Milkweed plants: benefit and risk to Monarchs

Milkweed plants are the sustaining plants for the Monarch and Queen butterflies. They also are the vector for transmission for the protozoan parasitic OE (Ophryocystis elektroscirrha) infection. The three are intimately related. The Monarch depends exclusively on Milkweed for survival. The butterfly and its parasite cannot propagate without the plant. The insect and protozoan both mature through their growth and reproduction cycles* in perfect harmony on the leaves of the milkweed. Apparently, at this stage in our environment no Monarchs been found in the wild without some level of the parasitic infection. The infection is apparently only a matter of degree. Compared to uninfected individuals Monarchs have reduced survival rate and longevity, lower reproductive success, and compromised flight ability. This substantially alters their ability to migrate and reproduce. We have seen this in an earlier blog posting.

Healthy Milkweed leaf underside showing Monarch butterfly egg in direct center. (1:1)
Microscopic enlargement of healthy Monarch egg on Milkweed leaf. (~800X)
Milkweed leaf ladened with OE (1:1)
OE parasites on Milkweed leaf erupting from infected Monarch egg in initial single cell stage
OE parasite single cell stage spreading onto Milkweed leaf
OE parasite spread throughout leaf attached to small cellular fibers.
*The butterfly scatters spores on the eggs and milkweed plant. The parasite is ingested by the larva which erupted from the egg. We are highlighting the right side of this diagram.
New caterpillar hatchling larva starting to eat.
Hatchling larva covered with OE monocytes.
The larva will ingest the OE which will mature and divide in the caterpillar gut while the larva mature through the caterpillar and crysalis stages. When butterfly breaks through the chrysalis its wings are distorted, it is deformed and covered with spores. The OE in the spore stage will repeat the cycle.

Investigation of this process is important to the survival of the Monarch butterfly population. I highly recommend that you participate in a citizen scientist project. It is sponsored by the Odum School of Ecology, University of Georgia, Athens GA, 30602. Check out their site at Project Monarch Health.

Your comments and contributions to this topic are welcome. Please enter them in the comments box below. Please check out the recommended readings to discuss topics of prevention and control of OE.

For further reading:

Long-lived butterfly parasites can’t take the heat

Effects of the parasite, Ophryocystis elektroscirrha, on wing characteristics important for migration in the monarch butterfly

How This Popular Garden Plant May Spread Parasites that Harm Monarchs

Native Milkweed

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#OE #monarch #butterfly #parasite #spores #larva #crysalis #milkweed #vector transmission

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