Biagio Fernanda P, Tamaki Fabio K, Terra Walter R, Ribeiro Alberto F
Departamento de Genética e Biologia Evolutiva, Instituto de Biociências, Universidade de São Paulo, São Paulo, Brazil.
J Insect Physiol. 2009 Dec;55(12):1125-33. doi: 10.1016/j.jinsphys.2009.08.015. Epub 2009 Sep 2.
The evolution of the digestive system in the Order Orthoptera is disclosed from the study of the morphophysiology of the digestive process in its major taxa. This paper deals with a cricket representing the less known suborder Ensifera. Most amylase and trypsin activities occur in crop and caeca, respectively. Maltase and aminopeptidase are found in soluble and membrane-bound forms in caeca, with aminopeptidase also occurring in ventriculus. Amaranth was orally fed to Gryllodes sigillatus adults or injected into their haemolymph. The experiments were performed with starving and feeding insects with identical results. Following feeding of the dye the luminal side of the most anterior ventriculus (and in lesser amounts the midgut caeca) became heavily stained. In injected insects, the haemal side of the most posterior ventriculus was stained. This suggested that the anterior ventriculus is the main site of water absorption (the caeca is a secondary one), whereas the posterior ventriculus secretes water into the gut. Thus, a putative counter-current flux of fluid from posterior to anterior ventriculus may propel digestive enzyme recycling. This was confirmed by the finding that digestive enzymes are excreted at a low rate. The fine structure of midgut caeca and ventriculus cells revealed that they have morphological features that may be related to their involvement in secretion (movement from cell to lumen) and absorption (movement from lumen to cell) of fluids. Furthermore, morphological data showed that both merocrine and apocrine secretory mechanisms occur in midgut cells. The results showed that cricket digestion differs from that in grasshopper in having: (1) more membrane-bound digestive enzymes; (2) protein digestion slightly displaced toward the ventriculus; (3) midgut fluxes, and hence digestive enzyme recycling, in both starved and fed insects.
通过对直翅目主要类群消化过程的形态生理学研究，揭示了该目消化系统的进化情况。本文研究的是代表鲜为人知的螽斯亚目的一种蟋蟀。大多数淀粉酶和胰蛋白酶活性分别出现在嗉囊和盲囊中。麦芽糖酶和氨肽酶以可溶性和膜结合形式存在于盲囊中，氨肽酶也存在于胃中。将苋菜喂给斑腿泛树蟋成虫或注入其血淋巴中。对饥饿和进食的昆虫进行了相同结果的实验。喂食染料后，最前端胃的管腔侧（以及少量中肠盲囊）被严重染色。在注射染料的昆虫中，最后端胃的血腔侧被染色。这表明前端胃是水分吸收的主要部位（盲囊是次要部位），而后端胃则将水分分泌到肠道中。因此，推测从后端胃到前端胃的液体逆流可能推动消化酶的循环利用。消化酶排泄速率低这一发现证实了这一点。中肠盲囊和胃细胞的精细结构表明，它们具有可能与其参与液体分泌（从细胞到管腔的移动）和吸收（从管腔到细胞的移动）有关的形态特征。此外，形态学数据表明，中肠细胞中同时存在局部分泌和顶浆分泌机制。结果表明，蟋蟀的消化与蝗虫的消化不同之处在于：（1）有更多的膜结合消化酶；（2）蛋白质消化略微向胃转移；（3）在饥饿和进食的昆虫中，中肠通量以及因此的消化酶循环利用。
