Morphology, ultrastructure, and chemical compounds of the osmeterium of Heraclides thoas (Lepidoptera: Papilionidae)

Abstract

The osmeterium, found in papilionoid larvae, is an eversible organ with an exocrine gland that produces substances in response to the mechanical disturbances caused by natural enemies. The anatomy, histology and ultrastructure of the osmeterium, and the chemical composition of its secretion in Heraclides thoas (Lepidoptera: Papilionidae) were studied. Heraclides thoas larvae have a Y-shaped osmeterium in the thorax. The surface of the osmeterium has a rough cuticle lining cells with papillae and irregular folds, whereas the cells that limited the gland pores are irregular, folded, and devoid of papillae. Two types of cells are found: (i) cuticular epidermal cells on the surface of the tubular arms of the osmeterium and (ii) secretory cells of the ellipsoid gland within the region of the glandular pore. Cuticular epidermal cells show a thick cuticle, with several layers divided into epicuticle and lamellar endocuticle. Secretory cells are polygonal, with extensive folds in the basal plasma membrane that formed extracellular channels. The cytoplasm has mitochondria, ribosomes, and numerous vacuoles, whereas the nucleus is irregular in shape with decondensed chromatin. The chemical composition of the osmeterial secretion comprised (Z)-α-bisabolene (25.4%), α-bisabol (20.6%), β-bisabolene (13.1%), (E)-α-bisabolene 8%), β-pinene (9.91%), longipinene epoxide (8.92%), (Z)-β-farnesene (6.96%), β-caryophyllene (2.05%), farnesol (1.86%), linalyl propionate (1.86%), and 1-octyn-4-ol (1.07%). The morphological features suggest that the cuticular epidermal cells play a major role in the maintenance and protection of the osmeterium, whereas secretory cells are responsible for production of osmeterial secretions.

Pyriproxyfen, a juvenile hormone analog, damages midgut cells and interferes with behaviors of Aedes aegypti larvae

“…Vacuolization and damage to brush border suggests that digestive cells are dying, due to the insecticide toxicity (Costa et al, 2014; Hazarika et al, 2018; Vasantha-Srinivasan et al, 2018). The same histopathological effect was observed in midgut cells of Aedes aegypti (Gaban et al, 2015; Costa et al, 2014) and other insects when treated with different bio and chemical insecticide (Fiaz et al, 2018a, 2018b; Martínez et al, 2018a, 2018b).…”

“…Midgut of treated larvae has damaged epithelial layer, with cell debris released in the midgut lumen, similar to found in this insect exposed to other new chemistry insecticides (Gaban et al, 2015). Cytoplasm vacuolization followed by cell breakdown releasing cell debris into the midgut lumen has been associated with digestive cell death caused by xenobiotics in different insects (Costa et al, 2014; Fiaz et al, 2018a; Suresh Kumar et al, 2013; Mangia et al, 2018; Martínez et al, 2018b).…”

Defensive eversible organ in swallowtail larvae: morphology, structure, chemistry and defensive efficacy

“…The osmeterium is a Y-shaped eversible organ located dorsally just behind the head [11,12]. It possesses two exocrine glands at the base of each arm [5,13,14]. Its color is usually yellow/orange, acting as an aposematic warning of both sight and smell [15].…”

“…The osmeterial secretion of Papilionidae larvae comprises a mixture of volatile organic compounds (VOCs) with an unpleasant odor. The chemical composition has been studied in about 20 species, and several compounds have been identi ed to be part of the secretions, including mono-and sesquiterpenes, aliphatic short-chain acids, and esters [11,14,[18][19][20][21][22][23][24][25][26]. In general, the osmeterium's defensive role appears to be more effective against invertebrate predators, including ants and praying mantids [18,[26][27][28], than against vertebrates [23,29].…”

“…Honda [20][21][22] observed in different papilionids that monoterpenes showed a considerable toxic effect against ants, whereas most aliphatic acids exerted weak toxicity against them. The origin of the osmeterium odor has been linked to volatiles released by exocrine glands [14].…”