Speaking of seawater aquariums, the picture of a clown drilling a sea anemone is a classic. But if you ask a random person to represent the underwater world with an animal, I am afraid that people will blurt out "starfish". Many people will take a starfish back to the beach, dried it and put it on the bookshelf as their memories of the good times on the seaside and a trophy, of course, Xiaobian also believes that starfish symbolizes luck
The biological classification of sea stars belongs to the Phylum Echinodermata class Asteroidea, which is a well-deserved symbol of the marine environment. In fact, they are indeed the only creatures in the underwater world, and many times dominate. Although numerous, their dominance does not stem from this. The real reason for this is that starfish are the keystone predator in the marine environment. The so-called cornerstone species refer to species that can actively control and build an ecological environment. (Simply put, the presence or absence of cornerstone species directly affects the diversity of other organisms in the same ecosystem.) Below is the ochre star, Pisaster ochraceus. In fact, the term cornerstone species comes from the changes that this most common starfish brings to the intertidal environment off the coast of North America.
(Pictured is an ochre starfish, about 5 inches in diameter.) Of course, the starfish in the picture is not reddish-brown as its name suggests. It has two variations of body colors, which is the most appealing one)
If you've been to the rocky seashore, you're familiar with the intertidal environment. The living environment in the intertidal zone is parallel to the seabed. In the case of the intertidal zone of the northeast Pacific Ocean, the characteristics of land flora and fauna do not extend to the edge of the sea, and their distribution ends a few feet above sea level, thus forming a zone with neither land life nor marine life. This is the intertidal zone, the zone between the highest and lowest levels of the tide. In general, the highest points in the intertidal zone are usually bare rocks with few organisms. The salinity of the environment there is too high for land creatures to adapt to, and at the same time there is not enough water to cover, and marine life is difficult to survive, only tenacious golden shell lichens can survive. Lower locations, where they can be covered by more waves, are dominated by mussels. Where the waves are not very fierce, there are many types of shellfish. There are varieties such as Mytilus edulis/trossulus/galloprovincialis, which can be directly distinguished from the appearance. Lower positions are covered with different kinds of barnacles. Further down, there are intertidal anemones (Anthopleura elegentissma). At the bottom are the dominant algae.
The rocks near the intertidal zone are steep and densely packed with cracks and crevices. Large green anemones (Anthopleura xanthogrammica) are common in channels where surges rise, while purple or orange starfish (Pisaster ochraceus) are more common on vertical rock walls, which are the protagonists of this article. These starfish are relatively robust animals, up to 6 inches in diameter, with a sturdy and thick body.
About 40 years ago, a researcher at the University of Washington wanted to determine the role of starfish in this ecosystem through interesting experiments. In the years that followed, he went to a patch of intertidal zone in Washington to clear starfish at each time the tide came down. A few years later, that intertidal beach underwent a wonderful change. The 1-3-inch-long mussels that originally grew here grew rapidly, reaching a length of 8-14 inches. Their crazy growth has led to the death of a large number of barnacles. At the same time, the seaweed that originally grew in the lower layer gradually spread to the upper layer, distributed on the shallower reef. Four years later, the barnacles were extinct, leaving only mussels and seaweed.
Pisaster starfish are selective hunters who specialize in mussels. The lowest position for mussel growth is the highest position where starfish are active after retreat. With no starfish present, mussels grow rapidly in conditions with abundant seawater and plenty of food. Before the experiment, when starfish could not eat mussels, they would choose to eat barnacles, but now without starfish restrictions, barnacles have become larger. The barnacles then become an excellent place for seaweed to attach, and the dense growth of seaweed kills the barnacles. Basically, in times when there were no starfish cleaning up mussels and barnacles, competitors in the ecosystem here were reallocating roles and relationships changed a lot. Researcher Robert T. Paine named starfish the cornerstone creatures here, without which they play an important cornerstone role in the ecosystem, the original ecology would quickly collapse.
You have to ask, of course, what does this have to do with our reef ecology?
Reef ecology is like an experimental intertidal zone, and biological diversity is inseparable from the predatory behavior of starfish. In the reef ecology, the acanthaster planci is also an extremely important cornerstone organism. In the higher positions of the reef environment, most of them are fast-growing, competitive small hydra-bodied bony corals. In aquariums we call them SPS corals. As we all know, if the conditions of light, water, food and so on are suitable, these corals will grow wildly, and even burn other corals. In the competition of creatures, the second place can only win the silver medal awarded by the Grim Reaper. For these creatures, there is no competition, only the choice between life and death.
(Pictured is crowned spinosa starfish.) This individual is about 15 inches in diameter)
You may also ask, if SPS is so competitive, why are there so many other corals in the area where they grow?
The problem is the same as in the case of intertidal beaches where experiments were conducted. Crown of thorn starfish are the main hunters who prey on SPS corals, but not the only ones.
