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.
The Platyhelmthes is divided into three different classes including Turbellaria, Trematoda, and Cestoda. This phylum does not have a skeletal, circulatory, and respiratory system but does have an excretory system where the flatworm uses flame cells and its associated ducts to regulate its excretory system.t works but sucking food into the intestine where phagocytic cells of the gastrodermis complete digestion. The Cestoda, one of the three classes of the Platyhelmthes, does not have a digestive system and the rest of the parasitic classes rely on the host for digestion.