Functional morphology of pylorus and rectal glands in Reduviidae (Insecta—Heteroptera)

Abstract

Anatomical and histological studies of the alimentary organs of sixteen reduviids, with diverse food habits indicate structural variations. The terminal part of the tubular second midgut of these predaceous insects has a permanent sac-like region with distinct histology, concerned with absorption of digested food. In addition, the digestive system is characterised by a reduced pylorus with pyloric-intestinal and pyloric-rectal valves, surrounded by flask-shaped ampullae of the four malpighian tubules. The ampullary cells with their filamentous apices and with fibrillar cytoplasmic processes are concerned with. water absorption. Commonly in all these terrestrial insects, the anterior end of the rectum also bears a well-developed, inverted cup-like rectal gland, the cells of which also absorb water from the excreta stored in the impermeable, intima lined rectum. Members of Ectrichodiinae show simple ampullary cells and a unique rectum, reported for the first time among reduviids with scattered dome-shaped glandular cells as found in Homoptera and in some phytophagous Heteroptera. The simple nature of the alimentary organs indicates its primitive organization within the reduviid subfamilies.

The Diversity of Venom: The Importance of Behavior and Venom System Morphology in Understanding Its Ecology and Evolution

“…In contrast, proteins and peptides obtained by electrostimulation are produced in the posterior gland lumen and are likely to be used for predation as they potently paralyze and kill prey insects [96]. Similar functionally distinct compartments have been found in the main venom glands of other assassin bugs [101,102], although neither the role nor functional specialization of these compartments appears to be shared across all assassin bugs [103,104]. Interestingly, this venom system architecture is also shared with the homologous salivary glands of non-venomous non-heteropteran hemipterans, such as cicadas, where they are thought to perform different roles while feeding on plant sap [105], supporting the idea that this distinction is a morphological pre-adaptation that enables qualitative venom modulation.…”

Proteotranscriptomic Analysis and Toxicity Assay Suggest the Functional Distinction between Venom Gland Chambers in Twin-Spotted Assassin Bug, Platymeris biguttatus

“…Previous studies have mostly focused on AMG and PMG, and empirical studies on different species have yielded inconsistent results. For instance, through toxicity assays, Haridass et al [15] studied the extracts of the different gland compartments of three assassin bug species and found that the AMG of these species were the primary source of venom used to paralyze the prey, and PMG secreted enzymes for the EOD. Combining the toxicity assay and proteomic and transcriptomic analysis, Walker et al [13] analyzed the roles of AMG and PMG extracts of Pristhesancus plagipennis (Reduviidae: Harpactorinae) during predation and defense.…”

“…horrida, the extent of involvement of these two chambers is context-dependent, with PMG responding to minor harassment and AMG to intensive harassment. Although the highly complex function of the main venom gland chambers from assassin bugs has been studied across several species [7,[13][14][15], the function of AG remains largely unexploited.…”

“…rhadamanthus was studied, which found that the injection of AG extract has no effects on the American cockroach, Periplaneta americana [9]. In 1981, Haridass et al [15] studied the function of salivary gland of three assassin bugs, Haematorrhophus nigroviolaceus (Ectrichodiinae), Pirates affinis (Peiratinae), and Triatoma rubrofasciata (Triatominae), conducted the injection experiment on the beetle Omphora pilosa, found AG has no significant effects on the immobilization or EOD, and suggested AG was the production of water saliva. Although later generations have discovered the existence of proteins in AG in the relative studies of the salivary gland [13,16,17], the exact functions of these protein venoms are unclear.…”

Hexapod Assassins’ Potion: Venom Composition and Bioactivity from the Eurasian Assassin Bug Rhynocoris iracundus

“…P. plagipennis PMG venom, which can be elicited by electrostimulation, paralyzed and killed their prey, whilst AMG venom, extracted via harassment, did not paralyze prey in the studied species [25]. However, paralytic effects of AMG venom were found in other assassin bug species [28]. AMG venom was suggested to serve defensive purposes and might deter common predators such as birds and small mammals [18,25].…”