Histological characterization of the ambrosia beetle Xylosandrus compactus (Eichhoff, 1875) female as an important destroy pest on Mitragyna speciosa

The ambrosia beetle Xylosandrus compactus (Eichhoff, 1875) is a serious pest of economically important plants including Mitragyna speciosa, but its body structure and cellular composition remain uncharacterized. In this study, we described whole-body histological characteristics of female X. compactus. Our observation found two district regions in the nervous system: frontal ganglion and ventral nerve cord. The frontal ganglion contained two layers: outer cortex and inner medullae, and the outer cortex was lined with three major types of cells including neurosecretory cells, neuroglia, and neurons. The integumentary system contained three different layers: epicuticle, exocuticle, and endocuticle in the head, thoracic, abdomen, and leg regions. Apparently, only skeletal muscles possessed muscle fibers in the muscular system. The main organ of the urinary system was the Malpighian tubule, the epithelium of which was lined with the simple cuboidal layer. The digestive system consisted of several distinct parts including foregut (for example esophagus, crop, and proventriculus), midgut, and hindgut (or rectum). Three different cell types were identified in the epithelial midgut. The respiratory organ was visible among the adipose tissue close to the integument system. Although this organ was not easily identified, it was covered by a simple squamous epithelium. The female reproductive system of this insect was a telotrophic meroistic ovary. The distribution of nurse cells was restricted to the anterior tropharium, connected to oocytes. All the above results provide the first histological description of X. compactus, which might be useful for advancing research in the related fields.