Physiology and Multi-Omics Provide Insights into Sperm Activation and Movement in Euryhaline Spotted Seabass...

Sperm activation and movement are pivotal determinants of fertilization success in teleosts, yet the molecular mechanisms in euryhaline species remain largely unresolved. Here, we integrated physiology and multi-omics to elucidate the osmolality, ions, and regulatory networks underlying sperm activation and movement in spotted seabass (Lateolabrax maculatus). Spotted seabass sperm showed strong motility across a broad osmotic range of 500 to 1200 mOsm/kg, with Na⁺ and K⁺ promoting motility and Ca²⁺ exerting inhibitory effects. Integrated transcriptomics and proteomics identified 29 genes and 6 proteins as candidate molecules associated with Na⁺ and K⁺ signaling, Ca²⁺ signaling and apoptosis, and energy metabolism. Up-regulation of NHE1 suggested a potential involvement of Na⁺/H⁺ exchange that regulated Na⁺ influx, while K⁺ influx via activated K⁺ channels may depolarize membrane potential. The capn1 was up-regulated, which may be associated with Ca²⁺-mediated apoptosis. Euryhaline fishes exhibited a broader osmotic activation range than freshwater and marine species, underscoring the critical roles of osmotic adaptability in fish sperm physiology. Ionic regulation patterns of euryhaline fishes are generally consistent with their environmental adaptation, with seawater-adapted species resembling marine fishes and freshwater-adapted species resembling freshwater fishes. Our findings highlight the integrated roles of osmotic effects and ionic regulation, providing insights into sperm activation and movement in euryhaline spotted seabass.