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Barrel Jellyfish - Rhizostoma pulmo
Barrel Jellyfish - Rhizostoma pulmo

[Image: Rizostoma_pulmo_zpsb103227a.jpg]

Scientific classification
Kingdom: Animalia
Phylum: Cnidaria
Class: Scyphozoa
Order: Rhizostomae
Family: Rhizostomatidae
Genus: Rhizostoma
Species: Rhizostoma pulmo

Rhizostoma pulmo, commonly known as the barrel jellyfish, the dustbin-lid jellyfish or the frilly-mouthed jellyfish, is a scyphomedusa in the family Rhizostomatidae. It is found in the northeast Atlantic, and in the Adriatic and Mediterranean Sea. It is also known from the southern Atlantic off the western South African coast and into False Bay.

It is common in the Irish Sea. It typically is up to 40 cm (16 in) in diameter, but can exceptionally reach 90 cm (35 in), making it the largest jellyfish in British waters (Cyanea capillata reaches an even larger size, but is generally smaller in Britain).

It is a favourite food of the Leatherback Sea Turtle.

Lowly Jellyfish Uses High-Tech Strategy to Find Food

By Elizabeth Palermo, Staff Writer | August 05, 2014 07:01pm ET

[Image: barrel-jellyfish_zpsca4c77d0.jpeg]
The barrel jellyfish uses a complex search strategy to locate food, a new study finds.

The barrel jellyfish, isn't just the largest jelly found in the waters around the United Kingdom, it's also one of the animal kingdom's most strategic searchers, according to a new study.

To locate the best possible meal in the vast waters of its marine habitat, the barrel jellyfish (Rhizostoma octopus) uses a strategy most commonly associated with the world's fastest supercomputers — an approach known as fast simulated annealing.

For mathematicians, fast simulated annealing is an algorithm, implemented by a supercomputer, which can find optimal solutions to complex problems in a relatively short amount of time. For jellyfish, fast simulated annealing is a highly evolved search strategy categorized by a series of predictable movements that bring the jelly closer and closer to large numbers of plankton, its preferred prey. 

This complex search strategy has never been observed before in nature, according to study lead author Andy Reynolds, a scientist at Rothamsted Research, an agricultural research center in the U.K.

Yet, other mathematical patterns of movement have been widely observed in the natural world, Reynolds said. The most common of these patterns, the "Lévy walk," is a less complex version of the barrel jelly's approach.

"A Lévy walk is [a] random walk in which frequently occurring small steps are interspersed with more rarely occurring longer steps, which in turn are interspersed with even rarer, even longer steps and so on," Reynolds told Live Science in an email. (The Lévy walk was named after French mathematician Paul Levy, who was noted for his work in the theory of probability.)

While this may sound like a fairly complex way of searching for something, Reynolds said it's similar to the way you might search for your lost car keys in the living room sofa and then, not finding them there, head over to the closet to check your coat pocket.

"This hierarchical nested pattern is highly effective when searching because once an area has been intensively surveyed, the searcher is relocated to another area and then begins a new bout of intensive searching," Reynolds said. 

Some of the species that have been observed using Lévy walks to locate their meals include sharks, penguins, honeybees, ants, turtles and even human hunter-gatherers.

But among these many species, the barrel jelly stands out because, in addition to exhibiting this Lévy walk pattern, it also engages several search methods that others species don't seem to use.

Move like a jellyfish

One of the barrel jelly's search-optimizing behaviors, often referred to as a "bounce," occurs when the jellyfish starts out in one depth of water and then makes a long glide either upwards or downwards to a different depth of water. If it doesn't find a meal in the new location, the jellyfish will "bounce" again to return to its original position.

Some scientists believe that the jelly's tendency to bounce around in the water may actually hinder its ability to search for food, but according to Reynolds, these unusual animals have had it right all along.

The jellyfish, which will sometimes repeat its pattern of bounces dozens of times a day, uses this strategy to slowly home in on the highest concentrations of plankton, Reynolds explained.

The behavior therefore makes the barrel jelly even more efficient than other marine animals, such as penguins and sharks, that only use Lévy walks to search for prey, Reynolds said.

Is bouncing better?

If the barrel jelly's unusual way of searching for food really is the best way to do it, then why aren't other marine species using the same strategy?

The answer has to do with diet, Reynolds said. The barrel jellyfish benefits from spending long periods of time searching for concentrations of prey because it needs to eat a lot of plankton before it is satisfied, Reynolds said. This is different from sharks and penguins, which Reynolds said can survive by eating the occasional fish.

"A Lévy search is highly effective in finding the next meal, when any meal will do. Fast simulated annealing, on the other hand, takes the forager to the best possible meal," Reynolds said. "This is what makes jellyfish special — they are very discerning diners, unlike bony fish, penguins, turtles and sharks, which are just looking for any meal."

This high level of discernment is also what draws certain mathematicians and engineers to the strategy of fast simulated annealing for supercomputing, Reynolds said.

Based on mathematical and computer models, Reynolds' study found that like barrel jellyfish, mathematicians tend to implement this strategy only when they're looking for the best possible solution to a problem, not a variety of potential solutions.

The new study was published online today (Aug. 5) in the Journal of the Royal Society Interface. 
[Image: wildcat10-CougarHuntingDeer.jpg]
Jellyfish 'can sense ocean currents'

Victoria Gill
By Victoria Gill
Science reporter, BBC News
23 January 2015

Jellyfish can sense the ocean current and actively swim against it, according to a study that involved tagging and tracking the creatures.

The research, by an international team, could help scientists work out how jellyfish form "blooms".

These blooms may comprise between hundreds and millions of jellyfish, and can persist in a given area for months.

It remains unclear just how the jellyfish sense changes in water, the paper in Current Biology journal says.

