Unit 10 – Flatworm, Roundworm and Segmented Worms Flatworms

Characteristics of Flatworms

Flatworms (phylum ______________________________) are a step “up” the ladder of

evolution being ________________________________________________________.

Flatworms have a _____________________________. This body plan means they have

___________________________________________________________________________

__________________________. However, _______________________________________

___________________________________________________________________________

___________________________________________________________________________

___________________________________________________________________________.

These specialized systems are exemplified by the Planaria which is a heterotrophic free-living

flatworm.

There are three Classes of flatworms.

Class Turbellaria – example Planaria -

free living, incomplete gut, no suckers or

hooks.

Class Trematoda – example flukes -

parasitic, incomplete gut, _____________

_________________________________.

Class Cestodae – example tapeworms -

parasitic, no gut, ___________________

_________________________________

_________________________________.

Body Plan Summary - Both primitive and advance characteristics - ____________________________________________. - ______________________________________ - ______________________ - concentration of sensory organ and nervous tissue at anterior end of body - ________________________________________

___________________________________________ (germ layers).

- Ectoderm – forms outer epidermis. - Mesoderm - forms muscle tissue and reproductive, and excretory organs. - Endoderm – forms inner gut. - ____________________________________________

Movement Some larval stages move using cilia while adults move using muscle contractions.

Class Turbellaria Planaria __________________________________________________________________

___________________________. The __________________________________________

___________________________________________________ on the end of a muscular

___________________________________________________________________________

___________________________________________________________________________

to the body. Indigestible wastes leave the same way they came in through mouth.

There are approximately 4,500 species that live in the ________________. Some live in

________________________

Planaria Digestive System

The digestive system in Planaria is similar to that of the cnidarians. It consists of a _________

_____________________________. A pharynx extends from the underside of the flatworm

and sucks up food through the mouth. The food is then ______________________________

___________________________.

Wastes are expelled through the

same opening. Nutrients can be

carried through the organism

efficiently by ________________

because the flatworm is so thin.

Label Planaria Digestive System

Planaria Excretory System Excretion is the expulsion of excess water and wastes. These wastes differ from those

expelled from the gastrovascular cavity in

that wastes excreted by the excretory

system were first digested and entered

the body of the flatworm. Planarians have

specialized cells called

_________________________________

_________________________________

_________________________________

_________________________________

_________________________________

_________________________________

_________________________________

Planaria Reproductive System

Planarians are ___________________________, meaning they

are ______________________________________, but they

______________________________________ between

organisms. Adjacent flatworms will align themselves so that they

will simultaneously fertilize each other. Planaria also have

amazing _________________________________________. If a

planaria is cut lengthwise, it will grow into two separate animals.

And, if a planarian is cut down the center, but not completely, it

will develop two heads.

Label Planaria Reproductive System

Planaria Nervous System The nervous system of the planarian consists of

______________________________________

______________________________________

______________________________. This type

of nervous system is referred to as a

___________________________. The

cephalization consists of a brain, chemosensitive

organs, and two eyespots. The chemosensitive

organs guide the flatworm toward food and the

eyespots are sensitive to light. Planaria will move

away from light probably to avoid predation. The

nervous system also controls muscles used for movement.

Other Systems in Planaria CIRCULATORY and RESPIRATORY SYSTEMS – not true systems

- part of the gastrovascular cavity.

- ____________________________________________________________________

_______________________________________________.

MUSCULAR SYSTEM – a true system.

-controlled by longitudinal, circular, and oblique layers of muscle

sometimes assisted by secreting a layer of mucus.

SKELETAL SYSTEM – NONE

Class Trematoda There are an estimated 9000 species of Trematoda. Many of these are ______________

(liver, lung, heart, intestine).

Flukes are _________________________. Flukes have _____________________________

___________________________________________________________________________

___________________________. They absorb nutrients through the gastrovascular cavity.

They have ___________________________ for excretion. Nerve cords and anterior ganglia

make up the nervous system. They are _______________________________. Flukes have a

_______________________________________ with numerous larval stages that infect a

number of hosts.

The entire external surface of a fluke is covered by a continuous sheet of fused cells called the

____________________________. The ________________________ consists of a layer of

protein and carbohydrates that __________________________________________________

______________________________________________________.

Liver Fluke Life Cycle

Class Cestoda There are an estimated 5000 species of Cestoda. An example is tapeworms.

