introduction to trematodes
TRANSCRIPT
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Introduction to the Helminths
Although the Protozoans are an extremely successful group, their organizational plan is limited due to their small size.
Limit in size has been escaped through:
1. _____________________________________________
2. ________________________________________________________________________________________________
The ________________________________ contains some _________________ and includes a number of parasitic organisms.
The first group of parasitic animals we will examine are the HELMINTHS – ________________________________
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Helminth Phyla
Phylum _____________________________ -
Phylum _____________________________ -
Phylum _____________________________ - (of little economic importance – we will not study them)
______________________________ - study of parasitic worms.
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Phylum Platyhelminthes – Chapter 13
The flatworms are the planarians, trematodes, and tapeworms.
Forms present in the phylum?
____________________________________________
____________________________________________
____________________________________________
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Phylum Platyhelminthes – Chapter 13
Characteristics of the Phylum Platyhelminthes:1.
2.
3.
4.
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Characteristics of the Phylum Platyhelminthes cont.
5.
• first animal group to have this system
• Function?
6.
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Characteristics of the Phylum Platyhelminthes cont.
7. ________________________________________ ________________________________________
- absent in the tapeworms
8. _______________________________________
_______________________________________
- limits size so most flatworms are small and soft-bodied.
9. ________________________________________
- most flatworms are _________________
- both male and female organs occur in an individual
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Taxonomy of the Phylum Platyhelminthes
We will use the traditional taxonomy:
Phylum Platyhelminthes
Class Turbellaria – planarians
Class Monogenea – monogenetic flukes
Class Trematoda – digenetic flukes
Class Cestoidea – tapeworms
As in the Protozoa, a new taxonomic scheme has been proposed which divides the Turbellaria into several taxa. However, we will not use the new scheme and use the traditional taxonomy.
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Class Turbellaria
Most turbellarians are free-living scavengers, but some are ___________________________ on other invertebrates.
Characteristics of the Turbellaria:
1. _____________________________________________________
- Epidermis is _______________________on the ventral surface to aid in locomotion
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Class Turbellaria
2. Anterior end:
3. Digestive tract:
• One anterior and 2 posterior branches
• No anus – all wastes have to leave via the mouth
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Characteristics of the Turbellaria cont.:
4. ____________________________ ____________________________are present but do not stain in whole mounts
5. ____________________________
larval stages?
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Representative Turbellaria
Dugesia – freshwater planarian
It is a free-living scavenger.
Bdelloura – commensal on the __________________________
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Class Monogenea
All members of the Monogenea are parasitic
• most are ____________________________________________
• a few species occur _____________________________________________________
• one species in the hippopotamus eye
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Characteristics of the Class Monogenea1. Characteristic structure is the
_______________________
- posterior attachment structure consisting of suckers &/or hooks
- function?
2. Anterior feeding and attachment structure is the _______________________ that contains the mouth
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Characteristics of the Class Monogenea
3. Digestive tract consists of:
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Characteristics of the Class Monogenea
3. Monogeneans are monoecious but cross-fertilize
• Male reproductive system consists of _______________ ________________________
• Female reproductive system consists of:
________________________ – produces oocytes
________________________ scattered throughout the body – produces eggshell protein
________________________– contains 1- few eggs
4. Pathology
____________________________
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Characteristics of the Class Monogenea
5. Life cycle is a direct cycle involving one host.
Adult on fish gill or in Egg shed into water urinary bladder of frog or turtle
hatches
attaches to host
Free swimming ____________________________
- ciliated - opisthaptor distinct - 2 eyespots - digestive tract & protonephridia present
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2 members of Class Monogenea
Polystomoidella – parasite in the urinary bladder of the snapping turtle
Microcotyle – parasite on the gills of the sheepshead fish.
Note numerous clamplike structure on the opisthaptor.
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Class Trematoda
Trematodes are __________________________________ in all classes of vertebrates.
These worms have become structurally adapted for a parasitic existance:
1. possess ___________________for attachment to host
2. have many types of ____________________to produce secretions for ___________________________________ or to produce a ___________________________
3. have high _________________________(reproductive capacity) to increase chances of completing complex life cycles
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Subclasses of the Class Trematoda
Of the 3 subclasses in the Class Trematoda, we will examine 2 of them:
Subclass Aspidobothrea (= Aspidogastrea)
Subclass Digenea
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Subclass Aspidobothrea
Most are parasites in the viscera of ____________________
A few are parasitic in the intestines of ________________________________________________
Cotylogaster - a parasite in the small intestine of the sheepshead fish- is a representative of this subclass.
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Subclass Aspidobothrea - Cotylogaster
Characteristic structure is ______________________ composed of numerous shallow depressions called ____________________
(this sucker resembles bottom of tennis shoe)
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Subclass Aspidobothrea - Cotylogaster
Digestive tract consists of:
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Subclass Aspidobothrea - Cotylogaster
Adults are monoecious:
Male and female reproductive organs are similar to those of digenetic trematodes (I will discuss these shortly)
Importance?
