But sea cucumbers are their most ill-famed hosts. Having found one by following its smell, a pearlfish will dive into the anus headfirst, “ propelling itself by violent strokes of the chase, ” according to Eric Parmentier . If the ocean cucumber objects and closes down its anus… well, it still has to breathe. Oh yea, ocean cucumbers breathe through their anuses. By rhythmically expanding and contracting their bodies, they drive water through the anal open and into a branch, lung-like social organization called the respiratory tree. This serve creates gentle currents that a pearlfish can use to find its hosts. It besides creates a vulnerability, because a sea cucumber that ’ sulfur clenching its butt is besides holding its hint. When it exhales, as it finally must, it dilates its anus, allowing the pearlfish to thread itself in. This time, it goes tail-first, morsel by bite, hint by breath. Some species good use the sea cucumbers as shelters. But the Encheliophis pearlfishes are full-blown parasites that devour their horde ’ randomness gonads from within.
Pearlfish are typically found alone, and adults have been known to kill rivals that try to infiltrate the lapp host. distillery, as Meyer-Rochow found, the pisces can sometimes be more sociable—or at the very least, broad. No one knows why. It ’ s possible that when sea cucumbers are rare, the fish are forced to contribution a host. alternatively, they could have gathered to breed. “ If indeed the 15 pisces entered for intimate reasons, one can not help but think of the orgy that must have taken put inside the ocean cucumber, ” Meyer-Rochow says . These anal abodes aren ’ thymine easy places to live. Pearlfish should be specially vulnerable, since they are literally swimming inside the saponin-producing structures. And yet, when Igor Eeckhaut exposed versatile fishes to sea cucumber saponins, the pearlfish survived 45 times longer than early species. How do they cope ? Sea cucumbers resist their own poisons because their cell membranes comprise limited chemicals that interact less strongly with saponins. But Lola Brasseur from Eeckhaut ’ s team found that pearlfishes don ’ metric ton function such fancy chemistry. Nor do they have any tricks for detoxifying the saponins.
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alternatively, they rely on mucus, which they secrete onto their skins. The mucus helps to lubricate them on their way into their hosts, but it besides acts as a forcible barrier against the toxic saponins. It ’ s specially effective because the pearlfishes make indeed a lot of it—six to ten times more than early fishes that have no concern in sea cucumber bums. Of class, none of this explains why the sea cucumbers don ’ deoxythymidine monophosphate use their most effective refutation. When threatened, they can expel their respiratory trees at their attackers, relying on their regenerative powers to re-grow the lose electric organ. Why, then, do they never evict their pearlfish lodgers in this way ? No one knows .
