Deep-sea fish don’t predict Japanese earthquakes


This 2014 video is called GIANT OARFISH FILMED IN MEXICO.

From the Seismological Society of America:

Appearance of deep-sea fish does not signal upcoming earthquake in Japan

June 18, 2019

The unusual appearance of deep-sea fish like the oarfish or slender ribbonfish in Japanese shallow waters does not mean that an earthquake is about to occur, according to a new statistical analysis.

The study published in the Bulletin of the Seismological Society of America contradicts long-held Japanese folklore that deep sea fish sightings are a sign of an imminent earthquake, say Yoshiaki Orihara of Tokai University in Japan and colleagues.

There is such folklore in Taiwan as well.

When the researchers examined the relationship between deep-sea fish appearances and earthquakes in Japan, however, they found only one event that could have been plausibly correlated, out of 336 fish sightings and 221 earthquakes.

“As a result, one can hardly confirm the association between the two phenomena,” the authors write in the BSSA paper.

The study included data from November 1928 to March 2011, looking at records of deep-sea fish appearances 10 and 30 days ahead of earthquakes that occurred 50 and 100 kilometers away from the fish sighting.

They confined their search to earthquakes of magnitude 6.0 or larger, since these are the earthquakes that have been linked to “precursor phenomena like unusual animal behavior in previous reports,” said Orihara.

There were no recorded deep-sea fish appearances before an earthquake of magnitude 7.0, and no earthquakes with a magnitude greater than 6.0 occurred within 10 days of a deep-sea fish appearance.

Orihara became interested in the deep-sea fish stories after the 2011 magnitude 9.0 Tohoku earthquake in Japan. If the stories were true, he said, deep-sea fish appearances could be used in disaster mitigation efforts.

“From this motivation, we started compiling the event catalog for statistical study,” said Orihara. “There were some previous papers to survey deep-sea fish appearances. However, their reports were insufficient for a statistical study. To collect a lot of events, we focused on local newspapers that have often reported the events.”

The researchers scoured a digitized database of newspaper articles to find mentions of the unusual appearance of deep-sea fish that folklore says will appear before an earthquake, including oarfish, several kinds of ribbonfish, dealfish and the unicorn crestfish.

Orihara said that he and his colleagues expect that their results “will have an influence on people who believe the folklore,” and they hope that their findings will be shared throughout Japan.

What makes jellyfish unique?


This 4 October 2018 video says about itself:

Jellyfish 101 | Nat Geo Wild

How much do you really know about jellyfish? Given their diverse evolutionary history, jellies exhibit a fantastic range of shapes, sizes, and behaviors. Learn all about these squishy, brainless, beautiful creatures. Also make sure to read the full October 2018 National Geographic magazine feature story.

From the Okinawa Institute of Science and Technology (OIST) Graduate University in Japan:

What makes a jellyfish?

April 15, 2019

Summary: Genomic study reveals how jellyfish develop into floating beauties, rather than staying stationary like corals or sea anemones.

Translucent jellyfish, colorful corals and waving sea anemones have very different bodies but all fall on the same big branch in the animal family tree. Jellyfish actually start out anchored to the sea floor, just like corals and anemones. Researchers at the Okinawa Institute of Science and Technology Graduate University (OIST) recently uncovered which genes allow jellyfish to graduate from this stationary stage and swim off into the sea.

Early in their life cycles, jellyfish develop from larvae into polyps — immobile, stalk-like structures rooted into the sediment. Anemones and coral live out their lives in this state, which earned them the name anthozoa or “flower animals” in Greek. Jellyfish set themselves apart from anthozoans by being able to develop from the polyp stage to the medusa stage, blossoming into the luminous, bell-like creatures we know and love.

The new study, published in April 16, 2019 in Nature Ecology & Evolution, reports the genomes of two jellyfish species and investigated why some creatures can enter the medusa stage while others remain frozen as polyps. The genomes can be browsed online and compared to other species on the OIST BLAST server.

Newly Decoded Jellyfish Genomes

OIST researchers and colleagues from Japan and Germany compared the genomes of a moon jellyfish (Aurelia aurita) and a giant box jellyfish (Morbakka virulenta). In Japanese, these species are known as the “water jellyfish” and “fire jellyfish”, respectively. The fire jellyfish is highly venomous and owes its name to its painful, burning sting.

“By comparing two different types of jellyfish we expected to identify some universal rules on how to make a medusa stage,” said Dr. Konstantin Khalturin, first author of the study and a scientist in the OIST Marine Genomics Unit led by Prof. Noriyuki Satoh. As a jellyfish exits its polyp stage and leaves the sandy sea floor, different genes switch on to drive its development. To identify these special genes, the researchers first had to catalogue all the genes present in their sample jellyfish species.

“We then looked at how these genes behaved in the polyp and jellyfish stages of their lifecycles,” Khalturin said.

The researchers sequenced the complete genome of a moon jellyfish from the Baltic Sea and giant box jellyfish from Japan. Genomes contain all the instructions to build and maintain an organism, encoded in individual building blocks known as genes. Along with a creature’s genetic composition, the order in which these building blocks are lain helps determine how a creature develops. The researchers compared their freshly decoded jellyfish genomes to those from corals and anemones, pinpointing which genes appeared in each animal and in what sequence.

“We expected that the genome organization in the two jellyfish would be more similar to each other than to the genomes of sea anemones or corals,” said Khalturin. Surprisingly, the gene order in the moon jelly genome resembled anthozoans much more closely than fire jellyfish. In contrast, the genetic composition of the two jellyfish hardly overlapped; their genomes differ as drastically as humans do from sea urchins.

