Gene might help sponges see

Scientists provide a glimpse at how simple multicellular organisms handle light

Some larval sponges search for a shady place to settle down, but they don’t have optic nerves or the genes that are important for vision in most animals. Now biologists have new insight into how sponges might see light.

In the eye cells of Amphimedon queenslandica larvae, a gene called cry2 is turned on. This gene makes light-sensitive proteins that may help cilia (purple) steer the sponge larvae toward or away from light. Sally Leys

Larvae of the sponge Amphimedon queenslandica have unique eyes made up of cells that contain pigment, a chemical that absorbs certain wavelengths of light, and cilia, which look like tiny hairs.  Right next to these pigmented cells are cells with high levels of activated cry2, a gene that makes light-sensitive proteins, Todd Oakley of the University of California, Santa Barbara and others report in the April 15 Journal of Experimental Biology.

These light-sensitive proteins could be involved in directing movement in cilia and steering these sponges.The finding could provide clues in how vision developed in these simple animals, Oakley says.

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