Ultrastructure of the midgut and blood meal digestion in the adult tickDermacentor variabilis
Ultrastructure of the midgut and blood meal digestion in the adult tickDermacentor variabilis
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DOI：
10.1007/bf01193300
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发表时间：
1989-05
影响因子：
2.2
通讯作者：
B. Tarnowski;L. Coons
中科院分区：
文献类型：
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作者：
B. Tarnowski;L. Coons
雌雄中肠的消化细胞以包被的小泡和光滑的瓶状小泡的形式摄取血粉，并将其储存在通过异噬作用消化的内体中。铁主要集中在残余体中。交配雌虫的消化经历了三个不同的阶段：(1)缓慢充血时的连续消化(由取食开始)；(2)交配雌性在快速充血期间消化减少(由交配开始)；(3)第二连续消化阶段(由从寄主分离开始)发生在产卵前和产卵后的整个摄食期。消化细胞存在于所有三个消化阶段。只有在第一个连续消化阶段，消化细胞才充满残留体，破裂并塌陷到管腔，或者整个细胞塌陷到管腔。在其他两个消化阶段，没有观察到消化细胞的脱落。产卵结束时，消化细胞内充满残留体。替代细胞仅在第一个连续消化阶段出现。推测卵黄生成细胞仅在减少消化阶段和第二连续消化阶段存在。未喂食雄鼠的干细胞只发育成喂食雄鼠的消化细胞。被喂养的雄性和未交配的雌性只有第一个连续消化阶段。从寄主分离后，13天的未交配雌虫经历了与交配雌虫的减少消化阶段和第二连续消化阶段相关的细胞变化，然后开始产卵。基础迷路系统和侧隙的最大发育与已知的水和离子通过中肠上皮的最大移动时间相匹配。从寄主脱离后采集的管腔内容物和中肠细胞的光度分析表明，在产卵开始后的第一天，蛋白质和血红蛋白的浓度下降了一半，而血红素的浓度在产卵结束时增加了大约两倍。这支持了存在第二个连续消化阶段的想法。
Digestive cells in the midgut of male and femaleDermacentor variabilis(Say) took up the blood meal in coated vesicles and smooth flask-shaped vesicles, and deposited it in endosomes which were digested via heterophagy. Iron was concentrated in residual bodies.Digestion occurred in three distinct phases in mated females: (1) continuous digestion (initiated by feeding) occurred during slow engorgement; (2) reduced digestion (initiated by mating) occurred in mated females during the period of rapid engorgement; (3) a second continuous digestion phase (initiated by detachment from the host) occurred throughout the post-feeding periods of preoviposition and oviposition.It is proposed that the stem cells in the midguts of unfed females were progenitors of digestive, replacement, and presumed vitellogenic cells in midguts of mated feeding females. Digestive cells were present in all three digestion phases. Only during the first continuous digestion phase did digestive cells fill up with residual bodies, rupture and slough into the lumen, or did whole cells slough into the lumen. During the other two digestion phases no sloughing of digestive cells was observed. At the end of oviposition the digestive cells were filled with residual bodies. Replacement cells were present only during the first continuous-digestion phase. Presumed vitellogenic cells were present only during the reduced-digestion phase and during the second continuous-digestion phase. Stem cells in unfed males developed only into digestive cells in feeding males. Fed males and fed unmated females had only the first continuous-digestion phase. After being hand-detached from the host, unmated 13-day-fed females went through cellular changes associated with the reduced-digestion phase and second continuous-digestion phase of fed mated females, then began ovipositing. Maximum development of the basal labyrinth system and lateral spaces matched the known time of maximum water and ion movement across the midgut epithelia.Spectrophotometric analyses of lumen contents and midgut cells, sampled after detachment from the host, showed that concentrations of protein and hemoglobin at day 1 post-detachment decreased by one-half at the beginning of oviposition, while hematin increased about twofold by the end of oviposition. This supported the idea of the presence of a second continuous-digestion phase.