Chelsea O. Bennice ^1,2* Lauren Krausfeldt ^3,4 W. Randy Brooks ^1,2 Jose V. Lopez ^3,4

• ¹ Florida Atlantic University, Boca Raton, United States
• ² Charles E. Schmidt College of Science, Florida Atlantic University, Boca Raton, Florida, United States
• ³ Guy Harvey Oceanographic Research Center, Nova Southeastern University, Dania Beach, Florida, United States
• ⁴ Halmos College of Arts and Sciences, Nova Southeastern University, Dania Beach, Florida, United States

Microbial communities play a crucial role in the physiology of animal hosts; however, little is known about bacterial symbionts with the group cephalopods, specifically octopuses, and the function of these symboints. The goal of this study was to determine if octopuses have a unique skin microbiome. The skin microbiome of two sympatric octopuses (Octopus vulgaris and Macrotritopus defilippi) was compared with the surrounding environment, sediment and seawater, to determine if octopus have a unique skin microbiome. High throughput sequencing of the bacterial 16S rRNA gene (V3-V4 region) amplicons was performed using an Illumina MiSeq. Sediment showed the greatest Alpha diversity followed by octopus then seawater. Beta diversity revealed a difference in microbial composition between the octopus skin microbiome and sediment and seawater. While phylum Bacteroidetes appeared rare in environmental samples, it was most abundant for the octopus skin microbiome with the majority of the bacteria comprising the family Flavobacteriaceae. Proteobacteria, the largest group of bacteria, also constituted the octopus skin microbiome. Many of these groups occur on both octopus species; however, certain taxa differed in relative abundance between octopus species and may show species-specific host selection. Several bacteria that were identified for the octopus skin microbiome have been isolated from other marine animal hosts, identified as biodegraders and/or produce pigments and squalene, or act as predators of other bacteria. These groups may play a role in defense against environmental stressors or pathogenic bacteria. This is the first study to characterize the skin microbiome in two wild sympatric octopuses. Due to the importance of bacterial symbionts, this can provide insight to the physiology, behavior, ecology, and ultimately the health of these important animals in marine environments as well as care in captive or laboratory settings.