They are the same, but different. Some insects like bees, ants
and wasps that live in the same colony grow from the same genetic
material, but they come to be very different organisms.
At a very early stage of development, these insects evolve
into castes. Some castes reproduce (queens) while others perform
different functions (soldiers, workers) that are essential
for colony survival. This type of development occurs in many
other types of animals too, and scientists like UGA’s
Michael Strand are just starting to understand how.
Two recent UGA studies have shed new light on this question
by finding that caste formation in a unique type of wasp is
strongly influenced by whether individuals possess a specialized
type of cells called germ cells.
The first study, published in a recent issue of the Proceedings
of the National Academy of Sciences, reveals a previously
unknown role for germ cells in development, according to Strand,
one of the authors of the study.
The wasp used in the study is "a particularly elegant
model [for this research] because its eggs develop clonally
to produce genetically identical offspring," Strand said.
So, in much the same way human identical twins are formed
from one egg, each egg laid by this wasp produces roughly
2,000 identical sibling wasps.
"Germs cells are formed very early in the embryogenesis
of wasps, long before any individuals develop into a soldier
or queen," Strand said. In humans as well as insects,
the main function of germ cells is to give rise to reproductive
cells (sperm and eggs) that will produce offspring in the
next generation. Germ cells usually remain dormant in humans
and other animals until they reach maturity and are able to
reproduce.
In the wasps used in this study, however, germ cells were
parceled out to some embryos and not others. The embryos that
inherited germ cells went on to develop into queens, while
embryos without germ cells developed into soldiers.
In a second study, published in a recent issue of the journal
Nature, Strand and coworkers build on these results
by demonstrating the significance of this unique caste forming
system. Sterile soldiers are capable of recognizing their
kin which allows them to protect queens that they are fully
related to and to kill non-relatives that can compete for
the same resources. These results provide important insight
into the evolution of altruistic and spiteful behavior that
biologists have been fascinated about for decades. They also
suggest important linkages between molecular events that occur
early in development and the function of organisms at later
stages of their life cycle.
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UGA
research has shown that germ cells determine whether the offspring
of wasps become queens or soldiers.