Tapeworms are ________________ animals

and are specialized for living within a host.

Most body systems have been lost as they are

not required as the host provides nutrients.

There are ___________________

___________________________________

__________________________. Tapeworms

____________________________________

__________________ through their skin. The

____________________________________

____________________________________

This adult tapeworm has a _____________________________________________________

___________________________________________________________________ While the

tapeworm grows in the host's intestine, ___________________________________________

__________________________________________________________________________.

This species occurs most often in rabbits, cats and rodents, but sometimes humans, causing

diarrhea, weight loss and abdominal discomfort. Adult tapeworms may grow 5-10 meters in

length.

Proglottids are body segments

specialized for reproduction

Tapeworms have a Scolex with hooks and

suckers used to attach to the inside wall of

the host intestine

Tapeworm Life Cycle Tapeworm Reproduction Summary

- Carried out by ______________________

______________________________.

- Tapeworms are ____________________ -

contain both ovaries and testes and ______

___________________________________.

- Zygotes are passed out of host’s body with

feces.

- Larvae hatch in water and in grass.

- Larvae are eaten by a herbivore

(________________________________)

and the larvae then burrows through the wall

of the intestine and into the blood stream.

Intermediate hosts contain tapeworm cysts

(__________________________________________________________________________

___________________________________________________________________________

______________________________________________________.

MMmmm Tapeworms

As part of a University of Salford experiment to develop a diagnostic test for beef tapeworm,

biologist Mike Leahy volunteered to grow this gruesome parasite inside his own gut. Mike

swallowed the immature tapeworm cyst with a glass of red wine and the worm started to grow

at an initial rate of four centimetres a week. Twelve weeks later he had to call a halt to the

unusual experiment because he was getting married! After a dose of anti-worm pill Mike

passed out an intact tapeworm three metres long.

Parasitic Flatworms Flatworms that are parasitic on humans fall into two categories, _______________________

_________________. Due to the fact that they live in the gut of a host animal these flatworms

have an anatomy __________________________________________. Generally, _________

___________________________________________________________________________

________________________. Parasitic flatworms will usually have hooks on the scolex

(anterior region) to attach it to the wall of the gut and they have an ______________________

______________________________________________ When a flatworm reproduces, the

eggs are passed out with the feces. When consumed by another host the life cycle continues.

Flukes and tapeworms can infect many different animal hosts. _________________________

___________________________________________. One host when sexually mature called

the primary host and a secondary host in which the eggs mature to larvae.

Roundworms

General Characteristics Roundworms Roundworms belong to the Phylum ______________________________ (also called

___________________________).

Nematodes are the most speciose phylum after the arthropods.

They occur in nearly every habitat including ________________

___________________________________________________

______________________ (they don't like dry places however).

One species is known that can live in old vinegar (Turbatrix aceti)

and another that has only been found in German beer mats.

Though only about 80 000 species have been described some

scientists estimate there may be as many as a million species all

told. They can occur in very dense numbers in the soil and rotting

vegetation, as many as 90 000 have been found in a single rotting apple, while millions occur

in the top 3cm (1 inch) of a square metre of good quality soil.

While there are a huge number of ______________________ Nematodes there are also a

large number of __________________________________, many of which cause diseases to

man and other animals as well as to plants, nearly every living organism has been found to be

parasitised by one species of nematode or another.

Most nematodes are reasonably small, they range in size from 100 micrometres in length

(1/10th of a mm or 1/250th of an in) to the female Giant Nematode Dioctophyme renale which

may be up to 1 metre, or 3 ft long.

Body Systems in Roundworms

Roundworms (phylum ____________) have a _________________________ _______________________________. This body plan is more advanced than the Platyhelminthes and Cnidarians which, you should recall from previous units, have a single opening functioning as a mouth and anus called a sac plan. Nematodes _____________________ _______________________________. This design allows for ____________ ______________________________ ______________________. At the anterior (head) end there is a mouth which has 3 lips behind which predatory species possess a few teeth, this leads to a ___________________. The pharynx of Nematodes is an efficient pump and forces food into the intestines as it can be used to suck liquid food into the mouth. ________________________________________________________________________.

