On the Structure and Function of the Alimentary Canal of Tigriopus japonicus (Copepoda; Harpacticoida)-I

Histological Structure

Abstract

This study was carried out to elucidate the structure of the alimentary canal of Tigriopus japonicus with special attention directed to the cellular constitution of the mid-gut epithelium. The fore-gut is a rather elongated narrow chitinized tube. The gut has two sets of striated muscles: a circular set participating in constriction and another set participating in dilation. The whole of the mid-gut, wide and sac-like in the anterior region of the body and cylindrical in the posterior region, is lined by a single layer of epithelium devoid of chitinous covering. Two separate glandularepithelia were seen in the mid-gut, and the secretory mechanism of the glandular epithelial cells is discussed. Interspersed among the ordinary mid-gut epithelial cells, darkly stained, slender cells were always visible inevery individual and the biological significance of the cells is considered to be a morphological picture of spontaneous senile decay of the mid-gut epithelial cells. The mid-gut has circular striated muscles arranged in bands and longitudinal non-striated muscles, The hind-gut is a weakly chitinized short tube occupying the level of the last two abdominal segments in the female. The gut has densely arranged circular striated muscles and strong striated muscles participating in dilation.