The Simplest Animals

Sponges

Jellyfish

Flatworms

Roundworms

Many images from: www.oceanicresearch.org/.../cnidarian.html

The Simplest Invertebrate Phyla are: -without a skeleton

-without segmentation:

• Porifera (sponges)

• Cnidaria (jellyfish, hydras, sea anemones, Portuguese man-of-wars, corals)

• Platyhelminthes (flatworms, including planaria, flukes, and tapeworms)

• Nematoda (roundworms, including rotifers and nematodes)

http://sps.k12.ar.us/massengale/images/brac-sponges-21.jpg

I. SpongesI. Sponges

Why areWhy are sponges sponges considered considered animals?animals?

• Early biologists thought they were

plants!

The most primitive of the

simplest animals: SpongesSponges• Phylum: Porifera-

• Invertebrate (no backbone)

• Asymmetrical

• No true tissues or organs• All species -Aquatic

• Adult is Sessile Sessile (do not move)

Sponges have key Sponges have key characteristics of animals:characteristics of animals:

• Heterotrophic

• Multicellular• Adults are sessile- but some

species can move up to 4mm/day (http://www.ucmp.berkeley.edu/porifera/poriferalh.html) –And sponge larvae have flagella

Basic Body plan of a SpongeBasic Body plan of a Sponge

Asymmetrical & Sessile

Vocabulary of sponge parts:• Osculum- Hollow cylinder shape, closed at

bottom, opening at top called

• Choanocytes ( collar cells) – flagellated cells that draw water into the sponge through pores in the body wall called Ostia.

• mesohyl – jelly-like material separates 2 layers of cells

Collar cells-Collar cells- w/ flagella beat water through the sponge

Purple Tube Sponge ColonyPurple Tube Sponge Colony on Dead Coralhead at

Rainbow Reef near Bimini, The Bahamas

www.reefnews.com/.../photos/corals/sponges.html

If Coral Reefs are in danger- are sponges that grow on them bad?• Animals that eat sponges and algae help

to keep a healthy balance on the reef.

• If there are too few of these animals, then the sponges and algae may take over.

• Examples of algae eaters are Parrotfish, Sea Urchins, and Crabs.

• Examples of sponge eaters are Hawksbill Turtles and Loggerhead Turtles.

www.reefnews.com/.../photos/corals/sponges.html

How does a sponge eat?How does a sponge eat?• Sponge cells work together, pumping water

through the body of the sponge. • The sponge eats the plankton, bacteria &

organic material it filters out of the water as the water is pumped through the body of the sponge.

• Amoebocytes- crawling cells that deliver nutrients from choanocytes to the rest of the body

• Sponges are filter feeders!www.reefnews.com/.../photos/corals/sponges.html

How does a sponge reproduce?1. Asexual

a. Budding- part of the parent pinches off & forms a new organism

b. Gemmules – a reproductive structure in sponges, -produced in harsh conditions-a food-filled ball of amoebocytes in a protective coat

c. Regeneration- regrowth of missing cells.

2. Sexuala. Sperm are released into water, enters next sponge through pores, choanocytes engulf sperm. Carry to ameobocytes, carry them to egg in mesophyl. Produces a flagellated Larvae (immature form)

b. Hermaphrodite- each sponge has both eggs & sperm

A sponge treated w/ dye

to show squirting action!

Some sponges grow quite

large. This barrel sponge is nearly large enough for the diver to climb

right inside! Other barrel sponges get

even bigger than this.

Porifera represent transition Porifera represent transition from unicellular from unicellular

to multicellular life.to multicellular life.

II. Phylum CnidariaII. Phylum Cnidaria• Hydra,

• Jellyfish,

• Sea Anemones,

• some corals

• Cnidarians are animals with 2 tissue layers

• Cnidarians are the simplest animals with nervous & muscle

tissue.

• They sting & eat their prey!

Purple-Striped Jelly ("Chrysaora Colorata"), Monterey Bay

Aquarium, Monterey, California, USA

Giant jellyfishGiant jellyfish (6-7 feet across)

www.divester.com/.../

Blue jellyfish

Monterey Bay

Aquarium. Monterey, California,

USA

Hydra Hydra (with bud)

http://www.isi.edu/robots/self_heal_html/hydra.JPG

Pink Hearted hydroids, members of the class Hydrozoa. They look like delicate plants but they are

animals that sting and capture food.

Fire Coral has a potent sting that leaves an itchy rash on human skin. A kind of

hydroid that encrusts other objects (including other corals).

