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28.3 Diversity Among the Spiralians
The basic features of spiralians are listed.
A diverse group of Protostomes are called Spiralia.
lophotrochozoans and platyzoans are included in the common classification of spiralians.
During at least one stage of their development, these animals are bilaterally symmetrical and undergo spiral cleavage.
As babies, they have three germ layers, and as adults, they have an organ level of organization.
The annelid worms are examples of a true coelom.
The lophotrochozoa can be divided into two groups.
All lophophorans have a feeding apparatus called a lophophore, which is a mouth surrounded by ciliated, tentacle-like structures.
The trochozoans have a stage of development.
A trochophore is a free-swimming, marine larva with bands of cilia that control the direction of movement.
Colonies are made up of individuals.
Zooid are single members of a colony that cooperate as a single organisms.
Some zooids specialize in feeding and others in reproduction, and some can do both.
Zooids communicate through chemical signals.
The bottoms of ships are where zooids cause a nuisance by increasing drag and making it difficult to maneuver.
molluscs have a left and right shell, but a small group of brachiopods have a top and bottom shell.
The bateiopods affix themselves to hard surfaces with a pedicle.
brachiopods use their lophophore to filter out particles from the water.
Phoronids live inside a long tube formed from their own secretions.
The tube is buried in the ground and can be pulled out very quickly.
There are only about 15 species of phoronids.
The trochozoans are the second group of lophotrochozoans.
The trocophore stage of development is what they are characterized by.
The molluscs have over 100,000 named species and are the second most numerous group of animals.
They live in freshwater and marine habitats.
There are a variety of animals in this phylum, including clams, oysters, scallops, squid, and octopuses.
The giant squid can reach lengths of over 20 m and weigh over 450 lbs.
The group includes animals.
molluscs share a three part body plan consisting of the mantle, foot, and visceral mass.
The is a covering that is either side of the mass.
It may contribute to the development of gills or lungs.
There is a space between the folds of the mantle.
The foot is a muscular organ that can be adapted for a variety of functions.
The molluscs have a three part body that includes a foot, a mantle, and aVisceral mass that includes the internal organs.
Food may be directed toward the mouth from the gills.
The radula is a tonguelike organ in the mouth of many molluscs.
The true coelom is limited to the region around the heart.
molluscs have an open circulatory system.
The heart pumps blood through vessels into the lungs.
The blue hemocyanin is the oxygen carrier.
The nervous system of molluscs has nerve cords.
The amount of sensory organs varies between clams and squid.
The mobility of the molluscs varies.
Oysters, snails, and squid are very fast moving.
The class Bivalvia includes clams, oysters, shipworms, mussels, and scallops, with a two-part shell that is hinged and closed by one or two powerful adductor muscles.
Bivalves have very little head, radula, and cephalization.
Clams and mussels use their feet to dig in the sand or muddy soil.
A scallops swims and burrows while rapid clapping of the valves causes the animal to move forward in a jerky fashion for a few feet.
Bivalves have two parts.
The scallops clap their valves and swim.
This scallop has blue eyes and a mantle.
There are dense beds in the intertidal zone.
The mantle has been removed from one side of the drawing.
The three ganglia are the anterior, foot, and posterior.
There is a reduced coelom.
pearls form if a foreign body is placed between the shell and mantle.
The clam moves forward by projecting its foot from the shell and expanding the tip of its foot.
The ciliated gills hang down on either side of the mass.
The beating of the cilia causes the water to enter the mantle cavity by way of the incurrent siphon and the exit by way of the excurrent siphon.
Small particles in the constant stream of water adhere to the gills and ciliary action sweeps them toward the mouth of the clam.
The mouth leads to a stomach and then to an anus, which can be seen in the picture.
An accessory organ of digestion is also present.
The only remains of the coelom are below the hump of the shell.
The nervous system consists of three pairs of ganglia, which are connected by nerves.
There are two excretory kidneys just below the heart that can remove waste from the pericardial cavity.
The clam excretes ammonia, a toxic substance that requires the excretion of water at the same time.
fertilization is internal Eggs that have been fertilized are released from the clam.
The parasites attach to the gills of the fish and sink to the bottom.
The evolutionary relationship between molluscs and annelids is reinforced by the fact that certain clams and annelids have the same type of larva.
slugs and garden snails are adapted to the outdoors.
The foot is shaped like a mollusc and has three parts.
