sporangia (Fig. 18.31), each containing thousands of minute, one-celled spores. The sporangia often are globe shaped, but in some species, they develop as long or wide stationary bodies that may resemble a jumbled network of tubes, or they may resemble erect hairs or end up as a shapeless blob. The sporangia may or may not have slender stalks, depending on the species. Others exhibit combinations of body forms. The spores are often distributed throughout a jumbled mass of threads called a capillitium.
When a spore is formed, a single nucleus and a little cytoplasm become surrounded by a wall. Meiosis takes place in the spore, and three of the four resulting nuclei degenerate. When the spore germinates, one or more amoebalike cells called myxamoebae emerge. Sometimes, these have flagella, in which case they are called swarm cells. Either form may become like the other through the development or loss of flagella. At first, myxamoebae or swarm cells feed on bacteria and other food particles. Sooner or later, however, they function as gametes, fusing in pairs and
forming zygotes. A new plasmodium usually develops from the zygote, although occasionally zygotes or small plas-modia may fuse and form larger plasmodia (Fig. 18.32).
Was this article helpful?
This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.