Shrimp from Finding Nemo could help keep your white bread white
Ben-Gurion University researchers discover new principle in optics
Peer-Reviewed Publication
BEER-SHEVA, Israel, May 30, 2023 – The Pacific Cleaner Shrimp may hold the secret to keeping white bread white. Inorganic nanoparticles such as titanium dioxide and zinc oxide are widely used as whitening agents in foods, cosmetics, and paints. However, due to health concerns, there is currently an intensive search to find organic, bio-compatible analogues to replace these materials. Now, Dr. Ben Palmer and his student Tali Lemcoff of Ben-Gurion University of the Negev have discovered a new material in cleaner shrimp that produces one of the most efficient white reflectors in nature which could inspire the development of novel, organic whitening materials. By studying the white material found in cleaner shrimp, the researchers discovered a completely new principle in optics. The findings were published late last month in the prestigious Nature Photonics (https://doi.org/10.1038/d41586-023-01415-0) journal.
The Pacific Cleaner Shrimp, also known as Jacques from Finding Nemo, uses white stripes on its cuticle and appendages to attract fish, which it then proceeds to clean by eating parasites off the fish’s body. When the researchers took a closer look at these white stripes, they discovered something amazing. The white stripes are made of an ultra-thin layer of densely packed particles of a small molecule, isoxanthopterin. Making white materials from thick materials is trivial. However, making efficient white reflectors from thin, dense materials is challenging due to an optical effect called ‘optical crowding’, whereby reflectance decreases at higher packing densities. Despite being less than 5 microns thick, the whiteness produced by the shrimp is extremely bright, making it one of the thinnest and most efficient white materials that exist.
The key to the optics is in the arrangement of molecules in the particles. The molecules are arranged in a ‘liquid crystal’, stacked in columns which radiate radially from the center of the nanospheres like the spokes of a wheel. “At first, I thought it was not interesting because the nanospheres were not classic crystals. However, when we looked closer using cryo-SEM and TEM microscopes, we realized not only that the particles are liquid crystals, like those in LCD displays, but that they exhibit birefringence (dual refraction), which is exceedingly rare in the animal world,” enthused Tali Lemcoff.
It turns out that this special arrangement of molecules is key to overcoming the ‘optical crowding’ hurdle, allowing the particles to be packed densely, reducing the thickness of the layer required to produce bright whiteness.
“It is really one of the first times we have learned an entirely new principle from studying an organism. The shrimp has overcome a seemingly fundamental hurdle in optics by creating particles with this special arrangement of molecules. Now the question is, how can we replicate this effect for creating new materials we could use as food additives in white bread, or in white paint and other applications?” says Dr. Palmer.
Additional researchers include: Lotem Alus, Johannes S. Haataja, Avital Wagner, Gan Zhang, Mariela J. Pavan, Venkata Jayasurya Yallapragada, Silvia Vignolini, Dan Oron, Lukas Schertel.
The study was supported by ERC Starting Grant (Grant number: 852948, ‘CRYSTALEYES’), HFSP Grant (Grant number: RGP0037/2022) awarded to Benjamin A. Palmer. Benjamin A. Palmer is the Nahum Guzik Presidential Recruit. Benjamin A. Palmer is a recipient of the 2019 Azrieli Faculty Fellowship.
JOURNAL
Nature Photonics
METHOD OF RESEARCH
Observational study
SUBJECT OF RESEARCH
Animals
ARTICLE TITLE
Brilliant whiteness in shrimp from ultra-thin layers of birefringent nanospheres
Jacques, the Pacific cleaner shrimp
We have many of the fish from 'Finding Nemo' at the Aquarium, but the non-fish we have from the film is the Pacific cleaner shrimp ('Lysmata amboinensis'), which is the character Jacques.
We love invertebrates and this shrimp is in our top ten! In the film, Jacques has what looks like an impressive moustache. His 'moustache' is the real life shrimp's antennae. If you look closely at Jacques you’ll see he actually has two moustaches.
This is the same with shrimps. They have a long antennae (usually longer than their body length) which they use to touch, and to help orientate themselves with their surroundings. This is also used for 'tasting' and 'smelling' what’s around them. Their shorter antennae are used to assess whether their prey is suitable for eating.
Cleaner shrimp 'clean up' other animals in the sea. Cleaning stations have been observed, occupied by a few cleaner shrimp waiting for fish like eels and groupers to come by. Once they’ve got their 'customers' they will climb on board and start to pick away at any external parasites which the shrimp then eat. Some fish may even open their mouths to allow the shrimp inside! You might think that this was a trap and that the shrimp will be guzzled. It’s no trap though, because the fish have worked out that having parasites removed is much better for their health in the long run, than making a meal of the little shrimp. They also 'clean up' the algae in the tank.
In 'Finding Nemo', when they’re plotting to escape the tank, Jacques is ordered by the other fish to stop 'cleaning', which results in a very algaefied tank within a few days. In reality a shrimp will pick at algae, but they wouldn’t be able to keep all algae at bay. It grows too fast and would be far too much for one shrimp to deal with it all.
If you were to ask us if our cleaner shrimp was a girl or a boy, we'd have to tell you they’re both! All these shrimps are born male, and then along their lifespan develop female organs as well. This is known as 'protandric simultaneous hermaphroditism'. They are able to function as a male or female when it comes to their reproductive life.
Our cleaner shrimp are a bit shy - they hide in their tank so you need to look hard if you want to spot them. If we ever need to clean their tanks, sometimes we get a shock when they come up to clean us! They have little claws at the end of their legs which they use to pick off parasites on fishes and dead skin on humans. For small claws they’re surprisingly sharp, though I guess this is a must for retrieving stuck in parasites. It’s not really painful, but it certainly feels a bit odd!
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