Sample collection and RNA extraction

The blood clams collected were mature and approximately two years old. Their shells had a mean length of 30.62±2.28 mm, mean height of 24.33±1.93 mm, mean width of 21.07±1.56 mm and a mean weight of 9.96±2.29 g. The testes of the blood clam were filled with white sperm, while the ovaries were filled with orange eggs, which can be easily identified with the naked eye. Gonadal tissues were dissected, and total RNA was isolated using an EASYspin Plus Tissue and Cell RNA Rapid Extraction Kit (Aidlab, Beijing, China), which also removed genomic DNA. RNA quality was then determined with a 2100 Bioanalyser (Agilent Technologies, CA, USA) and quantified using a NanoPhotometer spectrophotometer (Thermo Fisher Scientific, Wilmington, DE).