Morgan Hunt
Science A
Starfish Final Essay
When someone hears the word starfish, usually they automatically think of a five armed sea creature that looks rather lifeless. However, these asteroids are more complex than most would realize, playing an important role in the ecosystem. In the ocean, there are many different kinds of starfish with different physical attributes and behaviors. Despite their diversity, they all reproduce, develop and grow within their habitat and just like any other living organism, they face dangers and can only live so long.
They live in just about any habitat in the ocean; such as tidal pools, rocky shores, sea grass and kelp beds, beneath rock rubble, on coral reefs, sand, and mud. They are seafloor predators. They have certain features which allow them to withhold rough conditions, such as their suctions which allow them to stay stuck to sea beds or close to shore despite the crashing waves. As for diversity, there are roughly 1500 different species in the Asteroidea class (Hebert P.D.N, 2002). Considering there are so many different species, there are two starfish in which I will go into further detail about. The Asterias rubens and the crown-of-thorns starfish Acanthaster planci are both very different. The Asterias rubens are what most consider the common starfish, and the Acanthaster planci is a very different, unique starfish that most wouldn’t even realize is a starfish.
Physically, most starfish have five arms radiating off a central disk, such as the Asterias rubens. On the other hand, some star fish may have up to forty arms, while the crown-of-thorns as between 10-20 arms. Starfish come in a vast variety of colors which include bright red, cobalt blue, yellows, and the familiar orange-brown (Nicholson 2000). For size there have been sea stars as small as 2cm in diameter yet as big as one meter in diameter. On average, starfish are between 12 and 24 cm in diameter (Mulcrone, R. 2005). They have a very rough surface, some with short bumps and ridges, while others may have thorn-like spikes, such as the crown-of-thorns.
Another neat thing about starfish is that they can produce sexually and asexually. Although they are known to be able to regenerate arms if necessary, seven species (that tend to be very small) are known to willingly pinch off one or more arms that then redevelop a complete new disc and arms. However, most asteroids reproduce sexually. Each arm holds a pair of gonads that become almost filled with eggs or sperm during the time of breeding. Most species are broadcast spawners, meaning that the eggs and sperm are released into the water column to be fertilized (Freeman, S 2005). To increase the chances of fertilization, sea stars come together when they are ready to spawn. The crown-of-thorns sea star, for instance, releases a potent chemical into the water column to attract the opposite sex. As for the Asterias Rubens, the female produces small eggs that are released into the sea to become fertilized. This type of reproductive strategy is known as indirect-development.
Some females hold their fertilized eggs in a brood space (a place for their offspring) either under the arm, in the stomach, or keep them warm in the gonads. If they are kept in the stomach or gonads, they develop within and escape through small openings the female's body wall called gonopores.
When eggs become fertilized they become larvae, living in the ocean as plankton. They are free-swimming organisms, moving through the ocean by using cilia. Starfish are bilaterally symmetric, meaning that they are equal on both sides. Yet in the first stages of development, one side of the body grows more than the other; meaning you can tell which side is the left and which side is the right, unlike adults where everything looks the same. Eventually the bigger side absorbs the smaller side. After that, the body is formed into five parts around a central axis; resulting in radial symmetry. Soon, they go through a complete metamorphosis, settle to the bottom, and grow into adults.
Although a lot of information about the metamorphosis that they go through to become adults has not been documented, Asterias Ruben’s go through a period without a functional metanephridial system (excretory gland found in many types of invertebrates) where it also lacks other vital functions. Also, madreporite (opening used to filter water into the water vascular system of echinoderms) papulae (skin gills) and pedicellariae (they perform necessary cleaning functions) only first appear after metamorphosis has been completed. Not a lot is known about what affects survival during the planktonic phase of the crown of thorns starfish, besides the fact that sometimes fish eat newly released eggs, which leads us to our next topic: lifespan and dangers.
Some Sea Stars can live up to 35 years (Hebert P.D.N, 2002). Sea starts don’t have to worry too much about pray due to their texture and some species having bright colors, which often make other organisims hesitant to eat them. However, when they are young, like when they are in the planktonic stage of life they are most likely to be eaten. Triton Trumpet, Harlequin Shrimp, and the Reef Crab are all predators of the Sea Stars. Considering their size during their early stages, any organism bigger than them could easily eat them. However, once they are adults, the northern bottlenose whale is a predator for this creature.
Crown-of-thorns is one of the largest and the most venomous starfishes; it clearly does not have many if any predators due to its appearance- many thorns sticking out from its body are a clear sign to stay away. Even if star fish are attacked by a predator and lose an arm, they would be able to regenerate a new one.
