the Phylum Annelida
word "Annelida" comes from the Latin annelus,
Segmented body; (2) digestive tract with two
openings; (3) body cavity.
Size Less than an inch
to over 3 yards, with varied shapes.
Habitat Soil, also all
waters and sandy shores.
Segments are often provided with bristles, or
setae. The digestive tract, ventral nerve cord
and major blood vessels run uninterrupted the
length of the body; all other organs are placed
within certain segments.
Class Polychaeta --
(about 4,000 species) -- Common but inconspicuous
marine creatures, polychaetes burrow in the sand,
crawl under rocks or live within tubes partially
buried in sand or mud. Thousands of such tubes
may be seen dotting a tidal flat at low tide.
Polychaetes often have a well-developed head with
eyes and antennae. A pair of lateral appendages
on each segment aids in movement.
Class Oligochaeta -- earthworms (about 2,700 species) -- Lacking
appendages, these worms move by extending and
contracting the body. They live in the bottoms of
lakes, ponds and streams or burrow in soil.
Certain body segments are sometimes swollen by
glands which secrete mucus for the construction
of cocoons in which the hermaphrodite worms
deposit their eggs. Most species run several
inches in length but one Australian type may be
as much as 10 feet long.
Class Hirudinea --
leeches (300-plus species) -- These primarily
fresh-water annelids have rather flattened bodies
with a sucker at each end. Many are scavengers or
feed on small invertebrate animals. A large
number are bloodsuckers and attack snails, fish,
turtles and other aquatic animals.
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