Zombie shrimp playing dead

This video from the Monterey Bay Aquarium Research Institute (MBARI) in California in the USA says about itself:

Zombie shrimp play dead to avoid being eaten

28 November 2018

While exploring the depths of the Gulf of California with the remotely operated vehicle Doc Ricketts, MBARI researchers saw an eerie sight: the small shrimp, Hymenopenaeus doris, hanging upside down, motionless in the water. At first, the shrimp appeared dead, but a closer look revealed that the animal was making tiny adjustments of its antennae and legs to maintain a head-down position while very slowly sinking. When the submersible got too close, the shrimp sprang back to life and quickly swam away.

While performing this “zombie-like“ behavior, the shrimp looked a lot like a discarded exoskeleton sinking slowly through the dark midwater. The researchers speculate that the shrimp might reduce their chances of being eaten by mimicking a sinking molt.

This odd behavior might also be an adaptation to conserve energy, since the shrimp live at depths where the seawater contains very little oxygen. Animals found in low-oxygen environments have a harder time moving rapidly or for long distances.

The researchers observed three zombie shrimp hanging right underneath large mucous webs or nets. Many deep-sea animals use mucous webs to gather marine snow (small particles of debris drifting down from the surface) for food. The biologists were unable to confirm a connection between the shrimp and the webs, leaving this mystery to be solved on a future expedition.

For more information see here.

Publication: Burford BP, Schlining KL, Reisenbichler KR, Robison BH (2018) Pelagic shrimp play dead in deep oxygen minima. PLoS ONE 13(11): e0207249.

Video editor: Kyra Schlining
Music: Stranger Danger (YouTube audio library)


How water fleas detect predators

This 2017 video says about itself:

Daphnia magna under the microscope

Daphnia magna is a small crustacean that is related to crabs, shrimp and lobsters. They live in many aquatic environments and are very important to the food chain. Daphnia are plankton that feed on algae and other microbes and are themselves food for small fish and other aquatic animals. They are popular as fish food and studied in biology labs that look at evolution or ecology.

While there are both male and female daphnia that can mate and reproduce, females can actually clone themselves through a process called parthenogenesis.

The anatomy of the daphnia is labeled in certain shots. The magnification of each shot is shown in the bottom right corner.

From Ruhr-University Bochum in Germany:

How water fleas detect predators

November 27, 2018

Water fleas of the genus Daphnia detect via chemical substances if their predators, namely Chaoborus larvae, are hunting in their vicinity. If so, they generate defences that make them more difficult to consume. The signalling molecules that enable detection have been identified by biologists and chemists from Ruhr-Universität Bochum, the University of Duisburg-Essen and the University of Birmingham. It is a cocktail of substances that occurs during digestive processes of Chaoborus larvae. The researchers discuss their findings in the journal Nature Chemical Biology from 14 November 2018.

For the study, the team headed by Dr. Linda Weiss and Professor Ralph Tollrian from the Institute for Animal Ecology, Evolution and Biodiversity in Bochum collaborated with Professor Nils-Metzler-Nolte’s Chair of Inorganic Chemistry I in Bochum, Professor Oliver Schmitz’ Chair of Applied Analytical Chemistry in Duisburg, and Dr. Ulf Sommer from the University of Birmingham.

Neckteeth and spines against predators

Daphnia are able to grow neckteeth, i.e. thorns in their neck region, or spines on their exoskeleton, that make it more difficult for Chaoborus larvae to consume them. However, Daphnia grow these defences only if the predator is actually in their vicinity. “It had long remained a mystery why the predators alert to their presence via chemical substances even though it clearly is a disadvantage for them,” says Linda Weiss.

“As far back as 40 years ago, researcher tried to identify the substances with which predators betray their presence,” describes Ralph Tollrian, Head of the Institute for Animal Ecology, Evolution and Biodiversity, who has been studying this subject ever since his PhD thesis. But it took modern methods such as high-res mass spectrometry to unravel the mystery.

