Photograph by ROBERT C. PAULSON JR., ALAMY
Northwest United States, Pacific Coast,
A large number of sand coins have emerged,
(A species of sea urchin echinoderm)
The cause has not yet been identified.
SOURCE: Oregon Coast Aquarium
On August 19, OPB reported that countless sand coins were washed up on the Oregon coast and were alive when they ran aground; but once the tide receded, the sand coins would quickly decay within minutes. The staff of the local coastal aquarium did not know the reason for this strange situation, and it has been ruled out that the abnormal sea temperature is caused. Local staff also warned – don't take the sand coins home at will, it would smell bad if it was still alive.
In a period of up to 3 and a half minutes,
In the long shots shot without interruption,
Almost the whole time is full of sand coins,
The scale is more shocking,
Here's just a short cut of it —
Sand coins on the U.S. Oregon coast are hard to count
The picture shows the player in the game "Assemble It! A catalogue of Sand dollars collected from the Animal Forest Friends Association
Courtesy of Jubo Wong
They resemble coins and like to live in the sand, so they are named "Sand dollar", also known as sand coins, sea money; their close relatives also include sea urchins, starfish, sea cucumbers, sea lilies, sea snake tails, etc., which are also echinoderms; only in terms of morphology, the difference is very large.
Starfish and sand coins, although very different in form, are both echinoderm phylum; the picture shows the Arctic biscuit Ceramaster arcticus.
摄影：JOEL SARTORE, NATIONAL GEOGRAPHIC PHOTO ARK
Pictured here is the most common sand coin on the beach, the Latin scientific name Dendraster excentricus, with a sea urchin on the right
Image source: Wikipedia
Sand coins are widely distributed in warm waters around the world, and in North America alone, they are found in vast coastal areas from Alaska in the United States to the Baja California Peninsula in Mexico. They usually live in the sandy and muddy seabeds of the intertidal and subtidal zones, and are also distributed in deep sea areas of tens to thousands of meters.
At present, there are about 150 kinds of sand coins known worldwide, and the picture shows a comparison between various sand coins and close relatives of sea urchins.
The sand coin is covered with short spines and looks like it is wearing a furry, heavy coat. Most of the sand coins crawl on the ocean floor and solve the problem of food and clothing by feeding sand grains into the mouthparts located in the center of the ventral surface.
The sand coin Dendraster excentricus, which is taking advantage of its flat body to drill into the mud
Their ancestors date back to the Pliocene to Pleistocene period, about 2.5-500,000 years ago. For sand coins, the sand grains are full of "juicy delicacies", including foraminifera, nematodes, diatoms, etc.
GIF source: DEEP LOOK
The Denidraster excentricus, the most common sand coin on the beach, is covered with purple-red "fluff", which decomposes after death, and the white disc that is washed onto the beach is their skeleton, with a beautiful flower-like pattern on the top.
They can live for 15 to 20 years, and their sizes vary: they grow up to be 4 times larger than when they were children, about the size of a baseball.
The sand coin Dendraster excentricus in the Monterey Bay Aquarium in the United States is also the only sand coin currently living on the beach of the ocean, and it is furry purple-red instead of white when alive.
In addition to the above-mentioned oregon, where sand coins flock to, on the ocean beaches of San Francisco, California, the tide rises and falls throughout the year, and this kind of white disc is also quite common. Rich Mooi, a well-known expert at the California Academy of Sciences, explains that the unique five-petal pattern is common to all sand coins, and in essence, this pattern is their "gills", allowing them to breathe underwater.
There are currently about 150 kinds of sand coins in various forms around the world, and the vast majority of sand coins scattered on the beaches of San Francisco are Dendraster excentricus.
A girl playing on the beach, from Baja California to Alaska, can find the sand coin Dendraster excentricus, which is the only sand coin currently living on the beach of the ocean.
Photograph by IDA PAP, ALAMY
At San Francisco's Mussel Rock Park, the dunes have long since evolved into cliffs, and the formations containing fossils appear in front of you, and the fossils and specimens scattered everywhere are breathtaking. In addition, the amount of sand coins here is also amazing -
"Millions!"
Rich Mooi, a prominent expert at the California Academy of Sciences, estimated. In addition, Rich Mooi continues: "Despite their large numbers, they are not a souvenir for tourists, and the beach is protected, so the only thing you can take home is marine debris. ”
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