Bioluminescence Cruise: Vision in the Deep Sea: Blog 5
My name is Tom Iwanicki, I am a Masters student in Dr. John Taylor’s lab in Victoria, British Columbia, Canada. I am beginning a PhD in Dr. Megan Porter’s lab in Honolulu, Hawai’i this August. I was fortunate to be invited on this cruise out of Miami. My master’s research focused on fish vision, and this being chiefly a deep sea crustacean cruise, the learning curve on board has been a steep one! But with the help of the Frank, Bracken-Grissom, and Porter labs, I have already learned a lot in these past few days.
Vision is central to the human experience. We use it for foraging, predator avoidance, sexual reproduction, and it is important in the development of our culture. The fundamental molecular unit for vision is the opsin, a gene that encodes a light sensitive protein in the retina.
Humans have four visual opsins; one rod opsin, and three cone opsins. When the rod opsins are active our vision is like a black-and-white TV (greyscale). But when you turn up the light, something beautiful happens. The cone opsins become activated and enable us to accurately discriminate between wavelengths of light. This is colour vision. Vertebrates and invertebrates alike have evolved remarkably diverse sets of eyes. This is excellently illustrated by Dr. Danté Fenolio’s images attached to this post. The evolution of eyes and opsins intrigues me. The deep sea shrimp we are studying have three opsins – but you may be thinking, as I once did, that there is not much light in the ocean depths, right? What are these crustaceans doing with three opsins?
In fact, the deep ocean is illuminated with living organisms utilizing bioluminescence, and vision is vital to survival in the deep (read Charlie’s blog post to learn more about bioluminescence). The shrimp, Janicella spinicauda (pictured here), produces two forms of bioluminescence. When startled, they “spew” a cloud of bright, glowing blue light. This likely shocks whatever disturbed the unsuspecting Janicella and attracts larger predators to come to the rescue. Janicella also have a series of bioluminescent photophores lining their body that glow a bright – but different – colour of blue. The adaptive function behind these photophores is unclear. They may be defensive, similar to the spew, but alternatively, they may be used in communication. Shrimp possessing both the spew and photophore bioluminescence have one more opsin than their relatives that can spew, but lack photophores. Is this a coincidence, or are the photophore bearing shrimp using the extra opsin to distinguish the photophore light from other bioluminescence? That is one of many questions I hope to answer as I progress through my PhD.