LABORATORIO: Parte 1

Filo Platyhelminthes

EJERCICIO 9

Goals for today• Learn to recognized the Phylum

Platyhelminthes from other animals• Learn the main ‘diagnostic’ characteristics• Learn about some free-living and parasitic

species biology

Platyhelminthes: flatwormsThese are acoelomate

metazoans

More organized than radiate animals in that:

– Bilateral symmetry (distinct head and sense organs, which allows direct movement).

– Third germ layer-mesoderm (triploblastic animals)

– Excretory system made up of specialized flame cells and tubules for removal of nitrogenous waste

– Highly organized nervous and sense organs in the anterior part of the body (cephalization)

Porif

era

Parazoa

Deut

eros

tom

ia

Ecdy

sozo

a

Anne

lida

Mol

lusc

a

Loph

opho

rata

Rotif

era

Plat

yhel

min

thes

Lophotrochozoa

Eumetazoa

BilateriaRadiata

Protostomia

Cnid

aria

and

Cte

noph

ora

Lophotrochozoa

Platyhelminthes: Classification

Turbellaria: • Ciliated epidermis• Paraphyletic group• Mostly free-living

Classes:Monogenea: don’t have material

Trematoda: • Digenetic flukes• Syncytial tegument without cilia• Leaflike to cylindrical shape.• Organs to attach host in the oral and

ventral part of the body: suckers, NO hooks

• Parasitic in all classes of vertebrates

Cestoda:• Syncytial tegument without cilia• Long ribbon like body shape• Body divided in proglotids• Organs to attach host in the oral part of

the body: suckers, hooks• No digestive system• Parasitic in digestive tract of all classes

of vertebrates

Platyhelminthes: Your TasksExercise 9A:

– Phylum: Platyhelminthes – Class Turbellaria

• Genus: Dugesia

Planarias are freshwater usually under stones or submerged leaves or sticks. But other members of the class are marine

Platyhelminthes: Dugesia1. Take a slide from your box with a planaria: identify the eyespot, aurículas, intestino, faringe, y boca.

What is the function of the eyespot and the auricles? ____________ Check your book for answers!

bocaintestino

Platyhelminthes: DugesiaAs in cnidarians the digestive tract of turbellarians is a gastrovascular cavity, the branches of which fill most of the body.

They don’t have an anus so undigested food is ejected through the mouth! Yikes

Platyhelminthes: DugesiaReproduction: these animals are monoecious (hermaphrodites) they can reproduce sexually and asexually by transverse fission

http://www.youtube.com/watch?NR=1&v=8mXkSdIpFQ8

In asexual reproduction, the planarian detaches its tail end and each half regrows the lost parts by regeneration, allowing neoblasts (adult stem cells) to divide and differentiate. However, several problems can occur with this, so this does not happen often.

In sexual reproduction, each planarian transports its excretion to the other planarian, giving and receiving sperm. Eggs develop inside the body and are shed in capsules. Weeks later, the eggs hatch and grow into adults. Sexual reproduction is desirable because it enhances the survival of the species by increasing the level of genetic diversity.

wikipedia

Platyhelminthes: DugesiaExcretion and osmorregulation: the excretory system consist of canals and protonephridia called flamed cells.

http://www.youtube.com/watch?v=Rb_3KIB4CmE

See these cells in action!

Platyhelminthes: Dugesia2. Take a slide from your box with a planaria cross section cuts: identify intestino, diverticulos intestinal, lumen de la faringe, musculos dorsoventrales.

Planaria – cross section

epidermis

rhabditescircular muscle

longitudinal muscle

mesenchyme

intestine

pharynxlumen of pharynx

pharyngeal pouch

Platyhelminthes: Dugesia3. Observe live planarias. Take a look to their locomotion. How does it use the head and auricles? Does it ever move backwards?

http://www.youtube.com/watch?v=VplYBDSbRmA

Platyhelminthes: Dugesia4. Observe live planarias. Perform with your instructor the stimuli experiments described in page 136.

