*2.1. Source and Domestication of Test Animals*

*Daphniopsis tibetana* is an inland saline cladoceran that is widely distributed in saltwater lakes in Tibet and Qinghai, China, including NMKC (31◦83 N, 89◦79 E), PC (31◦89 N, 90◦95 E), and ZTGC (32◦00 N, 90◦90 E) (Figure 1).

**Figure 1.** Sampling points of each lake. SLC, Selincuo Lake; BGH, Bangehu Lake.

The *D. tibetana* used in the experiment were collected from NMKC, PC, and ZGTC in Tibet in October 2018. *Daphniopsis tibetana* were brought back to the laboratory and domesticated in diluted seawater with a salinity of 15–16 ppt at 15 ± 0.5 ◦C and fed with *Chlorella pyrenoidosa*. To avoid the negative impact of individual differences on the experiment, observation of life history started with the larval-stage of *D. tibetana* of the same maternal line. We isolated one gravid mother prior to the experiment and only used its offspring. For the process of domestication, pure water was added to sterilized seawater to adjust the salinity, and the seawater was diluted to 15~16 as culture water. The room temperature was controlled by air conditioning, and the temperature was adjusted to 15 ± 0.5 ◦C. The Chlorella pyrenoidesa was used as feed with one daily feeding. The culture medium was not replaced during the observation period.

#### *2.2. Experimental Design*

Some 30 larval *D. tibetana* cultured under seawater domestication conditions during the same period were selected for experimentation. One larval *D. tibetana* each was placed in a 16-mL test tube. During the experiment, its death, molting, time of first birth, interval between births, and number of births were observed and recorded. The experiment was conducted until the *D. tibetana* died.
