Skip to content. | Skip to navigation

Personal tools
Log in
You are here: Home Blog Ever see a pearlfish enter the anus of a sea cucumber? [video]

Ever see a pearlfish enter the anus of a sea cucumber? [video]

By Shane Graber - Posted Jan 12, 2012 09:00 AM
Some of us have heard of the commensal / parasitic relationship that pearlfish have with sea cucumbers, but how many of us have actually seen a pearlfish enter its host cucumber through the anus where it hangs out most of the time?
Ever see a pearlfish enter the anus of a sea cucumber? [video]

Pearlfish enters sea cucumber anus - rare weird Vieques Island sea life.

Pearlfish (family Carapidae) are scaleless, their bodies are somewhat translucent, and they look remotely like eels when they swim outside of their host.  They can be found in the Atlantic, Pacific and Indian oceans and have been found down to depths of over 2,000 meters. Some of the species can reach upwards of 50 cm in length when full grown.

These fish are unique in that the adults normally live inside invertebrates like clams, sea squirts, and starfish in a commensal relationship (not harming their host).  This trait is common throughout the Carapidae family.

Some species of this family, however, are possibly parasitic. These live inside sea cucumbers where they will first eat the gonads of their host and then live inside the anal pore. The Pinhead pearlfish (Carapus boraborensis) is suspected to be parasitic whereas the Silver pearlfish (Encheliophis homei) is suspected to be non-parasitic based on stomach content analysis and where they are found within a cucumber when dissected.

Before entry, a pearlfish will normally spend several minutes inspecting the entire body length of a cucumber before proceeding to the back end. A knocking or tapping movement is performed near the anus as if "asking" to gain entry. Reports indicate that pearlfish normally back in tail first but have also been observed to enter head first. More than one pearlfish has been known to live inside a cucumber at any one time as well making for a somewhat cramped living environment. This trait has been observed with the Silver pearlfish where sexual pairing has been found within a cucumber.

This pairing behavior is not often seen in our reef aquariums but occasionally members of various reefkeeping forums will report that they have one in their tank.

Watch the video below to see this relationship. If you're short on time, skip ahead to the 6 minute mark for the re-entry...

Author: Shane Graber
Location: Indiana

Shane has kept saltwater tanks for the last 12 years, is a research scientist, lives in northern Indiana, and is a proud Advanced Aquarist staffer.


Document Actions
Filed under: ,
blog comments powered by Disqus


Contribute to our blogs!

Do you have news or discussion topics you want to see blogged?  Let us know!