Asteroids have an important role in the ecosystem; they help keep things balanced. For the most part, asteroids are scavengers and carnivores. They eat sluggish moving prey, feeding on anything that is too slow to escape. They feed on sponges, shellfish, crabs, corals, worms, and even on other echinoderms. They obtain their prey by grasping it, turning their stomach inside out, and releasing secreting primary enzymes on the prey. The prey’s tissues are broken down by the enzymes, and then the asteroid sucks up the broken down tissues.
There is another form of eating, other than breaking down their prey with their stomach enzymes. It is called suspension feeding. This means that they filter prey and food particles from the water. Sometimes plankton and organic fragments sticks to mucus on the body surface. These are then moved by cilia to the mouth.
The Crown of Thorns Starfish generally feeds at night, known for eating hard coral. It is capable of eating an estimated 3.1 mi2 of coral per year. On the other hand, it can go 6 months without eating. Although they have food preferences, they often change due to the availability of prey, which can change geographically and seasonally.
Asteroids are becoming a problem for coral reefs, because some asteroids, such as Crown-of-Thorns, have increased in population and have damaged coral reefs as a result of their feeding, (Waggoner 1995) hence the reason some people believe starfish are becoming a hazard to the ecosystem.
When it comes to moving, asteroids move themselves by using what is called their water vascular system. This works by their internal muscles contracting to squeeze fluid to the tube feet, causing them to extend. Starfish have suckers at the end of their tubes, which chemically adhere to an underlying base that they are upon. Sea stars that live on soft bottom substrates have pointed tube feet (rather than suckers) to help them move about. Sea stars usually travel in large numbers at particular times of the year, typically for releasing eggs and sperm, feeding frenzies, or to find deeper water offshore. Some species of sea stars are more active at dawn and dusk, while others are lively during high and low tide, when the water is quiet enough for success in finding food.
They can sense their environment from all sides because of their non-centralized nervous system. They can sense light, contact, chemicals, and water currents because of their sensory cells on the epidermis. Higher concentrations of sensory cells are located on the tube feet and along feeding canal areas. Red pigmented eye spots are found on the end of each arm. These function as organs that can sense changes in light intensity.
Asteroids are much more complex than most would assume; from their different ways of reproduction, growth and development, and their water vascular system. Even the way they eat appears to be difficult, but to them it is just a way of life. True, they are beginning to harm our coral reefs, but that doesn’t mean they’re not important to our ecosystem.
Cites
Freeman, S. (n.d). Asteroidea (Sea Stars). In Answers. Retrieved December 27, 2008, from http://www.answers.com/topic/asteroidea-sea-stars-biological-family.
Mulcrone, R. 2005. "Asteroidea" (On-line), Animal Diversity Web. Accessed November 02, 2008 at http://animaldiversity.ummz.umich.edu/site/accounts/ information/Asteroidea.html.
GONDOLF Annette L The aboral surface of Asterias rubens L. retrieved February 2009 From http://cat.inist.fr/?aModele=afficheN&cpsidt=13964217
Zuba T. Invertabrates ECHINODERMS in Starfish Retrieved March 2, 09
from http://www.starfish.ch/reef/echinoderms.html#starfish
"Asteroidea (Sea Stars)." Grzimek's Animal Life Encyclopedia. The Gale Group, Inc, 2005. Answers.com 29 Apr. 2009.http://www.answers.com/topic/asteroidea-sea-stars-biological-family
Nicholson, F.C. (2001). Starfish. Retrieved June 11, 2009, from Starfish Web site: http://science.jrank.org/pages/6450/Starfish.html
Thursday, June 11, 2009
Wednesday, June 10, 2009
rought draft complete
When someone hears the word starfish, usually they automatically think of a five armed sea creature that looks rather lifeless. However, these asteroids are more complex than most would realize and play an important role in the ecosystem, at least, most of the time. In the ocean, there are many different kinds of starfish with different physical attributes and behaviors. Despite their diversity, they all reproduce,develop and grow within their habitat and just like any other living organism, they face dangers and can only live so long.
They live in just about any habitat in the ocean; such as tidal pools, rocky shores, sea grass and kelp beds, beneath rock rubble, on coral reefs, sand, and mud. They are seafloor predators. They have certain features which allow them to withhold rough conditions, such as their suctions which allow them to stay stuck to sea beds or close to shore despite the crashing waves. As for diversity, there are roughly 1500 different species in the Asteroidea class(CITE). Considering there are so many different species, there are two starfish in which I will go into further detail about. The Asterias rubens and the crown-of-thorns starfish Acanthaster planci are both very different. The Asterias rubens are what most consider the common starfish, and the Acanthaster planci is a very different, unique starfish that most wouldn’t even realize is a starfish.
