Woodring Joseph, Lorenz Matthias W
Department of Animal Ecology I, University of Bayreuth, 95440 Bayreuth, Germany.
J Morphol. 2007 Sep;268(9):815-25. doi: 10.1002/jmor.10554.
The flow of nutrients through the digestive tract of Gryllus bimaculatus is regulated by the proventriculus, which effectively triturates the partially digested food coming from the crop and shoves the mushy nutrient mass into the space between the paired caeca. The many folds at the base of the caeca form a sieve, and only fine food particles (4-10 microm) and fluids in the mush are filtered under pressure (produced by proventricular peristalsis) into the caeca. Combined with the release of enzymes in the caeca and the influx of water, the caeca are rapidly inflated on day 1 after the terminal molt. The remaining, mostly undigested food is shoved into a tube formed by the peritrophic membrane, which is first formed at the anterior end of the ventriculus. A mucous membrane (peritrophic gel) covers the caecal epithelium, and seems to merge with the true peritrophic membrane at the beginning of the ventriculus. The Type I peritrophic membrane is dragged posteriorly through the entire ventriculus and ileum by the posterior movement of the food bolus, which is shoved posteriorly at a rate of 6 mm/h by proventricular pressure. The growth rate of the peritrophic membrane is about 3 mm/h. Peristalsis does not occur in the midgut or ileum; the muscles in these regions function solely to counteract the internal pressure produced by the proventriculus. The exo- and endoperitrophic space in newly molted animals is open and fluids can flow in both directions. The endoperitrophic space becomes filled on day 1, and leads to a great reduction of the exoperitrophic space. In the ileal pouch (exoperitrophic space) the peritrophic membrane separates the mass of bacteria from the waste bolus within the endoperitrophic space. Feathery bristles arising from the cuticular covering of the finger-like invaginations of the ileal wall hold most of the bacterial mass in place. The crop weight decreases from day 1 to day 3 as the weight of caeca, ventriculus, and ileum increases. After day 3, food uptake and the weight of the entire gut system decrease in female crickets, partly in response to space restrictions in the abdomen caused by rapid ovarial growth.
双斑蟋消化道内营养物质的流动由前胃调节，前胃有效地研磨来自嗉囊的部分消化食物，并将糊状营养物质推挤到成对盲肠之间的空间。盲肠基部的许多褶皱形成一个筛子，在压力（由前胃蠕动产生）作用下，只有细小的食物颗粒（4 - 10微米）和糊状物中的液体被过滤进入盲肠。结合盲肠中酶的释放和水的流入，在最后一次蜕皮后的第1天，盲肠迅速膨胀。其余大部分未消化的食物被推挤到由围食膜形成的管中，围食膜最初在胃前端形成。一层粘膜（围食凝胶）覆盖盲肠上皮，并且似乎在胃的起始处与真正的围食膜融合。I型围食膜随着食团的向后移动被向后拖过整个胃和回肠，食团在前胃压力作用下以6毫米/小时的速度向后推挤。围食膜的生长速度约为3毫米/小时。中肠或回肠不发生蠕动；这些区域的肌肉仅起到抵消前胃产生的内部压力的作用。新蜕皮动物的外质和内质围食空间是开放的，液体可以双向流动。内质围食空间在第1天充满，导致外质围食空间大幅减少。在回肠袋（外质围食空间）中，围食膜将细菌团与内质围食空间内的粪便团分开。回肠壁指状内陷的角质层覆盖物上长出的羽状刚毛将大部分细菌团固定在原地。从第1天到第3天，嗉囊重量下降，同时盲肠、胃和回肠的重量增加。第3天后，雌性蟋蟀的食物摄入量和整个肠道系统的重量下降，部分原因是卵巢快速生长导致腹部空间受限。
