A wharf roach (Ligia exotica), sometimes referred to as a sea louse (plural: sea lice), is a crustacean of the order Isopoda, family Ligiidae. It has a pair of long antennae and large compound eyes on its head, and seven pairs of legs. It lives on seashores and reefs and feeds on algae and dead organisms.
The wharf roaches that inhabited the Big Shell were genetically engineered to help break down spilled oil, representing a promising form of bio-remediation. They were created in a lab to help deal with the frequent oil leaks that occurred in the Big Shell. Their genes had been spliced with those from the oil-eating Pseudomonas bacterium. The roaches produced an enzyme in their bodies that broke down oil, enabling them to absorb and eat it. These roaches were the reason why the Big Shell itself was oil-free.
During the Big Shell Incident in 2009, a wharf roach entered the clothing of Solid Snake after he secretly infiltrated the facility's deep sea dock. When Snake, disguised as Navy SEAL Iroquois Pliskin, later took rest following an attack in the transformer room, the roach left his person. The roach's presence aroused the suspicions of Raiden, who had earlier been told by Pliskin that he had entered the Big Shell via helicopter. A swarm of roaches later blocked the path of Fortune in the deep sea dock, though they parted for her as she approached them. Raiden later made use of a coolant spray to ward off a swarm of roaches, allowing him to escort an entomophobic Emma Emmerich to safety.
Behind the scenes
Although harmless, sea lice can infiltrate the player's inventory and eat any rations that are in their possession. To remove them, the player must quickly cycle through their equipment in the item window. Clearing the game with a sea louse attached to a ration will result in the player being awarded the Sea Louce [sic] code name.
Sea lice can be driven off using the coolant spray, which is useful for providing passage for Emma, during Raiden's mission to escort her through the facility. In addition, using C4 or grenades to blow them up while in First Person View, will result in the sea lice being sent flying in the player's direction and splattering over the camera lens, as if flying into the windshield of a moving car.
In Metal Gear Acid 2, the sea lice card is referred to by its Japanese name "Funamushi."