Caenorhabditis elegans is a non-parasitic nematode that is often used as a model organism for nematodes in scientific testing. It was the first multi-cellular organism to have it's genome sequenced.
it's cardiovascular system (and that of all Nematodes)
Caenorhabditis elegans does not have a true circulatory system. Instead, their bodies contain a pseudocoelom, which is a body cavity located between their epidermises and gut cavity that contains fluid that transports nutrients. From there, they use diffusion to circulate substances around it's body.