When it comes to starfish, the first thing that many people think of is probably the delicious iron starfish. It is undeniable that the edible part of starfish is less, and it is a bit troublesome to eat, but the taste really has nothing to say, and people who have eaten it say fresh!
Starfish (Asteroidea)
In the northern coast of China, starfish is generally called a sea car, which is more common in the Yellow Sea and the Bohai Sea. Although starfish looks harmless to humans and animals, it is an out-and-out predator, especially likes to prey on scallops, oysters, abalone, cockles and other economic shellfish, which has caused great harm to the shellfish farming industry in the north.
In Jimo, Shandong, Hongdao, Huangdao and other places, almost every few years will stage a starfish "out of control" event. Just on March 11, the "starfish army" struck again, and Jiaozhou Bay once again became a hard-hit area, with heavy losses of captive clams and sea oysters.
Qingdao starfish flooded, after landing at a low price
It is understood that the amount of starfish caught in Jiaozhou Bay exceeded 10,000 kilograms a day, and the fishing boat returned with a full load, and after arriving at the port, it was transported to the aquatic market at a low price of 4.5 yuan / kilogram. It is worth noting that dozens of boxes of starfish are all the same species, and its scientific name is Asterias amurensis, which especially likes to eat abalone, oysters and other valuable economic shellfish, which is the "heart of the shellfish farmers in Jiaozhou Bay".
So the question is, how does the seemingly "bad tooth" starfish break through the hard shell and eat the shellfish? How to get rid of the "out of control" starfish? To figure out these questions, we must first start with the biological characteristics of starfish.
Schematic diagram of the interior of starfish
Starfish is a very magical marine benthic creature, belonging to the echinoderm phylum, and belongs to the same family as sea cucumbers, sea urchins, and sea snake tails. There are more than 500 kinds of starfish in existence in the world, and there are more than 100 kinds in China, especially the most abundant varieties in the Xisha, Zhongsha and Nansha Islands.
Most of the starfish in the north of China are spiny sea disc cars, and most of the southern ones are heterochromatic sea disc cars (Asierias versicolor). Regardless of the type of starfish, its internal structure is similar: the starfish has both well-developed digestive glands (pyloric blind sacs) and reproductive glands in the wrist, and the two are easily confused.
Asterias amurensis
In fact, it is only during the breeding season of starfish that the reproductive glands in the wrist take on a visible yellow color, while the pyloric blind sac can be seen in any season and has a distinctly green appearance. For foodies, the most valuable part is the mature gonads of starfish, which taste extremely delicious, while in the non-reproductive season, the edible value of the entire starfish is greatly reduced. Therefore, if you want to eat the most delicious starfish, the timing is very important.
Starfish are hermaphrodites, but they cannot distinguish between males and females from their appearance alone. During the reproductive season, the male and female parents excrete the sperm eggs, and the fertilized eggs undergo complex metamorphosis outside the body to form a bipinnaria (bipinnaria) first, and then metamorphose again to form brachioloria.
Juvenile pattern diagram of starfish
Interestingly, there is a type of starfish called Luidia sarsii, which has many incredible features in the juvenile stage. The larvae of this starfish can grow up to 35 mm in size , and a small prototype of starfish grows inside the larvae. During metamorphosis, the baby starfish gradually detaches from the "mother" and shifts to the outside, similar to the human birth process.
The picture above shows the early larvae of Luidia sarsii starfish, and in the later stages, the starfish will be separated from the "mother" and begin to live independently
From the point of view of biological evolution, there are still many puzzling mysteries about the early development of starfish, such as why the larvae of Luidia sarsii starfish are separated from each other. What exactly is the relationship between two parts of an organism? There are many more problems such as these, and the scientific community has not yet reached a clear conclusion. But in later development, starfish don't have as many secrets — even the mysterious feeding behavior has been thoroughly studied.
Studies have shown that starfish prey is mainly divided into two types, the first is intraoral feeding, and the other is extraordinarily feeding.
The so-called intraoral feeding is to swallow the entire prey into the mouth, completely digest it, and then spit out the remaining part of the wreckage from the mouth. Most species of starfish with shorter wrists and firmer tongues belong to this way of eating, extremely greedy, able to swallow prey that is much larger than the mouth, and a few "extreme" starfish even break their stomachs in order to swallow their prey.
