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Biology and life cycle of Oe

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1 Biology and life cycle of Oe

2 What is Oe? Ophryocystis elektroscirrha (Oe)
Protozoan parasite that infects Monarch butterflies in NZ

3 What is Oe? Protozoans: single celled organisms
Share many characteristics with animals (often called animal-like protists) Protozoans are single celled organisms, living things that have many of the same characteristics as animals. In fact, protozoans are often called animal-like protists. This slide has several protozoans pictures at the bottom that you may be familiar with. The first two are ‘free living’ protozoans called Euglena and a ciliate called Paramecium. The third is a parasitic protozoan called Plasmodium – this is a blood parasite that causes Malaria in humans Euglena Paramecium Plasmodium

4 Obligate parasite: must live within a host to grow and multiply.
Monarch (and queen butterflies overseas) are the only known hosts of Oe Monarch Butterfly (Danaus plexippus) Queen Butterfly (Danaus gilippus)

5 Oe produces spores on the outside of Monarchs
Highly Magnified Image Spores: dormant cells that can resist harsh environmental conditions Found on the outside of infected Monarchs Between infections Oe survives as spores that are resistant to extreme environmental conditions. Photo of Oe spores is a scanning electron micrograph taken by Chip Taylor. Oe spores Monarch scales

6 Oe Spores Greatest concentration of Oe spores is on the abdomens of infected Monarchs Abdomen These tiny spores are sandwiched in between the scales that cover a butterfly’s body.

7 Oe Spores Spores are ~ 100x smaller than Monarch scales
Need to view under x power Spores are much smaller than scales. In fact, a Monarch scale is about 100 times larger than an Oe spore. You must use a light microscope set at 40 to 100X to see a spore. This slide shows a researcher using a stereomicroscope at 60 times magnification to examine Oe spores from an infected Monarch Looking for spores using a microscope

8 Oe Spores Spores appear as small, brown or black lemon-shaped objects.
Monarch scales Oe Spores Even at this magnification spores look like small, brown or black lemon-shaped objects.

9 Oe Spores At 400x Here is a picture of Oe spores at 400X.

10 Life cycle of Oe is closely related to the life cycle of the Monarch butterfly.

11 Oe Life Cycle Oe can only reproduce inside living Monarchs
Infected females pass the parasite to their offspring when they lay eggs Dormant spores on the outside of the female’s abdomen are scattered on the eggs and milkweed leaves Infected females lay eggs and scatter Oe spores on eggs and leaves Dark spots are Oe spores

12 Oe Infects the Caterpillar
When a caterpillar emerges, its first meal is the egg shell It ingests Oe spores along with the shell and milkweed Newly emerged caterpillar A caterpillar eating the egg shell and any Oe spores on the shell’s surface

13 Oe Moves to the Midgut The dormant spores move through the larva to the midgut Digestive chemicals break open the spores releasing the parasites The parasites then pass through the intestinal wall to the hypoderm (underneath caterpillar’s skin)

14 Oe Reproduces in the pupa
Most damage to the butterfly happens during the pupal stage Where Oe reproduces asexually Each Oe parent cell divides many times, greatly increasing the number of parasites The Oe parasite then goes through sexual reproduction, followed immediately by meiosis

15 Oe cells in the pupa Merozoites: vegetative, replicating stage of Oe
Single parent cell  many hundreds of daughter cells Oe merozoites in the hemolymph of a 5-day old Monarch pupa

16 Spores Form in the pupae
About three days before the adult emerges from the pupa, Oe spores begin to form Spores allow Oe to survive outside of the Monarch’s body The spores can be seen through the integument or outside layer of the pupa Oe Spores

17 Adult Emerges with Spores
Infected adults emerge covered with spores Once butterflies are infected, they do not recover By the time adults emerge with parasite spores, all physical damage by the Oe parasites has been done The parasites do not grow or reproduce on the adults The spores are inactive or dormant until they are eaten by another caterpillar

18 Parasitised emerging Monarchs
Monarchs that are heavily infected with Oe can have difficulty emerging from their pupal cases Infected Monarchs are covered with millions of tiny Oe spores

19 Where in the World do you Find Oe?
Monarchs have a wide geographic range Oe occurs in all Monarch populations examined to date Monarch geographic range: N. America Central and S. America Caribbean Islands Pacific Islands Australia New Zealand Oe was first discovered infecting Monarch and queen butterflies in Florida in the late 1960s. Since then this parasite has been found in all other Monarch populations world-wide. Monarchs and Oe have an extensive range that currently includes North America, Central America, central South America, Cuba and other islands of the Caribbean, Bermuda and Canary Islands of the Atlantic. During the 1800s, Monarchs were introduced to New Zealand, Australia, Philippines, south Pacific Islands, and Hawaii. Because Oe parasitises Monarchs all over the world, all indications are that this parasite has coevolved with Monarchs.

20 Where in the World do you Find Oe?
Prevalence of Oe Population Eastern NA Rockhampton, Australia Northern S America Western Sydney, S Florida n = 27 n = 25 n = 39 n = 1103 n = 717 n = 152 Prevalence: Measures proportion of Monarchs infected with Oe # infected / total # sampled (n) To see what fraction of Monarchs in different populations were actually infected, researchers have done extensive sampling of Monarchs collected throughout NA both in recent years and from past historical collections dating back to the early 1970's. An important measure of infection for any population is the fraction or proportion of animals that are infected. This is called prevalence. This graph shows the prevalence of Oe in 6 different wild Monarchs populations. Researchers went out, caught the butterfrlies, and examined them for Oe. … What they found is that the prevalence of this parasite is highly variable among populations, and declines with increasing host migration distances. As you go from L to R in this graph, you are seeing populations that go from migrating the longest distance to those that migrate short distances or are resident breeders. Highest prevalence in pops that breed continuously in the same area (such as Florida and Hawaii) and lowest in Eastern NA. To understand what might be going on here requires some working knowledge of Monarch butterfly migration