Chemical signals caused by digestive processes

Together with their colleagues, Weiss and Tollrian found out that Chaoborus larvae secrete at least five different substances into the water that Daphnia can detect. The substances play a crucial role in the larvae’s digestion processes, as they are released when the predator spits the indigestible components back out. “This explains why the animals cannot stop the release of chemical signals,” says Tollrian. “The advantage for the larvae when the substances are part of their digestive processes is greater than the disadvantage of betraying their presence to prey.”

Substances manufactured artificially

The researchers, moreover, developed the substances in the lab, in order to verify their effect. They added them to culture-bred Daphnia and analysed the defences grown in consequence. The Daphnia reacted to the artificially manufactured substances in the same way as to the presence of Chaoborus larvae in their vicinity.

In follow-up studies, the researchers intend to identify the receptors used by Daphnia to detect the signalling molecules and decode the precise pathway of signal transmission.

Shrimp healing injured fish

This July 2018 video says about itself:

These Shrimp Are a Clean-Up Crew For Dirty Fish | Nat Geo Wild

Along this Caribbean reef, Pederson cleaner shrimp wait to feast on the parasites of these fish.

From James Cook University in Australia:

Shrimp heal injured fish

August 23, 2018

James Cook University scientists in Australia have discovered that shrimp help heal injured fish.

PhD student David Vaughan is working on a project led by Dr Kate Hutson at JCU’s Centre for Sustainable Tropical Fisheries and Aquaculture.

He said it was important to know how the shrimp interact with fish, as the team is in the process of identifying the best shrimp species to use to clean parasites from farmed and ornamental fish.

“Between 30 — 50% of farmed fish in Southeast Asia, the largest fish producing region in the world, are lost to parasites.

“We know that shrimp clean parasites from fish and if we can identify a species that does it efficiently, and does no harm, it offers a ‘greener’ alternative to chemicals”, he said.

Mr Vaughan said scientists knew injured fish visited shrimp ‘cleaning stations’ to have parasites removed — but the question was whether shrimp then took advantage of the injured fish and fed on their wounds. He said the relationship between cleaner shrimp and their client fish was complicated, with the shrimp known to eat the mucus of the fish and the fish occasionally eating the shrimp.

The scientists used high-definition cameras to record the details of the interaction between the species. “We found that shrimp did not aggravate existing injuries or further injure the fish”, said Mr Vaughan.

He said image analyses showed the cleaner shrimp actually reduced the redness of the injury. “Injuries in fishes are susceptible to invasion by secondary pathogens like viruses and bacteria, and the reduction in redness by shrimp indicates that cleaner shrimp could reduce infections.”

Mr Vaughan said cleaner shrimp are also known to indirectly influence the health of client fishes by reducing stress levels as a function of cleaning — which also increased the ability of the fish to heal.

Beautiful colours in Chinese salt lake

This 1 August 2018 video says about itself:

Thousand-year-old salt lake shining like a painter’s palette in north China

Sweltering temperatures have caused a thousand-year-old salt lake to turn brilliant colours recently in Yuncheng City, north China’s Shanxi Province.

Small crustaceans, algae cause these colours in these dry circumstances.

New shrimp species named after Tolkien character Bilbo

This video says about itself:

22 February 2018

Observations on the symbiotic relationship between the caridean shrimp Odontonia sibogae (Bruce, 1972) and its ascidian host Herdmania momus (Savigny, 1816). Ya’arit Levitt-Barmats and Noa Shenkar (2018), PLOS ONE.

Now, relatives of this shrimp species have been discovered.

From ScienceDaily:

In a hole in a tunicate there lived a hobbit: New shrimp species named after Bilbo Baggins

June 7, 2018

Summary: A new species of shrimp was named after Tolkien‘s Bilbo Baggins thanks to its small size and hairy feet. The new species, Odontonia bagginsi, was described, figured and named together with another new species: Odontonia plurellicola. Both shrimps live symbiotically inside tunicates collected around Ternate and Tidore, Indonesia. In the present study anatomical and genetic character[istic]s were used to place the new species in the tree of life.

