Download Phylum Annelida

Phylum Annelida
Phylum Annelida
• Terrestrial, marine,
freshwater.
• Repeating segments.
• Triploblastic.
• True coelomates –
complete gut.
• Closed circulatory system.
Well developed nervous
system.
• Respiratory organs.
• Protostome development.
• Metamerism
(unspecialized)
segmentation.
• One or more pairs of
setae.
Phylum Annelida
• Ancestral Traits
–
–
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Coelomate
Lophotrochozoan
Protostome
Closed circulatory system
Cephalization
Spirobranchus giganteus
Christmas tree worm
• Derived Traits
– Segmentation
• Metamerism
• Septa
– Setae
• Bristles
– Myelinated neurons
~ 40K species of annelids
Systems
• Integument- epidermis is one cell layer with
mucous gland that secrete a moist cuticle.
• Skeletal -hydrostatic (using coelom)
• Muscle- longitudinal and circular muscles Each
segments muscles are independent of the other
segments.
• Digestive- complete, complex, with absorption and
digestive glands and excretory cells.
Systems (continued)
• Excretory- a pair of nephridia per segment.
• Respiratory -through skin, some through
parapodia; tubeworms have gills.
• Circulatory- closed system, use hemoglobin as
oxygen carrier.
• Nervous- dorsal brain; ventral, double, solid nerve
cord, with ganglia in each segment.
• Endocrine- hormones secreted by nervous system.
• Reproductive– Dioecious in Polychaeta; no special organs, posterior end
becomes gonads.
– Monoecious in Oligochaeta and Hirudinea; Clitellium.
Annelid Taxonomy
• Phylum Annelida (an-nel-i-da)
– Class Polychaeta (poly-key-ta)
• Nereis, Aphrodita, Chaetopterus,
Arenicola, Amphitrite
– Class Clitellata
– Subclass Oligochaeta (ol-e-go-key-ta)
• Lumbricus, Tubifex
– Subclass Hirudinea (hi-ru-din-e-a)
• Hirudo, leech
• Earthworm dissection
Annelid Taxomony
• Class Polychaeta (many bristles)
– most numerous # species
– marine
Hermodice
crunculata
Annelid Taxomony
• Class Polychaeta
• Class Clitellata
– Subclass Oligochaeta (few bristles)
• Freshwater, marine & terrestrial
Lumbricus terrestris
Annelid Taxomony
• Class Polychaeta
• Class Clitellata
– Subclass Oligochaeta
– Subclass Hirudinea
• Fixed # segments (34)
• Setae absent
Hirudo
medicinalis
Annelid Phylogeny
Annelid Body Plan
Setae
Class Polychaeta
• Highly specialized head
regions
– Antennae
– Sensory palps
– Feeding appendages
• Paired extensions of body
Bispira bunnea
(parapodia)
sabellid worm
• Often tube-dwelling
– Burrow into substrate and secrete mucus/CO3 materials
Polychaete Anatomy
Polychaete Anatomy (cross section)
Polychaeta
Amphitrite
Polychaeta
Lugworm (Arenicola sp)
Polychaeta
Polychaeta
Clade Siboglinidae
(Phylum Annelida?)
Riftia pachyptila
Ridgea sp
Giant tube worms (Vestimentifera)
trophosome
Riftia pachyptila
Polychaete Reproduction
• Dioecious
• Trochophore larvae
• Some species develop specialized
segments containing gametes
– Epitokes
– Segments are released and
gametes burst out
Polychaete Asexual Reproduction
• Epitokes are essentially
buds
• Clues to ancestral origin of
segmentation
– Segmentation may have
been derived from
incomplete budding
processes
Class Oligochaeta
Class Oligochaeta
• Defining characteristics
– Pronounced cylindrical
glandular region of the body
= clitellum
• Second largest class in the
phylum Annelida
• Most spp. are earthworms,
very few are marine
24
Phylum Annelida
Polychaetes and Oligochaetes
• Oligochaetes differ from
polychaetes in several
ways:
– No parapods, fewer setae (if
at all)
– Hermaphroditic with sex
cells produced in a separate
section
– No larval stages
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Phylum Annelida
Oligochaete Anatomy
Oligochaete Anatomy
Setae: a.k.a. Bristles
Oligochaete Reproduction
Oligochaete Development
• For terrestrial oligochaetes, development is direct without any
larval forms
• Some aquatic oligochaetes retain a trochophore-like larval stage
Common Terrestrial Oligocheates: Earthworms
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Octagonal-tail worm (Dendrobaena octaedra)
Red marsh worm (Lumbricus rubellus)
Dew-worm or nightcrawler (Lumbricus terrestris)
Pink soil worm (Aporrectodea rosea)
Canadian worm (Aporrectodea tuberculata)
Pasture worm (Aporrectodea turgida)
Woodland white worm (Octolasion tyrtaeum)
Redworm (Eisenia fetida )
Quick and Easy Earthworm Morphology Guide
Morphology
Number & location of GTs
and TPs, location &
shape of clitellum
Ecology
Location of burrows
Aporrectodea turgida Lumbricus rubellus
Earthworm
Dissection
Return to taxonomy
Cross section
Aquatic Oligocheates
Subclass Hirudinea
• Defining characteristics
– Posterior sucker
• Predominately freshwater,
but do occur in all seas and
moist soil
• Leeches do not burrow or
crawl, lack parapods and
setae
35
Phylum Annelida
Subclass Hirudinea
Leech Anatomy
• 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
37
Phylum Annelida
Hirudo medicinalis
Blood Sucker
• The salivary glands excrete hirudin which prevents the
blood from coagulating
– May also secrete an anaesthetic and substance to dilate
small blood vessels
• Blood is broken down by symbiotic bacteria that is then
used by the leeches
• Leeches were commonly used in the 19th century for
bloodletting
– Recent medical uses are to relieve pressure after vascular
tissue is damaged
– Snake bites or the reattachment of a finger or ear
39
Phylum Annelida
Leech Reproduction
• 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
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Phylum Annelida