RESEARCH

The vertebrate embryonic heart first forms as a valveless, tubular pump, and several different pumping mechanisms have been suggested to drive blood flow in these tubular hearts. We use the immersed boundary method to solve the fully-coupled fluid structure interaction problem of an elastic, valveless tubular heart immersed in a viscous and incompressible fluid and analyze flow behavior and wall movement produced by pumping mechanisms like peristalsis and dynamic suction pumping. Model organisms we study: zebrafish, Ciona savignyi.

ABSTRACT Studies on both model-based and empirical food webs have shown that perturbations to an ecological community can cause a species to go extinct, often resulting in the loss of additional species in a cascade of secondary extinctions. These effects can seriously debilitate a food web and threaten the existence of an ecosystem. Here, we consider niche model-based food webs with internal noise and investigate the effects of a control on a secondary extinction cascade triggered by a noise-induced extinction. We show that the forced removal of a nonbasal species immediately after a primary extinction can extend the mean time to extinction of individual nonbasal species as well as that of the complete extinction cascade. An analysis of numerical and statistical results illustrates the effectiveness of a control in delaying the mean time to extinction for endangered species in stochastic food webs.