Lovett D L, Felder D L
Biol Bull. 1990 Apr;178(2):160-174. doi: 10.2307/1541974.
Ultrastructure and histochemical distribution of enzymes were examined in the midgut of larval and postlarval stages of Penaeus setiferus. Acid phosphatase and esterase activities were present in all gut tissues at all stages. Protease activity was present in the anterior and lateral midgut caeca, as well as in the anterior portion of the midgut trunk (MGT) of larvae and early postlarvae (PL1-PL4). Amylase activity could not be detected histochemically in larvae or early postlarvae, even though it was detected in assays of whole-animal homogenates. In later postlarvae, both protease and amylase activities were present in the hepatopancreas and anterior MGT, but were absent from the anterior midgut diverticulum. In larvae, alkaline phosphatase activity is present throughout the midgut, suggesting that absorption is widespread. In juveniles, activity is restricted to the hepatopancreas and regions of the MGT within the cephalothorax. The abdominal MGT (or "intestine") is no longer absorptive by the time the hepatopancreas has attained its adult form. Although epithelial cells of the MGT synthesize protein and produce electron-dense secretory vesicles, they are substantially different in ultrastructure from those cells in the hepatopancreas responsible for digestive enzyme synthesis and secretion. Epithelial cells of the larval anterior and lateral midgut caeca are structurally and functionally similar to cells of the postlarval hepatopancreas. However, the lateral midgut caeca retain these features as they transform into the hepatopancreas, while the anterior midgut caeca lose these functions as they degenerate into the anterior diverticulum and change in ultrastructure during early postlarval development. The anterior and posterior midgut diverticula of postlarvae are similar ultrastructurally even though they differ in ontogenetic history.
对长角对虾幼体和后期幼体阶段的中肠进行了超微结构和酶的组织化学分布研究。在所有阶段的所有肠道组织中均存在酸性磷酸酶和酯酶活性。蛋白酶活性存在于幼体和早期后期幼体（PL1 - PL4）的中肠前盲囊和侧盲囊以及中肠主干（MGT）的前部。尽管在全动物匀浆测定中检测到淀粉酶活性，但在幼体或早期后期幼体中通过组织化学方法未检测到淀粉酶活性。在后期后期幼体中，蛋白酶和淀粉酶活性均存在于肝胰腺和中肠主干前部，但中肠前憩室中不存在。在幼体中，碱性磷酸酶活性存在于整个中肠，表明吸收广泛。在幼虾中，活性局限于肝胰腺和头胸部内中肠主干的区域。当肝胰腺达到成年形态时，腹部中肠主干（或“肠道”）不再具有吸收功能。尽管中肠主干上皮细胞合成蛋白质并产生电子致密分泌小泡，但它们在超微结构上与肝胰腺中负责消化酶合成和分泌的细胞有很大不同。幼体中肠前盲囊和侧盲囊的上皮细胞在结构和功能上与后期幼体肝胰腺的细胞相似。然而，侧中肠盲囊在转化为肝胰腺时保留了这些特征，而前中肠盲囊在退化为前憩室并在后期幼体发育早期超微结构发生变化时失去了这些功能。后期幼体的中肠前憩室和后憩室在超微结构上相似，尽管它们在个体发育史上有所不同。
