Chemical egg defence in the large milkweed bug, Oncopeltus fasciatus, derives from maternal but not paternal diet

Abstract

Many herbivorous insects sequester defensive compounds from their host-plants and incorporate them into their eggs to protect them against predation. Here, we investigate whether transmission of cardenolides from the host-diet to the eggs is maternal, paternal, or biparental in the large milkweed bug, Oncopeltus fasciatus (Dallas) (Hemiptera: Lygaeidae). We reared individual bugs on either milkweed seeds [MW; Asclepias syriaca L. (Apocynaceae)] that contain cardenolides, or on sunflower seeds [SF; Helianthus annuus L. (Asteraceae)] that do not contain cardenolides. We mated females and males so that all four maternal/paternal diet combinations were represented: MW/MW, MW/SF, SF/MW, and SF/SF. Using larvae of the common green lacewing, Chrysoperla (Chrysopa) carnea (Stevens) (Neuroptera: Chrysopidae), we conducted two-choice predation trials to assess whether maternal, paternal, or biparental transmission of cardenolides into the eggs of O. fasciatus increased protection against predation. Furthermore, we used high performance liquid chromatography (HPLC) to assess putative cardenolide content of eggs from the various parental diet treatment groups. The predation trials suggested that regardless of male diet, eggs were afforded better protection when females had been raised on milkweed. However, many eggs were at least partially consumed. This suggests that although chemical defence of eggs does not guarantee protection to eggs on an individual basis, they may increase the probability that some eggs in a clutch are left intact thereby potentially conferring a fitness advantage to more offspring than if eggs are left unprotected. Based on HPLC analysis we found that maternal contribution of cardenolides was significantly greater than paternal contribution of cardenolides to the eggs, supporting the results of our predation trials that a maternal diet of milkweed makes eggs more distasteful than a paternal diet of milkweed.

The role of maternal effects in adaptation to different diets

“…The changes in the two populations do seem to reflect adaptive evolution in response to novel host use. The wild and the laboratory populations do not differ in cardenolide allocation from milkweed seeds (Newcombe et al ., ), suggesting that altered maternal allocation to egg constituents is not simply a laboratory adaptation, but reflects adaptations to different diets. We suggest that overall changes in maternal effects did occur, but do not appear to have been central to evolving the capacity to use a new host in the experimental O. fasciatus population.…”

Maternal and paternal nutrition in a mosquito influences offspring life histories but not infection with an arbovirus

“…Mechanisms proposed for maternal effects in insects include differences in resource allocation and nutrient provisioning to offspring (Bonduriansky and Day 2009, Lyko et al 2010, Newcombe et al 2013, transfer of symbionts or hormones (Fox et al 1997, Koehler and Kaltenpoth 2013, Liu et al 2014, and changes in the epigenome (Chittka andChittka 2010, Oppold et al 2015). High and low larval food offspring development and survival were both reduced in treatments with two high food parents (H♀H♂-high and H♀H♂-low) relative to treatments with low larval food mothers mated with high larval food fathers (L♀H♂-high and L♀H♂-low).…”

The nutritional geometry of parental effects: maternal and paternal macronutrient consumption and offspring phenotype in a neriid fly

“…alternative hosts: see Fox, Waddell & Mousseau ; Newcombe et al . , ; Newcombe, Moore & Moore ), but is problematic in the more typical case where environments vary along a continuous gradient. Like direct effects of environment on phenotype (developmental plasticity), environmentally induced parental effects should generally be viewed as norms of reaction – i.e.…”