They shuttle between coral reefs and feed on corals. But they don't eat all the corals, nor do they eat in pieces. They tend to eat one coral, then wander around it and eat another. If a large number of crown of thorn starfish appear in an area to eat coral, the result is not the total death of the entire coral, but the scars of the entire coral.
Such a reef looks very scary. But these mottled white bones are the only places where newborn drifting polyps can attach. The distance between corals in nature far exceeds the distance they are in the aquarium. Corals with palm-sized palms are generally spaced one foot or more apart. If this safe distance is exceeded, they will attack each other. In the process of competition for living space, the loser will die. Why is there such a distance concept, because any polyp larvae that grow within 6 inches of a medium-sized coral will be killed by competitors.
The death zone after the crown of thorn starfish hunt provides space for newborn polyps to survive. Coral larvae, known as planulae, are about the size of brown flatworms inside aquariums and can swim in water. Polyps can only make this one decision in their lifetime, and once these mature plankton larvae have chosen a settlement, they can no longer regret it. Corals lay eggs in the seawater, where the eggs are fertilized and develop into larvae. The yolks of corals store energy, which the larvae feed on. They do not eat, and after a few days, resemble small flatworms. These little guys swim at the bottom, and after a few minutes they touch some surfaces and touch surfaces with the front part of their bodies. In effect, they are tasting the surface "taste" to discern whether they are suitable for colonization and growth. If there are many corals in this area, they will become every meal of other corals. However, if you encounter an open area where only bacteria and certain algae grow, the "taste" is still good, and coral larvae will settle on this surface. Over the next few days, it will turn into a separate coral hydra body and begin to grow. And these empty spaces can only be the result of those coral hunters hunting here, even a few years ago. A few years later, the sensen bones of the year were gone, and the hunters were back to hunt. In this cycle, the diversity of corals is preserved.
So, what exactly are starfish and how do they prey on them?
Starfish are classified as echinoderms in the phylum Echinoderms, with a total of about 6,000 species of echinoderms. All starfish live in the ocean, most are medium-sized, and there are very few miniature starfish, but none are microscopic. Most starfish live in undersea environments.
There are six main types of echinoderms; • Crinoidea class, feathered stars. • Asteroidea class, starfish. • Ophiuroidea or Brittle class, snake starfish, brittle starfish. • Echinoidea class, sea urchin. • Concentricycloidea class, sea daisies. • Holothuroidea class, sea cucumber.
In addition, there are many fossils of echinoderms available to study their evolution. Compared to other biological phylums, echinoderms are a strange biological species. Their main feature is the lack of a universal definition of front and back, and most of them are radial symmetrical structures, similar to sea anemones and corals. Its radial symmetry is the result of evolution or derivation. However, they have a double-ended structure from the beginning stage of the evolution of life, that is, the front and back, and then through a series of dramatic metamorphosis processes to obtain a radial structure. Sea cucumbers and some sea urchins have become quite biterpendal, even with an antecedent and left-right structures. Most echinoderms are radially symmetrical and are mostly 5-segment spoke symmetry, or multiples of 5.
They have no head, brain, large, obvious sensory structure at all. With the exception of a few larger nerves, their neural structures are very tiny and particularly dispersed, requiring an electron microscope to see. There is very little basic knowledge of echinoderms. Since there is no brain, many behaviors are thought of only as simple reflexes. However, they also have very complex behavioral manifestations, the mystery of which is still unknown. They have bones in their bodies that are a mixture of calcium carbonate and magnesium carbonate. With the exception of the spines of the pencil sea urchin, all echinoderm skeletal mechanisms are in the body, so the spines of the sea urchin, including the spines of other echinoderms, are covered by tissue. This property is very important for aquarium enthusiasts, as the structure is completely invisible from the outside. The body of echinoderms is mostly hollow structure, and the body is a linear cavity structure composed of thin tissue.
Starfish are perhaps the most classic echinoderms, and the most reminiscent of echinoderms. They belong to the Asteroidea class, which has about 1500 species. Although the body is somewhat stiff, starfish has a more or less flat structure and flexible body. Each tentacle has 2 or 4 rows of pipe feet.
(Pictured is Choriaster granulatus, 12 inches wide, looks relatively bloated and has an extremely stiff and rigid body.) It's also a starfish that feeds on corals.)