Physically, most starfish have five arms radiating off a central disk, such as the Asterias rubens. On the other hand, some star fish may have up to forty arms, while the crown-of-thorns as between 10-20 arms. Starfish come in a vast variety of colors which include bright red, cobalt blue, yellows, and the familiar orange-brown (http://science.jrank.org/pages/6450/Starfish.html). For size there have been sea stars as small as 2cm in diameter yet as big as one meter in diameter. On average, starfish are between 12 and 24 cm in diameter. They have a very rough surface, some with short bumps and ridges, while others may have thorn-like spikes, such as the crown-of-thorns.
Another neat thing about starfish is that they can produce sexually and asexually. Although they are known to be able to regenerate arms if necessary, seven species (that tend to be very small) are known to willingly pinch off one or more arms that then redevelop a complete new disc and arms. However, most asteroids reproduce sexually. Each arm holds a pair of gonads that become almost filled with eggs or sperm during the time of breeding. Most species are broadcast spawners, meaning that the eggs and sperm are released into the water column to be fertilized. To increase the chances of fertilization, sea stars come together when they are ready to spawn. The crown-of-thorns sea star, for instance, releases a potent chemical into the water column to attract the opposite sex. As for the Asterias Rubens, the female produces small eggs that are released into the sea to become fertilized. This type of reproductive strategy is known as indirect-development.
Some females hold their fertilized eggs in a brood space (a place for their offspring) either under the arm, in the stomach, or keep them warm in the gonads. If they are kept in the stomach or gonads, they develop within and escape through small openings the female's body wall called gonopores.
When eggs become fertilized they become larvae, living in the ocean as plankton. They are free-swimming organisms, moving through the ocean by using cilia. Starfish are bilaterally symmetric, meaning that they are equal on both sides. Yet in the first stages of development, one side of the body grows more than the other; meaning you can tell which side is the left and which side is the right, unlike adults where everything looks the same. Eventually the bigger side absorbs the smaller side. After that, the body is formed into five parts around a central axis; resulting in radial symmetry. Soon, they go through a complete metamorphosis, settle to the bottom, and grow into adults.
Although a lot of information about the metamorphosis that they go through to become adults has not been documented, Asterias Ruben’s go through a period without a functional metanephridial system (excretory gland found in many types of invertebrates) where it also lacks other vital functions. Also, madreporite (opening used to filter water into the water vascular system of echinoderms) papulae (skin gills) and pedicellariae (they perform necessary cleaning functions) only first appear after metamorphosis has been completed. Not a lot is known about what affects survival during the planktonic phase of the crown of thorns starfish, besides the fact that sometimes fish eat newly released eggs, which leads us to our next topic: lifespan and dangers.
Some Sea Stars can live up to 35 years. Sea starts don’t have to worry too much about pray due to their texture and some species having bright colors, which often make other organisims hesitant to eat them. However, when they are young, like when they are in the planktonic stage of life they are most likely to be eaten. Triton Trumpet, Harlequin Shrimp , and the Reef Crab are all predators of the Sea Stars. Considering their size during their early stages, any organism bigger than them could easily eat them. However, once they are adults, the northern bottlenose whale is a predator for this creature.
Crown-of-thorns (Acanthaster planci) is one of the largest and the most venomous starfishes; it clearly does not have many if any predators due to its appearance- many thorns sticking out from its body are a clear sign to stay away. Even if star fish are attacked by a predator and lose an arm, they would be able to regenerate a new one.
Asteroids have an important role in the ecosystem; they help keep things balanced. For the most part, asteroids are scavengers and carnivores. They eat sluggish moving prey, feeding on anything that is too slow to escape. They feed on sponges, shellfish, crabs, corals, worms, and even on other echinoderms. They obtain their prey by grasping it, turning their stomach inside out, and releasing secreting primary enzymes on the prey. The prey’s tissues are broken down by the enzymes, and then the asteroid sucks up the broken down tissues.
There is another form of eating, other than breaking down their prey with their stomach enzymes. It is called suspension feeding. This means that they filter prey and food particles from the water. Sometimes plankton and organic fragments sticks to mucus on the body surface. These are then moved by cilia to the mouth.
The Crown of Thorns Starfish generally feeds at night, known for eating hard coral. It is capable of eating an estimated 3.1 mi2 of coral per year. On the other hand, it can go 6 months without eating. Although they have food preferences, they often change due to the availability of prey, which can change geographically and seasonally.
Asteroids are becoming a problem for coral reefs, because some asteroids, such as Acanthaster planci, have increased in population and have damaged coral reefs as a result of their feeding, hence the reason some people believe starfish are becoming a hazard to the ecosystem.