The first way: intraoral intake, direct raw swallowing
In contrast, another way of eating is more "gentleman". The spiny starfish that is raging in the northern region belongs to the second way to eat - first wrap the entire prey with the wrist, then suck the prey through the suction cup at the end of the tube foot, and slowly pull the shell of the oysters, scallops, etc. through the continuous force of the tube foot. Even if the shell only reveals a tiny crack of 0.1 mm, the spiny starfish can digest the soft part of the shellfish through gastric juice.
The second way: digest in vitro and then eat
Some scientists believe that the gastric juice of spiny starfish has a certain paralyzing effect, which can make shellfish such as oysters unconscious, which also proves the superb predation skills of starfish. With this technique, starfish can take down almost every bivalve shellfish they can eat. It is recorded that a starfish can eat 5 to 6 sea clams or 20 oysters in a day, and the amount of food is also quite amazing.
Oyster farms in the United States and Australia spend a lot of manpower and material resources to remove the flood of starfish almost every year; the abalone and clam farming ponds in the north of our country are also unsettled, and a lot of effort has been made to fight against the "number one killer" of shellfish farming.
In the mid-to-late 1970s, fishing boats along the northern coast of China could salvage up to 200 boxes of starfish when they were trawling, a phenomenon that occurred in coastal cities such as Qingdao and Yantai. A foreign study also pointed out that each hectare of the seabed can accommodate about 150,000 starfish, although the research results were published in 1995, but until now it has also had high reference value.
Starfish flood, manually removed
It is no exaggeration to say that, with its numerical superiority, starfish's blow to the coastal shellfish industry during flooding is almost devastating. What is more headache is that at present, in response to the troubles caused by starfish, the most important prevention and control measures at home and abroad are artificial salvage, which not only consumes a lot of manpower and material resources, but also has a slow effect, which is difficult to eradicate (easy to repeatedly erupt).
The sudden eruption of starfish has a lot to do with the species' migratory behavior. Starfish move slowly, but when they perceive danger or look for prey, they move faster — for example, red starfish can move 5 to 8 centimeters per minute, and Starfish forethia can move 15 to 35 centimeters per minute.
Starfish move through tube feet
Professor Caltsoff abroad also found that a labeled Forstar starfish moved 1500 meters in 10 months, moving an average of 5.7 meters per day - this migration activity will undoubtedly increase the difficulty of starfish to kill.
One might ask, is it true that humans are helpless against starfish?
Of course not. There are three main measures to prevent and control starfish at home and abroad, namely manual cleaning, underwater injection and release of natural enemies. Among them, manual cleaning is the most direct and widely used, but it is only suitable for controlling short-term and small-scale starfish floods.
If it is a large-scale outbreak of starfish, it is necessary to use underwater injection drugs, which mainly include choline, acetic acid and sodium bisulfate. In Australia, scientists have also used underwater intelligent robots to identify starfish and inject drugs such as choline into them, greatly reducing labor costs.
The third way is to launch predators. Starfish's natural enemies are dafa snails and glazed waxy shrimp, and some reef fish and anemones can also prey on starfish. It should be noted that before the celestial body is released, it is necessary to examine the local ecological environment and assess the risk of introduction, otherwise the introduced natural enemies may become a new scourge.
Dafa snails prey on starfish
For human beings, starfish also has important development and utilization value. In the past few decades, researchers from all over the world have extracted more than a dozen physiologically active substances from starfish, such as saponins, polysaccharides, insulin, vitamins, proteins, zi alcohols, etc., which have great potential in biopharmaceuticals and health care.
For starfish spiny skin, many people may think that it is useless, but in fact it is not. The weight of the spinosaderm accounts for 75% to 80% of the body weight of starfish, and if it is ground into dry powder, the protein content in every 100 grams of dry powder is as high as 55 grams, which is an ideal material for feed or food additives.
In addition, the echinoderm of starfish also contains 11 kinds of trace elements that are beneficial to the human body, such as copper, iron, zinc, and important active substances such as saponins, alkaloids, and taurine, which have anti-inflammatory, blood pressure-lowering, anti-cancer and other effects. If you can make full use of the spiny skin of starfish, you will be able to turn waste into treasure and create considerable economic benefits.
What do you think about the flooding, prevention and control of starfish, and its development and utilization? Feel free to leave a message in the comments section to discuss!
#Popular science##Chinese scientists in my eyes ##青岛胶州湾海星泛滥吃光蛤蜊海蛎子 #