Practice question

Mammalian chemotaxis occurs over short distances near cumulus-oocyte complex mediated by gradients of soluble attractants. Cumulus cells and follicular fluid release progesterone at micromolar concentrations, detected by sperm membrane receptors including ABHD2 which relieves inhibition of CatSper channels. Localized calcium spikes modulate flagellar curvature, biasing trajectory up gradient toward egg. This steering supplements rheotaxis and thermotaxis with fine-scale targeting. Progesterone is primary validated chemoattractant linking ovulation signals to directional sperm guidance, enhancing fertilization efficiency and providing precise navigation toward oocyte microenvironment and cumulus mass.