Enteric microbial communities of mesopelagic calanoid copepods feeding on marine snow were examined using 16S rRNA gene amplicon pyrosequencing targeting the V4 region. Samples were collected from Sagami bay, Japan. We selected the following mesopelagic species as the targets: semi-transparent gut, Pleuromamma xiphias and Spinocalanus magnus red-colored gut, Scottocalanus helenae and Scottocalanus securifrons. A comparison was also made between the enteric bacterial communities of the copepods and the morphology of the guts of copepods. Some taxa of calanoid copepods have extremely elongated guts for efficient digestion. In the present study, attention was paid to the gut color of the calanoid copepods.