Calcitonin-immunoreactive cells of the digestive tract of the amphioxus are distributed concentrically in a restricted region of the mid-gut

Abstract

In amphioxus (Branchiostoma belcheri), calcitonin-immunoreactive cells of the digestive tract were distributed concentrically in a 1-mm region of the latter half of the mid-gut. In the mid-gut caecum these cells were also present, but were dispersed throughout the length. The total number of cells in both parts ranged from 280 to 1157, varying from individual to individual, although the number in the mid-gut caecum was only 100-200. These cells were morphologically typical gut endocrine cells. Considering their morphology and the characteristics of their distribution pattern, these cells may be related to some phenomena of digestive processes.