The tubular foot is an external system tissue unique to echinoderms that incorporates a step band system and a humoral system. The pipe foot is a hydraulic system that consists of thousands of pipes and valves inside. Each tube foot is connected by a tube to the center of the tentacle. Bodily fluids are pumped to each tube foot, and the valves for each tube foot can be closed individually. Within the tentacles of the starfish, a small balloon-like structure called an ampulla stretches out from the tube foot. The entire tube foot looks like an unopened dropper that can be bent. When the muscles of the dropper head (ampullary abdomen) contract and the bodily fluids in the judial abdomen are pressed into the tube, the tube foot is lengthened. When the solitary muscles relax, the fluid will flow back to the ampulla. The tube foot is connected to the body and can be contracted. Most starfish tube feet have adhesive pads on their heads, which act as temporary adsorption to the surface of the object. Therefore, when starfish walk, the tube foot will cooperate to stretch and contract. When the tube foot touches the surface of the object, there is a gelatinous substance that adheres the tube foot to the surface. When starfish travel, the tube foot moves like we walk on our legs. When a stretching cycle ends, the gel is released and the tube foot shrinks from the surface back into the tentacle. Now, it's easy to imagine the tube feet, and it's easy to control, but you can imagine how many tube feet, starfish has as many as 40,000 tube feet, moving quite fast. Without a brain to control and coordinate, how is this all done? We don't yet know the neural underlying behavior of any echinoderm.
(Pictured is the internal structure of mitromeromatoma starfish starfish)
Inside each tentacle are two pyloric sacs and two reproductive glands, although only one is very clear. From this perspective, the starfish's intestines are located in its center, and its mouth is inside it. The intestinal structure is represented by a variety of different colors, red, pink, purple, orange and brown. The gonads are yellow and the step bands are indicated in blue.
The intestines in starfish are short, starting with an opening in the middle of the body and ending upwards at the anus in the middle of the body surface. The mouth is facing down, and within the mouth is the esophagus. The first part of the stomach is located here, called the "heart" stomach. This part can be turned over some, but not all, when eating, and the initial digestion is outside the intestine. The heart and stomach are connected to the "pyloric" stomach, which is basically the core organ of food storage, and from it extends two sack-like structures, located in the tentacles, called pyloric blind sacs, which have the function of storing food and can be highly elastic. The pyloric stomach is followed by a very short bowel leading to the anus. Attached here is a pair of rectal sacs of unknown action.
On or near the pyloric blind sac are gonads whose outlets are located at the end of each tentacle. There are no gender differences in the appearance of the gonads. Starfish have many different ways to eat. Many starfish, including ochre starfish and crown of thorn starfish, spit out their hearts and stomachs when they eat and digest most of their food outside the body. The sand starfish eats food into the body and digests it. Pycnopodia helianthoides, one of the largest starfish, eats food into its body. When examining the food these starfish eat, I found that two of them still had bird remains in their bodies, suggesting that they could even catch birds. Other starfish such as The Blue-fingered Starfish (Linckia laevigata) are introduced into aquariums by many aquarists, and they spit out their entire stomachs when they digest, as if to digest the world. They eat sponges, small microbes, small, fixed-growing organisms, and other things that can't move around. Finally, there are the henricia species, which are common in temperate seas, reaching out their tentacles when eating and spitting out large amounts of mucus. Plankton is glued to the mucus, and starfish eats the plankton along with the mucus.
(Pictured is the sunflower starfish (Pycnopodia helianthoides).) It can be more than 5 feet in diameter and is an internal feeding type. Major predators in the Northeast Pacific)
Raising starfish requires attention
In the ocean, starfish tend to be delightful ornamental animals. Starfish from the rocky waters are likely to be masters of predatory corals, and putting such a starfish in an aquarium is like starting a military exercise. Some medium-sized starfish can be kept for a while, but will soon starve to death because they feed on sponges and sacs.
Few breeds of starfish can be successfully raised in aquariums. Perhaps these are the most common: small cushion starfish, most likely belonging to Asterina. These starfish are gray, white, or green and are almost 1.5 inches in diameter. They multiply in splits and rarely see individuals intact with each tentacle. There are probably three different types, probably different species. One of the most common feeds on algae and thin film-like substances. The second is rare and feeds on buttons and soft corals. The less common white variety feeds on bony corals. Fortunately, it's easy to control them in the aquarium. If you find that they have a tendency to do bad things, eliminate them regularly.
Large starfish have a very low success rate in aquariums. Like chocolate starfish and sand-sifting stars, they are super predatory and difficult to maintain. Turning sand starfish can stir up a living sand bed in a short time. Only large starfish such as Linckia can successfully breed for a long time. Linckia starfish, no matter how big or small, seem to feed on algae and do not harm corals. Raising starfish focuses primarily on salinity. They are extremely unaccustomed to changes in salinity, and transport pressure, requiring salinity of 35 ppm-37 ppm at a temperature of 80-84 degrees Fahrenheit. Starfish should slowly cross the water, at least 6 hours is the safe thing to do. Even so, the survival rate of starfish is still very low. About 1/10 of starfish survive in aquariums for only 1 week. If they exceed this time limit, they will live well.
In the long run, we need starfish to maintain coral diversity in the ocean, and starfish itself are beautiful and interesting creatures. Unfortunately, most starfish are not suitable for aquarium rearing. Even for those breeds that are suitable, our breeding success rate is very low. They need to be more delicately fished, packed, transported, and watered to ensure that these elves can live in aquariums healthily.
Note: Original author Ronald L. Shimek, Ph. D.
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