Sea AnemoneSea Anemone

library.thinkquest.org/.../01819/SeaAnemones.htm

Tealia anemone a good example of an Anthozoan. Flower-like animals resemble plants, but they have a mouth at the center of their tentacles, & a primitive digestive system.

Cnidarian Body PlanCnidarian Body Plan2 types of bodies or Stages:

Medusa –bell shaped, swims

Polyp – vase-shaped, sessile

2 cell tissue layers-

Epidermis outside layer

Gastrodermis inside layer

-with Mesoglea (jelly) in between)

1 opening Gastrovascular cavity (gut)

Many TentaclesTentacles with cnidocytescnidocytes

http://biology.unm.edu/ccouncil/Biology_203/Images/SimpleAnimals/cnidariaDiagram.jpeg

POLYP

MEDUSA

How do Jellyfish eat?1.Cnidocytes (special defensive cell) have

Nematocysts (coiled organelle with stinging filament)

2. Tentacles push prey in mouth & intogastrointestinal cavity

3. Digestion is

Extracellular, wastes

expelled through mouth.

http://www.emc.maricopa.edu/faculty/farabee/biobk/cnidaria_1.gif

Jelly fish are the 1st animals to have nervous & muscle tissue

Nerve Net -Nerve cells interconnect and form a nerve net throughout the body.

Movement – using pulsing tentacles

Cnidarians have both muscle fibers and nerve fibers, making these animals capable of directional movement.

Cnidarian classes:Cnidarian classes:

1. Hydrozoa. Hydrozoa ( 3,700 species) ex- Obelia, Portuguese Man-O War.

2. Cubozoa. Cubozoa ex- box jellies, sea wasp

3. Scyphozoa. Scyphozoa “cup-animals” jellyfish

4.4. AnthozoaAnthozoa (6,100 species) “flower animals” like sea anemones, corals

Deadly danger: Portuguese man

o'war

can in extreme cases provoke a cardiac arrest and death in particularly sensitive persons.

www.dailymail.co.uk/news/article-1050187/Pict...

Lucky escape: Jonathan Asplin was only

saved from worse harm by his wetsuit

Pictured: Horrific scars suffered by boy, 8, stung by deadly Man o' War on British coast

www.dailymail.co.uk/news/article-1050187/Pict...

The Freshwater Hydrozoan

Hydra:Polyp with early

and mature bud.

www.micrographia.com/.../hydr0100/hydra-01.htm

Sea WaspSea Wasp

The venom of an adult sea wasp is so powerful that the victim may not even have time to swim to shore.

www.jyi.org/features/ft.php?id=189

Box jelly

http://www.visualdiving.com/pics/uw144_27.jpg

Jellyfish Sting TreatmentJellyfish Sting Treatment • Rinse with seawater. Avoid fresh water because it will

increase pain. Do not rub the wound or apply ice to it. • For classic box jellyfish stings, apply topical acetic acid

(vinegar) or isopropyl alcohol. • Remove tentacles with tweezers. • Apply shaving cream or a paste of baking soda or mud to the

wound. Shave the area with a razor or knife and then reapply vinegar or alcohol. The shaving cream or paste prevents nematocysts that have not been activated from discharging toxin during removal with the razor.

• Immobilize the extremity because movement may cause the venom to spread.

• Hydrocortisone cream may be applied 2-3 times daily to relieve itching.

• CPR may be necessary for all stings if the person stops breathing and/or no longer has a pulse.

http://firstaid.webmd.com/wilderness-jellyfish-sting-treatment

The animals we usually call jellyfish

belong to the class ScyphozoaScyphozoa.

-almost all are drifters. Some of the jellyfishes are big, measuring many feet across with long, trailing tentacles. Like other cnidarians, the tentacles are lined with stinging cells

Anthozoa:Anthozoa: Giant Green Anemone

Jelly fish Reproduction:

• Some reproduce asexually – especially in warmer temperatures.

– (Hydra-buddingbudding)

• Sexual reproduction- – lower temps

– hermaphrodites.hermaphrodites. – Motile sperm, egg in ovary.

And now for … worms…• The term "worm" has no systematic value

whatsoever. • Basically, any elongated invertebrate can be called

a "worm", regardless if it is or not related to similar creatures.

