A. Location of the mir-1991 in the Post clusters in Crassostrea gigas, Lottia gigantea and Capitella teleta. Arrow shows the strand orientation of the gene. B. The expression pattern of oyster miRNA cgi-miR-1991 and oyster gene CgPOST1 in different development stages. The samples are abbreviated as follows: s01.E, egg; s02.B, blastula; s04.T2, trochophore; s05.D, D-shape larva; s06.U, umbo larva; s08.P2, pediveliger larva; s09.S, spat; s10.J, juvenile. c. The expression pattern of oyster miRNA cgi-miR-1991 and oyster gene CgPOST1 in different organs. The samples are abbreviated as follows: t01.Mao, outer edge of mantle along the margin of the shell; t02.Mai, inner pallial part covering the inner surface of the shell; t03.Dgl, digestive gland; t04.Gil, Gill; t05.Amu, adductor muscle; t06.Hem, hemolymph; t07.Lpa, labial palps; t08.Fgo, female gonad.