to produce light: it makes it faster, slower, or not working at all. He also hopes to restore the group's ancestral enzyme and check its functions to see how it can differ from those used today by animals.
At the same time, the team addresses the behavioral aspects of the ostracod mating display. For example, they want to determine how many pulse lengths are important for women with ostracod compared to aspects such as distance or direction. Some species synchronize their images when surrounded by other men, creating a delightful underwater light show. Hensley plans to take a closer look at this behavior in collaboration with colleagues at the University of Kansas.
"Just describing how this diversity is, is our goal," said Hensley, "and it can give us an insight into how it actually happens."
Microscopic shrimp desires highlight the evolutionary theory
Nicholai M. Hensley et al., Phenotypic Evolution, Based on Current Enzyme Function in Marine Firefly Bioluminescent Solar Signals Royal Society B: Biological Sciences (2019). DOI: 10.1098 / rspb.2018.2621