Light and electron microscopic studies on the gastrointestinal tract of the suckling echidna (Tachyglossus aculeatus)

Abstract

The stomach of the suckling echidna is lined by a tall columnar epithelium that is bounded basally by a delicate basement membrane. Adjacent cells are held in close apposition by tight junctions near the apex and by extensive implications of the remaining lateral surfaces. The basal cell surface is smooth and without apparent specialization. The lining epithelium is characterized by an abundance of mitochondria and a relative paucity of other organelles. Scattered argentaffin cells extend between the bases of the gastric lining cells and rest upon the luminal side of the basement membrane.Absorptive cells lining the small intestine of the suckling echidna exhibit invaginations of the apical plasma membrane which branch and anastomose, forming a dense network of tubules in the apical cytoplasm. Adjacent to this network is a series of small vacuoles of varying diameters which come into direct relation with a single, large, supranuclear vacuole. The vacuolar system contains both a fine granular substance and clusters of a flocculent amorphous material thought to be of a proteinaceous nature. The surrounding cytoplasm contains numerous profiles of smooth endoplasmic reticulum, several (Colgi systems, and a relative abundance of mitochondria. Clusters of homogeneous droplets are found in the cytoplasm and in the intercellular space.

Intestinal Glycosidase Activities in one Adult and two Suckling Echidnas: Absence of a Neutral Lactase (b-D-Galactosidase).

“…It may well be that the extensive network of tubules in the apical cytoplasm of the intestinal absorptive cells in suckling echidnas observed by Krause (1972) provides such a mechanism. These tubules are in communication with invaginations of the apical cell membrane located between the microvilli and lie close to small spherical vacuoles (probably lysosomes) and a large supranuclear vacuole.…”

über lysosomale Strukturen im Darmepithel des Säugers während seiner prä‐ und postnatalen Entwicklung. Eine mikromorphologisch‐funktionelle Synopse*

“…a,;proximaler Dickdarm: ONO, 1976, 1977Abb. 7); desgleichen ebenso beim Jungen des Schnabeligels (KRAUSE, 1972) und der Beutelratte (KRAUSE et al, 1977. Diese auch als ,,giant vacuoles" (WISSIG/GRANEY, 1968;KNUTTON et al, 1974) und als ,supranuclear vacuoles" (ONO, 1976 bezeichneten Gebilde sind ,,.…”

Prenatal and postnatal development of the small intestine in the insectivore Suncus murinus

“…On the other hand, (Dunn, 1967). As mentioned above, epithelial cells concrypts appear at between 25 and 30 day posthatching in tain the structural components needed for absorption, the echidna (Krause, 1972) and at 75 days after birth in such as microvilli and cytoplasmic organelles, in the last the opossum (Krause et al, 1977). In the Suncus they few days of gestation and accomodate the intestine to appeared at 15 days after birth, just before weaning.…”

“…The complexes are considered to indicate a n absorption of intact protein from the intestinal lumen (Staley et al, 1968;Cornell and Padykula, 1969;Clarke and Hardy, 1970;Staley et al, 1972;Wooding et al, 1978;Gonnella and Neutra, 1985). The apical endocytotic complexes and supranuclear vacuoles were also studied along these same lines in the opossum (Metatheria) and in the echidna (Monotremata) (Krause, 1972;Krause et al, 1977). It is well known that most insectivores have a short intestine that has no cecum.…”