Testes from Blm^cko/neo mice show impaired growth and reduced spermatozoa compared with control littermates. (A) Organ weights from both Blm^flox/neo and Blm^cko/neo mice. Spleen, seminal vesicle (SV), and testes weights from Blm^flox/neo (black) and Blm^cko/neo (gray) animals. Although spleen and seminal vesicle weights were not significantly different between the two genotypes (P = 0.352 and P = 0.325, respectively), testes weights were significantly lower in Blm^cko/neo mice (mean testes weights of 649 mg and 723 mg, respectively; *, P = 0.023). (B) Sperm number per animal was significantly reduced in Blm^cko/neo animals compared with Blm^flox/neo mice (means of 1.456 × 10⁷ and 2.297 × 10⁷, respectively; **, P = 0.006). Mean values for each group are shown by the black lines, with significance indicated by asterisks.