LONDON -- Brace yourselves for this one -- it isn't for the faint-hearted.

On Thursday evening,Chris Cassidy Archives BBC Earth tweeted the following, slightly unexpected gif.

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Yep, that is a pearlfish worming its way up the rear-end of a sea cucumber. Just think about that for a moment. The pearlfish actually scouts the ocean looking for sea cucumbers with the express purpose of cheerfully burrowing its way into their anal cavity for protection.

Needless to say, BBC Earth's tweet drummed up some mixed reactions.

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Some people were appalled.

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Others, meanwhile, were clearly torn between shock and intrigue.

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Others were impressed with the BBC's choice of hashtag.

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If you can stomach it, here's a longer video about the adventures of the pearl fish.

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