Download septa - Jutzi

Unit 5.3
Phylum Annelida
Uniramia
Echinodermata
Chelicerata
Vertebrata
Lophophores
Crustacea
Other Chordata
Arthropoda
Annelida
Hemichordata
Other
pseudocoelomates
Nematoda
Mesozoa
Sarcomastigophora
Ciliophora
Apicomplexa
Microspora
Mollusca
Nemertea
Platyhelminthes
Ctenophora
Cnidaria
Placozoa
Porifera
Myxozoa
Phylum Annelida
• Segmented body
– Each segment is
called a metamere
• Each segment
contains tiny hairs
called setae that are
used for various
purposes
– Absent in leeches
• Coelom (internal body
cavity) is divided by
septa
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Phylum Annelida
• Annelids were the
first organisms to
develop a closed
circulatory system
• Several onechambered hearts
connect vessels on
either side of the
esophagus and flex
via peristalsis as the
worm moves
Phylum Annelida
Pygidium
Septa
Prostomium
Annelid bodies are divided by septa into repeating segments.
Each segment contains their own set of excretory organs
called nephridiopores. This attribute is called Metamerism
Annelid larva
Apical tuft
Stomach
Ciliary band
Mouth
Anus
Annelid development
Class Polychaeta
• Generally marine
• Each body segment
has a pair of fleshy
protrusions called
parapodia
• Parapodia function in
locomotion as well as
in respiration (think
external gills)
• Well developed heads
compared to other
annelids
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Class Polychaeta
Parapodium
Tentacle
Head
Class Polychaeta
Predatory
Jaw
Tentacle
Palp
Cirrus
Parapodium
Everted pharynx
Eye
Class Polychaeta
Class Polychaeta
• Epitoky – a
transformation into
the breeding form of
an organism
• Epitokes are given
the task of
reproduction
• Some species bud
epitokes from the
body and remain in
their habitat while the
epitokes move to the
surface to breed
Class Polychaeta
• Dioecious
• Many species
reproduce en masse
at the water’s surface
at night
• Moonlight and
artificial light attract
spawning masses
• The Palolo worm is
harvested in Samoa
and eaten as a
delicacy
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Tube-Dwelling Polychaetes
• Tubeworms &
Featherdusters
• Defining characteristic
– Gut tissue forms an
organ (trophosome)
that becomes filled
with chemosynthetic
bacteria
– Segmentation
confined to small rear
portion of animal
• Small intriguing class of
tube dwelling worms
found throughout the
worlds oceans
Tube-Dwelling Polychaetes
• The most interesting
aspect of tube worms is
the lack of a digestive
system
– Bacteria in the
trophosome fix the
chemicals leaving the
vents
– The bacteria can occur
at concentrations of 10
billion per gram of
trophosome tissue
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Burrowing Polychaetes
• Lugworms
• Castings can be seen
on the beach at low
tide
• Lives in a U-shaped
burrow in the sand
• Eat sand, extract
biological material
from the rock, and
then expel the
castings outside of
the burrow
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Free-living Polychaetes
• Common sandworms
and fireworms
• Use parapodia like
little legs for
locomotion
• Roam the ocean floors
searching for food
• Fireworm setae
contain potent
neurotoxins and can
cause a painful rash if
touched
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Class Oligochaeta
• Earthworms
• Few setae – very
hard to see hairs
compared with
polychaetes
• Clitellum – barrel
shaped sexual
structures near the
anterior end of the
worm
• No parapodia
• Monoecious
Class Oligochaeta
• Extremely important
ecologically
• Biological – breaks
down organic matter
leaving rich, dark soil
• Chemical – frees
phosphates for use in
plants
• Physical – aerates the
soil by digging tunnels
that allow air and
water to penetrate
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External Structures of an Earthworm
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Internal Structures of an Earthworm
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Class Oligochaeta
• Copulation &
fertilization are
separate
• Copulation –
two earthworms
line up with
their anterior
ends facing
each other and
exchange
sperm
Class Oligochaeta
• Fertilization –after the
worms exchange sperm,
the clitellum turns bright
pink and secretes a
chitinous cocoon around
the worm
• The worm then wriggles
out of the cocoon and
deposits its eggs and its
partner’s sperm into the
cocoon allowing
fertilization to take place
• Worms hatch as small
adults – no larval stage
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Earthworm Reproduction
Class Hirudinea
• Leeches
• Anterior & posterior
suckers
• Predominately
freshwater, but do
occur in all seas and
moist soil
• Leeches do not burrow
or crawl, they lack
parapodia and setae –
instead they move like
an inchworm
Class Hirudinea
• Anterior sucker is small
and contains the mouth
– Anterior sucker
creates a wound with
saw like jaws
• Leeches drink other
animals’ blood, usually
vertebrates
– Can be carnivores, or
scavengers; leeches
are not set in their
feeding habits
• Leech saliva contains an
anticoagulant that numbs
the wound and keeps the
blood flowing
Class Hirudinea
• Leeches are
simultaneous
hermaphrodites that
lack a free-living
larvae stage
• Fertilization is internal
through copulation
• Development occurs
in a cocoon similar to
the Oligochaetes
The End