When it comes to moving, asteroids move themselves by using what is called their water vascular system. This works by their internal muscles contracting to squeeze fluid to the tube feet, causing them to extend. Starfish have suckers at the end of their tubes, which chemically adhere to an underlying base that they are upon. Sea stars that live on soft bottom substrates have pointed tube feet (rather than suckers) to help them move about. Sea stars usually travel in large numbers at particular times of the year, typically for releasing eggs and sperm, feeding frenzies, or to find deeper water offshore. Some species of sea stars are more active at dawn and dusk, while others are lively during high and low tide, when the water is quiet enough for success in finding food.
They can sense their environment from all sides because of their non-centralized nervous system. They can sense light, contact, chemicals, and water currents because of their sensory cells on the epidermis. Higher concentrations of sensory cells are located on the tube feet and along feeding canal areas. Red pigmented eye spots are found on the end of each arm. These function as organs that can sense changes in light intensity.
Asteroids are much more complex than most would assume; from their different ways of reproduction, growth and development, and their water vascular system. Even the way they eat appears to be difficult, but to them it is just a way of life. True, they are beginning to harm our coral reefs, but that doesn’t mean they’re not important to our ecosystem.
They live in just about any habitat in the ocean; such as tidal pools, rocky shores, sea grass and kelp beds, beneath rock rubble, on coral reefs, sand, and mud. They are seafloor predators. They have certain features which allow them to withhold rough conditions, such as their suctions which allow them to stay stuck to sea beds or close to shore despite the crashing waves. As for diversity, there are roughly 1500 different species in the Asteroidea class(CITE). Considering there are so many different species, there are two starfish in which I will go into further detail about. The Asterias rubens and the crown-of-thorns starfish Acanthaster planci are both very different. The Asterias rubens are what most consider the common starfish, and the Acanthaster planci is a very different, unique starfish that most wouldn’t even realize is a starfish.
Physically, most starfish have five arms radiating off a central disk, such as the Asterias rubens. On the other hand, some star fish may have up to forty arms, while the crown-of-thorns as between 10-20 arms. Starfish come in a vast variety of colors which include bright red, cobalt blue, yellows, and the familiar orange-brown (http://science.jrank.org/pages/6450/Starfish.html). For size there have been sea stars as small as 2cm in diameter yet as big as one meter in diameter. On average, starfish are between 12 and 24 cm in diameter. They have a very rough surface, some with short bumps and ridges, while others may have thorn-like spikes, such as the crown-of-thorns.
Another neat thing about starfish is that they can produce sexually and asexually. Although they are known to be able to regenerate arms if necessary, seven species (that tend to be very small) are known to willingly pinch off one or more arms that then redevelop a complete new disc and arms. However, most asteroids reproduce sexually. Each arm holds a pair of gonads that become almost filled with eggs or sperm during the time of breeding. Most species are broadcast spawners, meaning that the eggs and sperm are released into the water column to be fertilized. To increase the chances of fertilization, sea stars come together when they are ready to spawn. The crown-of-thorns sea star, for instance, releases a potent chemical into the water column to attract the opposite sex. As for the Asterias Rubens, the female produces small eggs that are released into the sea to become fertilized. This type of reproductive strategy is known as indirect-development.
Some females hold their fertilized eggs in a brood space (a place for their offspring) either under the arm, in the stomach, or keep them warm in the gonads. If they are kept in the stomach or gonads, they develop within and escape through small openings the female's body wall called gonopores.
When eggs become fertilized they become larvae, living in the ocean as plankton. They are free-swimming organisms, moving through the ocean by using cilia. Starfish are bilaterally symmetric, meaning that they are equal on both sides. Yet in the first stages of development, one side of the body grows more than the other; meaning you can tell which side is the left and which side is the right, unlike adults where everything looks the same. Eventually the bigger side absorbs the smaller side. After that, the body is formed into five parts around a central axis; resulting in radial symmetry. Soon, they go through a complete metamorphosis, settle to the bottom, and grow into adults.
Although a lot of information about the metamorphosis that they go through to become adults has not been documented, Asterias Ruben’s go through a period without a functional metanephridial system (excretory gland found in many types of invertebrates) where it also lacks other vital functions. Also, madreporite (opening used to filter water into the water vascular system of echinoderms) papulae (skin gills) and pedicellariae (they perform necessary cleaning functions) only first appear after metamorphosis has been completed. Not a lot is known about what affects survival during the planktonic phase of the crown of thorns starfish, besides the fact that sometimes fish eat newly released eggs, which leads us to our next topic: lifespan and dangers.
Some Sea Stars can live up to 35 years. Sea starts don’t have to worry too much about pray due to their texture and some species having bright colors, which often make other organisims hesitant to eat them. However, when they are young, like when they are in the planktonic stage of life they are most likely to be eaten. Triton Trumpet, Harlequin Shrimp , and the Reef Crab are all predators of the Sea Stars. Considering their size during their early stages, any organism bigger than them could easily eat them. However, once they are adults, the northern bottlenose whale is a predator for this creature.
