**1. Intraducation**

*Daphniopsis tibetana* Sars, 1903 belongs to Daphniidae and is a rare saltwater cladoceran [1] that is mainly distributed in high-altitude areas such as Tibet, Qinghai, and Xinjiang in China. *D. tibetana* preferentially live in low temperatures. Moreover, they are well-suited for living at high altitudes in cold and nutrient-poor saline water bodies. *D. tibetana* also plays an important role in the study of cladoceran biology [2].

With the rapid development of mariculture, the demand for live farmed animals is increasing. China and other countries have conducted several series of studies on the cultivation and domestication of cladocerans. Among them, a euryhaline species of cold water, *D. tibetana* is suitable for the water temperature conditions used during the nursery period of northern marine fish and shrimp. Its low temperature tolerance makes *D. tibetana* preferable to warm-adapted species that need to be raised for cultivation in high-temperature environments. *D. tibetana* has a longer developmental period and lower fecundity than Moinidae and *Daphnia* but higher fecundity than marine copepods and marine zooplankton [3]. Additionally, the amino acid composition of *D. tibetana* can fully meet the essential amino acid needs of most marine and freshwater fish and shrimp, and the contents of certain unsaturated fatty acids in the body are even higher than those of many common species, such as *Moina mongolica*, *Moina* spp., *Tigiopus japonica*, *Brachionus plicatilis*, and *Artemia.*

To date, there have been reports on the influence of *D. tibetana* morphology and structure [4], living habits [5], ecological distribution [3], and classification and evolution [6],

**Citation:** Zhang, W.; Zhao, W.; Zou, J.; Wei, J.; Wang, S.; Yin, D. Comparative Biology of *Daphniopsis tibetana* from Different Habitats under Seawater Acclimation. *Water* **2023**, *15*, 34. https://doi.org/ 10.3390/w15010034

Academic Editors: Xiangli Tian and Li Li

Received: 15 October 2022 Revised: 12 December 2022 Accepted: 17 December 2022 Published: 22 December 2022

**Copyright:** © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

and on how environmental factors influence *D. tibetana* population growth and physiological metabolism [7,8]. However, there has been no research on the biology of *D. tibetana* from three lakes in Tibet (Lake Namukacuo, NMKC; Lake Pengcuo, PC; and Lake Zigetangcuo, ZGTC) or on the genetic difference between wild-type and seawater-domesticated *D. tibetana*. This article reports on and compares some biological observations of *D. tibetana* from these three locations that were domesticated indoors to enrich the biological data on *D. tibetana.* This information can be used for in-depth study of indoor seawater domestication and large-scale cultivation of *D. tibetana*.

#### **2. Materials and Methods**
