Structure of the mouthparts and alimentary canal of Eusomus ovulum Germar, 1824 (Coleoptera: Curculionidae)

ABSTRACT

The structural morphology of mouthparts, the distribution of sensilla on the mouthparts, histology, and the morphology of the alimentary canal in adult Eusomus ovulum Germar, 1824 were examined under both light and scanning electron microscopy (SEM). The mouthparts are located at the tip of the short rostrum. The mandibles, the maxillae and the labial palpi comprise the moveable mouthparts. Also there are sensillae which act as chemoreceptors on the terminal segment of the snout.

Alimentary canal of adult E. ovulum is divided into three main regions, foregut, midgut and hindgut. The first part of the gut is foregut, which is made up of a pharynx, esophagus, crop and proventriculus. The pharynx extends from the mouth, having muscle attachments radiating out from its surface and connecting with the head region. The esophagus is a narrow epithelial tube contiguous and posterior to the pharynx. The proventriculus consists of 8 sclerotized plates. The midgut, which is anteriorly bulbous with a tubular posterior half. Gastric caeca were found on the posterior region of the midgut. The midgut is surrounded by outer muscles and inner columnar epithelium. The hindgut has pylorus, ileum, colon, and rectum. There are three histological layers of the hindgut from lumen to hemocoel: intima, epithelium, muscles. The hindgut has a cryptonephridial attachment for the six Malpighian tubes anterior to the rectum.

The aim of the present study is to contribute information on the morphology of mouthparts, and the morphology and histology of the alimentary tract of the insect.

Keywords:
Mouthparts; Foregut; Midgut; Hindgut; Histology; Morphology