Thank you to Mr. Wei Peng for providing relevant literature and terminology correction.
Where the water flows well, it always brings more resources, whether it is oysters firmly attached to the hard substrate or clams lurking in the sediment, they can simply open their two shells as the water flows through, and they can obtain the food they need "for free", which is the feeding method used by almost all bivalve members.
The laid-back life of mussels | Pixabay
Gastropod members who also belong to mollusks have well-developed gastropods, making them more suitable for moving around, and rely on the large number of teeth and tongues in their mouths to help them feed. However, there will always be a few maverick species in nature that jump out of the traditional way of life of their own families, innovate different ways of life, and prove the biodiversity of the earth with practical actions.
Slippers screws stacked on top of each other
The Atlantic conch (Crepidula fornicata) is one of them. Atlantic snails are small , with shell lengths generally ranging from 20 to 50 mm , and the largest recorded shell length is only 70.56 mm. The spire is short. The shell mouth is large, with a plate frame or partition, and the length is half the length of the body. The shell is smooth with irregular growth lines, and the shell is white, creamy, yellow or pink with red or brown stripes or spots. Like the species name fornicata, the shell has a distinct arch.
The ventral surface of the Atlantic snail | Rudolphous / Wikimedia Commons
The Atlantic snail has a peculiar shape, irregular "snail towers" or layers of high, or crooked. It wasn't until you took a closer look that you realized that this was not an Atlantic snail, and it is not an exaggeration to describe it as a group. Holding an Atlantic snail in the hand alone is somewhat similar to the dàn snail, there is no too obvious "snail tower" structure on the shell, and the ventral surface looks like a slipper, so the English directly call them slipper shells.
Although the conchs clustered together can still be seen on the seashore, they are also each staying on their own acres and three-quarters, neither of them infringing on anyone, maintaining the independence of the individual. But the Atlantic snail takes a different route: like a stacked arhat, one climbs on top of the other, layered high, and at most 12 individuals can be stacked on top of each other.
The Atlantic boat snails overlapping on top of each other | Andrew C / Wikimedia Commons
This overlaps, can't bear to look directly!
Why do they have to live like this? For breeding, of course!
There is a gender transition phenomenon in many animals, such as the most familiar clownfish, the largest in the group is female, the second largest is male, and the rest are undifferentiated small fish. When the female dies, the original male will transform into a female, and the largest of the undifferentiated small fish will become a male. Another example is the long-fronted shrimp (Pandalus spp.), all the juvenile shrimp hatched from the eggs are males, they will develop testicles, through in vitro insemination to reproduce offspring. However, when male shrimp reach a certain age, their sex automatically changes to female. This condition is called protandric hermaphrodite.
Pandalus borealis, commonly known as Arctic sweet shrimp | Tomasz Sienicki / Wikimedia Commons
The Atlantic snail is no exception. After a free life in the planktonic stage, the dough disc larvae will look for a suitable place to stay and metamorphose into snails. If it falls alone in an area where there are no other Atlantic snails, then the sex is male at this time, but it will not be long before its sex will change to female.
However, if it happens to land on the shell of another Atlantic snail, its sex will remain male. As mentioned earlier, several individuals of the Atlantic snail will be stacked together, and only the sex of the lowest and largest Atlantic snail will become female, and other individuals will remain male (recorded for up to 6 years) under the influence of the pheromone released by the female individual. Like clownfish, the Atlantic snail in the second largest position has a chance to become female only when the largest female, the Atlantic snail, returns to the west. The sex change lasts about 60 days, during which time the penis, an important mating organ of the male, will gradually disappear and the female seminal vesicles and reproductive glands will develop.
Stacked arhats, facing the sea | Daniel Davis / Wikimedia Commons
Getting lazier, lazier to eat
Atlantic snails with shells smaller than 5 mm are extremely active, but as their bodies grow, they become more and more lazy, and finally directly live themselves into the shape of oysters, becoming a fixed organism, motionless. Their unique group lifestyle has led Atlantic snails to choose another way of eating similar to bivalves - "filter feeding".
