Cuticular Plasticization Caused by Cuticular pH Descent, and Mitochondria-Rich Acidophilic Epidermal Cells in Adult Female Haemaphysalis longicornis (Acari: Ixodidae)

Measurements of pH in minced cuticle from the alloscutum of non-copulated and copulated female Haemaphysalis longicornis revealed a descent of cuticular pH after copulation. Sample cuticular loops were cut from the alloscutum of non-copulated females and immersed in buffers adjusted to pH 4, 5, 6, 7 or 8. Extensions of the cuticular loops subjected to a constant applied load were measured using a creep test. The cuticular loops at pH 7 and 8 showed small extensibilities. However, as the acidity of the cuticle increased, the sample loops displayed larger extensibilities. Extensibilities of sample loops from copulated females were significantly larger than those from non-copulated females. Based upon this difference of extensibility, the descent of cuticular pH after copulation is presumed to be about 0.5 pH units. These data suggest that the cuticular plasticization is caused by the cuticular acidification in the female tick. Moreover, novel acidophilic epidermal cells were situated around dermal glands. Their cytoplasm have an affinity for eosin, because of numerous mitochondria. A smooth endoplasmic reticulum like tubulovesicular system appeared in the apical cytoplasm after copulation. Such morphological features suggest that the acidophilic epidermal cells actively transport ions and provoke the pH descent of the cuticle after copulation.