Details

Autor(en) / Beteiligte

• Saggiorato, Guglielmo
• Alvarez, Luis
• Jikeli, Jan F
• Kaupp, U Benjamin
• Gompper, Gerhard
• Elgeti, Jens

Titel

Human sperm steer with second harmonics of the flagellar beat

Ist Teil von

• Nature communications, 2017-11, Vol.8 (1), p.1415-9, Article 1415

Ort / Verlag

England: Nature Publishing Group

Erscheinungsjahr

2017

Link zum Volltext

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• Sperm are propelled by bending waves traveling along their flagellum. For steering in gradients of sensory cues, sperm adjust the flagellar waveform. Symmetric and asymmetric waveforms result in straight and curved swimming paths, respectively. Two mechanisms causing spatially asymmetric waveforms have been proposed: an average flagellar curvature and buckling. We image flagella of human sperm tethered with the head to a surface. The waveform is characterized by a fundamental beat frequency and its second harmonic. The superposition of harmonics breaks the beat symmetry temporally rather than spatially. As a result, sperm rotate around the tethering point. The rotation velocity is determined by the second-harmonic amplitude and phase. Stimulation with the female sex hormone progesterone enhances the second-harmonic contribution and, thereby, modulates sperm rotation. Higher beat frequency components exist in other flagellated cells; therefore, this steering mechanism might be widespread and could inspire the design of synthetic microswimmers.