Biology Reference
In-Depth Information
and animal husbandry that have made the use of nonmodel organisms for research
more feasible, which will hopefully promote and encourage further advancement in
the knowledge of circannual timing.
1. INTRODUCTION
Circannual behavior is an adaptation to the physical world. Animals
have no control over the physical environment so they have developedmany
different strategies to anticipate seasonal changes and prepare accordingly for
survival and/or maximum fitness. One example of an adaptation to environ-
mental stresses is diapause, a developmental arrest mechanism implemented
by some invertebrate species, including the nematode
Caenorhabditis elegans
(reviewed in
Carey, Andrews, & Martin, 2003
) and some insects (discussed
in
chapter 8
). Here, we focus on circannual events utilized primarily by ver-
tebrates. Examples of some of these events are provided in
Fig. 9.1
. The
molecular pathways underlying the timing of these circannual events are
not well characterized, but active research on this subject has provided many
advances in the field. Here, we will describe some well-known examples of
JAN
FEB
MAR
APR
MAY
JUN
JUL
AUG
SEP
OCT
NOV
DEC
Song sparrow
Melospiza melodia
(seasonal courtship behavior)
Song
onset
Reproduction
Dark-eyed junco
Junco hyemalis
(migration)
Migration
Reproduction
Migration
Thirteen-lined ground squirrel
Ictidomys tridecemlineatus
(hibernation)
Hibernation
Reproduction
Hibernation
Human
Homo sapiens
(seasonal affective disorder)
Winter depression
Winter depression
Figure 9.1 Circannually timed events. Representative examples and approximate
annual timing of different seasonal events are provided along with an example species.
Light/dark cycles illustrated above the months are representative of the annual changes
in photoperiod in the northern United States of America. Reproduction represents both
mating behavior and gestation.
