A Game of Shrimp and Glow
Hi! My name is Stormie Collins, and I am a PhD candidate at Florida International University. I have been involved in processing samples collected from DEEPEND|RESTORE cruises since 2019, however, this is my first time getting to go to sea with the group! I am largely interested in the way that organisms perceive the world around them, and the associated adaptations they have evolved to survive within their environment. In the deep-sea, many organisms utilize bioluminescence; a process through which a chemical reaction produces light. My dissertation focuses on vision and bioluminescence in deep-sea shrimps. Being able to see the animals freshly collected allows me to observe color as they are in life and provides a better opportunity to consider bioluminescence across species as many light organs become invisible after animals are placed in preservative.
Shrimps can be bioluminescent through dermal light organs called photophores, internal photophores that arise as a modification of the hepatopancreas, or through a luminous secretion, which may also be referred to as “spew”. Among decapod shrimps, luminous secretions are most common, and many species use this as a defense mechanism to evade approaching predators. Dermal photophores are embedded within the cuticle and are obvious. Internal photophores are obvious in sergestid shrimp (see below), however, they are also present in other shrimps, where they are much easier to overlook, particularly in red pigmented shrimps. The caridean shrimp Plesionika richardi is documented to have internal photophores, however, they have never been previously observed in this species by our team. Upon collection of 2 P. richardi, observation of internal photophores were indeed confirmed (see below), and when looking for them, are obvious. It is likely that this has been overlooked as the red pigmentation sort of masks the internal organs and they are no longer visible in preserved material.
The most up-to-date count of bioluminescence depicts 94 independent origins across the tree of life, making this perhaps the most common form of communication on the planet. Though our current understanding of bioluminescence in shrimps with both dermal and internal photophores suggest they are used for counterillumination camouflage, I believe that the functional role of bioluminescence should be considered separately for each species. The presence of internal photophores in P. richardi provide an excellent example of how underestimated and overlooked bioluminescence may be in decapod shrimps, as well as many other marine organisms.
P.s.- the view from the ship is NOT too shabby ?