A combination of factors is likely causing the decline of blue spruce trees throughout Michigan. Posted on March 7, 2011 by Dennis Fulbright, Michigan State University Extension, Department of Plant Pathology, and Jill OâDonnell, Michigan State University Extension.
Flatworms lack a respiratory or circulatory system; these functions take place by absorption through the body wall. Nonparasitic forms have a simple, incomplete gut; even this is lacking in many parasitic species. Movement in some flatworms is controlled by longitudinal, circular, and oblique layers of muscle.
Porifera Circulatory System. Sponges have no real circulatory system.Sponges have flagellated cells over the surface of their bodies, these are cells that have tails that wiggles. The collective effort of all these cells creates a water current through the many porous openings in the sponges body.