Chromosome-scale genome assembly of the freshwater cladoceran crustacean Chydorus sphaericus: A resource for discovery of genes responsive to ecological challenges

•We present a high-quality of Chydorus genome.•We identified 303 gene families specific to C. sphaericus.•We found 53 significantly expanded gene families in C. sphaericus.•Most expanded gene families with functions related to detoxification.