Exam 3 - Class Trematoda Flashcards
Class Trematoda
The phylum _____ includes ______ animals called _____
Platyhelminthes
dorsoventrally flat
flatworms
Typically Platyhelminthe members are:
bilaterally symmetrical triploblastic acoelomate cephalized incomplete or no gut
3 systems that are usually absent in Platyhelminthes
Skeletal, circulatory, and respiratory
the space between body wall and internal organs is filled with:
connective tissue and muscle fibers
called parenchyma
2 parasitic classes of Platyhelminthes
Trematoda (flukes) & Cestoda (tapeworms)
Adult trematodes are parasites of:
inverts & verts, incl. humans
Trematodes may inhabit:
intestinal tract, bile ducts, liver, gall bladder, lungs, blood vessels, pancreatic duct, ureter and urinary bladder
Diagnostic features of trematodes include:
presence of ecto- and endoparasitic forms, with incomplete gut
have complex heteroxenous life cycles involving at least one intermediate host, a gastropod (snail)
body wall is covered by thick cuticle
with suckers, usually around the mouth and on ventral surface
_____ is the outermost covering of the trematode’s body
Tegument
_____ is synonymous with ____, it is a tough, resistant structure
Tegument
Cuticle
Tegument is syncytial, which means:
it is multinucleated, without cell boundaries between nuclei
Outer portion of the tegument forms the ______, its covered by cell membrane on surface and extends inside to the _____
distal cytoplasm
basal lamina
glycocalyx
is linked with the plasma membrane and is a surface coat
Glycocalyx functions:
attachment to host
protection from antibodies and digestive enzymes
uptake & storage of vital molecules from the environment
Proximal cytoplasm
=cyton region
is the inner zone of the tegument and connected to the distal region by cytoplasmic bridges
Proximal cytoplasm consists of
nuclei
cell organelles like the ER, golgi body, mitochondria, etc.
________ responsible for the _____ maintenance
Proximal cytoplasm
tegument’s
Muscle layers include:
circular, longitudinal, and diagonal muscles
Tegument Functions:
protection nutrient absorption synthesis and secretion of various nutrients excretion osmoregulation sensory role
Of all organ systems, the ________ is the one that is most highly developed in platyhelminthes
reproductive system
Trematodes are _________ or __________
Monoecious
Hermaphroditic
Self fertilization
Does NOT occur`
protandryorandrogyny
The male organs tend to mature first and produce sperm that are stored until needed
protogyny or gyandry
In a few free-living species, the ovary matures first
Male Reproductive System:
Usually two testes vas efferens vas deferens seminal vesicle (storage) ejaculatory duct cirrus (penis)
penis
cirrus
Sperm pathway
Testis Vas efferens Vas deferens Cirrus sac (with seminal vesicle and prostate gland) Cirrus
Female reproductive organs:
Single ovary with an oviduct, a seminal receptacle a pair of vitelline glands with ducts the ootype Mehlis’ gland
seminal receptacle:
sperm storage
vitelline glands with ducts
yolk and egg-shell production)
ootype
chamber where eggs are formed
Mehlis’ gland
lubricates uterus for egg passage
Laurer’s canal
Vestigial vagina
Present in come but not all
serves as an outlet of excess sperm
Metraterm
helps propel the eggs out of the uterus.
During copulation, _____ is inserted into ____ and sperms are ejaculated
cirrus
metraterm
operculum
Lid like structure in eggs
Allows miracidium to hatch
Eggs house:
Developing miracidium
Hatching occurs only under certain conditions of:
pH, light, and temperature
Life cycle generic:
Egg –> Miracidium –> Sporocyst –> Redia –> Cercaria –> Adult
Miracidium is
free swimming and ciliated
Sporocyst
present in 1st intermediate host
Cercaria
Free swimming and enters 2nd intermediate host
Sexual cycle in:
Definitive host
Asexual cycle in:
Gastropod
Within ____ hrs miracidium must find a suitable gastropod
24
Upon entry into snail:
penetrates the snail’s integument, sheds its ciliated epidermis, and metamorphoses into primary sporocyst stage
The most common site of development of sporocysts is:
around the digestive gland
Unlike sporocysts, rediae have functional _____
gut/pharynx
primary sporocysts may produce:
other secondary sporocysts or primary rediae asexually
Rediae give rise to a tailed ____ larva
cercaria
______ escapes from the gastropod, swims freely but do not feed and can either find a _________ or attach to vegetation, lose its tail and encyst to become a _______
Cercaria
second intermediate host
metacercaria
Apical papilla
Retractable non ciliated anterior tip
glands secrete degradative enzymes
Some sporocysts change the morphology or the behavior of their hosts
bird trematode has colorfully banded and pulsating sporocysts, which reside in snail’s tentacles
The transformation from miracidium to sporocyst involves
disappearance of all the structures except the protonephridia
procrusculi or ambulatory bud
stumpy appendages that facilitate movement
redia migrate towards
snail digestive gland
If sporocysts give rise to daughter sporocysts, the latter give rise directly to:
cercariae and rediae are not formed
parasitic castration
some larval parasites secrete chemicals that inhibit the development of the snail reproductive system
The transformation from miracidium to sporocyst involves disappearance of all the structures except the _____
protonephridia
cercaria have following structures:
Mouth oral sucker pharynx intestine ventral sucker genital primordium
genital primordium
mass of cells that develop into reproductive system
glands involved in penetration
penetration and mucoid glands,
escape glands
contents are expelled during the emergence of the cercaria from the snail host
preacetabular gland’s
secretion contains calcium and a variety of enzymes including a protease
postacetabular glands
produce mucus and help the cercaria to adhere to surfaces
the “dormant” stage between the cercaria and the adult
Metacercaria
When the free-swimming _____ locates ________ or penetrates a _________ host, it sheds the tail and encysts
cercaria
suitable vegetation
2o intermediate
This stage may also allow survival over unfavorable periods, such as the absence of the definitive host during a particular season
Metacercaria
Once the metacercaria has reached its definitive host:
it excysts and then undergoes migration, growth, and eventually gamete production
If the species does not have a metacercaria:
the cercaria penetrates the definitive host directly (schistosomes)
