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.
Transcript
Introduction to the Helminths
Although the Protozoans are an extremely successful group, their organizational plan is limited due to their small size.
- limits size so most flatworms are small and soft-bodied.
9. ________________________________________
- most flatworms are _________________
- both male and female organs occur in an individual
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.
Class Turbellaria
Most turbellarians are free-living scavengers, but some are ___________________________ on other invertebrates.
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.
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
Subclasses of the Class Trematoda
Of the 3 subclasses in the Class Trematoda, we will examine 2 of them:
Subclass Aspidobothrea (= Aspidogastrea)
Subclass Digenea
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.
Subclass Aspidobothrea - Cotylogaster
Characteristic structure is ______________________ composed of numerous shallow depressions called ____________________
(this sucker resembles bottom of tennis shoe)
Subclass Aspidobothrea - Cotylogaster
Digestive tract consists of:
Subclass Aspidobothrea - Cotylogaster
Adults are monoecious:
Male and female reproductive organs are similar to those of digenetic trematodes (I will discuss these shortly)
Importance?
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
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
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
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
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 -
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 __________________________
Trematode Anatomy – Representives
We will examine the anatomy of Prosthogonimus macrorchis, the chicken and duck oviduct fluke, in lab.
Trematode Anatomy – Representatives
We will examine the anatomy of Quinqueserialis, the muskrat cecal fluke, in lab.
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.
