Meeting Abstract
The hemopoetic organs of Artemia franciscana have been described by several workers. These nodules are found in each of the eleven pairs of swimming appendages. The clusters of these blood cells are surrounded by a thin membrane and are located among the musculature of the appendages. Hemocytes from these nodules are released into the hemocoel. Several researchers have suggested that hemocytes produced in these nodules are the source for replenishing the blood cells. Using routine histological, transmission and scanning electron microscopic techniques, this study attempted to demonstrate the division of the blood cells in the nodules in adult as well as in several younger stages of the animals. In this study few, if any, mitotic figures were evident in these animals. Even in those animals exposed to several concentrations of colchicine, mitosis of developing blood cells within the nodules was not especially evident. In addition to adult animals, immature Artemia with 2, 5, and 7 appendages showed minimal evidence of cell division. Within these nodules there are cells with a high nucleus to cytoplasmic ratio and very few cytoplasmic granules. The cells contain large quantities of RNA, and at the EM level a well-developed RER and Golgi apparatus. As these cells mature there is an increase in the number of cytoplasmic granules. Since there are large numbers of mature hemocytes circulating within the hemocoel of adult and immature animals, these blood cells must be produced during the very early stages of development or in response to some physiological challenge to the organism, such as molting or the invasion of foreign organisms.