Crown-of-thorns (Acanthaster planci) is one of the largest and the most venomous starfishes; it clearly does not have many if any predators due to its appearance- many thorns sticking out from its body are a clear sign to stay away. Even if star fish are attacked by a predator and lose an arm, they would be able to regenerate a new one.
Asteroids have an important role in the ecosystem; they help keep things balanced. For the most part, asteroids are scavengers and carnivores. They eat sluggish moving prey, feeding on anything that is too slow to escape. They feed on sponges, shellfish, crabs, corals, worms, and even on other echinoderms. They obtain their prey by grasping it, turning their stomach inside out, and releasing secreting primary enzymes on the prey. The prey’s tissues are broken down by the enzymes, and then the asteroid sucks up the broken down tissues.
There is another form of eating, other than breaking down their prey with their stomach enzymes. It is called suspension feeding. This means that they filter prey and food particles from the water. Sometimes plankton and organic fragments sticks to mucus on the body surface. These are then moved by cilia to the mouth.
The Crown of Thorns Starfish generally feeds at night, known for eating hard coral. It is capable of eating an estimated 3.1 mi2 of coral per year. On the other hand, it can go 6 months without eating. Although they have food preferences, they often change due to the availability of prey, which can change geographically and seasonally.
Asteroids are becoming a problem for coral reefs, because some asteroids, such as Acanthaster planci, have increased in population and have damaged coral reefs as a result of their feeding, hence the reason some people believe starfish are becoming a hazard to the ecosystem.
When it comes to moving, asteroids move themselves by using what is called their water vascular system. This works by their internal muscles contracting to squeeze fluid to the tube feet, causing them to extend. Starfish have suckers at the end of their tubes, which chemically adhere to an underlying base that they are upon. Sea stars that live on soft bottom substrates have pointed tube feet (rather than suckers) to help them move about. Sea stars usually travel in large numbers at particular times of the year, typically for releasing eggs and sperm, feeding frenzies, or to find deeper water offshore. Some species of sea stars are more active at dawn and dusk, while others are lively during high and low tide, when the water is quiet enough for success in finding food.
They can sense their environment from all sides because of their non-centralized nervous system. They can sense light, contact, chemicals, and water currents because of their sensory cells on the epidermis. Higher concentrations of sensory cells are located on the tube feet and along feeding canal areas. Red pigmented eye spots are found on the end of each arm. These function as organs that can sense changes in light intensity.
Asteroids are much more complex than most would assume; from their different ways of reproduction, growth and development, and their water vascular system. Even the way they eat appears to be difficult, but to them it is just a way of life. True, they are beginning to harm our coral reefs, but that doesn’t mean they’re not important to our ecosystem.
Saturday, June 6, 2009
halfway through essssay
When somoneone hears the word starfish, usually they automatically think of a five armed sea creature that looks rather lifeless. However, these asteroids are more complex than most would realize and play an important role in the ecosystem, at least, most of the time. In the ocean, there are many different kinds of starfish with different physical attributes and behaviors. Despite their diversity, they all reproduce,develop and grow within their habitat and just like any other living organism, they face dangers and can only live so long.
They live in just about any habitat in the ocean; such as tidal pools, rocky shores, sea grass and kelp beds, beneath rock rubble, on coral reefs, sand, and mud. They are seafloor predators. They have certain attributes which allow them to withhold rough conditions, such as their suctions which allow them to stay stuck in seabeds or close to shore despite the crashing waves. As for diversity, there are roughly 1500 different species in the Asteroidea class(CITE). Considering there are so many different species, there are two starfish in which I will go into further detail about. The Asterias rubens and the crown-of-thorns starfish Acanthaster planci are both very different. The Asterias rubens are what most consider the common starfish, and the Acanthaster planci is a very different, unique starfish that most wouldn’t even realize is a starfish.
Physically, most starfish have five arms radiating off a central disk, such as the Asterias rubens. On the other hand, some star fish may have up to fourty arms, while the crown-of-thorns as between 10-20 arms. Starfish come in a vast variety of colors which include bright red, cobalt blue, yellows, and the familiar orange-brown (http://science.jrank.org/pages/6450/Starfish.html). For size there have been sea stars as small as 2cm in diameter yet as big as one meter in diameter.
On average, starfish are between 12 and 24 cm in diameter. They have a very rough surface, some with short bumps and ridges, while others may have thorn-like spikes, such as the crown-of-thorns.