Digestive System

Roundworms have a __________________________________________. It is a long tube shaped digestive tract with _____________________________________________________ ___________________________________________________________________________. As food is pushed through digestive tract it is digested and ____________________________ _________________________ into the cells of the body. Undigested remains continue on through tract and are _________________________________________________________ _________________________. Free living round worms are often _______________________________________________

______________________________________________________________________________________________________________________________________________________. They excrete metabolic waste through their body walls by __________________.

Circulatory and Respiratory Systems

Roundworms have __________________________ _____________________________________. They breathe and excrete waste through their body walls. They do not have an internal transport (circulatory) system and rely on ________________________. The _____________________________ is filled with fluid and it distributes digested foods and dissolved oxygen to the body. It also acts as ___________________________________.

Excretory System

In roundworms, ____________________________________________________________ _______________________________________________________________________.

Nervous System

Nematodes, especially free living forms generally have a reasonably well developed nervous system. This is comprised of a circum-pharyngeal nerve ring and longitudinal nerves that extend down through the body to the various parts of the gut and the reproductive organs. ______________________________________________________________________________________________________________________________________________________. They have simple sense organs.

Reproduction

Nematodes are copiously reproductive and most of their body cavity, which is a _________________________________, is filled with paired sets of reproductive organs, either ovaries or testes. _______________________________________________________ _____________________________________. The female has long coiled ovaries that produce thousands of eggs every day. Eggs are stored in a uterus. The vagina leads to an external opening. ____________________________________________________________ _____________________________________________. Sperm cells pass through the sperm duct though an opening at the posterior end of the worm. During copulation sperm is released into the vagina resulting in internal fertilization. After fertilization, _______________________ ______________________________________. The females lay eggs over a prolonged time period, thus a female Ascaris lumbricoides may lay her eggs at the rate of 200,000 per day and have had a total 27 million eggs within her at the start of her reproductive career.

Summary Primitive Characteristics :

- ___________________________. - No circulatory System. - No skeletal system. - ________________________________________________

Advanced Characteristics: - ______________________________________________. - Cylindrical shape (round worms). - _____________________________________________.

Ectoderm – produces tough cuticle. Mesoderm – muscle and various organs. Endoderm – digestive tract.

- ____________________________________________________ – mouth to anus! - ___________________________ - between the mesoderm and the gut is a fluid filled space.

Ascaris Ascaris is usually diagrammed to typify roundworm anatomy. Ascaris is a roundworm that is ___________________________. The entire life cycle can take place in the human body and the eggs can be passed out with feces. Eggs in food or water are _____________________ _____________________________, the eggs hatch in the small intestine, larvae enter the blood vessels and are carried to the lungs, larvae then travel to the throat and are swallowed. Adult ascaris worms live in the small intestine with eggs leaving the host in the feces. With a longitudinal cross section the tube within a tube design can be observed. It can also be observed that the digestive system is not very well developed as the length of the gut after the pharynx is unchanged and reproductive organs are quite large in comparison to the body. This is a characteristic of an internal parasite to have a simple digestive system and well developed sex organs. Ascariasis is the human disease caused by ____________________ with as many as ______________________________________________________. It is common in tropical regions, regions with poor sanitation, poor personal hygiene, and places where human feces are used as fertilizer. Intake of food or drink contaminated with Ascaris eggs causes the infection. The symptoms of Ascariasis are listed below.

Passing worms in stool. Vomiting up worms. Worms exiting through the nose or mouth. Low-grade fever. Cough. Bloody sputum.

Wheezing. Shortness of breath. Skin rash. Vomiting. Stomach pain. Note: There may be no symptoms.

Label Ascaris

Other Parasitic Roundworms Even though ________________________________________________________________ ____________________________________ are typically enough to ward off roundworm infection many roundworm diseases are common worldwide including some in North America. _________________________________ are common in North America, while more serious infections such as ______________________________________ are common in Africa and are rarely seen here. Trichina worm causes Trichinosis when the host eats __________ ____________________

____________________

____________________.

Trichinosis forms cysts in

the muscles of its victims

and causes symptoms

such as pain, blisters,

muscular weakness, and anemia. The images below show a

trichina worm and a cyst formed in muscle around a worm.

