Light electron microscopic and morphometricanalyses of the hindgut of the waterbug, Notonecta glauca L. (Heteroptera : Hyprocorisae) - Gross, A.; Sitte, H.; Werner, G. (Elsevier)
The present study was undertaken to provide quantitative data of the transportepithelium in the hindgut of Notonecta glauca, thus allowing a better correlation of structural and functional findings. The ileum of N. glauca is made of 2 different epithelia: (1) a columnar epithelium with an average height of 110 μm and all characteristics of transporting cells, forming a ''U''-shaped pillow in the dorsal and lateral parts of the wall; (2) the ventral part consists of an unspecialized flat epithelium only 1 - 2-μm high. The adjustment between these extreme differences in height is achieved by a narrow zone of transitional cells. The pillow-cells, as essential elements for transport function of the hindgut, have been studied by light and electron microscope and analyzed by morphometric methods. The most conspicuous ultrastructural feature is the abundance in mitochondria and theenormous enlargement of the apical and basal cell membrane which, in addition to the relatively small enlargement in the narrow border zones, traverses the whole cell body in the form of deep infoldings. Thus, remarkable differences exist in form and size of the mitochondria in the apical and basal part of the cell, as well as in the structure of the complexes that are seen between mitochondria and membrane folds. These morphologically visible differences could express diverse transport functions in the apical and basal part of the cell. By morphometry, the length (7.7 mm), the surface (4.9 mm^2) and the volume (0.4 mm^3)of the ileum pillow were determined. For the main cellular compartments, the following relative volumes were found: apical and basal folds, 6.1 %; tracheoles, 0.8 %; total extracellular space, 6.9 %; total intracellular space, 93.1 %; cytoplasm, 43.0 %; mitochondria, 54.7 % and cell nuclei, 2.3 %. The cell surface is enlarged by the factor of 1:500, from which the total surface of the plasmalemma is calculated to be 24.5 cm^2. As a further parameter important for the function, the S/V (surface/volume) relation was determined. S/V relation of the plasmalemma area to intracellular space: 8.6 [fd]275-1 S/V relation of the plasmalemma area to mitochondria volume: 15.7 [fd]275-2 The possible functional mechanisms of the ileum pillow are discussed.
http://dx.doi.org/10.1016/S0020-7322(81)80014-1
Keywords: W