Quantification and ultrastructure of oosorption inEretmocerus eremicus (Hymenoptera: Aphelinidae)

Abstract

The potential for and ultrastructure of oosorption were examined in Eretmocerus eremicus, a short-lived whitefly parasitoid that obligately produces anhydropic oocytes. In the absence of hosts, median egg load decreased by approximately 12% per day between 2 days and 8 days following eclosion. Parasitoid mating status had no significant effect on either egg load alone or the relationship between egg load and age. Yolk degradation in E. eremicus is autolytic, with the enzymes required for yolk sphere digestion apparently being derived from within the ooplasm. The exochorion appear to be digested by the follicular epithelium concurrent with the uniform degradation of the entire ooplasm. The potential adaptive benefits of this novel oosorption mechanism to E. eremicus females include a reduction in the total digestion time per oocyte and resorption of chorion remnants. Finally, to our knowledge, the results of this study provide the first unequivocal ultrastructural evidence of a purely autolytic oosorption mechanism in Insecta.

Biochemical changes in the transition from vitellogenesis to follicular atresia in the hematophagous Dipetalogaster maxima (Hemiptera: Reduviidae)

“…In the hemipteran P. c. stali, once oosorption was induced, the aminoacids and peptides arising from vitellin degradation would return back to the hemolymph (Kotaki, 2003). More recently, yolk digestion within the ooplasm in the hymenopteran Eretmocerus eremicus was demonstrated by ultrastructural analysis (Asplen and Byrne, 2006). In D. maxima, expression of vitellogenin protein in the fat body was detected even at late atresia (results not shown), but in a lesser extent than in vitellogenesis (Aguirre et al, 2008).…”

Oosorption in the Endoparasitoid,Pteromalus puparum

“…This process has been demonstrated in various insect species (King and Ratcliffe 1969; Bell and Bohm 1975; Rivero-Lynch and Godfray 1997; Rosenheim et al 2000; Kotaki 2003; Asplen and Byrne 2006; De Souza et al 2007). Resorption of oocytes is assumed, in most cases, to be a way of recycling eggs that have reached maturity, but which have not been used in oviposition (Rivero and Godfray 1997).…”

“…Oosorption in the cockroach Leucophaea maderae was induced when the adult females were starved for several days (Engelmann and Mala 2005). Structural variations revealed the presence of oosorption in host-deprived Eretmocerus eremicus (Asplen and Byrne 2006). Egg resorption at the basal part of ovariole was observed in the starved Nasonia vitripennis (King and Richards 1968).…”

“…It may be considered to be an adaptive means of recruiting resources for future reproduction (Barrett et al 2007). When oosorption is induced, eggs load in the ovary are decreased and apoptosis of the oocytes occurs, but the physiological mechanisms involved in this process have never been well elucidated (Papaj 2000; Rosenheim et al 2000; Asplen and Byrne 2006). …”

“…Both of these processes are critical to understanding the reproductive mechanisms of insects. From the previous studies, oosorption was characterized by reduction in total number of oocytes in the ovary and the appearance of space between oocytes (King and Ratcliffe 1969; Kotaki 2003), but only a few studies have been conducted on variations of oocyte ultrastructure during this process (Richards and King 1967; Asplen and Byrne 2006). Whether this phenomenon and the associated physiological mechanism commonly occur in insects, especially in parasitic wasps, has not been well reported (Kotaki 2003).…”