What Makes the Difference

The results suggest that the giant box jellyfish genome must have been vigorously reshuffled at some point in its evolution. The dearth of similarities between moon and giant box jellies convinced the researchers that there is no universal region within jellyfish genomes responsible for orchestrating the medusa stage formation.

One question remained: why can’t corals and anemones enter the jellyfish stage?

To solve this mystery, the researchers assessed which genes were active in the polyp and medusa stages of both jellyfish. They compared these distinct patterns of gene expression to those observed in 11 different cnidarian species — the taxonomic group that encompasses medusozoans and anthozoans. Remarkably, they found that coral and anemones contain about two-thirds of the genes active in the moon jellyfish’s medusa stage.

But moon jellyfish have a special genetic toolkit: an elite arsenal of genes that activate during their medusa stage but are absent in anthozoans. Devoid of a jellyfish stage, corals and anemones lack the genes to grow certain organs and tissues, such as eyes and specialized swimming muscles. The researchers found that water and fire jellyfish share about 100 of these species-specific genes that only switch on in their jellyfish stages. A large proportion of these genes code for transcription factors, proteins that fine tune which genes are expressed, when and in what quantities.

Looking forward, the researchers plan to sequence the genome of a local box jellyfish called the Okinawan sea wasp (Chironex yamaguchii, “habu-kurage”), which will provide a closer comparison to the fire jellyfish. Future studies could advance our understanding of how jellyfish evolve and what sets them apart from their blobby brethren and other creatures of the deep.

A new article might make you squirm if you plan to hit the beach. This article presents the draft genomes of three jellyfish species, which have a range of physical traits and level of toxicity. Jellyfish kill more people than sharks, stingrays, and sea snakes combined; thus, having sequences and their analyses available provides an essential resource for future investigation of toxin gene evolution and body shape differences: here.

Japanese eels, new research


This 2015 video is called The Mystery of the Eel – Documentary Film.

From Kobe University in Japan:

Endangered eel located using DNA from one liter of water

March 1, 2019

Researchers have shed light on the distribution of Japanese eel by analyzing environmental DNA (eDNA) from small samples of river water. This could enable faster and more effective surveys of Japanese eel populations, and help to conserve this endangered species. The finding was published on February 27 in Aquatic Conservation: Marine and Freshwater Ecosystems.

Eels are migratory fish that spawn in the ocean and grow up along the coast and in rivers. There are 16 known species in the world, distributed in 150 countries. The Japanese eel (Anguilla japonica) is found across East Asia. Since ancient times it has been an important part of Japanese life: as a food source, a subject of traditional poems and art, and sometimes even as a target of worship. However, eel catches have fallen drastically since the 1970s, and in 2014 it was added to the International Union for Conservation of Nature (IUCN) Red List of Threatened Species.

Most river surveys of Japanese eel use electrofishing. However, this method requires a lot of time and resources, and for widely distributed species it may not collect enough data. Surveys are usually carried out in the daytime, while the nocturnal eels hide among vegetation and dirt.

Rapidly-advancing eDNA technology can monitor aquatic lifeforms through extraction and analysis of DNA present in water, without capturing the organisms themselves. In this study, the team investigated whether eDNA analysis could be used to show the distribution of Japanese eel. They collected 1-liter samples from 125 locations upstream and downstream in 10 rivers in Japan, and analyzed the eDNA from these samples using a Real-Time PCR system. At the same time they carried out an electrofishing survey in the same locations, and compared this with the eDNA analysis results.

Japanese eel eDNA was found in 91.8% of the locations where eel had been confirmed using electrofishing (56 of 61 locations), and eDNA was also detected in an additional 35 areas (mainly upstream) where eel individuals were not found. This shows that eDNA analysis is more sensitive than conventional surveys for detecting the presence of Japanese eel in rivers. Electrofishing data for eel numbers and biomass also positively correlated with eDNA concentrations, showing that eDNA could help us estimate the abundance and biomass of Japanese eel.

In this study, electrofishing required three or more people for each river and took at least three days. Collecting water samples for eDNA analysis only needed two people, took half a day at the most, and data processing was finished by one person in one and a half days. When carrying out a large-scale distribution survey the eDNA analysis method is better in terms of human and time resources.

This method could potentially survey populations on an even wider scale. It is non-lethal, making it ideal for monitoring endangered species. The team is currently using eDNA analysis to monitor eels in Japan and overseas: it can be used as an international unified method for widely-distributed species. This could be a great help in the conservation and sustainable use of eel species worldwide.

The eDNA analysis method is also effective in dealing with the invasion of foreign eel species. For 20 years there have been reports of foreign eels (European eels and American eels) being released into Japanese waterways. These species look the same as Japanese eel, making them hard to detect. They are also long-lived so they may impact the ecosystem over long periods of time. By carrying out a wide-ranging investigation using eDNA analysis, we can swiftly identify foreign eel species and their distribution.

This study was carried out by Research Associate Hikaru Itakura (Kobe University Graduate School of Science), Assistant Professor Ryoshiro Wakiya (Chuo University), Assistant Professor Satoshi Yamamoto (Kyoto University), Associate Professor Kenzo Kaifu (Chuo University), Associate Professor Takuya Sato and Associate Professor Toshifumi Minamoto (both from Kobe University).

Itakura comments: “Concentration of eDNA in rivers is influenced by physical properties such as water depth and the speed of the current. Next we must increase the accuracy of eDNA analysis by clarifying the impact of these physical properties on eDNA concentration.”