'Mucus house': Tiny sea creature inspires scientists to build efficient pumps

Researchers at the University of Oregon (UO) have been inspired by the efficiency of pumping inside a "mucus house" built by a tiny sea creature and plan to replicate the mechanism in an industrial setting. Peristaltic pumps typically used in large scale facilities such as wastewater treatment plants are .

Just like contraction in the human gut pushes wastes outside the system, the peristaltic pump also uses external squeezing to push liquids further. While this approach has worked well in most applications, researchers are always looking for improvements in existing technology. They found their inspiration in a tiny sea creature scientifically known as Pumps are everywhere in nature, but this pump is unique in driving fluid through a filter by beating a tail inside a sealed chamber,” said Kelly Sutherland, a biologist at UO who was involved in the study.

What makes the sea creature special? belongs to a group of tiny creatures that consume food through filter feeding. The creatures are often clubbed together as larvaceans that have small, wriggly tails that help in locomotion through the ocean. When it is time to feed, larvaceans create a "mucus house" or a "snot palace" that encases their millimeter long body and use their wriggly tail to pump it up.

The mucus casing , trapping the foot inside and expelling the water outside. The creature then slides out of the house through an escape hatch while abandoning the mucus house it had built. A larvacean creates multiple mucus houses in a day, and OU researchers were keen to know more. So, they visited a research facility in Norway to study them using high speed cameras and microscopes.

What the researchers found When observing the videos captured, the OU researchers discovered that the little critter used a unique pumping system when using its tail under the mucus casing. While swimming in the water, the creature wiggles its tail and uses a side to side bending of its body to propel itself forward.

However, after building the "mucus house," the larvacean remains stationary. It allows the water and particles to move parallel to the tail. This propels food particles and water across the filter like mesh, enabling feeding. The creature's tail fits snugly inside the mucus house while touching the sides several times.

Each wiggling movement then seals and unseals the mucus case at these attachment points, much like a Velcro, researchers said in a . Doing so helps build pressure that pushes fluid continuously forward and prevents backflow, a common problem with pumps and plumbing systems. As particles collect on the filters, the next wave pushes them toward the mouth of the organism, enabling feeding.

Unlike the peristaltic pump, where the forward movement of the fluid comes from an external push, the larvacean pump enables propulsion from movement that comes from within the pump. OU researchers believe that such a design could help protect moving parts of the pump and lower risks of wear out. The research findings were published in the .

Planktonic organisms feed while suspended in water using various hydrodynamic pumping strategies. Appendicularians are a unique group of plankton that use their tail to pump water over mucous mesh filters to concentrate food particles. As ubiquitous and often abundant members of planktonic ecosystems, they play a major role in oceanic food webs.

Yet, we lack a complete understanding of the fluid flow that underpins their filtration. Using high speed, high resolution video and micro particle image velocimetry, we describe the kinematics and hydrodynamics of the tail in Oikopleura dioica in filtering and free swimming postures. We show that sinusoidal waves of the tail generate peristaltic pumping within the tail chamber with fluid moving parallel to the tail when filtering.

We find that the tail contacts attachment points along the tail chamber during each beat cycle, serving to seal the tail chamber and drive pumping. When we tested how the pump performs across environmentally relevant temperatures, we found that the amplitude of the tail was invariant but tail beat frequency increased threefold across three temperature treatments (5°C, 15°C and 25°C).

Investigation into this unique pumping mechanism gives insight into the ecological success of appendicularians and provides inspiration for novel pump designs..