This study aimed to deepen our understanding of male spotted wolffish (Anarhichas minor ) reproductive biology using two distinct experimental designs involving juvenile and mature broodstock fish.
The first experiemental design involved a detailed histological examination of testes to identify the onset of gonadal maturation and characterize spermatogenic stages in two- and three-year-old juvenile specimens. Light microscopy analysis revealed clear differences between the age groups. Two-year-old fish displayed well-defined interstitial tissue, Sertoli cells, and cysts housing spermatogonia stem cells where meiosis had not yet been initiated. In contrast, three-year-old fish exhibited cysts containing spermatocytes, spermatids, and abundant spermatozoa, indicating the initiation of the spermatogenic cycle, albeit with asynchronous puberty. Immunostaining revealed a significant presence of smooth myoid cells in the interstitial tissue of sexually mature fish, while electron microscopy further revealed synaptonemal complexes with chromatin differentiation and the emergence of centriolar structures.
The second experimental design focused on optimizing semen freezing and cryopreservation procedures in mature broodstock individuals aged over 10 years. Seven freezing extenders (KT, TS-2, OP, MT, MH, HBSS, or SR), with seawater (SW) as a control, were assessed alongside two cryoprotectants dimethylsulfoxide (DMSO) or methanol to evaluate their impact on pre- and post-thaw semen quality.