Studies On The Midgut Structure, Protein And Their Changes Of Haemaphysalis Longicornis Neumann (Acari: Ixodidae)

Ticks are very important vectors, transmitting a variety of infectious pathogens and causing serious damage to human and livestock. What's more important, all kinds of pathogens not only develop in ticks but also preserve infection for a long time. Midgut is the primary peptic, reservoir of nutriment and vector of multiplicate pathogens simultaneously. Thus, researches on midgut have important significance on the theoretical and practical level.A series of researches were conducted on the midgut of female Haemaphysalis longicornis Neumann, including the shape, ultrastructure and protein components of female midgut, and their changes during different developmental stages, using scanning electron microscope (SEM), transmission electron microscope (TEM), biuret method and SDS-PAGE. The present results will provide foundation for further investigations on the new approaches of ticks bloodmeal digestion, prevention and cure. The main results were as follows:1. The midgut of H. longicornis consisted of a central ventriculus, a pair of anterior lateral diverticulum and posterior lateral diverticulum, which were divided into 7 pairs of diverticula in females, and 6 pairs of diverticula in males.2. The structure of midgut changed obviously with the developmental stages. In unfed adults, the midgut was flat and had many tracheas, fat bodies on its surface. With the process of feeding, the midgut and fat body increased correspondingly. At mating stage, the midgut increased obviously, and many fat bodies were on the surface of the central ventriculus, moreover, some diverticula had vesicles and fat bodies on its unbulgy parts. The midgut reached its maximum at engorgement. On the day 2 after engorgement, the midgut began to minish and was rough on its surface. After oviposition, the midgut shrinked.3. The bulk (length and width) of midgut on female changed obviously during developmental stages. In unfed adults, the midgut was small, every part was as follows: the blind diverticulum (bd) 1 (Length: 0.47mm; Width: 0.08mm), the bd 2 (Length: 0.58mm; Width: 0.09mm), the bd 3 (Length: 0.69mm; Width: 0.08mm), the bd 4 (Length: 0.59mm; Width: 0.08mm), the bd 5 (Length: 2.02mm; Width: 0.10mm), the bd 6 (Length: 1.37mm; Width: 0.13mm), the bd 7 (Length: 1.77mm; Width: 0.14mm), the central ventriculus (Length: 0.31mm; Width: 0.11mm). With the process of feeding, the midgut was changed. On the day 3 after attachment, the bulk increased. After mating, the change was prominent comparing with unfed adults. The midgut reached its maximum on the day of engorgement, the results were as follows: the bd 1 (Length: 1.97mm; Width: 0.39mm), the bd 2 (Length: 2.78mm; Width: 0.60mm), the bd 3 (Length: 3.93mm; Width: 0.57mm), the bd 4 (Length: 3.30mm; Width: 0.61mm), the bd 5 (Length: 8.11mm; Width: 0.66mm), the bd 6 (Length: 7.08mm; Width: 0.69mm), the bd 7 (Length: 8.37mm; Width: 0.70mm), the central ventriculus (Length: 1.62mm; Width: 0.80mm). On days 4 after engorgement, the midgut minished.4. Only one cell type, the stem cells, was found in the midgut epithelium of unfed femal and the nucleus were near the base of cells. The stem cells didn't have microvillis and also contained a large amount of lipid inclusions, glycogens, mitochondrias. residual bodies and a few endosomes. Lipid inclusions appeared to be the reserve of food. The first continuous phase was initiated by feeding (from attachment to the premating), midgut epithelium consisted of replacement cells and digestive cells. Mating was required to initiate the delayed or reduced phase of digestion (from mating to the outset of detachment), midgut epithelium was composed of digestive cells and vitellogenic cells. The second continuous phase of digestion was initiated by detachment from the host (from the preoviposition through the oviposition periods), the midgut epithelium still had digestive cells and vitellogenic cells.5. The protein level of the midgut changed obviously during female developmental stages. In unfed females, the protein concentration was low (0.001mg/T), and increased rapidly on the day 3 after attachment (0.061mg/T). After mating, the protein level increased significantly, which was 242 times than that of unfed female, and reached its...