Infertility of biofloc-reared Litopenaeus vannamei males associated with a spermatophore mycobacterial infection: Description of the pathological condition and implications for the broodstock management and larval production

This study describes a mycobacteriosis in spermatophores of reared Litopenaeus vannamei, which had relevant implications for the management of broodstock and larval production. The broodstock was reared in mixed-sex biofloc-dominated systems composed of two grow-out phases. Melanization was observed in males during the grow-out II phase. The affected males showed melanization restricted to the spermatophores, varying in color from brown to black and showing swelling in the later. The histological analysis showed the presence of acid-alcohol fastness bacilli in black spermatophores. In addition to the histology, the sperm quality was evaluated in non-melanized and melanized. Based on the results on the sperm count and abnormal and dead sperm rates, it was possible to infer that the males were most likely experiencing a progressive process of spermatophore degeneration related to stressful culture condition, which then resulted in the bacterial infection. The animals that had the spermatophores extruded at the advanced stage did not show the capacity to produce the structure again or died. No fertilized spawning was obtained when males with non-melanized spermatophores were transferred to the maturation laboratory.