Another neat thing about starfish is that they can produce sexually and asexually. Although they are known to be able to regenerate arms if necessary, seven species (that tend to be very small) are known to willingly pinch off one or more arms that then redevelop a complete new disc and arms.
However, most asteroids reproduce sexually. Each arm holds a pair of gonads that become almost filled with eggs or sperm during the time of breeding. Most species are broadcast spawners, which means that the eggs and sperm are released into the water column to be fertilized. To increase the chances of fertilization, sea stars come together when they are ready to spawn. The crown-of-thorns sea star, for instance, releases a potent chemical into the water column to attract the opposite sex. As for the Asterias Rubens, the female produces small eggs that are released into the sea and fertilized externally to develop as planktotrophic larvae. This type of reproductive strategy is known as indirect-development.
Some females hold their fertilized eggs in a brood space either under the arm, in the stomach, or keep them warm in the gonads. If they are kept in the stomach or gonads, they develop within and escape through small openings the female's body wall called gonopores.
They live in just about any habitat in the ocean; such as tidal pools, rocky shores, sea grass and kelp beds, beneath rock rubble, on coral reefs, sand, and mud. They are seafloor predators. They have certain attributes which allow them to withhold rough conditions, such as their suctions which allow them to stay stuck in seabeds or close to shore despite the crashing waves. As for diversity, there are roughly 1500 different species in the Asteroidea class(CITE). Considering there are so many different species, there are two starfish in which I will go into further detail about. The Asterias rubens and the crown-of-thorns starfish Acanthaster planci are both very different. The Asterias rubens are what most consider the common starfish, and the Acanthaster planci is a very different, unique starfish that most wouldn’t even realize is a starfish.
Physically, most starfish have five arms radiating off a central disk, such as the Asterias rubens. On the other hand, some star fish may have up to fourty arms, while the crown-of-thorns as between 10-20 arms. Starfish come in a vast variety of colors which include bright red, cobalt blue, yellows, and the familiar orange-brown (http://science.jrank.org/pages/6450/Starfish.html). For size there have been sea stars as small as 2cm in diameter yet as big as one meter in diameter.
On average, starfish are between 12 and 24 cm in diameter. They have a very rough surface, some with short bumps and ridges, while others may have thorn-like spikes, such as the crown-of-thorns.
Another neat thing about starfish is that they can produce sexually and asexually. Although they are known to be able to regenerate arms if necessary, seven species (that tend to be very small) are known to willingly pinch off one or more arms that then redevelop a complete new disc and arms.
However, most asteroids reproduce sexually. Each arm holds a pair of gonads that become almost filled with eggs or sperm during the time of breeding. Most species are broadcast spawners, which means that the eggs and sperm are released into the water column to be fertilized. To increase the chances of fertilization, sea stars come together when they are ready to spawn. The crown-of-thorns sea star, for instance, releases a potent chemical into the water column to attract the opposite sex. As for the Asterias Rubens, the female produces small eggs that are released into the sea and fertilized externally to develop as planktotrophic larvae. This type of reproductive strategy is known as indirect-development.
Some females hold their fertilized eggs in a brood space either under the arm, in the stomach, or keep them warm in the gonads. If they are kept in the stomach or gonads, they develop within and escape through small openings the female's body wall called gonopores.
Friday, June 5, 2009
behavior and communication reaalll
Asteroids move themselves by using what is called their water vascular system. This works by their internal muscles contracting to squeeze fluid to the tube feet, causing them to extend. Starfish have suckers at the end of their tubes, which chemically adhere to an underlying base that they are upon. Sea stars that live on soft bottom substrates have pointed tube feet (rather than suckers) to help them move about.
Sea stars usually travel in large numbers at particular times of the year, typically for releasing eggs and sperm, feeding frenzies, or to find deeper water offshore. Some species of sea stars are more active at dawn and dusk, while others are lively during high and low tide, when the water is quiet enough for success in finding food. The Crown of Thorns for example feeds at night.
They can sense their environment from all sides because of their non-centralized nervous system. They can sense light, contact, chemicals, and water currents because of their sensory cells on the epidermis. However, higher concentrations of sensory cells are located on the tube feet and along feeding canal areas. Red pigmented eye spots are found on the end of each arm. These function as organs that can sense changes in light intensity.
Mulcrone, R. 2005. "Asteroidea" (On-line), Animal Diversity Web.
Accessed.April.03,.2009..at..http://animaldiversity.ummz.umich.edu/site/accounts/information/Asteroidea.html.
Sea stars usually travel in large numbers at particular times of the year, typically for releasing eggs and sperm, feeding frenzies, or to find deeper water offshore. Some species of sea stars are more active at dawn and dusk, while others are lively during high and low tide, when the water is quiet enough for success in finding food. The Crown of Thorns for example feeds at night.