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Life cycle of Cotylogaster
Life Cycle – Addition of fish host:
Adult in fish intestine
clam eaten by fish
Adult in clam viscera egg released into water
hatches
enters clam via free-swimming _______________________ incurrent siphon
- has tufts of cilia - eyespots - long unbranched intestine
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Subclass Digenea
Most abundant subclass - contains the digenetic trematodes
All are _________________________ in all classes of vertebrates
• inhabit many vertebrate organs (not limited to the intestine)
• many species infect humans and domestic animals and are of medical and veterinary importance
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Subclass DigeneaLife cycles are complex involving at least 2 hosts - term "digenea" means 2 beginnings representing the 2 hosts
• first intermediate host is a ______________________________
• definitive host is a ________________________________
• many life cycles have a third host between the snail and vertebrate - the second intermediate host - this is an __________________________ ___________________________________________________________
Many larval stages occur in the intermediate host(s) - _____________________________________occurs in some of the larval stages Adults occur in the definitive host - ___________________________________ occurs in this host
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Morphology of an Adult Digenetic Trematode
Size -
Characteristic structures are the 2 suckers
1. _____________________________ - at anterior end surrounding mouth - for attachment and feeding
2. _____________________________ (= ventral sucker) - located midventral to oral sucker - no internal opening - for attachment to host
Suckers are strongly muscularized consisting of bands of smooth muscle
Taxonomic importance -
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Body wall is a tegument
It consists of 2 layers:
1. Syntegument
- outer ____________________ ____________________layer
- contains mitochondria, secretory bodies, and occasional spines
- a chemical layer called the ___________________ lies on top of outer cell membrane
syntegument
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Tegument
2. Cytotegument
- cell bodies or ___________________ beneath the syntegument
- each cell contains a nucleus and organelles (RER & Golgi)
- involved in production of ____________________
- separated from syntegument by layers of tegumental muscle
- connected to syntegument by cytoplasmic bridges
syntegument
cytotegument
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Tegument
syntegument
cytotegument
cyton
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Tegument
Functions of the Tegument:
(1)protects trematode from ____________________________
(2)protects trematode from _____________________________
(3) absorbs ______________________________________for trematode nutrition
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Trematode Digestive Tract
___________________________ is contained in oral sucker
Muscular ___________________ creates sucking action
Short esophagus leads into 2 long blind-ending _________________ (= intestinal ceca)
No anus so ______________________________________________________
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Digestion and the Parenchyma
Food taken into the digestive tract consists of ______________________________
______________________________
Proteins are digested in the lumen of the intestine and _______________________________are absorbed through the intestinal epithelium.
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Parenchyma
PARENCHYMA- loosely arranged cells filling space between internal organs.
Major function is:
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Trematode Excretory System
EXCRETORY SYSTEM removes excess water that has diffused into worm
_______________________________ _______________________________ occur throughout the body
-cells contain beating flagella that create a hydrostatic pressure which draws water from the parenchyma into the collecting duct
- flame cells are seen only _______________________________
- at the posterior end of the worm:
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Trematode Nervous System
Ladder-type system consisting of anterior ganglionic mass, lateral nerve trunks, and connecting commissures.
Sense organs of adults are at the cellular level within the tegument - ______________________________________________________________
Sense organs of free-swimming larval stages (miracidium & cercaria) are well developed: ______________________________________________________________
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Trematode Reproductive Systems
Reproductive systems are extremely elaborate and specialized
Digenetic trematodes have ___________________________ - some produce as many as 25,000 eggs per day.
Most digenetic trematodes are _________________________
- schistosomes are only dioecious group
- monoecious forms commonly cross-fertilize but self-fertilization is possible
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Male reproductive systemTwo testes – function?
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Male reproductive systemTrematode sperm are unusual for 2 reasons:
1. ________________________________________________________
2. ________________________________________________________
nucleus 2 flagella mitochondrion
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Male reproductive systemShape and position of the 2 testes are important taxonomic characters
Shape: Position:
Combination of shape/position: branched tandem testes; lobed opposite testes, etc.
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Male reproductive systemSperm ducts consist of 2 ____________________________ which join to form a single _______________________
Vas deferens leads into the cirrus sac (= cirrus pouch) that contains:
- ____________________________ - sperm-storage area
- _____________________________- produces fluids to maintain sperm
- _____________________________- male copulatory organ which can be everted through the ______________________________ for copulation
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Female reproductive systemSingle ovary produces ___________________________ which pass along the oviduct to the ___________________________
Taxonomic importance?
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Female reproductive systemShape and position of the ovary in relationship to testes important in identification
Shape:
oval
lobed
branched
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Female reproductive systemOotype is region of female system where:
(1) ____________________________
(2) ____________________________
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Female reproductive systemStructures associated with the ootype:
1. ________________________ - sperm storage area of the female system
2. _________________________ is a short duct which leads from the seminal receptacle to the outside.
• Laurer's canal was once a vagina but has lost this function and now serves to ________________________________________________
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Female reproductive systemVitellaria (= vitelline glands)
- occur in _____________________ which generally stain intensely
- secrete ______________________ which will coalesce in the ootype to form the _______________________
- vitelline cells containing this protein pass along vitelline ducts which join and lead into the ootype
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Female reproductive system
Mehlis' gland - surrounds the ootype
- produces secretions that ______________________________ ______________________________in the ootype
- stains a light pink
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Female reproductive system___________________________
leaves from the ootype and consists of a long, often highly coiled duct containing eggs and sperm
As the eggs pass through the uterus, 2 processes occur:
1.
2.
Uterus function -
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Female reproductive system Anteriorly, the uterus leads into a
strongly muscularized duct called the __________________________
- this functions as an ovijector, forcing eggs out the common genital pore
- metraterm joins the cirrus sac at the __________________________
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Trematode Anatomy – Representives
We will examine the anatomy of Prosthogonimus macrorchis, the chicken and duck oviduct fluke, in lab.
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Trematode Anatomy – Representatives
We will examine the anatomy of Quinqueserialis, the muskrat cecal fluke, in lab.
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Trematode Anatomy – Representatives
We will also examine the anatomy of the immature adult of Leucochloridiomorpha from a snail. We’ll examine living specimens to see excretory system and beating of the protonephridia. We will compare living specimen to stained whole mount.