Sperm motility of the marine teleosts <i>Boops boops, Diplodus sargus, Mullus barbatus</i> and <i>Trachurus mediterraneus</i>

<jats:p>The spermatozoa of <jats:italic>Boops boops, Diplodus sargus, Mullus barbatus</jats:italic>, and <jats:italic>Trachurus mediterraneus</jats:italic> were motile in sea water, and in electrolyte solutions (NaCl) and non‐electrolyte solutions (glucose) with an osmolality of 600–1000 mosmol kg<jats:sup>−1</jats:sup>. Their mean motility rate 10 s after initiation was about 80%, while about 10% of the motile spermatozoa moved non‐linearly, 45% linearly, and 45% circularly. The average path swimming velocity was significantly higher in <jats:italic>M. barbatus</jats:italic> (about 90 μm s<jats:sup>−1</jats:sup>) than in the other species (70 μm s<jats:sup>−1</jats:sup>). The number of motile spermatozoa decreased to 0% within 50 s after initiation of motility in <jats:italic>T. mediterraneus</jats:italic>, within 90 s in <jats:italic>M. barbatus</jats:italic> . In <jats:italic>B. boops</jats:italic> and <jats:italic>D. sargus</jats:italic> about 90% of the spermatozoa stopped movement during the first 90 s of the motility period, while the rest remained motile for 2–3 h. Motility of <jats:italic>B. boops</jats:italic> and <jats:italic>D. sargus</jats:italic> spermatozoa was reversibly suppressed in the seminal plasma, and in electrolyte and non‐electrolyte solutions of 100–200 mosmol kg<jats:sup>−1</jats:sup>. The trigger for motility activation was hyperosmolality (700–1000 mosmol kg<jats:sup>−1</jats:sup>). Motility of <jats:italic>M. barbatus</jats:italic> and <jats:italic>T. mediterraneus</jats:italic> sperm was only partly suppressed in the seminal plasma since freshly collected semen contained about 25–50% locally motile spermatozoa. When sperm was activated immediately after collection with electrolyte and non‐electrolyte solutions of 700–1000 mosmol kg<jats:sup>−1</jats:sup> spermatozoa moved progressively. The motility of those spermatozoa which had not yet been motile after collection was completely and reversibly suppressed in <jats:italic>M. barbatus</jats:italic> at osmolalities of 1200 mosmol kg<jats:sup>−1</jats:sup>, and at osmolalities of 100–200 mosmol kg<jats:sup>−1</jats:sup> in <jats:italic>T. mediterraneus</jats:italic> . Therefore two triggers were necessary for initiation of motility. The nature of the first trigger was uncertain, the second trigger was a switch to hypoosmolality in <jats:italic>M. barbatus</jats:italic> and to hyperosmolality in <jats:italic>T. mediterraneus</jats:italic> . The sperm organisation of <jats:italic>B. boops, D. sargus, M. barbatus</jats:italic> and <jats:italic>T. mediterraneus</jats:italic> revealed species‐specific parameters which could not be related with the sperm motility behaviour.</jats:p>