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
Illustration of a developing fetus surrounded by a clear fluid with a subtle yellow tinge, representing amniotic fluid.
January 2026, Issue 1

What Is the Amniotic Fluid Composed of?

The liquid world of fetal development provides a rich source of nutrition and protection tailored to meet the needs of the growing fetus.

View this Issue
Skip the Wait for Protein Stability Data with Aunty

Skip the Wait for Protein Stability Data with Aunty

Unchained Labs
Graphic of three DNA helices in various colors

An Automated DNA-to-Data Framework for Production-Scale Sequencing

illumina
Exploring Cellular Organization with Spatial Proteomics

Exploring Cellular Organization with Spatial Proteomics

Abstract illustration of spheres with multiple layers, representing endoderm, ectoderm, and mesoderm derived organoids

Organoid Origins and How to Grow Them

Thermo Fisher Logo

Products

Brandtech Logo

BRANDTECH Scientific Introduces the Transferpette® pro Micropipette: A New Twist on Comfort and Control

Biotium Logo

Biotium Launches GlycoLiner™ Cell Surface Glycoprotein Labeling Kits for Rapid and Selective Cell Surface Imaging

Colorful abstract spiral dot pattern on a black background

Thermo Scientific X and S Series General Purpose Centrifuges

Thermo Fisher Logo
Abstract background with red and blue laser lights

VANTAstar Flexible microplate reader with simplified workflows

BMG LABTECH