The salivary glands of Brontocoris tabidus (Heteroptera: Pentatomidae): Morphology and secretory cycle

Morphological structure of salivary glands, alimentary canal, and Malpighian tubules in adult Eurydema spectabilis Horváth, 1882 (Heteroptera, Pentatomidae)

Eurydema spectabilis (Heteroptera: Pentatomidae) has a piercing-sucking mouth type and feeds on plant sap. In this study, the morphological structure of the salivary glands, alimentary canal, and Malpighian tubules of E. spectabilis was examined using light and scanning electron microscopy. Salivary glands consist of the principal and accessory salivary glands. In E. spectabilis, digestion begins in the mouth and ends in the anus. Alimentary canal is divided into three parts: foregut, midgut, and hindgut. The foregut consists of pharynx, esophagus, and proventriculus. The esophagus connects to the proventriculus and resembles a narrow tube. The wall of the proventriculus has a recessed structure and is surrounded by a single cylindrical layer of epithelium and muscle. The midgut is divided into three regions: the first, second, and third ventricles (V1-V3). V1 and V2 consist of single-layered cylindrical epithelium. V3 contains a single layer of cuboidal epithelium. Gastric caeca were found in the midgut. The hindgut consisted of a pylorus followed by a well-developed rectum. The wall of the rectum consists of a single-layer cuboidal epithelium and muscle. Its lumen contains numerous bacteria and uric acid crystals. The pylorus consists of a single-layered cylindrical epithelium. It is also the origin of Malpighian tubules. Malpighian tubules consist of two regions: proximal and distal. The morphological structure of the salivary glands, alimentary canal, and Malpighian tubules of E. spectabilis, which has not been studied before, was examined and discussed in comparison with other orders. It is also aimed to contribute to future studies. RESEARCH HIGHLIGHTS: In E. spectabilis, the salivary glands are divided into principal and accessory salivary glands. Microvilli and numerous secretory granules were found in Malpighian tubules. Numerous uric acid crystals and bacteria were found in the rectum lumen.

Morphological, functional, compositional and transcriptional constraints shape the distinct venom profiles of the assassin bug Sycanus croceovittatus

Predatory bugs employ a salivary venom apparatus to generate complex venoms for capturing and digesting prey. The venom apparatus consists of different glands for the production of distinct venom sets, but the underlying mechanisms behind this process remain poorly understood. Here we present a comprehensive analysis of the morphological, functional, compositional and transcriptional characteristics of venoms derived from posterior main gland (PMG), anterior main gland (AMG), and accessory gland (AG) of the assassin bug Sycanus croceovittatus. Structural observations revealed the intricate constructions of the venom apparatus, enabling the production and storage of three distinct venom sets in anatomically varied glands and allowing them to be modulated in a context-dependent manner upon utilization. There were remarkable differences in the biological activities exhibited by PMG, AMG, and AG venoms. Proteotranscriptomic analysis demonstrated that these venoms displayed compositional heterogeneity at both the quantity and variety levels of proteins. Transcriptional profiles of the identified venom proteins revealed gland-specific or biased expression patterns. These findings indicate that the divergence in venom profiles among different glands arises from morphological, functional, compositional and transcriptional constraints on the venom apparatus, reflecting remarkable morphogenesis and regulatory gene networks responsible for the compartmentalized production of venom proteins in different glands.

Ultrastructural Characterization of Salivary Glands, Alimentary Canal and Malpighian Tubules of the Red Shield Bug Carpocoris mediterraneus Tamanini, 1958 (Heteroptera, Pentatomidae)

In this study, the gut structure and excretory system of Carpocoris mediterraneus which is phytophagous insect, were described with light and electron microscopies and discussed in relation to other Heteroptera species. The salivary system has two principal and accessory salivary glands, two principal and accessory gland ducts. The salivary gland and duct wall have a single layer of cuboidal cells. The duct lumen is surrounded by a thick intima layer. In the cytoplasm of the epithelial cells are seen vesicles. The gut includes fore, mid, and hindguts. The foregut consists of a long narrow tubular pharynx which opens into a slightly wider esophagus. The esophagus is thin walled and in turn opens into the midgut. The midgut has four regions (V1–V4). V1–V4 walls have a monolayered epithelium. V1 epithelium is double-nucleated. V1 cytoplasm contains numerous vesicles, secretory granules, spherocrystals, and cytoplasmic inclusions. Rod-shaped bacteria are seen in V4 lumen. The hindgut has pylorus and rectum. Malpighian tubules were attached in the pylorus. Malpighian tubules have a single-layer cuboidal epithelium. In their lumen, there are spherocrystals. The rectum wall has a monolayer of squamous epithelium and muscle layer. Numerous bacteria and uric acid crystals are seen in its lumen.