This isopod crustacean — from the same group as pill bugs — must be one of the most stomach churning of all parasites. These tongue eaters are a huge pest in global fish farms; however, on coral reefs divers can sometimes spot them in an unusual place: the mouths of anemonefishes. All that’s usually visible of this sinister parasite in the anemonefish’s open mouth are the beady, black eyes set on a white head in the place you’d expect the tongue to be. Initially, the parasite grub crawls through the fish’s gills and attaches to the tongue.
The daintily named sea pig is actually a kind of locally abundant sea cucumber that inhabits the world’s abyssal plains up to 3.7 miles beneath the surface. It gets its name from a characteristic pink, eggplant-shaped body and bloated legs that give it a porcine appearance. Like their shallower cucumber cousins, sea pigs play an important role in marine ecosystems. They feed on detritus that falls to the seafloor from the rich waters above, whether plankton or a whale carcass. They walk along on a few large tube feet, using a combination of muscle contractions and body fluids. Modified pairs of legs can act as antennae to detect food.
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