Effect of steady and unsteady flow on chemoattractant plume formation and sperm taxis

• Published in: Journal of marine systems Vol. 148; pp. 236 - 248
• Main Authors: Bell, Allison F., Crimaldi, John P.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.08.2015
• Subjects: Broadcast spawning; Chemotaxis; Computer simulation; Formations; Gametes; Marine; Mathematical models; Plumes; Shear rate; Strategy; Swimming; Two dimensional; Gametes; Broadcast spawning; Chemotaxis
• ISSN: 0924-7963; 1879-1573
• DOI: 10.1016/j.jmarsys.2015.03.008

The formation of chemoattractant plumes around benthic invertebrate eggs in steady and unsteady shear flows is investigated for a range of shear rates, and the ability of sperm to navigate within these plumes is assessed using several chemotactic strategies. Although many of the details of sperm taxis remain uncertain, we investigate the role of basic processes using a toy model in two dimensions. Search strategies in 2D are intrinsically less complex than 3D, but many of the basic components are similar, and the simplified geometry permits an understanding and identification of the key factors of navigation tactics. Numerical simulations are used to model the advection and diffusion of the chemoattractant within the different flows, using three different sperm swimming behaviors. A Monte-Carlo approach is then used to determine the probability of a sperm reaching an egg for a range of flow conditions, initial conditions, and swimming behaviors. The spatial structure of chemoattractant plumes at the scale of the gametes is also investigated. Success rates for locating an egg decrease monotonically with increasing shear rates, and a definitive hierarchical ordering of the tested swimming strategies is identified. A conceptual framework to study and identify important aspects of this fundamental process to support further studies is provided. •We model chemoattractant plumes surrounding eggs, and sperm taxis within these plumes.•Flow fields consist of both steady and unsteady shearing for a range of shear rates.•The efficacy of three different chemotactic strategies for swimming sperm is tested.•Cumulative fertilization rates are quantified for each strategy in each of the flows.