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Name : Pearlfish ( Carapidaefamily )
Where it live : Inside invertebrate hosts in shallow , tropical waters around the world
A graceful pearlfish (Encheliophis gracilis) peering from the anus of the sea cucumber Bohadschia argus.
What it eat : Plankton , lowly atom and sea cucumbers ' gonads
Why it ’s awesome : This long , slender fish does n’t look unusual until you see it pass home — into a sea cucumber ’s butthole .
Pearlfish do n’t have graduated table or any means of protecting themselves , so instead they have to obtain a safe hideaway . But rather than sheltering in a seagrass hayfield or hiding in the cleft of a rock , they have chosen an unusual refuge : sea cuke ' anuses .
" The rearward end of a sea Cucumis sativus may seem like undesirable material estate , but for a pearl-fish , it does just the trick , " according to theSmithsonian Oceanwebsite .
ocean cuke suspire through their butts , giving pearlfish an easy chance to abstract into their unknowing host . The pearlfish sniffs out its host , then just has to wait " for the cucumber vine to open for a breathing space and swim in spite of appearance , " Smithsonian Ocean said . They do this every time they call for to re - enter their home , which they leave to find food .
Even the sea cuke ' Cuvierian tubules — especial viscous threads that ocean cuke eject from their bums in self - defense — do n’t strike pearlfish . And cuke mintage with anal tooth still succumb to these pesky rump - dwellers . " I have found a new species that is smaller that was able to go within , even with the teeth,“Eric Parmentier , a pearlfishresearcherat the University of Liège , Belgium , told Live Science in an e-mail .
Related : Sea cucumbers abstract out ' 5 Eiffel Towers deserving ' of turd per Rand , per year
These eel - same Pisces the Fishes often — but not always — make a home for one inside their host . " As far as we roll in the hay , there is usually one [ pearlfish ] to a ocean cucumber vine , but some species have been report to pair up in a undivided cucumber,“Matt Girard , a investigator in the Division of Fishes at the Smithsonian National Museum of Natural History assure Live Science in an email .
— Pigbutt louse : The deep - ocean ' enigma blob ' with the rump of a pig and a ballooned venter
— Sun bear : The slight carnivores that see so similar to humans they ’ve been slip for people wearing costumes
— peaceable geoduck : The large , phallic clam that can live longer than 165 yr
The number of pearlfish shacked up in a individual sea cucumber can tally double figures . In 1975 , scientist Victor Benno Meyer - Rochow line up a leopard sea cucumber ( Bohadschia argus ) with15 pearlfishinside it .
Some metal money can live inside sea cuke without doing them harm , Girard said . They live in mutualism and " neither host nor invader is harmed . "
But there are also parasite coinage that " eat on the sea Cucumis sativus ’s gonads , " Parmentier tot . " It does not kill the host but it can vex its reproduction . "
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