Biology and life cycle of Oe

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

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

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)

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

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.

Oe Spores Spores are ~ 100x smaller than Monarch scales Need to view under 40-100x 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

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.

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

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

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

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

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)

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

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

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

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

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

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.

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

Monarchs in North America Summer Ranges and Migratory Routes Eastern migratory population There are three Monarch populations in North America. Two populations migrate and the third one, which is in South Florida, does not migrate. The Rocky Mountains separate the two migratory groups of Monarchs. 2. Western migratory population 3. South Florida resident population

Eastern Migratory Monarchs The eastern migratory population is the largest and most famous These Monarchs spend the winter in the transvolcanic mountains of central Mexico Transvolcanic Mountains

Monarchs Overwintering in Oyamel Fir Trees in the Mountains of Central Mexico

Eastern Migratory Monarchs Spring: After mating, migrate north to their summer breeding grounds in the United States and Canada Summer: Several generations of Monarchs inhabit lands east of the Rocky Mountains from Alberta to Maine

Eastern Migratory Monarchs Fall: tens of millions of Monarchs return to Mexico in a spectacular migration

Western Migratory Monarchs Shorter, less dramatic migration to their roosting areas on the coast of California Overwinter in much smaller groups than the ones in Mexico Spring: migrate north and east Rocky Mountains Summer Range for Western Monarchs Overwintering Sites for Western Monarchs

Monarchs of South Florida Do not migrate Milkweed plants grow here all year round, the butterflies do not need to leave the area Resident Monarchs reproduce throughout the entire year Monarch larva feeding on tropical milkweed, a common but non-native host plant species in S. Florida

How common is Oe in North America? 1. Eastern migratory population – Less than 10% heavily infected 3. South Florida resident population – Over 70% heavily infected Oe is found throughout North America, but the prevalence (fraction of the population infected) varies dramatically among populations. Fewer than 10% of Monarchs in eastern N. America re heavily infected, about 30% of Monarchs on the west coast are infected, and over 70% of Monarchs in S. Florida are heavily infected. 2. Western migratory population – 30% heavily infected

Differences between populations have persisted for many decades Western migratory By examining historical collections of Monarchs, scientists have found that differences in prevalence between populations have persisted for up to 30 years. This graph shows the % heavily infected Monarchs for each year where collections were available from the 3 populations, including samples from the most recent 5 years. Despite the inter-annual variations, the eastern migratory population has been less than 8% infected for the past 30 years, with a sign of some recent increases in the past 5 years, whereas more limited data suggests that the western population has been 30% infected, and the S. Florida population near Miami has had high parasite loads, 75-100% heavily infected. Eastern migratory

Do my Monarchs have Oe? What are the symptoms? Butterflies can become sick for many different reasons Monarchs infected with Oe have a variety of symptoms Caterpillars may have damage to their gut walls Infections may be fatal Monarch caterpillars often turn brown within a few hours of death.

Damage to the pupa Infected pupae may develop dark spots or blotches 2-3 days before the butterfly emerges These abnormal dark areas are parasite spores Spores form on the eyes, antennae, wing veins, but mostly on the abdomen You can see the spores through the outside layer of the pupa a day or two before pigments that color the butterfly normally darken the pupa

Dissected pupa Showing Oe Spores The dark spots are Oe spores Head Abdomen Infected pupa before dissection Before a butterfly emerges from the chrysalis, pigments are laid down coloring the scales that cover the butterfly. This normal change in the color of the pupa is symmetrical. The color change of an infected Monarch happens earlier and does not create a balanced pattern on the pupa. Wings Dissected pupa

Damaged Adult Monarchs Heavily infected adults are weak and often have difficulty emerging from the chrysalis Some Monarchs die before emerging Others emerge, but are too weak to cling to the pupal case They fall to the ground before fully expanding their wings These severely deformed Monarchs do not survive long

Mild infections also harm butterflies Infected adults are often smaller than healthy Monarchs They weigh less and have smaller wings and shorter lifespans than normal Monarchs Parasites also damage the cuticle or outside layer of the Monarch’s abdomen This causes the butterfly to dry out and lose weight faster than normal. Especially a problem if there is a shortage of nectar or water

Parasite infection hinders Monarch flight ability Studies have shown that Monarchs infected with Oe can not fly as far or as long as healthy butterflies Flight mill A flight mill is used to measure a Monarch’s flight endurance

Monarchs with mild infections can transmit disease Infected adults that survive to reproduce will pass the infections on to their offspring

Many infected Monarchs look the same as healthy butterflies These are all symptoms of Oe, but many infected Monarchs look healthy They emerge normally and are not deformed The only way to really know if your Monarch is infected is to check for parasite spores on its body. Easy way to test for infections: swabbing

How to test for Oe

Use sterile protocols when handling Monarchs Oe spores are difficult to destroy Use latex, nitrile or vinyl gloves when touching butterflies Sterilise all tools and surfaces that contact Monarchs (counter tops, rearing containers) with 20% bleach solution

Can You Tell Which Monarchs are Infected with Oe?

Can You Tell Which Monarchs are Infected with Oe? ALL OF THEM! Admittedly, the one in the lower right had a mild infection.

Adapted with thanks from an original presentation of the Monarch Health Project, Odum School of Ecology, University of Georgia Athens, GA, USA.