The isopod to my fish or the fish to my isopod???

A success story of combining data across collections to aid research

Dr. Ryota Kawanishi, from Hokkaido University, Japan, is an aquatic ecologist studying isopods in the family Cymothoidae, which includes little shrimp-like animals, similar in appearance to “pill bugs” or what I used to call “roly-polies” as a child.

However, the type of isopod Dr. Kawanishi studies lives in the ocean and has a very interesting home;  it lives on fish, including commercially important (edible) species.  This parasitic isopod invades fish mouths, attaching to the tongue, or lodging within gills, and lives on/in the fish for its entire life.  This isopod “infection” surely negatively affects growth and viability of the fish hosts, reflected in, at best, loss of taste sense, but also moderate to severe gill tissue degradation.

mouth_dwelling_ceratothoa_original     gill_dwelling_mothocya_female

Dr. Kawanishi visited the Bishop Museum’s Invertebrate Zoology Collection where he examined specimens of the isopod genus Mothocya, an essential part of completing his research.  While successfully concluding his examination of the isopods, he still had questions regarding the isopod hosts – the particular fish in which they were discovered.


A check of the Invertebrate Zoology specimen database (digital catalog of specimens) revealed information that linked the isopod specimens to their fish hosts which happened to reside, luckily, within the Museum’s own Ichthyology Collection.

Ichthyology Collections Manager, Arnold Suzumoto, was able to find the fish hosts and provide length measurements for Dr. Kawanishi, giving insight into possible fish size at time of infestation, and, importantly, what size the fish was able to attain prior to live capture.


Arnold Suzumoto, Ichthyology Collection Manager

Dr. Kawanishi recently wrote, “Although BPBM5823 consists of six fish individuals without information corresponding one-to-one to the types of Mothocya sajori, Dr. Suzumoto’s detailed observations enabled me to identify fish individuals from which the types of Mothocya sajori have been collected.”

Without the link between the fish host and the isopod parasite, Dr. Kawanishi’s work would have been incomplete.  Without the detailed host information, the same is true.  Now that he is back in Japan with all the information he needs, he can complete his research and publish his results.  We look forward to learning what he finds!

20161104_135747 | Bishop Museum

(left to right) Aki and Ryota Kawanishi, with Holly Bolick, Invertebrate Zoology Collection Manager

To learn more about Dr. Kawanishi and his research:

And before you decide isopods are just nasty little parasites on your delicious fish, I offer you a different perspective (found on the internet): delicious isopod crackers, adorable plush toys, and iPhone cases.  What an interesting world!

isopod-crackers isopod-plushy isopod-iphone-case


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