Reduced nutrition as the factor controlling the population of pinworms following endocrine gland removal in Periplaneta americana L.

Abstract

The effects of allatectomy and cardiacectomy of adult female Periplaneta americana on the numbers of adult females of Leidynema appendiculata and Hammerschmidtiella diesingi (Nematoda: Thelastomatidae) in the hind gut were examined. All surgical manipulations reduced the food intake – fecal output of the cockroaches. It is shown that the level of nutrition determines the relative numbers of the two species of adult female nematodes. At normal or moderately reduced levels of nutrition, L. appendiculata is present in greater numbers than H. diesingi. When the level of nutrition in a group of insects is greatly reduced by either surgery or supplying a limited amount of food, H. diesingi predominates. However, the total number of adult female nematodes in the various experimental groups of cockroaches does not change significantly even when the fecal output is reduced to less than half the normal level. Hence, there is a significant negative linear correlation between the mean numbers of the two species of nematodes in the experimental groups of insects. From these data, it is concluded that neither allatectomy nor cardiacectomy significantly affects the total numbers of adult female parasites. Any effect which these operations have upon the relative numbers of the two species of parasites is explicable on the basis of a reduced level of nutrition for the operated cockroaches. These findings are discussed in relation to those of previous workers who concluded that a relationship exists between the endocrines of cockroaches and their thelastomatid parasites. Furthermore, the significance of these findings in explaining the size and composition of the population of nematodes in various stages and both sexes of P. americana is discussed.