Kingdom Animalia:
Annelida
Key words
hermaphrodite
segment
Earthworm
Lateral view
segments
Earthworms
●
The 2,700 earthworm species are
members of the annelida.
Body structure
●
oviduct opening
spermathecal
openings
vas deferens opening
mouth
seminal groove
prostomium
dorsal surface
ventral surface
Earthworms have a segmented
body, with each segment bearing
the same fundamental structures.
● Visible external structures
include the setae, tiny bristles
that allow the worm to grip
surfaces to help with
movement.
● Earthworms have no eyes,
but they do have lightsensitive cells on their
outer skin that help them
detect light levels.
● Earthworms eat by pulling
food into their mouth using
their prostomium.
Reproduction
Earthworms are hermaphrodite
but cannot fertilize their own
eggs. Sperm travels from the
opening of the vas deferens
along the seminal groove to the
clitellum.
● When two earthworms copulate,
they lie side by side and head to tail
so that the clitellum segments in each
are opposite the segments containing
the sexual organs of the other. Each
exchange sperm, which is stored in
internal sacs called spermathecae.
The clitellum then secretes a slime
tube, the cocoon, around each
animal.
● The earthworm then wiggles out of
the tube headfirst. While the tube
passes from the clitellum to the
prostomium, it passes over the
oviduct, which deposits eggs into the
cocoon, and then the spermathecal
opening, which release the stored
sperm.
● Once the worm is out of the cocoon,
it seals to form an incubator.
clitellum
setae
anus
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