In December 2016, Current Biology published an article about some amazing discoveries they made after studying the noses of zebrafish!

They wrote: “Our data showed for the first time how the motile cilia decorating the nose pit act as a very powerful water turbine and generate strong and robust flow fields that allow fish to quickly exchange the content of the nose. Importantly, this mechanism increases the sensitivity and temporal resolution of odor computations both in stagnant and running aquatic environments and does not require muscle contraction.”

Earlier in the paper, they refer to “these microscopic jet turbines” that help better a fish’s sense of smell.

Cilia are fine hair-like biological structures which are made up of more than 600 different proteins, working together with hundreds of others in a tightly-packed layer to move like a crowd at a sports game doing “the wave.” “Motile” (or moving) cilia are found in the lungs, respiratory tract and middle ear as well as inside the noses of zebrafish and salmon. These cilia have a rhythmic waving or beating motion. In humans they work, for example, to keep the airways clear of mucus and dirt, allowing us to breathe easily and without irritation.

They are microscopic nanomachines which produce a high-speed beat but no one knows precisely how they keep time.

In the nose of a zebrafish and salmon these cilia beat in synchrony and create a flow of water, just like a turbine. This dynamic flow, requiring no muscle movement, accomplishes several functions. First, it draws water into the nose, even in stagnant water or when the fish is idle. Second, it creates a flow pattern that directs odorant molecules over the sensory neurons and then out to the sides. This increases the sensitivity of the sense of smell dramatically. Third, the flow pattern helps the fish detect changes in odour patterns much more rapidly than it could otherwise.

The paper’s title sums this up: “Motile-Cilia-Mediated Flow Improves Sensitivity and Temporal Resolution of Olfactory Computations.” By using that word “computations,” they go on to describe what goes on in the fish’s brain as it processes the combination of odour codes sent from the olfactory bulb. Visualize that salmon swimming upriver, trying to follow a faint trail of odour molecules on its way to its natal stream. The fish can do a better job of computation if the information comes in faster. The ciliary turbine helps the fish turn up its response time.

How do these cilia work? An individual cilium is a sheath made up of an outer ring of 9 microtubules and a centre core of 2 microtubules. These microtubules are connected to each other by a lattice of fibrous bridges which provides strength and stability, much like rungs on a ladder. Radial spokes from the 2 central microtubules connect with the outer ring of 9 microtubules, just like bicycle spokes connect the axle to the wheel. Here are basic engineering structures at the microscopic level.

Whilst our bodies use muscles to move our skeleton, cells use proteins. Dyneins are powerful protein motors that pull and slide microtubule pairs against one another. One side of the sheath is inactive, the other side active, and then the process is reversed. This causes the sheath to bend in a whip-like fashion. Scientists still don’t know how a group of cilia work in conjunction with their neighbours to create waves. They have no real understanding how multiple cilia behave in groups.

Cilia are examples of irreducible complexity. If any one of their components is missing the mechanism would fail, but the irreducible complexity doesn’t stop there. The cilia in a tissue have to work in concert. They have to line up in certain locations in the nose to create the flow pattern. And the brain has to be tuned to respond rapidly enough to the increased rate and lower dwell times of each odorant. This discovery adds another level of complexity and elegance to what we already knew about fish. How forthright was Paul’s declaration that the living God “made heaven, and earth, and the sea, and all things that are therein” (Acts 14:15). The fish with the nose turbines is a wonderful testimony to the creative power of a living and all-powerful God.