Midgut remodeling during the metamorphosis of Chironomus riparius, Meigen (1804)

Abstract

The holometabolous insects go through a complete metamorphosis that includes four life stages: egg, larva, pupa, and imago (adult). Chironomus riparius is a suggested model organism by the Organization for Economic Cooperation and Development (OECD) that is used in acute and chronic tests of chemicals. Tissue morphology of healthy non-biting midge larval stage was already described but the faith of the midgut digestive cells and tissue organization during the metamorphosis is unknown. We here described histological alterations of the midgut during ecdysis to distinguish them from the ones caused by toxins’ negative effects. The present study showed differences in tissue architecture of the midgut in the larval, prepupal, and pupal stages of development of C. riparius. During ecdysis, larval digestive cells detached from the midgut epithelium and moved to the lumen. In the pupa, the larval midgut layer was replaced with an adult midgut that had considerably reduced width. These changes in the midgut tissue morphology and organization probably follow changes in the environment and feeding behavior of C. riparius at different stages of development.