Date of Award
Master of Arts
Dr. Jean M. Lawrence
Dr. Thane S. Robinson
Dr. Imy V. Holt
Masters Thesis-Open Access
Because cephalization and centralization of the earthworm are more pronounced than in less complex forms, it is a relatively simple operation to remove a portion of the central nervous system to investigate its functions. However, the extripation of various parts of the central nervous system of the earthworm has been the subject of only a few research papers. It is the purpose of this study to investigate the influence of extripation of the suprapharyngeal ganglia on the oxygen uptake of the resting earthworm, Lumbricus terrestris.
Of the studies concerned with the influence of extirpation of some parts of the central nervous system of Annelids on gaseous exchange and other physiological functions, by far the greatest interest has been centered on the suprapharyngeal ganglia.
Bennett and Suttle (1960) removed the suprapharyngeal ganglion from the earthworm, L. terrestris, and found that it is the possible source of factors which affect general metabolism and seems to have an inhibitory effect on the seminal vesicles and receptacles of the earthworm. Clark and Clark (1959) found that the removal of the suprapharyngeal ganglion at the same time as that of a number of posterior body segments inhibits posterior regeneration. The effect of the removal of the suprapharyngeal ganglia from an earthworm is described in Prosser and Brown (1962). The anterior segments are lifted, the worm crawls normally, appears restless and active, can right itself, copulates, eats and burrows in one half hour as compared with the normal time of one to two minutes. Kovaleva (1961) found that the removal of the suprapharyngeal ganglion led to intensification of the animal's motor activity. Further, the oxygen consumption of the worm at rest was increased and its body weight diminished gradually.
It has been established that neurosecretory cells are present in the suprapharyngeal ganglion of the earthworm. They have been thoroughly studies and described by Scharrer and Brown, (1961). The function of these granules has not been established. However, it is assumed that they may be hormonal in nature (Scharrer and Brown, 1962).
According to Kovaleva (1961) the motor activity of the earthworm is intensified with the removal of the suprapharyngeal ganglion. This increase in motor activity in turn increases the oxygen consumption of the worm and tends to mask any influence that the suprapharyngeal ganglion may have on tissue metabolism. In the present study attempts were made to control the activities of the worms by lowering the ambient temperature and reducing the environmental light to nearly darkness in order to measure oxygen consumption of the worms at rest. In this way, the results should indicate if the suprapharyngeal ganglion contains a factor or factors which influence the rate of oxygen consumption rather than the reflection of increased motor activity.
Elzinga, William E., "An Investigation of the Influence of the Suprapharyngeal Ganglion upon Oxygen Consumption of Resting Lumbrious Terrestris" (1963). Masters Theses. 4480.