Microanatomical and secretory characterization of the salivary gland of the Rhodnius prolixus (Hemiptera, Reduviidae, Triatominae), a main vector of Chagas disease

Rhodnius prolixus is the principal vector of Trypanosoma cruzi , the aetiological agent of Chagas disease in American countries. This insect is haematophagous during all life cycles and, to antagonize its haemostatic, inflammatory and immune systems, it secretes saliva while feeding on the vertebrate host's blood. Here, we investigated characteristic changes of the salivary glands (SG) that occur during insect development. Two pairs of lobules and ducts comprise the SG of R. prolixus . The organ's size increases over time, but the microanatomical structures are preserved during insect development. Both lobules have a single layer epithelium formed by binucleated cells, which surrounds the saliva reservoir. The principal lobule presents higher polysaccharide and total protein contents than the accessory lobe. A network of external muscle layers is responsible for organ contraction and saliva release. Apocrine, merocrine and holocrine secretion types occur in the secretory epithelium. Dopamine, serotonin and tyrosine-hydroxylase are neural-related molecules that regulate SG function both during and after feeding.

Evolution and role of the follicular epidermal gland system in non-ophidian squamates

Many lizard and amphisbaenian lineages possess follicular glands in the dermis of the inner thighs and/or the area anterior to the cloaca. These tubular glands produce a holocrine secretion that finds its way to the external world through pore-bearing scales (femoral and/or preanal pores). Secretions are composed of proteins and many lipophilic compounds that may function as chemosignals in lizard and amphisbaenian communication. In recent years, we have begun to develop an understanding of the adaptive significance of these secretions, and they are currently thought to play an important role in a variety of processes in these animals. While it appears that epidermal gland secretions function in intra- and interspecific recognition and territoriality, research has focused largely on their role in mate assessment. Despite these recent studies, our knowledge on the true role of the chemicals found in epidermal secretions remains poorly studied, and there are many possible avenues for future research on this topic. Here, we review the literature on the follicular epidermal glands of non-ophidian squamates and provide a first taxon-wide overview of their distribution.

Nectary ultrastructure and secretory modes in three species of Tillandsia (Bromeliaceae) that have different pollinators

The floral nectaries of three Tillandsia L. spp. having different pollinators were investigated with transmission electron microscopy (TEM) to describe the previously unstudied ultrastructure of the nectar-producing tissues (primarily the epidermis) and also to determine if any differences in the ultrastructural features could be correlated to pollination mode. We determined that there were variations in nectaries among the three species, and that these may be linked to pollinator choice. Tillandsia seleriana Mez, which has a strict relationship with ants, had a nectary epithelium characterized by abundant dictyosomes and endoplasmic reticulum (ER), and a final degeneration stage possibly leading to holocrine secretion. The presence of protein crystals in epithelial plastids was correlated to a nectar enriched with amino acids and proteins, likely functioning to provide a protein-enriched diet and possibly defence against pathogens. Epithelial cells of the hummingbird-pollinated Tillandsia juncea (Ruiz et Pav.) Poir. nectary displayed cell wall ingrowths and dictyosomes and also contained cytoplasmic lipid droplets and protein crystals within plastids, both of which would enrich the nectar for hummingbirds. The nectary epithelium and the parenchyma of bat-pollinated Tillandsia grandis Schltdl. possessed a few cubic protein crystals in the plastids and its secretion product appeared electron transparent.