For Mates to Fuse Bodies, Some Anglerfish Have Lost Immune Genes

In most vertebrates, the absence of adaptive immunity would be catastrophic, but in some deep-sea angler fish species, it enables their “wild” and “wacky” mating habits.

Written byKatarina Zimmer
| 6 min read
deep-sea anglerfish Melanocetus johnsonii mating parasitic male immunology adaptive immune system cytotoxic t cell antibody

Register for free to listen to this article
Listen with Speechify
0:00
6:00
Share

ABOVE: A 75-mm-long Melanocetus johnsonii female with a 23.5-mm-long male attached to her belly
EDITH A. WIDDER

Krøyer’s deep-sea anglerfish, Ceratias holboelli, does not spawn, copulate, or do anything a fish would ordinarily do to mate. Instead, the male—just a few inches long—clasps onto the comparatively gigantic female’s body and never lets go. Slowly, his body morphs into hers, his cells becoming hers, including his testicles, which are used to make offspring. As he vanishes, two individuals become one—taking the concept of monogamy to a new level.

The sub-order of deep-sea anglerfish, composed of nearly 170 known species, arguably displays the most dramatic mating habits in the animal kingdom. In some species, males only temporarily attach to females and then part ways. In others, such as C. holboelli, males permanently “fuse” with females, or females absorb multiple males—in some cases up to eight at a time.

Among the many mysteries surrounding ...

Interested in reading more?

Become a Member of

The Scientist Logo
Receive full access to more than 35 years of archives, as well as TS Digest, digital editions of The Scientist, feature stories, and much more!
Already a member? Login Here

Related Topics

Meet the Author

  • katya katarina zimmer

    After a year teaching an algorithm to differentiate between the echolocation calls of different bat species, Katarina decided she was simply too greedy to focus on one field of science and wanted to write about all of them. Following an internship with The Scientist in 2017, she’s been happily freelancing for a number of publications, covering everything from climate change to oncology. Katarina is a news correspondent for The Scientist and contributes occasional features to the magazine. Find her on Twitter @katarinazimmer and read her work on her website.

    View Full Profile
Share
Image of a woman with her hands across her stomach. She has a look of discomfort on her face. There is a blown up image of her stomach next to her and it has colorful butterflies and gut bacteria all swarming within the gut.
November 2025, Issue 1

Why Do We Feel Butterflies in the Stomach?

These fluttering sensations are the brain’s reaction to certain emotions, which can be amplified or soothed by the gut’s own “bugs".

View this Issue
Olga Anczukow and Ryan Englander discuss how transcriptome splicing affects immune system function in lung cancer.

Long-Read RNA Sequencing Reveals a Regulatory Role for Splicing in Immunotherapy Responses

Pacific Biosciences logo
Research Roundtable: The Evolving World of Spatial Biology

Research Roundtable: The Evolving World of Spatial Biology

Conceptual cartoon image of gene editing technology

Exploring the State of the Art in Gene Editing Techniques

Bio-Rad
Conceptual image of a doctor holding a brain puzzle, representing Alzheimer's disease diagnosis.

Simplifying Early Alzheimer’s Disease Diagnosis with Blood Testing

fujirebio logo

Products

Eppendorf Logo

Research on rewiring neural circuit in fruit flies wins 2025 Eppendorf & Science Prize

Evident Logo

EVIDENT's New FLUOVIEW FV5000 Redefines the Boundaries of Confocal and Multiphoton Imaging

Evident Logo

EVIDENT Launches Sixth Annual Image of the Year Contest

10x Genomics Logo

10x Genomics Launches the Next Generation of Chromium Flex to Empower Scientists to Massively Scale Single Cell Research