Although Atlantic snails, like other gastropods, have a well-developed toothed tongue, they rarely actively scrape algae on rocks. For Atlantic snails, the main function of the tooth tongue is to help transfer food from the gills to the mouth. In 2014, researchers at the University of Connecticut and Stony Brook University observed and photographed the Atlantic snail feeding on a certain flat algae (Tetraselmis sp.) through a microscope. When the Atlantic snail breathes through the gills, the tiny algae in the water are captured by the gills on the front and collected by the mucus, which is then transported to the edge of the gills and forms a relatively strong line of slime, which is then moved into the end of the neck.
These tiny algae gradually form a food cord that, when it passes through the neck canal, is brought to the mouth, the Atlantic snail scrapes the food into the mouth with its own tongue and eats it.
The process by which the Atlantic snail eats flat algae:
Sandra E Shumway et al. / Journal of Shellfifish Research (2014)
Initially, the food line (fc=food cord) is formed in the cervical canal under the right cervical lobe (nl=neck lobe).
B. The food line is completed
C. The food line is delivered to the mouth (m=mouth)
D. Food line 1 (fc1) is scraped by the teeth and tongue and eaten
E. Uneaten food line (fc1). Uneaten pieces of food are collected at the edge of the shell. At this point the food line 2 (fc2) is forming.
The food line is sent to the food storage bag (fp=food puch). During the feeding process, the food line is scraped off by the teeth and tongue and eaten, and 2 small fragments (fc1a and fc1b) are sent to the food storage bag.
The two food fragments rotate in the food storage bag to form a small ball of mucus and algae flakes (mab=mucus-algae ball). Eight minutes later, the ball was eaten again.
When the head and neck are bent 90 degrees to one side, the food line is not eaten, but is sent directly to the shell edge. At this time, a small ball is forming in the food storage bag.
Interestingly, the researchers also observed the fecal-eating behavior of Atlantic snails. When the feces were discharged, they were mixed in the newly formed food line and eaten by the Atlantic boat snails.
The fecal eating behavior of Atlantic snails is | Sandra E Shumway et al. / Journal of Shellfifish Research (2014)
Although the process may seem slow, the filtration efficiency of Atlantic snails is quite high. In a 24-hour period, an Atlantic snail produced a total of 217 food lines, an average of 7.5 per hour. On average, each food line is 2.25 mm long and 0.2 mm in diameter, of which more than 80%, a total of 183 food lines are completely eaten by it. Of the remaining food lines, 16 were partially eaten and 18 were completely discarded, and some of them were packed into food storage bags, mixed with mucus into a ball, but only a small part was eaten again, and the specific function and function of food storage bags were not clear.
Invasive species that attack cities
Atlantic snails are native to the western Atlantic coast, as far north as the Canadian province of Nova Scotia and south to Mexico. Influenced by human activities, it was carried to other regions, and in the 1870s, the Atlantic boat snail was first discovered in Europe. Later, with the curtain clam and oyster trade, the Atlantic snail was brought to different countries in Europe several times, and now they have successfully invaded the other side of the west Atlantic, including Denmark, France and the United Kingdom, and even the northwest Pacific coast across the land has become a new home for the Atlantic boat snail.
In some invasion sites, layers of Atlantic snails even covered more than 60% of the area, and there were almost 18 kilograms of Atlantic snails per square meter, which were carpeted over the substrate. Many studies show. Their large populations compete with native benthic fauna for habitat and food resources, and they prefer to live on any hard object, thus having a great impact on the local oyster farming industry.
The snail adsorbed on the golf ball | Eric A. Lazo-Wasem / Wikimedia Commons
It is not easy to remove these uninvited guests, and the seemingly simple and effective removal method of removing the Atlantic snail directly from the surface will cause more serious and difficult to recover damage to the habitat. However, studies have also shown that the food dispute between atlantic snails and oysters may not have as great an impact as the competition between oysters themselves, and the accumulation of Atlantic snails can even change the benthic environment, providing more hiding places for some benthic animals, thereby increasing the number and diversity of benthic animals in this area.
"Stacked Arhat" adsorbed on seaweed snail | Paul Morris / Wikimedia Commons
It is difficult to measure in terms of beneficial or harmful, these successfully settled invasive organisms. The environment changes over a long period of time, and other organisms adapt with it, but no matter which time scale is too long for humans to wait. We are constantly concerned about biological invasion issues and avoid similar incidents as much as possible, which is the most active way to deal with them.
This article is from the species calendar, welcome to forward
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