Unveiling the Evolution of Anglerfishes: How Sexual Parasitism Emerged During Global Warming

The evolution of sexual parasitism in anglerfishes has been linked to a period of major global warming and rapid transition for these unique deep-sea creatures, according to a new study published in the journal Current Biology.

Researchers from Yale University, led by Chase D. Brownstein, analyzed genome-scale DNA sequence data from over 100 anglerfish species, along with fossil evidence, to better understand the relationships and ages of these fascinating creatures. They found that the transition of ancestrally bottom-dwelling anglerfishes to open-ocean habitats occurred during a period of major global warming 50 to 35 million years ago.

This transition coincided with the origins of sexual parasitism, a characteristic in which males temporarily attach or permanently fuse with females to mate. The researchers suggest that sexual parasitism likely facilitated the rapid diversification of anglerfishes in the deep sea, providing them with ecological opportunities in their new habitat.

Brownstein explains, “We show that this sexual parasitism trait is ancestral for all deep-sea anglerfishes and appears to have evolved as a synergistic combination of ancestral lability in the genetic basis of the adaptive immune system and body size dimorphism. This explains the origins of such an odd trait.”

The study also highlights the potential implications of global warming on deep-sea life today. The researchers suggest that the current warming trends could modify the course of deep-sea life for millions of years to come. They plan to further investigate the evolutionary histories of other deep-sea fish groups to gain a better understanding of how these unique creatures have adapted to their environment over time.

Brownstein concludes, “We are really at the starting line for investigations of the evolution of most deep-sea life forms, and the genomic data we have now for some groups suggests evolutionary histories in the deep sea might be very different from our initial hypotheses. For example, the idea that all deep-sea life is ancient is clearly wrong; anglerfishes only swam into the open waters of the bathypelagic zone in the last 50 to 60 million years. This is a long time ago, to be sure, but it is much more recent — on the order of 50-60 million years — than we inferred previously using smaller DNA datasets and less informative fossils.”

Overall, this study sheds new light on the evolution of deep-sea life and underscores the importance of understanding how global warming may impact these unique ecosystems in the future.