Gross Morphology and Histology of Head and Salivary Apparatus of the Predatory Bug,Rhynocoris marginatus

Abstract

Rhynocoris marginatus Fabricius (Hemiptera: Reduviidae) is an important biological control agent against more than 25 insect pests in India. For a better understanding of the feeding adaptation of this bug, the gross morphology and histology of its head and salivary apparatus were studied using both a light microscope and scanning electron microscope. The head is more or less elongate, mobile, and immersed into the eyes. R. marginatus has a three-segmented curved rostrum; the middle segment is longer than the other two segments. The terminal rostral segment bears spines and trichobothria externally. Stylet bundles bear two pairs of maxillary and mandible stylets in the curved rostrum with serrations. The stylets help to penetrate into the tissue and directly pump the toxic venomous saliva deep into the prey. The principal gland is bi-lobed (anterior lobe and posterior lobe), whereas the accessory gland is uni-lobed, exhibiting distinct functional and histological differences. These glands receive tracheal and nerve supply. Mononucleated, binucleated, trinucleated and polynucleated cells are distributed both in anterior and posterior lobes of the principal gland. The cytoplasm has collecting vacuoles with secretions. Therefore, this predator is highly equipped with well-developed mouthparts that are attached to the salivary apparatus.

Cytochemical study of Rhodnius neglectus and Rhodnius prolixus salivary gland cells (Hemiptera, Triatominae)

“…Orcein (for proteins-DNA complexed), Feulgen reaction (specific to DNA) and C-Banding (for constitutive heterochromatin), which are specific for chromatin staining, showed a predominance of decondensed chromatin, as already described for salivary glands of other Hemiptera (laCoMBe, 1999;anHê & azereDo-oliVeira, 2008;serrão et al, 2008;kuMar & saHayaraj, 2012;De Castro et al, 2013;Martínez et al, 2014). These characteristics indicated increasing nuclear mass in relation to the cytoplasm and increasing metabolic activity (li et al, 2007), necessary to produce saliva.…”

“…Since fully active nucleoli are large (nanya & BiCuDo, 1995;CarMo-FonseCa et al, 2000), it can be suggested that this large nucleolar area was related with high cellular metabolism. Large nucleolar area was described for salivary glands of other Hemiptera (laCoMBe, 1999;anHê & azereDo-oliVeira, 2008;serrão et al, 2008;kuMar & saHayaraj, 2012;De Castro et al, 2013;Martínez et al, 2014). A previous study showed acid phosphatase activity in salivary gland cells of R. neglectus and R. prolixus.…”

Tissue-specific transcription of proteases and nucleases across the accessory salivary gland, principal salivary gland and gut of Nezara viridula

“…The two lobes of the stink bug salivary gland are believed to produce watery saliva (ASG) and sheath saliva (PSG) (Kumar and Sahayaraj, 2012;Miles, 1972;Will et al, 2012). Watery saliva is involved with digestion of plant food and contains essential digestive enzymes.…”

Reduviids and Their Merits in Biological Control

“…Considering the feeding adaptive features, reduviid predators have mandibular stylet tips with barbs or tooth or knifelike (Cohen 1996;Sahayaraj and Vinothkanna 2011;Kumar and Sahayaraj 2012), an organ usually used for predator. Though more than 96 % of reduviid predators are zoophagous, Harpactorinae species live in a specific relationship with certain plant species from which they obtain carbohydrates from food bodies, extrafloral nectar and hemipteran honeydew, or from sap by biting the plants (says Stoner et al 1975;Bérenger and Pluot-Sigwalt 1997;Tallamy et al 2004).…”