Egg Formation in Lepidoptera

Abstract

Reproductive biology in the Twentieth Century produced comprehensive descriptions of the mechanisms of egg formation in most of the major orders of insects. While many general principles of ovarian development and physiology emerged, every order turned out to have a set of its own special motifs. Discovery of the lepidopteran motifs is summarized in this essay. The emphasis is on developmental mechanisms, beginning with the early growth and differentiation of female germ cells and ending, after many turns in morphogenesis, physiology and biosynthesis, with eggs that are filled with yolk and encased in chorions. Examples of uniquely lepidopteran traits include the cellular composition of ovarian follicles, the number of tubular ovarioles in which they mature, the functions of cell-to-cell junctional complexes in their maturation, their use of glycosaminoglycans to maintain intercellular patency during vitellogenesis, the role of proton and calcium pumps in their ion physiology, a separate postvitellogenic period of water and inorganic ion uptake, and the fine structure and protein composition of their chorions. Discovery of this combination of idiosyncracies was based on advances in the general concepts and techniques of cell and molecular biology and on insights borrowed from studies on other insects. The lepidopteran ovary in turn has contributed much to the understanding of egg formation in insects generally.

The maternal transfer of bacteria can mediate trans-generational immune priming in insects

“…We postulate that the bacteria are translocated from the hemocoel into the developing eggs passively, concomitant with the uptake of lipophorins and vitellogenins during oogenesis. 26 Vitellogenin is a yolk precursor which acts as a ligand to promote the massive uptake of lipophorins by endocytosis. Apolipoproteins such as apolipophorin III in the G. mellonella hemolymph are known to bind bacteria and bacterial cell wall compounds such as lipopolysaccharides and β-1,3-glucans and to contribute to the extracellular encapsulation of entrapped bacteria within nodules.…”

Sex pheromones in mate assessment: analysis of nutrient cost of sex pheromone production by females of the mothHeliothis virescens

“…Especially given the relatively high contribution of adult food to pheromone production in H. virescens females, it seems highly unlikely that pheromone production can impose a significant metabolic cost to virgins. For mated females, the amount of nutrients used for pheromone production is similar to that for virgins; however, nutrient use for other metabolic activities, especially oocyte production, is much greater (Foster, 2009;O'Brien et al, 2002;Telfer, 2009). When mated females feed on abundant exogenous sugar, they maintain pheromone (Foster, 2009) and increase egg production (Ramaswamy et al, 1997).…”

Identification and functional characterization of an ovarian aquaporin from the cockroachBlattella germanicaL. (Dictyoptera, Blattellidae)

“…Blattella germanica has panoistic ovaries, which is the less modified insect ovarian type (Büning, 1994). During oocyte maturation, basal oocytes increase in size through the incorporation of vitellogenin, other yolk precursors and water (Belles et al, 1987;Ciudad et al, 2006;Martín et al, 1995;Telfer, 2009). Moreover, although B. germanica is well adapted to xeric environments (Appel, 1995), water stress readily leads to oocyte resorption.…”