Why is the Iconic Bioluminescent Dinoflagellate Noctiluca not Bioluminescent along the West Coast of the USA?

The dinoflagellate Noctiluca scintillans was described as ‘animalcules’ in the 1750’s using early microscopes and is now known as a major source of bioluminescence in the world’s oceans. But reports going back to the 1960’s describe non-bioluminescent Noctiluca along the west coast  of the USA. In this study, published in the November 2019 issue of Limnology and Oceanography, an international team of scientists including Dr. Latz investigated the mechanisms behind the loss of bioluminescence in this Noctiluca population using molecular, cellular and biochemical analyses of isolates from different geographic regions. Non-bioluminescent Noctiluca lacked luciferin, the substrate molecule for the bioluminescence chemical reaction. The gene for the catalyst luciferase was present but was not expressed as mRNA, most likely because of potentially deleterious mutations. Phylogenetic analysis based on the large subunit rDNA showed no divergence between non-bioluminescent and bioluminescent populations; the only morphological difference was that non-bioluminescent cells were 43% smaller. The ecological significance of the loss of bioluminescence in this population is unknown, as dinoflagellate bioluminescence serves in predator avoidance. The loss of this important functional state provides an opportunity to investigate the evolutionary and ecological mechanisms involved in intraspecific variation in natural populations.

This article is highlighted on the Scripps Oceanography web site.