The anterior end has a head region with a cerebral ganglion and eyes.
Land snails shoot calcareous darts into each other's body wall as a part of premating behavior.
Each inserts a penis into the vagina of the other to provide sperm for the future fertilization of eggs, which are deposited in the soil.
The arms that circle the head are used to capture prey.
A powerful beak is used to destroy prey.
They have well-developed sense organs, including eyes that are similar to those of animals, and focus like a camera.
There is a remarkable capacity for learning in octopuses.
There are arms in place of a head.
The chambered nautilus is the only shell they have.
The worms vary in size from small to large and can be over 4 m long.
The earthworms, marine worms, and leeches are the most familiar members of this group.
Annelids are the only trochozoan with a well developed coelom.
Annelid can crawl on a surface instead of burrowing in the mud.
The bristles protrude from the body wall and can anchor the worm.
muscle contraction and the setae are used in Locomotion.
When longitudinal muscles contract, the setae protrude into the soil, and when circular muscles contract, the setae are withdrawn.
Look at the parts of the GI tract that are specialized.
The body wall of the earthworms is moist due to the fact that there is adequate moistness in the soil.
They are scavengers that feed on leaves and dirt.
There has been an increase in the specialization of the digestive system components.
Food drawn into the mouth is stored in a crop and ground up in a thick, muscular gizzard.
Digestion and absorption occur in a long intestine with a typhlosole, which increases the surface for absorption.
The anus is where waste is eliminated.
There are septa that occur between segments on Page 526.
There are swellings and nerves in the nerve cord leading from the brain.
The excretory system has a pair of nephridia.
There are coiled tubules in each segment.
There are two openings in a nephridium, one is a ciliated funnel and the other is an exit in the body wall.
The waste material is removed from the blood vessels between the two openings.
The coelom, the pair of setae and the nerve cord are found in the cross section.
Blood flow can be traced back to the pulsations of the blood vessel and the five pairs of hearts.
The worm's body is covered with branches when the blood goes to the anterior regions.
Two worms are facing in opposite directions as they lie parallel to each other.
After the worms separate, the clitellum of each produces a tube, which is moved over the anterior end by muscular contraction.
Eggs and sperm are deposited as it passes.
The hatched worms are protected by the slime tube.
There isn't a stage in earthworms.
The clitellum holds earthworms in place when they mate.
The worms are hermaphroditic, and when they mate, sperm pass from the seminal vesicles of each to the seminal receptacle of the other.
Most of the annelids are marine polychaetes.
Polychaetes have setae in bundles.
Most segments have paddlelike appendages called feet.
The expanded surface area allows for exchange of dissolved gases in swimming and respiratory organs.
The majority of polychaetes live in crevices or burrows.
They prey on crustaceans and other small animals, which are captured by a pair of strong, chitinous jaws that extend with a part of the pharynx when the animal is feeding.
The clams are predaceous polychaetes.
The parapods are used for swimming and as respiratory organs.
All of the pages have radioles.
The beautiful radioles make the animal look like a feather duster.
Christmas tree worms are feeders that have their mouth appendages spiral.
During the breeding season, the worms have sex organs.
The zygote develops quickly.
Leeches live in freshwater habitats.
They range from less than 2 cm to 20 cm in length.
Most of them are brown or olive green.
The body of a leech is flattened.
They have the same body plan as other annelids, but they have no setae and each body ring has several grooves.
They are blood suckers.
Most of the time, leeches are fluid feeders that attach themselves to open wounds.
There are two suckers, one around the mouth and one in the back of the neck.
Some bloodsuckers can cut through tissue.
Hhirudin is a powerful blood thinner that leeches can use to keep blood flowing.
The bite of a leech is usually not painful because the saliva contains a chemical with local anesthetic properties.
Blood-letting and other procedures have been done with the help of Medicinal leeches.
They are used in plastic surgery for severed digits.
The second group of Spiralia is called Platyzoa.
Flatworms and rotifers are included.
There are no circulatory or respiratory systems in these groups.
Flatworms have a sac body plan that only has one opening, the mouth.
The third germ layer, the mesoderm, fills the space between the organs.
Planarians are free-living, while flukes and tapeworms are parasites.
A planarian captures food by wrapping itself around the prey and pinning it down.
The pharynx is extended through the mouth and the prey is sucked into it.
The pharynx leads into a three-branched stomach, in which digestion is both internal and external.
