Parasitic Pearlfish Seen with Sea Cucumber in Captivity

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Pearlfish

Pearlfish

Recently, a good friend and fellow marine biologist found an interesting hitch hiker in with one of the Holothuroid cucumbers he had recently imported. Don, from FragsandMore, was bagging up the Florida sand sifting sea cucumber and noticed a very thin fish in the bag as well. Recalling pictures and videos he had seen, he immediately knew the fish came from within the cucumber. Called the Pearlfish, this interesting fish inhabits the anal cavities of sea cucumbers. They can either be commensal, ie the relationship neither benefits or harms the host, or parasitic. Parasitic pearlfish typically live in the anus of the cucumber and eat the gonads. Pictures of the actual specimen can be seen below.

This fish hasn’t been identified as either a commensal or parasitic species. The pictures are not very clear and information on these fish isn’t exactly widespread, but my suspicions lie with this fish being the parasitic type. And as far as I know, this is one of the few times these fish have been seen in the aquarium community.

Parasitic Pearlfish and Sea Cucumber

Parasitic Pearlfish and Sea Cucumber

Parasitic Pearlfish and Sea Cucumber

Parasitic Pearlfish and Sea Cucumber

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  • Felicia

    Very, very cool, Brandon. I would be really excited to find that fish.

  • Don

    it was just a cucumber, then, it was a cucumber AND a fish in that bag, lol Strangest thing I ever found!

  • Wow. The picture of this thing is really interesting, but the description of what it does is rather scary. I'm very glad these guys aren't more prevalent in saltwater tank inhabitants, because although they are interesting, I definately wouldn't want one living in my tank.

  • Eric

    Hi,
    In Florida, there is one species of pearlfish, Carapus bermudensis. This fish is commensal. Best. Eric

  • rick

    I just bought some sea cucumbers from the Keys and and one of the sea cucumbers died. There was a fish in the bag just as described. It is still alive although I am afraid to release it into my tank for fear it may pass on diseases to my fish inhabitants. It looks very much like the pictures…extemeley long and thin. It swims by whipping it's tail. The stess of the shipment and sea cucumber dying must have caused the pearlfish to leave the sea cucmber.

  • rick

    it looks just like the fish on page 79 of Dr Burgess's Atlas of Marine Fish