Award: DEB-1542679

Below are brief highlights of the results from our project. A more complete report can be found at https://jellywatch.org/nsf-deepc.pdf Transcriptomes -- generated by sequencing messenger RNA -- provide a snapshot of all the genes that an organism is using at a given time. Once we have generated high-quality transcriptomes from rare deep-sea species, we can explore a wide diversity of adaptations without collecting more specimens. Our transcriptomes from shallow tropical and Arctic specimens as well as from species living at 4000 meters depth, enabled many of the studies that we have undertaken for the DEEPC project. Of particular interest were metabolic enzymes: proteins that allow animals to respire and move. We identified, cloned, and generate proteins from deep and shallow species to test how their efficiency differed under high pressure. Working initially with the species Hormiphora californensis, we published the first chromosome-scale ctenophore genome, in which more than 99.7% of the sequence was assembled into 13 chromosome pairs. This enables whole new types of analyses going forward with this emerging model organism. When people talk about DNA fingerprinting of animals, they typically employ the "barcoding" gene, cytochrome oxidase 1 (COI). Until now, this gene has been barely usable for ctenophores, because their mitochondria, where the gene resides, are so different from other animals. We created tools that let us sequence the full range of ctenophore diversity, and increased the number of species represented in GenBank by more than 5 times. Using samples collected from tropics to polar to deep-sea habitats, we tested how ctenophore lipid membranes maintain function at low temperature and high pressure. Surprisingly, we found that the adaptations in chain length and number of double bonds were different for temperature and for pressure. Using the synchrotron at Cornell University, we examined the x-ray scattering of lipids under high-pressure, revealing for the first time exactly how the structures of the lipids change when pressurized. This will lead to new insights on the mechanisms that allow ctenophore cells to function down to 7000 meters. As part of these experiments, we built a computer-controlled high-pressure cuvette chamber. This device allows us to characterize the properties of enzymes and lipids while sweeping across a range of environmental conditions. This project gave research experience and training to many diverse scientists, and allowed more than 50 people to experience deep-sea fieldwork. Results were covered in many high profile media channels, raising public awareness of these fascinating animals. In total, using genetic and biochemical methods on ctenophores from the tropics to the deep sea, we learned a great deal about how life adapts to a range of challenging conditions, and laid the foundation for many future studies. Last Modified: 12/13/2021 Submitted by: Steven H Haddock