Cuticular hydrocarbons and wax esters of the ectoparasitoid Habrobracon hebetor: Ontogenetic, reproductive, and nutritional effects

Abstract

Hydrocarbon and wax ester components of cuticular lipids of the braconid parasitoid Habrobracon hebetor Say reared at 25 degrees C on larvae of a pyralid moth have been identified by GC-MS and analyzed with respect to adult age, mating status, and diet. The hydrocarbons range in carbon number from C(21) to C(45) and consist of a homologous series of n-alkanes, 11-, 13-, and 15-methyl alkanes, 13,17-dimethyl alkanes, and Z-5, Z-7, and Z-9-alkenes. The wax esters found in the cuticular lipid fraction are a series of homologous compounds with the acid portion being short chain, unbranched, even carbon number acids from C(8) to C(20) (predominately C(8) to C(16)). The alcohol portions of the esters are secondary alcohols with carbon number from C(22) to C(25) (predominately C(23) and C(25)) with the hydroxyl function located at C(6), C(7), C(8), and C(9). Gender, age, and nutritional states were significant factors for variation in several of the individual esters, but mating status did not affect wax ester composition. Ontogenetic examinations indicated that prepupal, and early pupal cuticular lipids contain only hydrocarbons. Low levels of wax esters are detectable in late stage pupae, and somewhat greater quantities of wax esters are present on newly eclosed adults. When pharate adults emerge from the cocoon, however, their cuticular lipids consist of approximately equal amounts of hydrocarbons and wax esters, and 6d post emergence from the cocoon, wax esters are the predominant lipid component.

Arrhythmic adult ecdysis but rhythmic emergence from the host chorion in Trichogramma embryophagum (Hymenoptera: Trichogrammatidae)

“…Particularly, the difference in chemical composition of cuticle between newly ecdysed and emerging adults of Habrobracon hebetor Say was revealed (Howard & Baker, 2003). In our experiments, the individuals that stayed in the host chorion after the peak of mass emergence also differed from just emerged adults by having a more transparent cuticle.…”

“…Unfortunately, as was noted above, in only a few earlier studies with insect parasitoids were ecdysis and emergence separated (e.g. Teraoka & Numata, 1995;Howard & Baker, 2003). However, it was recorded that ecdysed Trichogramma adults may spend at least more than several hours within the host chorion (Dahlan & Gordh, 1996).…”

Reflectance-based identification of parasitized host eggs and adult Trichogramma specimens

“…However, several studies have described how cuticular hydrocarbon composition of adult individuals of other minute parasitoids is influenced by age, mating status and diet, and how it also may vary among males and females (Howard and Baker, 2003;Howard and Pérez-Lachaud, 2002). Thus, our reflectance-based profiling of parasitoid species is likely associated with species-specific variation in cuticular composition.…”

“…A recent review article claims that UAVs (unmanned aerial vehicles) will revolutionize research methods in spatial ecology (Anderson (Dowell et al, 1999;Roux et al, 2008), (2) in relative composition (Geiselhardt et al, 2009) or in actual composition (Howard and Pérez-Lachaud, 2002) among males and females within a species, (3) during the lifespan of insect individuals (Butler et al, 2009;Howard and Baker, 2003;Lapointe et al, 2004;Roux et al, 2008;Zhu et al, 2006), (4) among eusocial individuals with different tasks (Ferreira-Caliman et al, 2010;Nunes et al, 2009), (5) according to mating behavior and status (Howard and Baker, 2003;Howard and Pérez-Lachaud, 2002;Steiner et al, 2007), and (6) in response to environmental conditions (Howard and Baker, 2003;Howard and Pérez-Lachaud, 2002;De Loof et al, 2010). Thus, there is ample evidence of the composition of the insect cuticula being highly dynamic and tightly associated with complex internal physiological processes in insects.…”

Remote Sensing and Reflectance Profiling in Entomology

“…The results from this reflectance-based study underscore the potential of hyperspectral imaging of the insect body as an approach to nondestructively and noninvasively quantify stress detection. The role of epicuticular hydrocarbons in both intra-and interspecific communication among insects is well established (50), as they tend to vary (a) among closely related species (33,119), (b) in relative (40) or actual (51) composition among males and females within a species, (c) among life stages and age of adults (14,49,70,119,159), (d ) among eusocial individuals with different tasks (38,104), (e) according to mating behavior and status (49,51,129), and ( f ) in response to environmental conditions (27,49,51). Owing to the intra-and interspecific variations in epicuticular hydrocarbon profiles, it seems reasonable to assume that reflectance profiles acquired from insect surfaces may be used to study physiological responses by insects and quantify differences among species.…”