• However, two of the most primitive types of organisms receive that common name: WORMSWORMS

• Phylum PlatyhelminthesPhylum Platyhelminthes -flatworms

• Phylum NematodaPhylum Nematoda -roundworms

www.kingsnake.com

III. PlatyhelminthesIII. Platyhelminthes(flatworms)

• Planaria (free-living predators)

• Flukes (parasitic)

• Tapeworms (parasitic)

Flatworms (Platyhelminthes)

• Bilateral symmetry– Are the simplest of animals to have bilateral symmetry – Body flattened, leaf or ribbon-like (dorsal-ventral)

• All 3 tissues layers– Ectoderm, – Mesoderm– Endoderm

• Acoelomate (No body cavity) – solid body– completely filled in with tissue.

A pretty flatworm

http://www.islandream.com/wakatobi/flatworm02.jpg

A Planaria species

www.fcps.edu/.../zoo00/zoo00/zoowor/platy.shtml

Planaria sp.

www.fcps.edu/.../zoo00/zoo00/zoowor/platy.shtml

A marine turbellarian

flatworm

• ribbonlike movement

• body surface covered in mucus-covered cilia• The ripples create waves of mucus, through which the

creature pulls itself smoothly forward, using the hairlike projections.

encyclopedia.farlex.com/Platyhelminthe

Three common marine flatworms

from south-eastern Australia.A: Paraplanocera oligoglena.B: Pseudoceros sp.C: Eurylepta fuscopunctatus.Photo: Bill Rudman.

A Planarian is a free living hunterA Planarian is a free living hunter

-hunts small organisms

-eats with it’s Pharynx (a muscular feeding tube/opening)

- 1 opening gastrovascular cavity

-sac body plan, with mouth serving as both a mouth and anus (there is no anus).

Body of a planarianBody of a planarian

No true Circulatory / Respiratory systems-cells exchange oxygen & CO2 directly from environment

It looks like it has eyes: but these are just EYESPOTSEYESPOTS

Nervous System- cerebral ganglia serves as a simple brain- transmits signals down “ladder-like” nerve network.

Can respond to light, chemicals, touch & water currents in the environment

Excretory SystemPlatyhelminthes are the simplest animals to have a dedicated excretory

system.

-Flame cells -a specialized excretory cell to eliminate excess water

-function like a kidney, removing waste materials.

-are "cup-shaped", with cilia covering the inner surface

The beating cilia resemble a flame, giving the cell its name.

-Excretory tubules -Beating of the cilia moves liquid through the excretory tubule & pores-out of the organism.

Infestation in a fishtank w/ flatworms

Owners have tried poison, cleaning, etc but can’t get rid of them

www.neilcreek.com/.../

Testimony on flatworms infestation in the fish tank…

• These hideous creatures are a huge pest in our marine aquarium. They are called flatworms and they have overrun our tank.

• They must have come in to our tank from a bought coral, and found the conditions to their liking.

• They are in huge numbers, and any exposed surface is about 30% covered by them.

• On three seperate occasions we’ve poisoned them and syphoned out all that we could see, but within a month they’re back to the same population level.

• We hate them, they make the tank ugly and we have no idea how to get rid of them… :(

4 Classes of Flatworms:

-Class Turbellaria (free-living flatworm predators)

-Class Trematoda & Monogenea (flukes)

-Class Cestoda (tapeworms). flukes and tapeworms are adapted to a parasitic mode of life

COOL THING ABOUT FLATWORMS:– If cut- they will re-grow parts missing (regeneration)

RegenerationPlanarian morphogenesis is complicated & mysterious. When its part of body is cut, each piece of the part regenerates itself. In some cases, it gets 2 heads or tails.

users.design.ucla.edu

Class Turbellaria

• 4, 500 species (ocean or fresh water)• Scavenger lifestyle, eat with pharynx• Flame cells (cilia- aids excretion)• eyespots sense light on “Spade” shaped head.• Example is Dugesia, freshwater (family Planariidae)

www8.nos.noaa.gov/.../index.aspx?letter=e http://www.discoveryscope.net/images/circleworm.gif

The classes Trematoda and Monogenea consist of parasitic flukes.

• Some are endoparasites;

• others are ectoparasites.

Structure of Flukes• clings to the tissues of its host by an anterior

sucker and a ventral sucker.

• External surface is covered by a protective layer called the tegument.

Reproduction & Life Cycle of Flukes

• Most flukes are hermaphroditic.• Complicated life cycles

– involve more than one host species.

• For example, the trematode blood flukes of the genus Schistosoma – use humans as a primary hosts

–snails as intermediate hosts. – They can cause schistosomiasis.

