The Manta Ray’s Filtration System

Manta rays feed by capturing with their mouth a mix of seawater and plankton as they swim. The mixture strikes a filter, causing the plankton to bounce into the manta ray’s throat, where it is swallowed as food. The water keeps moving through the filter and is flushed through the manta ray’s gills. However, manta rays can filter out plankton that is much smaller than their filter openings. According to science journalist Ed Yong, this ability is “a feat that should have been impossible.”

Consider: The ray’s filtering system looks like five arches, which resemble double-sided combs. Some of the combs’ teeth, or lobes, angle forward and some backward. These lobes separate the seawater, forcing some to flow above the lobes and some to flow between the lobes, creating tiny whirlpools.

When plankton or other food particles strike the leading edge of the lobes, they rebound into the faster moving stream and end up in the ray’s throat, where they can be swallowed. Even plankton small enough to fit between the lobes are carried into the ray’s throat because the whirlpools accelerate their travel, forcing them to ricochet into the stream. This filtration system allows the ray to capture particles that could have otherwise passed through the gaps between the lobes and back out into the seawater.

In addition, the manta ray’s filter-feeding system resists clogging and is self-cleaning, regardless of how fast the ray swims or how heavily concentrated the plankton are in the water.

Researchers hope to copy principles from the ray’s filtering mechanism to design filters that could clean wastewater and extract harmful microplastic particles.

What do you think: Did the manta ray’s filtration system evolve? Or was it designed?