ID the Reef Hitchhiker

02 Oct, 2015

There is a marine hitchhiker in this reef scene waiting to be identified. Image by Denise Nielsen Tackett.

There is a marine hitchhiker in this reef scene waiting to be identified. Image by Denise Nielsen Tackett.

It came out of the archives as CORAL editors are working on the upcoming magazine issue about Reef Hitchhikers, and it was found among a batch of images of life forms whose identification had previous stumped even some veteran marine aquarists.

The first five readers to correctly identify the invasive animal hidden in this image will win a free REEF LIFE 2016 Wall Calendar.

Just leave your answer (scientific name and/or common name), your name, and email address in the COMMENTS box below.

Image by the late Denise Nielsen Tackett. Courtesy Microcosm, Ltd. and Tackett & Tackett Productions.

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About the author

Reef To Rainforest
Reef To Rainforest

Reef to Rainforest Media, LLC is the publisher of award-winning magazines and books in the fields of aquarium keeping, aquatics, and marine science. It is the English-language publisher of CORAL and AMAZONAS Magazines and is based in Shelburne, Vermont, USA.


  1. October 02, 2015

    The reef hitch hiker is a isopod it eats the tounge then ides the fish as a host

  2. October 02, 2015

    Cymothoa exigua.

  3. October 02, 2015

    the tongue-eating louse or Cymothoa exigua. that is what i think it is!

  4. October 02, 2015

    Yeah its an isopod or Cymothoa exigua

  5. October 02, 2015

    Cymothoa exigua, tongue eating louse

  6. October 02, 2015

    Cymothoa Exigua !!

  7. October 02, 2015

    Dang these guys are quick. Cymothoa Exigua

  8. Kat
    October 02, 2015

    Isopod in the mouth. Poor fish.

  9. October 02, 2015

    Cymothoa Exigua… known as a tongue eating louse

  10. October 02, 2015

    Isopod in fishes mouth

  11. October 02, 2015

    Grrrrrrr, I’m too slow. Tongue eating louse, Cymothoa exigua

  12. October 03, 2015

    Cymothoa exigua, I know I missed it but here’s to my one new thing learned today.

  13. Reef To Rainforest
    Reef To Rainforest
    October 03, 2015

    Editor’s Note

    Nice work everyone. When we first got this image almost 10 years ago from one of our favorite underwater photographers, the late Denise Nielsen Tackett, neither she nor anyone in our offices knew what we looking at, except that it had two little black eyes.

    It is, indeed, Cymothoa exigua, the Tongue-eating Isopod or Tongue-eating Fish Louse. Wikipedia has quite a good description here:

    Everyone who got it right up to this post will get a free copy of the 2016 REEF LIFE Calendar, which features other images by Denise Tackett and her dive partner Larry Tackett.

    Thanks to all who posted answers.


  14. October 03, 2015

    Cymothoa exigua what a great pic!

  15. October 03, 2015

    cymathoid isopod parasite (Cymothoa c.f exigua

  16. October 05, 2015

    Cymothoa exigua

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