• Response to touch• Response to food• Response to directional illumination

Write your answers this is part of the Planaria report

Platyhelminthes: Dugesia5. Regeneration Experiment: Some planarians exhibit an extraordinary ability to regenerate lost body parts. For example, a planarian split lengthwise or crosswise will regenerate into two separate individuals

http://www.youtube.com/watch?NR=1&v=gZmk80fw0nc

When a planaria’s head is cut off, the remaining tail section will first regenerate a head. Even if the cut is made very close to the tail, the small tail section first regenerates the head and then continues to regenerate the rest of the tissue between the head and the tail. We will use this property and compare how long it takes for worms cut in different places to regenerate a head. If different parts of the planaria body have equal ability to regenerate, they should all regenerate the head in the same amount of time. If not, they should regenerate the head in different amounts of time. The regenerative capacity of different body sections may be an indicator of the location of stem cells called neoblasts. For instance, if one body segment has a low capacity to regenerate, perhaps only a few neoblasts exist in the area around the cut. Additional neoblasts may need to migrate to the area or be created by cell division, slowing down the rate of regeneration.

Platyhelminthes: Your TasksExercise 9B:

– Phylum: Platyhelminthes – Class Trematoda

• Genus: Clonorchis sinensis

Clonorchis lives in the human bile duct (bilis) where it feeds on bile and lacerated cells from the inflamed bile duct very common in Asia

Platyhelminthes: Clonorchis1. Observe slide of Clonorchis sinensis: identificar ventosa oral, boca, faringe, intestino, ventosa ventral, glandula de yema, poro genital, vesicula semina, ovario, receptabulo seminal, testículos, vejiga, poro excretor

Platyhelminthes: Your TasksExercise 9B:

– Phylum: Platyhelminthes – Class Trematoda

• Genus: Schistosoma mansoni

Schistosoma are blood flukes of humans that affect ~ 200 million people in Asia, Africa, the Caribbean (including Puerto Rico!) and South America.

Schistosomiasis

Platyhelminthes: Schistosoma1. Ciclo de vida: Observe slides of Schistosoma mansoni adults, eggs, and cercariae

adults

eggs miracidum cercariae

You need to understand the life cycle

Platyhelminthes: Your TasksExercise 9C:

– Phylum: Platyhelminthes – Class Cestoda

• Genus: Taenia pisiformis- dog tapeworm

They are extreme parasites in that they don’t have a digestive system. Their tegument is a specialized epidermis that absorbs nutrients and rejects toxins and digestive enzymes.

Live is all about maximize reproduction. In fact tapeworms are egg factories, some species can even fertilize their own eggs an strategy that guarantees offspring.

Platyhelminthes: Taenia1. Observe slide of Taenia. Noticed the scolex and the body composed of units called proglottids which are not segments, but units formed by budding behind the scolex.

Scolex

proglottids

Platyhelminthes: Taenia1. Observe slide and model of Taenia scolex which is equipped with suckers and hooks. Note the neck from which new proglotids are budded off.

A= suckersB=hooks scolex

Platyhelminthes: Taenia2. Observe slide and model of Taenia mature proglotid. They have reproductive organs: testículos, vaso deferente, poro genital, glandula de yema, ovario, vagina, utero, cordon nervioso, canales excretores.

Uterus

Platyhelminthes: Taenia2. Observe slide and model of of Taenia gravid proglottid, with the uterus fulled with eggs or embryos. Where do you find gravid proglottids? These proglottids break off and shed in the feces of the host. Outside the host the proglottid breaks releasing thousands of infected eggs.

Uterus with eggs

Platyhelminthes: TaeniaTaenia life cycle

Important LinksPlatyhelminthes

http://www.savalli.us/BIO385/Diversity/05.Platyhelminthes.html

http://es.wikipedia.org/wiki/Platyhelminthes

http://www.pbs.org/kcet/shapeoflife/episodes/hunter.html