Species C elegans
A tiny nematode; lives in garden soil, feeding on
Free-living, transparent nematode, about 1 mm
in length, lives in temperate soil environments.
Unsegmented, vermiform, and bilaterally
Has cuticular integument, four main epidermal
cords, and a fluid-filled pseudocoelomate cavity
Generally feeds on bacteria.
C. elegans has two sexes: hermaphrodites and
Males have a single-lobed gonad, vas
deferens, and a tail specialized for
Hermaphrodites have two ovaries,
oviducts, spermatheca, and a single
The hermaphrodite gonad produces first
sperm and then oocytes
Hermaphrodites have about 10
eggs inside--the older eggs are laid
about as fast as new eggs are
Oocytes pass into the spermatheca and are
fertilized. Embryos develop in the uterus, and
have a few cleavages before the eggs are laid,
so the embryos have a few dozen cells when
the embryos are laid. The embryos develop
into worms over the next 8-18 hours
Simple body organization
Easy to grow
Short life cycle: 3 days per generation
Powerful genetics (both self-fertile and cross-fertile)
Transparent body wall
Fully described anatomy and development
Post-genomic tools -- RNAi
Simplest organisms with a nervous system.
It is an eukaryote, shares cellular and molecular structures and control
pathways with higher organisms.
It goes through a complex developmental process, including
embryogenesis, morphogenesis, and growth to an adult.
The biological information obtained from C. elegans may be directly
applicable to more complex organisms.
About 35% of C. elegans genes have human homologs.
C. elegans was the first multicellular organism to have its genome
Young, freshly starved larvae best survive freezing in 15% glycerol
solution, can also be stored at −80 °C for over ten years
About 35% to 45% of the worms stored in liquid nitrogen survive.
There are six chromosomes: five pairs of autosomes and the sex
Hermaphrodites have two X chromosomes (XX).
Males have one X chromosome (XO); having only one chromosome
instead of a pair is called the hemizygous state.
It lives a total of about 2 weeks.
The eggs are fertilized within the adult
hermaphrodite and laid at about the 40 cell
They hatch and it proceeds through 4 larval
C. elegans can adopt an alternative life
form, called the dauer larval stage in
Dauer larvae are thin and can move but
their mouths are plugged and they cannot
eat & can remain viable for three months.
General form of life cycle of
LIFE CYCLE OF
Daurer larvae appear to be
non-aging: they can roam
around for months and then
re-enter the L4 stage when
they encounter a food
source and live about 15
RNA interference (RNAi) has been extensively used on C. elegans
C. elegans are fed with transgenic bacteria or injected with RNA into
the body cavity that express double-stranded RNA that complements
the gene of interest, thereby causing RNA silencing.
Live samples of C. elegans used to explore the effects of zero gravity on
muscle development and physiology.
The research was primarily about genetic basis of muscle atrophy,
which relates to space travel
Studying meiosis is considerably simplified in the sperm and egg nuclei
in the gonads, the difficulties of heterogeneous cellular populations are
eliminated because every nucleus at a given position in the gonad
therefore is at roughly the same step in meiosis.
It can also be used to study nicotine dependence because it exhibits
behavioral responses to nicotine that parallel those of mammals; e.g.,
acute response, tolerance, withdrawal, and sensitization.