Lighting research sheds new light on the evolution of light response systems

Researchers at the University of Tsukuba have discovered that sea urchin larvae swim backwards and exhibit a ciliary response to intense light irradiation. Because it is difficult to detect ciliary responses in deuterostomes, they can be masked by more pronounced muscle activity, so by identifying the ciliated response to sea urchin light, the visual response of the animal to the naked eye It provides important information about the evolution and diversification of systems.Credit: University of Tsukuba

Light is essential for most life on Earth, and it is most likely that unicellular or small multicellular organisms first developed the ability to respond to light. But now, Japanese researchers have identified interesting behaviors in sea urchin larvae that may provide insights into the evolution of macroscopic animal photoresponsive tissues / organelles.

In a study published this month PLOS GeneticsUniversity of Tsukuba researchers, sea urchin Larva When exposed to strong light, it swims in the opposite direction (Light) Usually due to the effect of light on the neuronal pathways that cause the neuronal pathways to swim forward.

Photoresponse systems typically include a combination of photoreceptors (cells of the retina that respond to light), components of the nervous system, and organs that respond to neural impulses. These organs tend to be the muscles of most visible animals, and cilia (hair-like structures) play a role in microscopic aquatic organisms. Cili-based reactions probably occur first and then replace muscle-based reactions during the evolution of deuterostomes or more complex animals. However, the ciliary reaction is so subtle that it is difficult to identify.

“The cilia-based response to light is probably not well understood in deuterostomes. Muscle activity Professor Shunsuke Yaguchi, the lead author of the study, said, “Since sea urchins have free-living planktonic larvae that move mainly using cilia rather than muscles, they provide a valuable opportunity to investigate their existence and mechanism. A cilia-based reaction in deuterostomes. “

To do this, researchers used a powerful light source to irradiate the larvae from different types of sea urchins in a dish of seawater and used a microscope to observe their behavior. Prior to exposure to light, the larvae remained primarily on the surface of the water.

“The results were interesting,” says Professor Yaguchi. “The larvae quickly fell off the surface and some swam backwards. Similar behavior was observed in some species, suggesting a common response among groups of sea urchins.”

To visualize and quantify behavior, researchers added diatoms, or unicellular algae, to the dish. The movement of these diatoms reflects the changes in water flow caused by the beating of the ciliary body from the larva, indicating that the ciliary reaction is present and functioning in the sea urchin.

Given that cilia are present in histiocytes and promote important functions in most organisms, including humans, the identification of this cilia response in uni is useful for understanding the mechanisms of human behavior and emotions that respond to light. May be important.Clarify these signaling pathways Sea urchin Therefore, it sheds new light on the evolution and diversification of optical response systems.

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For more information:
Shunsuke Yaguchi and other planktonic sea urchin larvae change their swimming direction under strong light irradiation. PLOS Genetics (2022). DOI: 10.1371 / journal.pgen.1010033

Quote: Lighting research, optical response system acquired on February 10, 2022 from https: // (February 10, 2022) Shines a new light on the evolution of

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Lighting research sheds new light on the evolution of light response systems

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