PLGA-mediated alarelin delivery in male pikeperch (Sander lucioperca): Endocrine and sperm quality responses

Spermiation induction in pikeperch ( Sander lucioperca ) remains constrained by short hormonal responsiveness and rapid post-activation decline in sperm quality. This study evaluated poly(lactic-co-glycolic acid) (PLGA)-mediated alarelin administration and its effects on sperm motility and endocrine responses. Mature males (n = 32; 706 ± 206 g) were assigned to four treatments (n = 8 per group): a blank PLGA control (0.813 mg kg −1 ), a commercial gonadotropin-releasing hormone analogue (mGnRHa; 10 µg kg −1 ), and alarelin-loaded PLGA formulations designed to release 1 µg kg⁻¹ (PLGA 1) and 10 µg kg −1 (PLGA 10) over 72 h. At 48 h, total motility did not differ among groups (p = 0.059). At 72 h, treatment significantly affected sperm motility (p ˂ 0.01); mGnRHa exceeded control, whereas PLGA 10 did not differ from mGnRHa. Motility at 72 h was 85.0 ± 5.3%, 75.0 ± 8.4%, 63.3 ± 8.2%, and 62.9 ± 22.1% in mGnRHa, PLGA 10, control, and PLGA 1, respectively. Early-phase average-path velocity was 100.01 ± 10.89 µm s −1 and 98.55 ± 9.80 µm s −1 in mGnRHa and PLGA 10, respectively. Milt volume, sperm concentration, and estimated sperm output did not differ among treatments. At 24 and 48 h, testosterone was higher in all hormonally treated groups than in control. At 72 h, both PLGA-treated groups were higher than control and mGnRHa, whereas mGnRHa did not differ from control. Thus, PLGA-treated males showed higher testosterone concentrations at the final sampling point, although temporal changes were not tested inferentially and in vivo alarelin exposure was not measured.