Physiological phases of nymphal molting defined by mobility, body weight decrease, and excretion in Haemaphysalis longicornis (Acari: Ixodidae).

Abstract

Based on the rate of body weight decrease, the nymphal premolting period in Haemaphysalis longicornis Neumann was divided into three phases: a period of rapid weight decrease following detachment, a period of slight decrease, and another period of relatively rapid decrease before molting. Phase 1 was characterized by increased guanine excretion and mobility. The rate of weight decrease during phase 1 was greater in males than in females. During the premolting period, excreta consisted only of guanine and were devoid of hematin. In phases 2 and 3, neither excretion nor mobility was observed. Twenty-eight percent of the females and 40% of the males did not undergo phase 3. Adult body weight decreased rapidly until about day 5 after molting, after which weight was maintained until the end of the experiment. Guanine was excreted in large quantities just after molting and in small amounts for 4 d thereafter. Hematin excretion followed guanine excretion and was concentrated in a 3-d period starting 4 d after molting. The beginning of hematin excretion coincided approximately with the point at which body weight was maintained at a constant state. There were no quantitative differences per unit of body weight between the sexes with the exception of the rate of body weight loss during nymphal phase 1.