Life Cycle of Schistosoma

Class Cestoda. • 5,000 species of tapeworms • Tapeworms can live in the intestines of

almost all vertebrates.

Structure of Tapeworms• surrounded by a tegument.• attach to the host with a scolex.• series of many sections: proglottids.• have no light-sensing organs, no mouth,

no gastrovascular cavity, and no digestive organs.

Life cycle of a human beef tapeworm, Taenia saginatus

• A man eats a poorly cooked piece of beef containing the encysted bladderworm (tapeworm cyst) in the skeletal muscle tissue.

• Tapeworm attaches to the intestinal wall by its anterior end called the scolex. (anchors it to the host's intestinal wall by four suckers.)

• Grows by budding as the scolex produces flattened segments called proglottids. – A human tapeworm may contain hundreds of proglottids and be

several feet in length. • Tapeworms compete with their host for nutrients. • Large tapeworms may obstruct food passages.• Excreted eggs in feces continues cycle for next host.

Want to lose weight?

• Note: Some early diet pills actually contained a tapeworm cyst enclosed in a gelatin

capsule, before they were banned by the Food & Drug Administration. You could take the pill and eat as much as you want without gaining weight! You were actually feeding a

large tapeworm which could be very dangerous.

• **The largest flatworm on record was 91 ft long

• several feet long. • San Diego Clinic case- A

man noticed a long white ribbon in his feces and thought he had swallowed his pajama draw strings during the night. The white ribbon turned out to be a tapeworm!

Story & photo from: http://waynesword.palomar.edu/trnov01.htm

Human tapewormsHuman tapeworms

Beef Tapeworm life cycle

II. Nematoda (Roundworms)

• Nonsegmented round worms that include many common parasites

• Long, slender bodies that taper at both ends.• Most species are free-living; some are parasites.

• A. Structure-Bilateral symmetry

-3 tissue layers-Pseudocoelomates • body cavity not completely lined by mesoderm• where organs are found • can serve as a hydrostatic skeleton.

• Roundworms have a ONE WAY digestive tract with two openings.

• Most roundworms have separate sexes

• are covered by a protective cuticle.

Most roundworms are free living • See following examples of parasites:

Ascaris (from page 696 Holt biology textbook)• The genus Ascaris infects pigs, horses, and humans. • The eggs enter hosts through contaminated food or

water, develop into larvae in the intestines, and can infect the lungs.

• The eggs are spread in the hosts’ feces.

Hookworms Intestinal parasites that feed on blood.• The eggs produce larvae in soil, and the larvae enter

hosts through the feet.• Infect about one billion people worldwide.

Trichinella Genus Trichinella infects humans, other mammals.

• Adults live in intestines and larvae form cysts in muscles. • People usually become infected from undercooked pork.

• Infection causes the disease trichinosis.

Other Parasitic Roundworms• Pinworms, genus Enterobius, are common parasites of

humans. They cause itching but do not cause any serious disease.

• Filarial worms infect many people in tropical countries. The most dangerous ones infect the lymphatic system & may cause elephantiasis.

hookworm

courses.bio.psu.edu/.../tutorials/tutorial39.htm

www.med-chem.com

Trichinella spiralis encysted larva

www.reuk.co.uk

Large roundworm of man(ascaris infection )

March 09, 2007: A guinea worm is extracted by a health worker from a child's foot at a containment

center in Savelugu, Ghana. foxnews.com

Guinea Worm

• occurs when people drink water contaminated with worm larvae.

• can grow to the size of a 3-foot-long spaghetti noodle.

• they emerge through the skin, often causing searing, debilitating pain for months.

PINWORMS!PINWORMS!• It is estimated that 40 million people in the U.S.

have pinworms at any given time.

• Approx.10 percent of children in daycare10 percent of children in daycare are likely to be infected with pinworms.

• Caregivers also can become part of the transmission cycle as you pick up toys and play with an infected child. Caregivers also may come in contact with the pinworm eggs during diapering or assisting with toileting.

http://www.healthychild.net/articles/sh35pinworms.html

Pinworm (human)

Heartworm(dog)

www.funkstownvet.com junior.britannica.com

Elephantiasis

http://www.smith.edu/news/2007-08/images/elephantiasis2.jpg

en.wikipedia.org/wiki/Elephantiasis www.answers.com

www.viewimages.com

Phylogenic tree of animal development

http://www.islandream.com/wakatobi/flatworm02.jpg