They can sense their environment from all sides because of their non-centralized nervous system. They can sense light, contact, chemicals, and water currents because of their sensory cells on the epidermis. However, higher concentrations of sensory cells are located on the tube feet and along feeding canal areas. Red pigmented eye spots are found on the end of each arm. These function as organs that can sense changes in light intensity.
Mulcrone, R. 2005. "Asteroidea" (On-line), Animal Diversity Web.
Accessed.April.03,.2009..at..http://animaldiversity.ummz.umich.edu/site/accounts/information/Asteroidea.html.
role in ecosystem
Morgan Hunt
Science A
April 29, 2009
Asteroidea
For the most part, asteroids are scavengers and carnivores. They eat slow moving prey, feeding on anything that is too slow to escape. They feed on sponges, shellfish, crabs, corals, worms, and even on other echinoderms.They obtain their prey by grasping it, turning their stomach inside out, and releasing secreting primary enzymes on the prey. The prey’s tissues are broken down by the enzymes, and then the asteroid sucks up the broken down tissues.
There is another form of eating, other than breaking down their prey with their stomach enzymes, it is called suspension feeding. This means that they filter prey and food particles from the water. Sometimes plankton and organic detritus sticks to mucus on the body surface. These are then moved by cilia to the mouth.
The Crown of Thorns Starfish generally feeds at night, known for eating hard coral. It is capable of eating an estimated 3.1 mi2 of coral per year, however, it can go 6 months without eating.
Although they have food preferences, they often change due to the availability of prey, which can change geographically and seasonally.
Asteroids are becoming a problem for coral reefs, because some asteroids, such as Acanthaster planci, have increased in population and have damaged coral reefs as a result of their feeding.
"Asteroidea (Sea Stars)." Grzimek's Animal Life Encyclopedia. The Gale Group, Inc, 2005. Answers.com 29 Apr. 2009. http://www.answers.com/topic/asteroidea-sea-stars-biological-family
Mulcrone, R. 2005. "Asteroidea" (On-line), Animal Diversity Web. Accessed April 29, 2008 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Asteroidea.html.
Science A
April 29, 2009
Asteroidea
For the most part, asteroids are scavengers and carnivores. They eat slow moving prey, feeding on anything that is too slow to escape. They feed on sponges, shellfish, crabs, corals, worms, and even on other echinoderms.They obtain their prey by grasping it, turning their stomach inside out, and releasing secreting primary enzymes on the prey. The prey’s tissues are broken down by the enzymes, and then the asteroid sucks up the broken down tissues.
There is another form of eating, other than breaking down their prey with their stomach enzymes, it is called suspension feeding. This means that they filter prey and food particles from the water. Sometimes plankton and organic detritus sticks to mucus on the body surface. These are then moved by cilia to the mouth.
The Crown of Thorns Starfish generally feeds at night, known for eating hard coral. It is capable of eating an estimated 3.1 mi2 of coral per year, however, it can go 6 months without eating.
Although they have food preferences, they often change due to the availability of prey, which can change geographically and seasonally.
Asteroids are becoming a problem for coral reefs, because some asteroids, such as Acanthaster planci, have increased in population and have damaged coral reefs as a result of their feeding.
"Asteroidea (Sea Stars)." Grzimek's Animal Life Encyclopedia. The Gale Group, Inc, 2005. Answers.com 29 Apr. 2009. http://www.answers.com/topic/asteroidea-sea-stars-biological-family
Mulcrone, R. 2005. "Asteroidea" (On-line), Animal Diversity Web. Accessed April 29, 2008 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Asteroidea.html.
lifespand and dangers
Morgan Hunt
Science A
March 2, 09
5th Month
Asteroidean Life Span and Dangers
Some Sea Stars can live up to 35 years. Sea starts don’t have to worry to much about pray due to their texture and some species having bright colors. However, when they are young, like when they are in the planktonic stage of life they are most likely to be eaten. Triton Trumpet, Harlequin Shrimp , and the Reef Crab are all predators of the Sea Stars. Considering their size during those stages, any organism bigger than it could eat it. However, once they are adults, the northern bottlenose whale is a predator for this creature.
Crown-of-thorns (Acanthaster planci) is one of the largest and the most venomous starfishes; it clearly does not have many if any predators due to is appearance- many thorns sticking out from its body are a clear sign to stay away.
Starfish have a very hard structure, weird texture, and hang around near the bottom, so it makes sense that they do no have too many predators unless they are just very young. I’m sure they can’t defend themselves well so they depend on their appearance to help them out. Bright colors can usually signal not to eat them, thorns also are a giveaway that they should not be eaten.
If Star fish are even attacked by a predator and lose an arm, they would be able to regenerate it.
