Study Sheds Light on Ciliate Feeding Strategies

It has long been known that ciliated microorganisms, which use hair-like structures to move through water, generate different flows to feed on planktonic and inorganic particles. How the motility and shape of such particles affect their feeding behavior, however, is murkier.

Taking into account these particle characteristics for the first time, Li et al. explored this aquatic territory through numerical simulations that included a squirmer model to represent ciliated starfish larvae and a point-particle model for particles. The squirmer model mode was used to identify each generated flow, with its rise representing the enhancement of ciliate attraction and weakness of ciliate swimming.

“For passive particles, the feeding ability is little disturbed by the ciliate-induced flow mode,” said author Lihao Zhao. “But for active particles, it is negatively correlated with the ciliate-induced flow mode.”

Indeed, the relationship between feeding ability and flow mode revealed that ciliates exhibit different efficiency-maximizing feeding strategies for particles with varying motility.

“This involves a trade-off between attracting more surrounding particles and swimming faster to scan more particles,” said Zhao.

When feeding on active particles, the study showed, ciliates can employ a strategy that enhances swimming over attraction, which differs from that used with passive particles.

As for shape, the researchers found that when the ciliate swimming is significantly stronger than attraction, elongated motile particles are less likely to be captured than spherical ones.

Altogether, the study builds a significant link between micro-hydrodynamic processes and ecosystem dynamics.

“We expect our findings to be corroborated by biological observations and our results to be useful in understanding food chain dynamics in aquatic environments,” said Zhao.

Source: “Feeding of planktotrophic squirmers: Effects of mobility and elongation of planktonic particles,” by Bocheng Li, Jingran Qiu, and Lihao Zhao, Physics of Fluids (2023). The article can be accessed at http://doi.org/10.1063/5.0180294 .