High expression of NANOS2 in type A SG in Larimichthys crocea. (a, a’) NANOS2 expression in stage I, (b, b’) stage II, (c, c’) stage III, (d, d’) stage IV, (e, e’) stage V, (f, f’) stage VI. (g) Representative image showing high NANOS2 expression in the cytoplasm of As SG. (h, i) NANOS2 expression gradually decrease in Apr and Adiff SG. (j) No NANOS2 signals were detected in type B SG. (k-r) No NANOS2 signals were detected in spermatocytes, spermatids, and spermatozoa. SG: As, type A single (1-cell); Apr, type A paired (2-cell); Adiff, type A differentiated (4, 8-cell); B, type B. Spermatocytes: L/Z, leptotene/zygotene; P, pachytene; D, diplotene; SS, secondary spermatocytes. ST1, spermatid I; ST2, spermatid II; ST3, spermatid III; SZ, spermatozoa. Scale bars: a-f = 20 μm; a’-f’, g-r = 10 μm.