...... Pinworms are tiny pin-shaped nematodes known as Enterobius vermicularis to the medical and zoology communities. Also called seatworms or threadworms these small, whitish roundworms are responsible for contagious intestinal _______ _______________________________________ _______________________________________ _______________________________________

____________________________________________ Although adult pinworms inhabit the large intestine, the eggs are laid outside of the anus during the night creating a severe itching sensation. Other symptoms include disturbed sleep, decreased appetite and weight loss. Spread from person to person usually occurs with ____________________________________________ ____________________________________________ ____________________________________________ The eggs can also drift through the air where they are inhaled or swallowed. Once they enter the new host the eggs hatch in the small intestine and travel down to the large intestine for maturation.

-_________________________________________________________________________________________________________________________________________________________

Filaria worms __________________ _______________________________________________________________________________________. Elephantiasis is transferred by mosquitoes and blocks lymph vessels as the worms increase in size. Lymph vessels return fluid to the bloodstream from the tissues so when the vessels are blocked the limbs increase greatly in size.

Loiasis, called eye worm or loa loa, is endemic to the rainforests of central and western Africa where mango flies of the Chrysops species serve as both intermediate host and the parasite vector. About 13 million people are currently infected.

This map shows the distribution of eye worm infections.

Guinea worms, also known as the stick worm, form ulcerating blisters in human skin. People get infected when they drink standing water containing a tiny water flea that is infected with the even tinier larvae of the Guinea worm. Over the course of a year in the human body, the immature worms pierce the intestinal wall, grow to adulthood, and mate. The males die, and the females make their way through the body, maturing to a length of as much as 3 feet, and ending up near the surface of the skin, usually in the lower limbs. The worms cause ____________________________ __________________________________ __________________. To soothe the burning, sufferers tend to go into the water, where the blisters burst, allowing the ______________ ___________________________________ ___________________________________. In the water, the larvae are swallowed by small water fleas, and the cycle begins again. These parasites can cause long-term suffering and sometimes crippling after-effects. The worms are slowly removed from the body by winding them slowly around a stick to pull them out.

Segmented Worms

General Characteristics of Annelids The annelids or _____________________________________________________________ _______________________________________________________________________________________________________________. The general characteristics of an Annelid are similar to those of a roundworm. They are _________________________________________ ______________________________________________________________________________________________________. However, an Annelid also has a _____________________ ___________________________. Both the coelom and segmentaion allow for greater specification of body parts. _____________________________________________________ and allow structural support by creating a hydroelastic skeleton. ________________________ ___________________________________________________________________________ which will be discussed in the anatomy of the earthworm later in this lesson. The ___________ _____________________________________________________________________________________________ (filtering organ) in each segment. The Annelid moves by alternating contractions of circular and longitudinal muscles. The circular muscles encompass the body wall and therefore contractions cause the body to become long and thin. The longitudinal muscles run the length of the body and cause the body to shorten and fatten.

The Phylum name Annelida means "Ringed in Form". _______________________________ ______________________________________________________________ within the animal for different purposes. The coelom is divided into separate compartments (septa) by partitions. These septa enable different compartments to contract or expand independently. Duplication of some of the organ systems in each segment provides insurance against injury. There are three Classes of Annelids that we will discuss in this book. 1. Class Polychaeta meaning "____________________________". 2. Class Oligochaeta which _________________________________________. 3. Class Hirudinea which ____________________________________.

Marine Worms Class Polycaeta are so named because they have many _______ on their segments. These _______________________________ ____________________________________________________ ____________________________________________________. In some marine worms they are arranged like a paddle and are called _______________________________________________ ___________________________________ because Annelids breath through their body wall by _________________ and parapodia expand the surface area of the animal. Some marine worms such as Nereis have a more noticeable cephalization. Nereis has an invertible pharynx that exposes chitinous (made of chitin - a strong complex carbohydrate common to fungi cell walls and some animals) jaws, eyes, and other sense organs. Some marine worms have bristles to aid in defense. Nereis seen below is an example of a free living predatory marine worm.

Predatory worms also have ____________________________________________________. Other marine worms live in tubes that may be made of calcium, silica (sand) or protein. These tube worms are filter feeders. Here's what these worms look like when retracted.

