Microscopic Observations on Form and Structure of the Worm Enchytraeus buchholzi (Clitellata: Enchytraeidae).

Background: The worm Enchytraeus buchholzi is a new record species for Shaanxi, China, and a key pest on American ginseng Panax quinquefolium. To distinguish the species, the authors prepared its whole mounts and paraffin-embedded sections, and microscopically observed, photographed and measured. Besides, we conducted an experimental study on its DNA barcode.  RESULTS: Cells, tissues and organs related to nervous, digestive, circulatory, excretory and reproductive systems were found, photomicrographed and described, including: prostomium, peristomium, segments, clitellum, pygidium, lateral and ventral chaetae; brain, cranial nerves, sensory papillae, ventral nerve cord; pharyngeal pad and glands, retractor muscles and muscular bundles, peptonephridia, esophagus, intestine; dorsal, lateral, ventral and intestinal parietal vessels, coelomocytes, coelomic cavity; nephridia, chloragogen cells; ovaries, groups of germ cells with developing oocytes, mature eggs, spermathecae; testes, seminal vesicles, sperm funnels, penial bulbs. Their shapes and sizes were given, and functions discussed briefly. The visual effect of staining specimens with hematoxylin plus eosin ranked the first, and that with acetocarmine the second.  CONCLUSIONS: The supplementary and objective descriptions, with the microphotographs as forceful pieces of evidence, have expanded biological knowledge in aspects of the form, structure and function of the worm, which is helpful for professionals to recognize and understand this species and provide a solid basis for its integrated pest management.