The animal does not have a respiratory system or a circulatory system.
The waste leaves through the mouth.
When a planarian extends the pharynx, food is sucked up into a body part that branches throughout the body.
Planarians have an excretory system.
There are canals that run the length of the body on each side of the organ.
There are structures at the ends of the canals.
The water is taken into the canals that are empty.
The excretory system is an osmotic-regulating system.
The excretory organ of the flatworm is called a flame cell because of the beating of the cilia.
The excretory system has flame cells.
Planarians usually have sex.
They have both male and female sex organs and gametes in one person.
When the penis of one is inserted into the other, the worms cross-fertilize.
Each planarian gives and receives sperm.
The tiny worms hatch in 2 or 3 weeks after fertilization.
The reproductive system has both male and female organs.
Planarians can reproduce asexually.
Each part of the planaria grows into a new worm when the tail breaks.
Because planarians have the ability to regenerate, they have been the subject of research.
Humans do not have the ability to regenerate parts of their body after amputation.
The study of how planarians are able to regenerate may lead to better treatments for humans and other animals.
The nervous system looks like a ladder.
Planarians are symmetrical.
The auricles on the head of a planarian are arrow-shaped and contain cells that detect food and enemies.
Planarians have three kinds of muscles that allow for varied movement: an outer circular layer, an inner longitudinal layer, and a diagonal layer.
The movement of cilia is accomplished in larger forms.
The animal glides on mucus that is produced by numerous cells in the gland.
There are two types of flatworms, trematodes and tapeworms.
The bodies of the two groups are very different.
There is a protective tegument on the surface of the tapeworms that is resistant to host juices.
The head with sensory structures has been replaced by hooks or suckers for attachment to the host, as the flatworms have lost their cephalization.
The nervous system is not well developed because they no longer hunt for prey.
A well-developed reproductive system helps ensure transmission to a new host.
Both tapeworms and flukes use a secondary host to transmit their offspring.
The primary host has the sexually mature adult and the secondary host has the stage or stages.
Human diseases are caused by parasites.
There are blood, lung, and liver flukes, which are named for the organ they live in.
Almost 11,000 species have an oblong shape with a 2.5 cm long body.
There is an oral sucker at the anterior end that is used for attachment to a host.
The conditions for widespread infections have been created by standing water in irrigation ditches.
According to the World Health Organization, schistosomiasis is one of several neglected tropical diseases that afflict the poor people in impoverished nations.
Female flukes deposit their eggs in small blood vessels close to the human intestine, and the eggs make their way into the GI tract by a slow migratory process.
After the eggs pass out with the feces, they hatch into tiny larvae that swim about in rice paddies and elsewhere until they enter a particular species of snail.
sporocysts, which are sacs, produce new forms that leave the snail.
If the skin of a human is penetrated by the larvae, they will be able to grow in the blood vessels of the small intestine.
The eggs of the flukes can cause a number of health problems.
Their condition was weakened.
Over 200 million people worldwide are afflicted with this disease.
Eggs are deposited in the bile ducts of the adults in order for them to be eliminated from their feces.
Humans are more likely to become infections through the fecal route than nonhuman species.
A full set of female and male sex organs can be found in a series of reproductive units called proglottids.
Depending on the species, the number of proglottids may vary.
The proglottids become full of mature eggs after fertilization.
100,000 eggs may be in proglottids.
Eggs of some species can be released through a pore in the proglottid into the host's intestine, where they exit with feces.
The gravid proglottids break off in other species.
These segments can be mistaken for flies, for example, in dog or cat feces, but tapeworm segments are flatter and appear in fresh samples, whereas fly eggs take up to a day to hatch.
The life cycles of most tapeworms are complicated.
After a pig 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 800-273-3217 They travel through the wall of the gut to get to the bloodstream.
There is a bladder worm in this cyst.
Humans get tapeworms when they eat meat that has not been cooked.
A human and pig are part of the life cycle.
The adult worm has been altered to have a different way of life.
There are bags of eggs in it.
More than 50 million people in impoverished nations of the world suffer from cysticercosis, an advanced tapeworm infection that is serious for growing children.
The bladder worms grow to adulthood after they break out of the cysts and attach themselves to the wall.
The cycle begins again.
The primary host can be affected by tapeworm infections.
The platyzoans are related to the flatworms.
The length of a rotifer is only 0.1- 3mm.
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