Download Phylum Annelida

Phylum Annelida
Annelid Characteristics
“annulatus” = ringed
Metamerism =>not limited to
external,
schizocoelous, vermiform
Protostomes
Successful invaded all moist
environments
Segments arise through
teloblastic growth
Head & tail = not considered
segments
General Anatomy
Metameres = annuli
Homonomous vs
heteronomous =
regional specialization
setae
Gut separated from bw
by coelom
Segmentation internally
Eversible pharynx with
jaws or proboscis
Complete digestive
tract
Meta-or protonephridia
Mircoanatomy
1
3
5
4 2
6
1. Dorsal blood vessel 4. Gut
2. Longitudinal muscles 5. Ventral nerve cord
3. Coelom
6. Ventral blood vessel
General Feeding/Digestion
Complete gut (oneway
food movement),
mesodermal
Mouth -> buccal cavity
(pharynx) -> esophagus
(crop/gizzard) ->
intestine -> rectum ->
anus
Protease, carbohydrase,
lipase, even cellulase
Digestion predominantly
extracellular
Feeding = great diversity
in form and function
Respiration/Circulation/Excretion
None to many gills
When none = whole body or
dorsal surface
Gills associated with parapodia,
i.e. 2-3 paired or fanlike gills
Respiratory pigments
hemoglobin, -erythrin and
chlorocruorin
Closed circulation, dorsal
(anterior)/ventral (posterior) bv
Unidirectional flow by valves
Metanephridia, pair/segment
Nervous System/Sensory Organs
1. Anterior ganglion
2. Circumesophageal
connectives
3. Single median nerve cord
4. Giant motor axons
1.
2.
3.
4.
5.
6.
7.
Eyes = prostomium
Chemoreceptors
Touchreceptors
Vibration receptors
Statocysts
Proprioceptors
Nuccal organ
Reproduction/Early Development
1. Asexual = uncommon,
fission
2. Sexual
Diecious, external
Spawning controlled
hormonally
Formation of epitoke
Gamete release =
nephridiophore
Copulation
Spiral development, zygote
Typical Protostome Larvae: Trochophore
1
4
3
2
Early trochophore
5
1. Apical tuft
2. Mouth
3. Stomach
4. Ciliary band
5. Anus
Trochophore
larvae of
different
polychaete
species.
Typical Protostome Larvae: Trochophore
Later stage trochophores. The specimen on the
right has already three segments.
No typicsl metamorphosis but growth by
segment addition.
Annelid Taxonomy
Class
Polychaeta
Photo of the anterior end of
the clam worm, Nereis.
2
3
5
1
1. Prostomial tentacles
2. Palp
3. Peristomial tentacles
4
4. Prostomium
5. Peristomium
Photo of a parapodium of Nereis.
1.
2.
3.
4.
5.
6.
Dorsal cirrus
Notopodium
Setae
Neuropodium
Ventral cirrus
Acicula
Biramous appendage
Ventral neuropodium and a dorsal notopodium
Each supported by a stiff chitinous rod = aciculum
Dorsal and ventral cirrus project
dark staining setae extend beyond the parapodium
Polychaete Jaws
Identifying characteristics for polychaete
Often distinct only on EM level
Sedentia
The sedentary polychaetes are the “couch
potatoes” that live in fixed tubes and
often do not contain parapodia, sensory
structures and a distinc head.
Lif e Habit
Sedent ia
Limit ed num ber,
may be
separ ated int o
diff ere nt re gions
May be ab se nt or
few t o many
si mil ar
ap pend ages
Bu rrow ing
Fee ding Mode
Filt er fee din g
Body Segment s
Anter ior
Appendag es
Err antia
A large num ber
Few in num ber and
diff ere ntia ted in to
pa lps, antennae,
cirri etc.
Fr ee li vin g a nd
generally
rap acious
All wit h ja ws
Errantia: Predators
This is an image of an
errant (mobile)
polychaete Nereis.
Clam worms (Nereis) crawl about on the oceans floor
hunting for food using well-developed sensory
structures. Once located, prey are seized with chitinous
jaws on a rapidly everted, muscular pharynx.
Errantia: Predators
This is an image of an
errant (mobile)
polychaete Glycera
(Japan).
Blood worms (Glycera) are gallery dwellers, “sit and wait”
or “lurking” predators with an eversible pharynx (1/2 to
1/3 total animal length with4 black jaws equipped with
venom glands.
Errantia: Direct Deposit Feeders
These are images of the tubes and the live animal
Arenicola.
Lugworms (Arenicola) live in L-shaped burrows in soft
substrate and draw water into their tube to create a
feeding current. They separate organic from inorganic
particles in their pharynx which is unarmed but mucous
covered.
Errantia: Direct Deposit Feeders
This is an image of
an errant
polychaete
Cymenella torquata.
Bamboo worms (Clymenella torquata) live in L-shaped
burrows in soft substrate and draw water into their tube
to create a feeding current. They separate organic from
inorganic particles in their pharynx which is unarmed but
mucous covered.
Errantia: Selective Deposit Feeders
This is an image of a
Terebellid worm
(Polychaeta).
Terebellids have mucous covered ciliated tentacles which
are curled into gutters. Ciliary beats cause food particles
to be moved into the mouth.
Errantia: Suspension Feeders
This is an image of
Sabella.
Feather duster worms (Sabellids) have radioles (pennate
structures) which are ciliated and mucous covered.
Particles get trapped on mucous and moved by ciliary beat
to the midrib. The midrib contains gutters that separate
particles according to size.
Errantia: Filter Feeders
This is an image of
Chaetopterus variopedatus.
Parchment worms (Chaetopterus variopedatus) live in Ushaped tubes and contain aliform (wingshaped) parapodia
which are mucous covered and created a feeding current.
Particles stick to mucous and are rolled up to form food
bolus.
Class Oligochaeta
Class Oligochaeta
No biramous appendages, contain seatae, lack of
cephalization, movement through peristalsis, digestive
regional specialization
Calciferous Glands
Gizzard
Esophagus
Pharynx
Crop
Intestine
Class Oligochaeta
1
2
3
4
5
1. Cuticle
3. Dorsal blood vessel
2. Longitudinal muscles 4. Chloragogue tissue
5. Intestinal lumen
1.
2.
3.
4.
5.
Setae
Cuticle
Hypodermis
Circular muscle layer
Longitudinal muscle layer
Class Hirudinea
Class Hirudinea
Superficial annulation, dorsoventrally flattened, two
pronounced suckers, ectoparasites, may contain
proboscis