Living and Adapting to Its Own Habitat - Building the Most Complex Structure on Earth - page 226

(A) (B)

CE

CE

FA

Figure 4.15 Female (A), male (B) D. magna. Differentiating sex characteristics include the
pair of minute first antennae (FA) of the females, the elongated FA of the males. The bivalved-
like carapace of the female has two uniform, symmetrical edges (CE). Both CEs of the male
are asymmetrical and are edged by setae.
Source : From Olmstead and LeBlanc (2007) .

receptor in the oocyte, activates a transduction pathway that induces the expression
of sex determining genes ( drmt?, sex?, fem? ) ( LeBlanc, 2007 ).
When attacked by its predators, the pea aphid, Acyrthosiphon pisum , releases an
alarm pheromone, (E)-β-farnesene (EBF), which triggers escape behavior in the col-
ony by dropping off the plant. The increased contact with other aphids as a result
of jostling and escape response and the direct action of the EBF induce increased
proportion of winged individuals in the offspring. Both inducing stimuli, the tactile
stimulus and the reception of the pheromone via olfactory neurons, are processed in
the brain, but the pathway from the brain to the aphid ovary, ovarioles, and oocyte is
not known. Experimental exposure of aphids to EBF alone increases the proportion
of winged individuals in the offspring ( Kunert et al., 2005 ).
TDP is also known in the plant kingdom where, like metazoans, it is an adaptive
response to stressful conditions in the environment. Seedlings of the third generation
of the annual plant, Polygonum persicaria , grown in dry soil produce longer roots
that extend deeper and faster into dry soil than the seedings of adequately watered
plants. They also produce a greater biomass and have greater survivorship ( Herman
et al., 2012 ).
The American bellflower, Campanulastrum americanum , is a 5-15 cm tall, bien-
nial or annual plant in North America. The type of life history that the offspring
adopts is determined maternally. When the mother plant is grown understory, it pro-
duces seeds that adopt the annual life history, which is adaptive under the maternal
shady-light environment; plants grown in a light gap produce seed that adopts the
biennial life history, which is also adaptive under this light environment. The fitness
of plants that are appropriately cued to their light environment is 3.4 times greater
than plants not grown in the maternal light environment ( Galloway and Etterson,
2007 ).
Maternal environmental effects are greater in dormancy and germination of seeds
in plants ( Donohue, 2009 ).