The Unusual Mating Strategy of Monkfish May Have Contributed to Their Evolutionary Success

The unique sexual strategy of deep-sea anglerfish may have helped their ancestors move into entirely new habitats, allowing for the incredible diversity of species that thrive today.

chase brownstein Researchers at Yale University have reconstructed the evolution of more than 160 species of deep-sea anglerfish (keratioids). Known for their large jaws and bioluminescent lures, serratioids are a subgroup of the larger order of the anglerfish family, which also includes monkfish and other bizarre benthic creatures such as monkfish, sea toads, and batfish. Using genetic sequencing, the researchers discovered that the ancestors of keratioids walked on pectoral fins at the bottom of the deep ocean. But 55 million years ago, some creatures began swimming in the ocean's vast deep-pelagic, or “midnight,” zone. There, over a period of just 5 million years, they became more genetically diverse than their ocean-floor relatives.

He said this is strange because the ocean floor and coral reefs typically have a greater variety of species. elizabeth miller At the University of California, Irvine. Environments with many topographical features lend themselves to the specialization of organisms. But with constant temperatures and vast expanses of waterless ocean, “the deep pelagic zone is truly the most homogeneous habitat on Earth,” she says.

Miller and her colleagues Monkfish species family tree Although her team and Brownstein's team used different methods, their studies are largely consistent regarding the timeline and scale of deep-sea monkfish diversification.

Brownstein's team found that this surprising diversification may be due to the serratioids' parasite-like reproductive strategy. That is, the small male uses his jaws to attach to the much larger female until he is ready to mate. In some species, the two can even permanently fuse together, such as sharing a circulatory system. This unique mating technique could theoretically benefit deep-sea monkfish, as they are very unlikely to encounter other members of their species during their lifetime.

Brownstein's analysis shows that the traits necessary for this parasitism, such as the difference in body size between males and females and the weakness of their immune systems that prevent them from attacking attached males, are the result of the evolution of monkfish diving into the deep sea. It turns out that it has existed for a long time.

“Most of this complex trait existed before the serratioids entered the deep ocean,” he says. “Basically, it's not the gas inside the engine, [of diversity]Sexual parasitism was like a preparation to press the gas pedal. ”

Miller said it's “possible” that a parasitic lifestyle helped the anglerfish invade deep-sea habitats, but it’s unclear how the fish subsequently achieved so much diversification. It remains as it is.

Answering this question will be a daunting task, especially since it is difficult to recover intact monkfish samples from the deep ocean.but cory evans Rice University in Texas says having two matching comprehensive family trees will help other researchers investigate.

“I think monkfish enthusiasts will be reading a lot of these two papers over the next six months,” he says.