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Anelasma squalicola and Etmopterus spinax

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*Update* (09/09/2014) - I have written a blog post about this parasite here: goo.gl/MiVHQS

Anelasma squalicola is a very peculiar barnacle. Unlike most barnacles that make a living by attaching onto a rock or other hard substrate and filtering tiny zooplankton to eat, it has evolved to be a parasite of the velvet belly lantern shark (Etmopterus spinax). Unlike parasitic barnacles like Sacculina ( theconversation.com/the-crab-c… ) which has completely transformed into something completely unrecognisable as a barnacle, Anelasma still retain some characteristics of its ancestral state.

It still have the limbs of a barnacles (called cirri), but they have been reduced down to a non-functional state (as I crudely described it here: twitter.com/The_Episiarch/stat… ), rather like the vestigial wings of a kiwi or the hind limbs of a baleen whale. Instead, it embeds a bulb-like part of its body into the flesh of its shark host. This bulb is covered in a web of fine rootlets, like that of a plant, which draws nutrients directly from the host's body.

I recently had the opportunity to write a Dispatch about this parasite for Current Biology ( www.cell.com/current-biology/a… ). The Dispatch was about a new paper that came out in the same journal which indicates  the closely living relatives of this parasites are, surprisingly enough, intertidal goose barnacles ( www.cell.com/current-biology/a… ).

I've also written a blog post about this parasite on the Parasite of the Day blog dailyparasite.blogspot.com/201…
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Comments8
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EmmetEarwax's avatar
It is calculated that at least 50% of all species of animals  are commensals, symbiotes, or parasites. So much for earth being life-FRIENDLY.
Alexanderlovegrove's avatar
This is absolutely crazy!  Great information and illustration!
Alexanderlovegrove's avatar
My girlfriend studies fish parasites, I'll have to tell her about this one
UmbraAtramentum's avatar
God, so creepy o_O nice illustrations as usual! :)
The-Episiarch's avatar
Thanks! :thanks:
An ordinary barnacles is already pretty weird - a crustacean that settles on its head and uses its legs to collect and kick food into its mouth. Anelasma takes it to the next level - its legs are shrunken and instead it grows roots from the top of its head, and sucks nutrient out of a shark! =P
UmbraAtramentum's avatar
The-Episiarch's avatar
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