When I think of migrations on a large scale I think of
wildebeest, flamingos and bats. But insects? The annual migration of the
Monarch butterfly, Danaus plexippus is
one of the largest in the word. They begin their migration in late summer from
the Great Lakes state and northern plains. It is sparked by decreasing day
lengths and temperatures that would otherwise make it impossible for the
monarch to survive. They head in a South-westerly direction to their
over-wintering site of Mexico and southern California, where the temperatures
are more suitable for hibernation, mating and feeding. As they travel towards
Mexico they occasionally stop to feed and roosts, accumulating in numbers as
other populations converge together. In spring survivors migrate in a
north-easterly direction back to their original breeding grounds. During this
spring migration the monarch butterfly rarely feed or roost. How do they
re-migrate without feeding or resting often to regain energy for the flight
home?
This is where the report Migration of the monarch butterfly,
Danaus plexippus: energy sources by J.
J. Brown and G. M. Chippendale talks about how the monarch butterfly retains
lipids as an energy source and as a metabolic reserve in order to re-migrate back
to their original grounds.
Brown and Chippendale found that there were six neutral
lipid classes and two major phospholipids present in the monarch. Triglycerides
(TGL) are one of the major groups present and comprised approximately 59% of
the male body and 71% of the females. In both sexes the Monarch has a large abdomen
with a nutrient reserve of 93% lipid and 7% protein, and acts as a major
storage area for reserves. These reserves were carried over to the adult stage
from the feeding of the larval stage. Greater than 99 % of TGL were located in
the abdomen where they contained 73% of the total lipid. With this said TGL is
the main fat reserve that is independent from the rest of the groups. Also as
they occasionally stop on the migration to Mexico the nectar they feed on is
stored as sugars by glycogens. The thoracic musculature is also rich in protein
and lipids but lack glycogen which stores sugars. However the thorax only
contains approximately 6 % total body lipids.
 |
| FIG. 1. Relationship between whole body weight, wing length, soluble protein, and total lipid composition of individual migrating male and female monarch butterflies collected in Boone County, Missouri. ∆, Wing length; ○, lipid content; □, soluble protein content. |
This shows that the
TGL in the abdomen is the major reserve lipid class compared to the thorax
which contains no substantial lipid storage. The amount of lipids present is dependent
upon the larval feeding activity. The results showed monarchs that were heavier
and the longer wings span contained more lipid reserves than smaller adults. As there is a large reserve of TGL lipids and
only smalls amounts of proteins and glycogens the monarch rely on the fat (lipid)
reserve and the sugars produced by glycogens, collected from feeding on nectar
while migrating, as a source of stored energy for flight. They also rely on
these to reserves to supplement the TGL reserves carried over and used from the
larval stage.
So pretty much they eat and eat and store all the lipids and
sugars from their larval stage and from the travel down to Mexico in order to
uses it as fuel for the flight home. Which I think is awesome, taking thinking ahead
to the next level!!!
Thanks for reading my blog!!
Hope you enjoyed it!!
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If you want to read this articles get it at :- http://www.sciencedirect.com.ezproxy.lincoln.ac.nz/science/article/pii/0022191074902182
Another article which looks at the stop-over sites of Monarchs as they migrate to Mexico is also a interesting read. find it at :- http://www.sciencedirect.com.ezproxy.lincoln.ac.nz/science/article/pii/0169534787900553
Don't forget to watch the video at the start of the blog, its a great watch!!!
