Anglerfish Mating: The Male That Fuses to His Mate for Life
Anglerfish mating sounds like science fiction. In some deep-sea species, a tiny male finds a female in the dark, bites onto her and never lets go. Their bodies fuse, their blood mixes, and he lives the rest of his life attached to her.
Quick Facts
- Who: Some deep-sea anglerfish (Ceratioidei)
- The lure: A glowing tip packed with light-making bacteria
- Males: Only a fraction of the female's size
- Record: A female once caught with eight males attached
- Known for: Sexual parasitism: the male fuses to the female
The Glowing Lure
Female deep-sea anglerfish have a fishing-rod spine on their head tipped with a luminous lure. The glow comes from bioluminescent bacteria living inside it, and it draws prey toward her mouth in the dark.
A Tiny Male in a Huge Ocean
In many deep-sea species, males grow to only a fraction of the female's size. They don't have the big head or the lure. Their job is to find a female in the dark.
How Do Anglerfish Fuse?
Once he finds her, the male latches on with his small, sharp teeth. In some species, the skin of the male and female grows together and their blood vessels join, so her blood flows through his body. Over time his fins and other unused body parts wither away.
Why Doesn't Her Body Reject Him?
A 2020 study in Science found that anglerfish species that fuse have lost or changed key parts of their immune system, which likely lets the female's body accept the male instead of attacking him.
Eight Males at Once
A female anglerfish was once caught with eight males attached to her, according to the Natural History Museum in London.
Frequently Asked Questions
Do all anglerfish fuse when they mate?
No. Only some deep-sea anglerfish species do. Many others, including shallow-water anglerfish, don't.
Why do male anglerfish fuse to females?
In the vast, dark deep sea, finding a mate is rare, so staying permanently attached means he's there when she spawns.
What is an anglerfish lure?
A modified fin spine on the female's head with a glowing tip full of light-producing bacteria.
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Sources
- Natural History Museum: The Bizarre Love Life of the Anglerfish: male size, fusion and the eight-male record
- National Geographic: Anglerfish, Taking Romantic Attachment to a Whole New Level: shared blood
- Swann et al. (2020), Science: The Immunogenetics of Sexual Parasitism: immune changes
- Isakov: Histocompatibility and Reproduction: Lessons from the Anglerfish (PMC): fusion and shared circulation
- Wikipedia: Anglerfish: the lure and its bacteria
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Cover photo: Emőke Dénes via Wikimedia Commons, CC BY-SA 4.0.