5 Clear Mark for Review Sacculina carcini is a barnacle that attaches to the underside of the green crab. The barnacle finds a hole in the green crab's exoskeleton, then uses microscopic hairs to feed on nutrients from the green crab's blood. The barnacle also lays its eggs in the green crab reproductive system, which sterilizes the green crab. Which term describes the role of S. carcini in this relationship?

Parasitism: In this case, one of the species is beneficiated, while the other suffers a consequence, reducing its fitness. These interactions are mostly about nutrition, although there might be other benefits too. Some parasite species might coexist with their host, while some others might get them ill to the point of causing death. Parasitic attacks might be very nocive, and even though they are not lethal in a short period of time, they might slowly kill the host.

Parasitic species consume part of the host, but not the whole body. They develop an intimate relationship with their host.

The Host increases the fitness of the parasite species
The parasitic species decreases the fitness of the host.

By taking the nutrients from the green crab's blood and sterilizing it, the barnacle causes a decrease in the fitness of the crab. The crab becomes weaker and its survival chances decrease, and they have no opportunity to reproduce. Meanwhile, the barnacle gets stronger and reproduces normally.