Earthworms Segmented worms of the class ___________ ___________ (maximum 20 setae per segment) and are exemplified by the common ____________________, Lumbricus terrestris. Earthworms do not have cephalization as advanced as marine worms such as Nereis, but they do _____________ ___________________________________ ______________________________. They do not have eyes, but are capable of detecting and avoiding water without actually coming in contact with it. Earthworms live in soil and freshwater while some types are found in the ocean. Earthworms act as ______________________, maintain the fertility of soil, release nutrients into the soil, loosen and ________________ ________________________________________. Some segmented worms such as the Tubifex (sludgeworm) seen in the third picture can survive in polluted sediments and areas with little oxygen.

Earthworm Digestion

The digestive system of the earthworm and other annelids is quite advanced. In the earthworm, ______________________________________________ as they burrow ____________________________________________. From the pharynx food moves through the ___________________________________________________________ ____________________________. It ____________________________________________ ___________________________________________________________________________. The _______________________________________________________________________ ________________________________________________________. The intestines have a typhlosole, which is a fold that increases surface area for absorption. ____________________ _________________________ (castings that are good for the garden) __________________ _____________________________. Here's an image showing Oligochaeta digestive system.

Earthworm Circulation The circulatory system of an Earthworm consists of a ________________________________ __________________________________________________________________________________________________ that connect the two vessels together behind the head region. The branches _______________________________________________________________ __________________________________________________________________________________________________________________________. Due to the pulsating action of the branches, which is similar to the action of hearts, they are termed "hearts" or pseudohearts. The purpose of this ___________________________________________________ is to transport oxygen, carbon dioxide, nutrients and wastes throughout the body of the earthworm. Earthworms have _____________________________________________________________ ___________________________________________________________________________ and into small blood vessels when the skin is moist.

Earthworm Excretion As stated in the general characteristics, ____________________________________ ________________________. In earthworms, ____________________________________ ____________________________________ ___________________________________. The cellular wastes and excess water are eliminated through these nephridia. Each segment of the earthworm except the first three and last one have nephridia.

Earthworm Nervous System The nervous system of an Earthworm is ____________ ____________________________________________ ______________________. Most body segments have a single ganglion. These worms also have an __________ _____________________________________________ and can respond to light, touch, chemicals, moisture, temperature, and vibrations. Movement in these worms is made possible by segmentation. ________________________________ ____________________________________________ ______________________. To move,______________ ____________________________________________ and contracts circular muscles in front of these segments. Hydrostatic fluid in the coelom increases pressure and elongates the worm. Then longitudinal muscles pull posterior segments forward as they contract and shorten.

Earthworm Reproduction

Earthworms are ____________________________________________________________ __________________________________________________________________________. The clitellum is the relatively large band around the earth worm. _______________________ ________________________________________ (an individual worm cannot fertilize its own eggs) by aligning head regions with clitellums. Two earthworms press their ventral surfaces together with the anterior ends pointing in opposite directions. _________________________ ____________________________________________________________________________________________________ as it transfers. Each earthworm injects sperm into the mucus which moves into a pouchlike seminal receptacle of each worm. After several days each worm secretes a tube of mucus and chitin (thick carbohydrate) which picks up the worms eggs and stored sperm. The sperm and egg are then expelled through a slime tube and fertilization takes place. The tube closes up to form a protective case for 2-3 weeks until the young worms hatch.

Leeches Class ________________________________________ _____________________________________________ with approximately 300 species. Although ___________ ____________________________________________, many leeches are annelids which are ______________ ________________________________________________ _________________________________________. They ________________________________________________ ________________________________________________ _____________________________________. They also ________________________________________________ ________________________________________________ ________________________. If undisturbed, a leech can ingest 10 times its own weight in blood. A leech will drop off once finished eating and will not need to eat again for up to a year. Leeches are used in medicine________________________ _________________________ in amputated digits (fingers or toes) that have been surgically reattached.

Body Plan comparison in the Worms This lesson compares the body plan of the three classes of worms discussed in this unit. The diagrams below are keyed as follows.

Ectoderm: blue Endoderm: yellow Mesoderm: red

_________________________ _________________________ Body cavity filled with mesoderm.

________________________ ________________________ Body cavity partially lined with mesoderm.

________________________ ________________________ Body cavity entirely lined with mesoderm.