Changes in the Fine Structure of the Integument of the Rabbit Tick, Haemaphysalis leporispalustris (Acari: Ixodides: Ixodidae), Which Occur during Feeding1,2

Abstract

Previously reported investigations into the ultrastructure of the integument of Haemaphysalis leporispalustris (Packard) have shown that there are 2 morphologically distinct types of cuticle. The sclerotized or “hard” cuticle serves as a skeletal surface for the musculature and is found in the dorsal shield, mouth parts, legs, etc. Nonsclerotized or “soft” cuticle is found elsewhere in the organism. These further investigations show that during feeding the fine structure of sclerotized cuticle does not become significantly altered, while both the soft cuticle and its underlying epidermal cells change dramatically. Within 24 hours of initial attachment the epidermal cells change from a low epithelioid type rich in electron-dense granular material to large cuboidal and columnar cells poor in granular material, but filled with mitochondria, rough endoplasmic reticulum, and free ribosomes, indicating a rapid increase in synthetic activity. The cuticle thickens rapidly, presumably as a result of this activity. This thickening provides for and is followed by a rapid stretching of the opisthosoma during the final stages of engorgement. Of considerable interest is the clear continuity of epidermal cytoplasm with the contents of the pore canals penetrating the soft cuticle which is clearly observable during this period.