Zuba T. Invertabrates ECHINODERMS in Starfish Retrieved March 2, 09
from http://www.starfish.ch/reef/echinoderms.html#starfish
Mulcrone, R. 2005. "Asteroidea" (On-line), Animal Diversity Web. Accessed March 02, 2008 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Asteroidea.html.
Science A
March 2, 09
5th Month
Asteroidean Life Span and Dangers
Some Sea Stars can live up to 35 years. Sea starts don’t have to worry to much about pray due to their texture and some species having bright colors. However, when they are young, like when they are in the planktonic stage of life they are most likely to be eaten. Triton Trumpet, Harlequin Shrimp , and the Reef Crab are all predators of the Sea Stars. Considering their size during those stages, any organism bigger than it could eat it. However, once they are adults, the northern bottlenose whale is a predator for this creature.
Crown-of-thorns (Acanthaster planci) is one of the largest and the most venomous starfishes; it clearly does not have many if any predators due to is appearance- many thorns sticking out from its body are a clear sign to stay away.
Starfish have a very hard structure, weird texture, and hang around near the bottom, so it makes sense that they do no have too many predators unless they are just very young. I’m sure they can’t defend themselves well so they depend on their appearance to help them out. Bright colors can usually signal not to eat them, thorns also are a giveaway that they should not be eaten.
If Star fish are even attacked by a predator and lose an arm, they would be able to regenerate it.
Zuba T. Invertabrates ECHINODERMS in Starfish Retrieved March 2, 09
from http://www.starfish.ch/reef/echinoderms.html#starfish
Mulcrone, R. 2005. "Asteroidea" (On-line), Animal Diversity Web. Accessed March 02, 2008 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Asteroidea.html.
Development & Growth
Morgan Hunt
Science Period A
Asteroidean Development and Growth
Asteroids are deuterostomes. When eggs become fertilized they become larvae. They live in the ocean as plankton. They are free-swimming organisms, moving through the ocean by using beating cilia. They are bilaterally symmetric but one side of the body grows more than the other in the beginning; meaning you can tell which side is the left and which side is the right, unlike adults where everything looks the same. Eventually the bigger side absorbs the smaller side. After that, the body is formed into five parts around a central axis; resulting in radial symmetry. Soon, they go through a complete metamorphosis, settle to the bottom, and grow into adults
Although a lot of information about the metamorphosis that they go through to become adults has not been documented, A. Ruben’s go through a period without a functional metanephridial system (excretory gland found in many types of invertebrates) where it also lacks other vital functions. Also, madreporite (opening used to filter water into the water vascular system of echinoderms) papulae (skin gills) and pedicellariae (they perform necessary cleaning functions) only first appear after metamorphosis has been completed.
Not a lot is known about what affects survival during the planktonic phase of Acanthaster planci (Linnaeus), the crown of thorns starfish, besides the fact that sometimes fish eat newly released eggs.
Freeman, S. (n.d). Asteroidea (Sea Stars). In Answers. Retrieved February 2009, from http://www.answers.com/topic/asteroidea-sea-stars-biological-family.
GONDOLF Annette L The aboral surface of Asterias rubens L. retrieved February 2009
From http://cat.inist.fr/?aModele=afficheN&cpsidt=13964217
Science Period A
Asteroidean Development and Growth
Asteroids are deuterostomes. When eggs become fertilized they become larvae. They live in the ocean as plankton. They are free-swimming organisms, moving through the ocean by using beating cilia. They are bilaterally symmetric but one side of the body grows more than the other in the beginning; meaning you can tell which side is the left and which side is the right, unlike adults where everything looks the same. Eventually the bigger side absorbs the smaller side. After that, the body is formed into five parts around a central axis; resulting in radial symmetry. Soon, they go through a complete metamorphosis, settle to the bottom, and grow into adults
Although a lot of information about the metamorphosis that they go through to become adults has not been documented, A. Ruben’s go through a period without a functional metanephridial system (excretory gland found in many types of invertebrates) where it also lacks other vital functions. Also, madreporite (opening used to filter water into the water vascular system of echinoderms) papulae (skin gills) and pedicellariae (they perform necessary cleaning functions) only first appear after metamorphosis has been completed.
Not a lot is known about what affects survival during the planktonic phase of Acanthaster planci (Linnaeus), the crown of thorns starfish, besides the fact that sometimes fish eat newly released eggs.
Freeman, S. (n.d). Asteroidea (Sea Stars). In Answers. Retrieved February 2009, from http://www.answers.com/topic/asteroidea-sea-stars-biological-family.
GONDOLF Annette L The aboral surface of Asterias rubens L. retrieved February 2009
From http://cat.inist.fr/?aModele=afficheN&cpsidt=13964217
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