Anatomical and histological studies of the alimentary canal of adult maize leaf weevil, Tanymecusdilaticollis Gyllenhal , 1834 (Coleoptera: Curculionidae)

Morphological Study of the Alimentary Canal and Malpighian Tubules in the Adult of the Pollen Beetle Meligethes (Odonthogethes) chinensis (Coleoptera: Nitidulidae: Meligethinae)

Meligethes (Odonthogethes) chinensis is a highly specialized species of Nitidulidae in China that takes pollen as its main food source, and its main host plant is Rubus idaeus L. (Rosaceae). In this study, the structural morphology of the alimentary canal and Malpighian tubules of adult M. (O.) chinensis was observed under light, fluorescence, and scanning electron microscopy. The alimentary canal of adult M. (O.) chinensis is divided into foregut, midgut, and hindgut. The foregut is the shortest and consists of the pharynx, esophagus, proventriculus, and cardiac valve. The midgut is a straight, distended, cylindrical, thin-walled tube. Numerous blunt-fingered gastric ceca are distributed irregularly throughout the midgut. The hindgut is subdivided into the ileum, colon, and rectum. The ileum is coiled. The colon gradually enlarges posteriorly. The rectum is thickly muscled and followed by a membranous structure. The openings of proximal Malpighian tubules are evenly inserted into the junction of the midgut and hindgut, and distal Malpighian tubules are evenly attached to the colon to form a cryptonephridial system. In this study, we also compare the structure and infer the function of the alimentary canal and Malpighian tubules among beetles, as well as discuss the evolutionary and taxonomical implications.

Larval and adult digestive tract of the carrion beetle Oxelytrum discicolle (Brullé, 1840) (Coleoptera: Silphidae)

Oxelytrum discicolle is a necrophagous beetle occurring in Central and South America, with potential use in forensic entomology for investigations in the context of legal medicine. The present work aimed to describe the morphology of the digestive tract of larvae and adults and contributes to the knowledge about the digestion associated with necrophagy. In the three larval instars, the foregut is short and narrow, the midgut is a dilated tube, elongated with a smooth surface, and the hindgut is narrow and long, with small lateral projections and a dilated terminal region. The gut epithelium in the second and third instar larvae is vacuolated in the mid- and hindgut, with high production of apocrine secretions in the midgut lumen. In adults, the foregut is short, with small spines in the cuticular intima that covers the flattened epithelium. The midgut is dilated, with many short gastric caeca with regenerative cells in the blind portion, which differentiate in digestive columnar cells towards the midgut lumen. The hindgut is long and narrow, with an enlarged distal portion with folded epithelium lined by a thin cuticle. The histochemical tests reveal the absence of protein storage granules in the gut epithelium of larvae and adults. The gut characteristics of the carrion beetle O. discicolle are similar to those of other predatory and phytophagous Coleoptera, which may indicate that ancestry may influence the alimentary canal morphology more than the feeding habits.

Anatomy and histology of the alimentary canal of larvae and adults of Chrysoperla externa (Hagen, 1861) (Neuroptera: Chrysopidae)

The larvae of the lacewing Chrysoperla externa are important predators with the potential to be used in the biological control in agriculture. Although some studies provide important data on the gut morphology in lacewings, they are limited to few species. This study describes the anatomy and histology of the alimentary canal in the predatory larvae and herbivorous adult of C. externa. In larvae, the crop is the larger part of the foregut and it is connected to the midgut by the stomodeal valve. The midgut is an enlarged sac-like organ. At the mid-hindgut transition, there are eight Malpighian tubules. The hindgut is a non-functional vestigial region in the larvae. In adults, the crop has a diverticulum associated with large tracheal trunks, a conic proventriculus with sclerotized lips followed by an elongated tubular midgut. Histological analyses of larval and adult midgut show the presence of a single-layered epithelium with columnar cells with well-developed brush border, nests of regenerative cells, and a peritrophic matrix lining the midgut lumen. The hindgut in adults has an epithelium with cubic cells lined by a thin cuticular intima and rectal pads in the rectum. These data are discussed in comparison with the digestive tract in other Chrysopidae.

Characterization of the alimentary canal and Malpighian tubules of Chrysolina herbacea (Duftschmid, 1825) (Coleoptera: Chrysomelidae): Anatomical and histological approaches

The mint beetle or green mint beetle, Chrysolina herbacea, is one of the most important insect pests of mint herb. These insects are associated with plants belonging to the Lamiaceae family, in particular the Mentha genus. They cause serious damages to plants by consuming their leaves. For this reason, it is an important agricultural pest, and the structure of the digestive system must be known well to combat these insects. The alimentary canal of adult C. herbacea divided into three main regions: foregut, midgut and hindgut. The foregut is characterized by the following parts; pharynx, esophagus, crop, and proventriculus. The proximal part of Malpighian tubules joins with the pyloric valve. Their distal parts are located in the hemocoel and have a wavy appearance and a flat surface. Malpighian tubules are surrounded by a single layer of cubic epithelium which is with brush border, and sheath. The hindgut is formed the following regions; pyloric valve, ileum, colon and rectum. In foregut and hindgut, the layers represented from within out are: intima, epithelium, muscle layer. In the midgut, the layers from within out are: peritrophic membrane, epithelium, muscle layer. The foregut has a monolayer cubic epithelium with oval nuclei. In the midgut, the epithelium is simple columnar while in the hindgut, the epithelium is simple cuboidal. This is the first report on alimentary canal and Malpighian tubules histo-anatomy in C. herbacea. The results will help guide the development of new strategies for managing this pest.