Figure 4.

Reproductive ability of hemizygous dsx1 knock-out male. Male and female individuals of the dsx1 reporter strain could reproduce normally. Typically, wild-type females clone themselves under favourable living conditions by producing asexual eggs, while under unfavourable conditions, females ovulate sexual eggs that need to be fertilised and deposited into protective structures called ephippia. In this reproduction test, daphniid populations were subjected to stressful conditions to induce sexual reproduction. For each strain (dsx1 reporter and wild-type), 175 females and 25 males were cultured, in triplicate, for 4 weeks, and ephippia were collected at the end of cultivation. Total ephippia were counted and the frequency of fertilisation was calculated (see Methods) separately for each population. Graphs show mean values from the triplicates. Error bars indicate standard deviation. *p < 0.05 (t-test).