Parasites from Miscellaneous Phyla & Apicomplexa (non-malaria) (Lab 11)
Phylum Mollusca; Class Bivalvia; Family Unionidae
Glochidium larvae
Freshwater unionid mussels are able to colonize upstream habitats by
producing larvae that parasitize fish. The larvae burrow into fin and gill tissues
where they feed upon host fluids as a true parasite. Upon completion of
development, the juveniles drop off hosts, who have moved up and downstream
since infection, burrow into the substrate of the stream and become filter feeders.
CBS Z 1480, 10X
Phylum Annelida; Class Hirudinea
Leech
Leeches are segmented worms with two suckers. Although many are true
predators of invertebrates, their infamous reputation comes from the few species
that are micropredators on vertebrates.
92W 1851, Dissecting scope
Phylum Annelida; Class Hirudinea
Leech
The species on display was taken from a bat ray in the Gulf of Mexico.
Specimen, Dissecting scope
Phylum Nematomorpha
Horsehair Worm
These fairly large worms have juvenile stages that parasitize the body
cavities of large arthropods. When nematomorphs mature in terrestrial hosts,
their hosts seek out and enter freshwater which stimulates the worms emerge
resulting in host death. This specimen was found in a well in Brazil. The sudden
appearance of adult horsehair worms in water troughs led to the “folk wisdom”
explanation that these worms developed from hairs that had been shed by
drinking horses. Nematomorphs can be distinguished externally from nematodes
by the presence of blunt (rather than pointed) ends.
Specimen, Dissecting scope
Phylum Nemertea
Carcinonemertes
Most nemerteans are free-living predatory worms that catch their prey with
a conspicuous proboscis that you cannot see on these specimens. Members of
the family represented by these specimens are symbionts that feed on the eggs
of crabs. They live in the external egg masses of egg-bearing females and feed
on the eggs and are known as “egg predators.”
Specimen, Dissecting Scope
Kingdom Plantae
Haustoria of Dodder
This twig is from an oak growing across the street from the Life Science
Building. It was parasitized by a dodder plant whose yellow tendrils have since
fallen off. Open “wounds” or scars where the dodder’s haustoria penetrated the
host tree are visible.
Specimen, Dissecting Scope
Kingdom Plantae
Dodder
Although some species of dodder contain low numbers of chloroplasts
giving them a slight yellow green tinge, the plants are true parasites as they
acquire nutrients from host plants. This specimen was taken from Dauphin
Island.
Specimen
Kingdom Plantae
Indian Pipe
This specimen was collected from the pine forest along the university’s
Nature Trail. Indian pipes have no chlorophyll and can be recognized in the wild
by their opaque white coloration. The dark coloration of this specimen is an
artifact of preservation. Indian pipes actually parasitize ectomychorrhizal fungi
that form mutualistic associations with plants. The parasitic plant extracts sugars
from the fungus that were produced in the tree.
Specimen
Phylum Myxozoa
PANSPOROBLAST
The cyst located on gills of this fish is a pansporoblast and is filled with
spores that will infect any predatory fish that feeds on this host.
CBS PS 445, 10X
Demonstration Sheets for Apicomplexa Coccidea that are not malaria (Lab 11)
Figures and page numbers from Roberts & Janovy 8th ed, 2009
Phylum Apicomplexa; Subclass Gregarinasina; Suborder Septatorina
Cephaline Gregarines
Gregarines in this suborder are common in insects. The two slides on
display are cross-sections through larval mealworms. Members of the Septatina
or cephaline gregarines are characterized by a septum that divides the cell into
two sections. The posterior portion or deutomerite contains the nucleus. Observe
the protomerite, septum, epimerite (hard to see), deutomerite, and nucleus in
deutomerite.
PS 415, 40X
Phylum Chordata; Subphylum Vertebrata; Class Osteichthyes
CANDIRU
These catfish live in the Amazon and Orinoco Rivers of South America.
They feed on gills of other fish which they locate by following an ammonia trail.
Strictly speaking, their trophic and ecological interactions classify them as
micropredators and along with vampire bats, they have adapted a life-style that is
close as vertebrates have come to true parasitism. Occasionally candiru,
responding to ammonia in a urine stream from a mammal “taking a leak” in a
stream, will become lodged in the urethra of the unfortunate victim.
Specimen
Phylum Cnidaria; Class Anthozoa
Parasitic Sea Anemone Edwardsia sp.
This specimen (undescribed species) was collected from the medusa
stage of another cnidarian, the moon jellyfish Aurelia, in the Gulf of Mexico. The
parasite feeds on the gonads of its hosts. Due to the fixation process, the
tentacles of the sea anemone have withdrawn into its body cavity.
Specimen, Dissecting Scope
Healthy Human Lung Tissue
Compare with the adjacent display taken from a patient with a chronic infection of
Toxoplasma gondii.
CBS H7745, 10X
Family Sarcocystidae
Toxoplasma gondii
Lung tissue from a person, probably with a suppressed immune system,
suffering from an infection of T. gondii. In situations such as this, the fast growing
type of merozoite (= tachyzoites) destroy cells causing extensive lesions in the
lung, liver, brain, heart, and eyes. Compare the density of cells and the surface
area available for oxygen absorption in this sample with the healthy lung tissue in
the adjacent display.
Carolina 31-7730, 10X
Family Sarcocystidae
Tachyzoite stage of Toxoplasma gondii
Merozoite stage known as tachyzoites (tachy = rapid) in the peritoneal
fluid of a mouse. These organisms cause toxoplasmosis in humans. Felines,
such as the domestic cat, are definitive hosts. See Figure 8.14 (p. 136).
CBS PS 965, oil
Family Sarcocystidae
Toxoplasma gondii in Brain
Cysts containing bradyzoites in brain tissue. In healthy vertebrate (nonfeline) intermediate hosts with non-compromised immune systems, T. gondii will
eventually become quiescent and form cysts such as these in the central nervous
system. Although alive, the parasites stop reproducing asexually. Sounding like
the plot of a science fiction story, infected hosts (including humans) walk around
with another organism literally living in their brains.
The parasite relies upon consumption of the intermediate host by a feline
predator for completion of its life-cycle. Lab studies have shown that infected
mice change their behavior and do not avoid areas scented with cat urine as do
uninfected mice. More recently, a study in Europe found that a higher percentage
of men involved in automobile accidents possessed antibodies to T. gondii than
expected suggesting infected men may lose their sense of danger.
92W 4841, 40X