The scientists, including researchers from Swansea University and Deakin University in Warnambool, Australia, tagged 18 large barrel jellyfish (Rhizostoma octopus) in the Bay of Biscay, off the coast of France.

The team caught the jellyfish and fitted them with loggers that measured acceleration and body orientation.

Lead researcher Prof Graeme Hays from Deakin University said it was "really easy" to attach the tags. "We loop a cable tie around the peduncle that joins the swimming bell to the trailing arms," he explained.

"It takes seconds, and the tag stays on indefinitely."

At the same time, the researchers used floating sensors to monitor and measure the ocean currents.

This showed that the jellyfish were able actively to swim against the current, apparently in response to feeling themselves drift.

In a second part of the study, the researchers used their data to create a realistic simulation of the movement of a bloom of jellyfish in the ocean.

This showed, said Prof Hays, that "active and directed swimming helps maintain blooms", by keeping jellyfish in a particular area rather than allowing them to be dispersed or washed ashore by the currents.

"With this knowledge of their behaviour we can start to have some predictive capability for bloom dynamics," the scientist told BBC News.

What is not yet clear is how exactly the jellyfish work out which way to travel.

The scientists think the animals might sense the current across the surface of their bodies. They also speculate that the jellyfish might use the Earth's magnetic field to navigate - an ability seen in some other migrating marine species, including sea turtles.

One ultimate aim of studying and tracking swimming jellyfish is to improve the forecasting of jellyfish blooms, which have increased in frequency over the past decade, disrupting fisheries and stinging swimmers.

Perhaps troublingly, these results show that swimming against the current helps hold blooms together, even in areas when currents are strong. 
[Image: wildcat10-CougarHuntingDeer.jpg]
Ceph Wrote:The Bright Side of Gelatinous Blooms: Nutraceutical Value and Antioxidant Properties of Three Mediterranean Jellyfish (Scyphozoa)
Antonella Leone, Raffaella Marina Lecci, Miriana Durante, Federica Meli and Stefano Piraino

[Image: 20130530_marmenor.jpg]

Abstract: Jellyfish are recorded with increasing frequency and magnitude in many coastal areas and several species display biological features comparable to the most popular Asiatic edible jellyfish. The biochemical and antioxidant properties of wild gelatinous biomasses, in terms of nutritional and nutraceutical values, are still largely unexplored. In this paper, three of the most abundant and commonly recorded jellyfish species (Aurelia sp.1, Cotylorhiza tuberculata and Rhizostoma pulmo) in the Mediterranean Sea were subject to investigation. A sequential enzymatic hydrolysis of jellyfish proteins was set up by pepsin and collagenase treatments of jellyfish samples after aqueous or hydroalcoholic protein extraction. The content and composition of proteins, amino acids, phenolics, and fatty acids of the three species were recorded and compared. Protein content (mainly represented by collagen) up to 40% of jellyfish dry weight were found in two of the three jellyfish species (C. tuberculata and R. pulmo), whereas the presence of ω-3 and ω-6 polyunsaturated fatty acids (PUFAs) was significantly higher in the zooxanthellate jellyfish C. tuberculata only. Remarkable antioxidant ability was also recorded from both proteinaceous and non proteinaceous extracts and the hydrolyzed protein fractions in all the three species. The abundance of collagen, peptides and other bioactive molecules make these Mediterranean gelatinous biomasses a largely untapped source of natural compounds of nutraceutical, cosmeceutical and pharmacological interest.

Leone, Antonella, et al. "The Bright Side of Gelatinous Blooms: Nutraceutical Value and Antioxidant Properties of Three Mediterranean Jellyfish (Scyphozoa)." Marine drugs 13.8 (2015): 4654-4681.

Ceph Wrote:The jellyfish Rhizostoma luteum (Quoy & Gaimard, 1827): not such a rare species after all
Karen Kienberger author Laura Prieto
Original Paper First Online: 24 January 2017 DOI: 10.1007/s12526-017-0637-z
Cite this article as:
Kienberger, K. & Prieto, L. Mar Biodiv (2017). doi:10.1007/s12526-017-0637-z

Rhizostoma luteum was first described in 1827 by Quoy and Gaimard under the name Orythia lutea, based on nine specimens collected from the Strait of Gibraltar (southern Iberian Peninsula). After 60 years of no scientific records existing for this species, in 2013, a phylogenetic analysis confirmed that R. luteum differed from Rhizostoma pulmo and Rhizostoma octopus. In the present study, we report historical and recent records of living and stranded specimens of R. luteum since 1998. We reviewed historical accounts and photographic and videographic materials taken by citizens from the northeastern Atlantic Ocean and the Alboran Sea. Because of its similarity with the closely related Mediterranean R. pulmo, R. luteum was frequently misidentified in the Alboran Sea and, likewise, with another medusa from the order Rhizostomeae, Catostylus tagi, in the adjacent Atlantic Ocean coastal regions in the last two decades. The results of this investigation confirm the existence of the scyphomedusa R. luteum in the coastal waters of the west and south coasts of the Iberian Peninsula and west and north shores of Africa. Through a citizen science initiative and our own observations, we were able to confirm more than 150 observations of R. luteum over the past 17 years, demonstrating that this medusa is not such a rare species after all.

Kienberger, Karen, and Laura Prieto. 
"The jellyfish Rhizostoma luteum (Quoy & Gaimard, 1827): 
not such a rare species after all." Marine Biodiversity (2017): 1-8.
[Image: wildcat10-CougarHuntingDeer.jpg]
Harmless stings:

Quote:These giant jellyfish swarms cause quite a stir. However they are gentle giants. Barrel jellyfish feed entirely on tiny plankton, so their sting is too weak to hurt humans.

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