Female anglerfish with a parasitic male fused to the underside of her body

Deep-sea anglerfish are unique and unusual for many reasons. They have strangely shaped bodies with horrifying teeth, attract prey using a lure attached to their snouts, and reproduce by fusing their bodies with their mates. Now, a new study suggests that these anglerfish have modified immunity genes that make this form of sexual parasitism possible.

Deep-sea anglerfish are commonly found below depths of 1,000 feet. Light, food, and mates can be hard to come by in these environments, so anglerfish have adopted a unique strategy to produce offspring. Tiny male anglerfish, which can top out at 1 centimeter in length, will attach to female anglerfish that are many times larger than they are. This arrangement can be temporary or permanent, depending on the species. But, in some cases, the skin, veins, gills, and stomachs of the two fish will connect during the mating process and they will become fully enjoined.

Such an event should trigger an aggressive immune response, such as when the body rejects an organ transplant or detects a pathogen. That anglerfishes do not have such a response could suggest that male and female anglerfishes (1) share similar genetics that allow them to harmoniously connect or (2) are genetically adapted to suppress their immune responses when they mate.

Genetic analysis by the scientists involved indicated that there is a consistent difference in immunity genes between species that temporarily attach versus those that permanently attach. Specifically, when looking at a group of immunity genes known as MHC genes, temporarily associated pairs had a greater diversity of these MHC genes compared to those that become permanently affixed to one another. Additionally, species that do not form such attachments had aicada genes, whereas intertwined species lacked this aicada gene.

Reduced genetic variation indicates that species whose mates fuse together may have evolved so that mating does not compromise their health or chances of successfully reproducing by triggering an immune response. It is unclear whether sexually parasitic mating itself has driven these changes in immunity genes or if there are other underlying causes. But, the multitude of unique adaptations that anglerfish possess means that there are many more questions waiting to be answered.

See more here:
Sexual Parasites And Altered Immune Systems Help These Deep-Sea Fish Mate - Forbes

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