During the preoviposition and oviposition periods of ixodid ticks, the salivary glands degenerate. It is unclear whether this degeneration is a necrotic or a programmed cell death event. We used a modified TUNEL technique in conjunction with fluorescence microscopy to determine if salivary gland degeneration involves apoptosis. Salivary glands were dissected from replete females at days 3, 5, 8, 11, 13, and 33 days post-detachment. There were no statistical differences in ticks based on weight at detachment, suggesting that changes observed was not due to engorgement abnormalities. The onset of apoptosis began at day 5 and continued through oviposition at day 33. The greatest amount of nuclei containing fragmented DNA was observed on day 8 post-detachment, suggesting this was the peak occurrence of programmed cell death. Further, the temporal organization of programmed cell death suggests that the granule-secreting acini undergo apoptosis first, and that during the first week of oviposition the type I acini do not exhibit programmed cell death. These data suggest that the type I acini may still function in maintaining off-host hydration state of ovipositing females. These data provide morphological evidence that salivary gland degeneration involves a temporal programmed cell death event. We cannot eliminate the involvement of necrosis as there appeared to be intact nuclei (especially surrounding the duct) at day 33 post-detachment.
Species 1: Acarina Ixodidae Dermacentor variabilis (American dog tick)
Keywords: apoptosis, autophagy
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