Cytologic and electron microscopic studies on the intestinal respiration of the loach (misgurnus anguillicaudatus)

Abstract

In addition to lung and gill respirations, there is a specific type of respiration in the Misgurnus anguillicaudatus which is generally called ‘Loach's intestinal respiration’ and is considered to be of as large as one third of the total respiration volume. Many experimental and physiological studies about the intestinal respiration have been made (SUYEHIRO 1933, KOYAMA 1958 etc.), yet no one has made any morphological study up to the present. After our cytological and electronmicroscopical studies of matured loach's intestines it has been confirmed that the respiration is carried out by straight intestine (lower intestine) and especially that columnar cells each are to play an active part in it. Furthermore comparative studies have been made between lung epithelium (LOW 1952, BARGMANN and KNOOP 1956, KARRER 1956 and GRONIOWSKI and DJACZENKO 1961) as well as gill epithelium (HAYEK 1960, MIZUHIRA et al. 1962) and loach's lower intestine epithelium from the respiratory functional view point. The results obtained are summarized as follows; Material and methods: Matured loachs (Misgurnus anguillicaudatus) were sacrificed after one day's starvation, and upper intestine (coiled intestine) and lower intestine (straight intestine) were extracted and fixed in LEVI'S solution, ZENKER-formol and 10% formalin. For the electron microscopy, small pieces of both intestines were fixed in 1% osmium tetroxide adjusted to pH7.4 with phosphate buffer, dehydrated through a series of alcohol, and then embedded in styrene and n-butyl methacryrate (1:1), epon, and new epoxy resine ‘epok 533′ recommended by KUSHIDA's method. Thin sections were cut on a PORTER-BLUM microtome with glass knives, stained with uranyl acetate, and examined in a HITACHI's HU-10 electron microscope and a NIPPON DENSHI's JEMT-6 electron microscope at magnification of 1,000-10,000. © 1963, International Society of Histology and Cytology. All rights reserved.