Glötzner J, Ziegler A
Z.E. Elektronenmikroskopie, University of Ulm, D 89069 Ulm, Germany.
Arthropod Struct Dev. 2000 Jul;29(3):241-57. doi: 10.1016/s1467-8039(00)00030-x.
Isopods shed first the posterior and then the anterior half of the body. Before molt, most terrestrial species resorb CaCO3 from the posterior mineralized cuticle. The mineral is stored in anterior sternal deposits, which are used to calcify the new posterior cuticle after molt. For Porcellio scaber it is known that the anterior sternal epithelium has specific structural differentiations for epithelial transport. These differentiations include the plasma membrane surface areas, and the volume fraction of the mitochondria. We analyzed the ultrastructure of the sternal epithelium and used a morphometric approach to study the variations of these parameters between species living in different terrestrial environments. In Ligidium hypnorum, which lives in moist environments, the plasma membrane surface area and volume fraction of mitochondria are much larger than in the semiterrestrial Ligia oceanica. This is in accordance with the relatively larger CaCO3 deposits and shorter time intervals for their formation and resorption in L. hypnorum. For P. scaber, which is adapted to mesic habitats, most values are between those of L. oceanica and L. hypnorum. However, P. scaber has even larger CaCO3 deposits which are formed and degraded within similar time intervals as in L. hypnorum. This unexpected result is considered from the standpoint of more effective mechanisms being present for epithelial ion transport.
等足目动物先蜕去身体的后半部分，然后是前半部分。在蜕皮前，大多数陆生种类会从后部矿化表皮中重新吸收碳酸钙。这些矿物质储存在前胸腺沉积物中，蜕皮后用于钙化新的后部表皮。对于鼠妇属动物而言，已知前胸腺上皮具有用于上皮运输的特定结构分化。这些分化包括质膜表面积和线粒体的体积分数。我们分析了胸腺上皮的超微结构，并采用形态计量学方法研究了生活在不同陆地环境中的物种之间这些参数的变化。生活在潮湿环境中的苔藓鼠妇，其质膜表面积和线粒体体积分数比半陆生的海蟑螂大得多。这与苔藓鼠妇中相对较大的碳酸钙沉积物以及它们形成和吸收的较短时间间隔相一致。对于适应中生栖息地的鼠妇来说，大多数数值介于海蟑螂和苔藓鼠妇之间。然而，鼠妇有更大的碳酸钙沉积物，其形成和降解的时间间隔与苔藓鼠妇相似。从存在更有效的上皮离子运输机制的角度来考虑这一意外结果。
