The effect of sexual selection on gene expression in decorated crickets

Sexual conflict, which originates when males and females have opposing interests during a sexual encounter, is very common among insects. Males often attempt to manipulate female behavior and physiology to increase their share of paternity. In the decorated cricket Gryllodes sigillatus, females will mate multiple times and use a mix of all of the obtained sperm to fertilize the eggs. Males offer the female a nuptial food gift when they mate, which is a gelatinous mass named the spermatophylax, that is part of the spermatophore. Spermatophylax feeding deters females from prematurely removing the sperm-containing portion of the spermatophore (ampulla), increasing sperm transfer and thus the paternity share of the male. Additionally, males might also influence female behavior and physiology in ways unrelated to simply increasing sperm transfer duration. We artificially altered the extent of sexual selection in G. sigillatus by keeping them under male-biased or female-biased conditions for 20 generations, leading to intensified sexual selection on respectively males or females. We set up a large-scale RNA sequencing experiment, focused on male accessory glands, female reproductive organs, and female head tissue for three replicate lines for each of these selection treatments. Contrary to our expectations, only small gene expression differences were found in male accessory glands and female head tissue, but a very clear signature of sexual selection was found in the female reproductive organs.