© Cedarville University International Conference on Creationism. The views expressed in this publication are those of the author(s) and do not necessarily represent those of Cedarville University. Cserhati, M. 2023. Molecular baraminology of marine and freshwater fish. In J.H. Whitmore (editor), Proceedings of the Ninth International Conference on Creationism, pp. 181-205. Cedarville, Ohio: Cedarville University International Conference on Creationism. MOLECULAR BARAMINOLOGY OF MARINE AND FRESHWATER FISH Matthew Cserhati, 1300 Hollydale Drive, Fullerton, CA 92831 matthew.cserhati@cui.edu ABSTRACT A pertinent question posed to the Creation/Flood model is how different fish species could adapt to the drastic changes in water salinity that were inevitable due to the upheavals during the Flood that affected land animals as well as aquatic ones. Uniformitarianism sees difficulties in this since it projects the stenohaline status of many fish species today into the past. However, according to the Creation model, fish genomes may have been more robust and varied in the past, allowing for the euryhalinity of many fish kinds during the Flood. Euryhaline fish species could have had a more varied genetic machinery that allowed them to survive in saltwater or freshwater environments. Due to gene loss, this genetic machinery was then constricted, forcing fish to adapt to one or another narrower level of water salinity. Several factors influence adaptation to differing water salinities, the most important being the presence or absence of various ion channels, including the sodium-potassium ATPase (NKA), Na+/K+/2Cl- cotransporter 1 (NKCC1), cystic fibrosis transmembrane conductance regulator (CFTR), apical Na+/H+ exchanger 3 (NHE3), and Na+/Cl- cotransporter (NCC). Other factors include the presence of different predators, parasites, and pathogens, water temperature, pH, and oxygen content, lighting, and even sexual factors. All these factors play a role, for example during the landlocking process, whereby fish species transition from facultative migration patterns involving adaptation to varying salinities to obligatory adaptation to freshwater environments. The mitogenomes of 655 fish species belonging to nine orders (Acipenseriformes, Anguilliformes, Beloniformes, Characiformes, Clupeiformes, Cyprodontiformes, Elasmobranchii, Pleuronectiformes, and Salmoniformes) were analyzed. Overall mtDNA sequence similarity was determined to cluster these species into putative holobaramins. A total of 47 putative holobaramins were discovered. The distribution of saltwater, brackish water, and freshwater species was noted in all groups. A total of 22 (46.9%) of all groups were found to be euryhaline, where a group was determined to be euryhaline if at least one of its species was known to live in all three water environments. This indicates that some fish baramins are still euryhaline, in the process of adapting to narrower levels of water salinity (either salt or freshwater). KEYWORDS freshwater, brackish water, saltwater, adaptation, molecular baraminology, Genesis Flood, mitochondrial DNA INTRODUCTION After the Flood, the Earth had become a very different place for organisms to inhabit. Entire biomes and ecosystems had changed during the massive upheaval, and aquatic environments were definitely not an exception. The Flood was a violent geological process that drastically changed the surface of the Earth, including its water sources, such as oceans, lakes, and rivers. The erosion of the different landmasses and volcanic activity would have drastically increased the salt level of the post-Flood waters compared to the preFlood waters. This means that fish would have had to rapidly adapt to changing water salinities. Skeptics raise the question, how could aquatic organisms, such as fish, survive such drastic changes in salinity? Elevated salt levels disrupt the osmotic balance within cells and draw water out of them. On the other hand, hypoosmotic conditions tend to bloat cells, which is also undesirable. How did freshwater and saltwater fish survive the Flood? Is it even possible for fish to adapt rapidly between saltwater and freshwater? What kind of biological mechanism makes this process possible? What is the distribution of freshwater and saltwater fish species in different fish baramins? Several initial explanations present themselves. First, changes in salinity may not have been that rapid for fish and other aquatic animals to be able to survive. Experiments performed by Smith and Hagberg (1983) on the blue damsel (Abudefduf uniocellatus), a species of marine reef fish, tested the organisms’ capability of surviving at different levels of salinity. Fast rates of dilution (15 0/00 salinity/hour) resulted in the loss of the fish’s locomotion at 0.88 0/00 salinity, where freshwater is defined as less than 0.5 0/00 of dissolved salts. 9th 2023
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