Two new species of tiny symbiotic shrimps are described, illustrated and named by biology student at Leiden University Werner de Gier as part of his bachelor’s research project, supervised by Dr. Charles H. J. M. Fransen, shrimp researcher of Naturalis Biodiversity Center (Leiden, the Netherlands).

Inspired by the extremely hairy feet of one of the species, the authors decided that they should honour Middle Earth’s greatest halfling, Bilbo Baggins.

Aptly named Odontonia bagginsi, the new shrimp joins the lines of other species named after Tolkien‘s characters such as the cave-dwelling harvestman Iandumoema smeagol, the golden lizard Liolaemus smaug and the two subterranean spiders Ochyrocera laracna and Ochyrocera ungoliant.

The newly described shrimps were collected during the Ternate expedition to the Indonesian islands of Tidore and Ternate, organised by Naturalis Biodiversity Center and the Indonesian Institute of Sciences (LIPI) in 2009.

Typically for the Odontonia species, the new shrimps do not reach sizes above a centimetre in length, and were found inside tunicates. It is believed that these symbiotic crustaceans are fully adapted to live inside the cavities of their hosts, which explains their small-sized and smooth bodies.

Unlike most Odontonia species, which live inside solitary tunicates, the new species Odontonia plurellicola was the first one to be associated with a colonial tunicate. These tunicates have even smaller internal cavities, which explains the tiny size of the new species.

To determine the placement of the new species in the tree of life, the scientists compared the shrimps’ anatomical features, including the legs, mouthparts and carapace. As a result, they were assigned to Odontonia. Further, the available genetic information and Scanning Electron Microscope (SEM) images of the unusual feet of the newly discovered shrimp provided a new updated identification key for all members of the species group.

“Being able to describe, draw and even name two new species in my bachelor years was a huge honour. Hopefully, we can show the world that there are many new species just waiting to be discovered, if you simply look close enough!” says Werner de Gier, who is currently writing his graduate thesis at Naturalis Biodiversity Center and working together with Dr. Charles Fransen on crustaceans.

Prawns have individual personalities, new study

This 2012 video shows rockpool prawns feeding.

From the University of Exeter in England:

Cautious prawns win battle for food

June 1, 2018

Prawns have personalities — and cautious crustaceans do better in the battle for food, new research shows.

Scientists from the University of Exeter studied rockpool prawns (Palaemon elegans) and found some were consistently shy, while others were bolder.

But this bravery may come at a cost — as the risk takers tended to do worse than other prawns when competing for food.

“We found that the shyer prawns were better at controlling a food source”, said first author Daniel Maskrey, formerly of the University of Exeter but now at the University of Liverpool.

“This means that when they found food and possible rivals were nearby, they stayed and fed for longer than bolder prawns.

“The reasons for this aren’t clear, but it’s possible that bolder prawns have a higher urge to go on and continue exploring.

“We witnessed prawns fighting over food, and it could be that some use a bold exploration strategy because they favour searching for new food over competing with stronger rivals.”

Boldness was tested by repeatedly putting prawns into an unfamiliar tank and seeing how much they explored and ventured into the middle.

Dr Tom Houslay, of the Centre for Ecology and Conservation on the University of Exeter’s Penryn Campus in Cornwall, said the study could help scientists understand why members of one species — and even the prawns in a single rockpool — have different personalities.

“Some individuals are more successful at monopolising food, while others are more willing to engage in potentially risky exploration,” he said.

“In different conditions and situations, either of these strategies might pay off — which might explain why evolution has not led to a single personality type.

“The rockpools where these prawns live change with each high tide, and having such variation among prawns could be crucial when it comes to adapting to these and other changes.”

The prawns in the study were all from Gyllyngvase beach in Falmouth, and their feeding behaviour was tested using parcels of brine shrimp. Prawns were split into groups of similarly sized individuals to compete for access to food.