Transcript ZOO 115 Invertebrate Zoology

ZOO 115 Invertebrate Zoology
Phylum Annelida
Class Clitellata
Subclass Oligochaeta
Subclass Oligochaeta - General
Characteristics
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> 3500 species
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Most terrestrial
or freshwater
but about 200
marine species
Includes
earthworms
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3m Australian
earthworm
http://www.ahc.gov.au/publications/pnh/images/ea10597.jpg
Subclass Oligochaeta - General
Characteristics
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They have few
chaetae
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Usually
simple with
typically four
bundles per
segment.
retractable
Retractor muscle
Protractor muscle
http://www.infovisual.info/02/img_en/007%20Internal%20anatomy%20earthworm%20cross.jpg
Subclass Oligochaeta - external
anatomy
http://www.howe.k12.ok.us/~jimaskew/botzo
/wormx.gif
Subclass Oligochaeta locomotion
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Like Polychaetes - have septae separating
segments into compartments making
peristalsis more efficient.
Musculature similar to Polychaetes
During dry seasons and winters,
earthworms burrow deeper (up to 3m)
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Become dormant (diapause) and dehydrated
Subclass Oligochaeta - Nervous system
Brain
Mechanoreceptors on each segment
- more concentrated in prostomium
Chemosensory tubercles
- form three rings on each segment
- more concentrated in prostomium
Photoreceptors on each segment
- more concentrated in prostomium
Ventral Nerve Cord
Subclass Oligochaeta - Nervous system
Brain
Segmental nerves
- attach to longitudinal muscles
How do you think
this animal responds
to a sudden stimulus?
Contains 5 giant axons
Ventral Nerve Cord
Subclass Oligochaeta - Feeding and
Digestion
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Scavengers
Muscular
pharynx
Deposit
 Suction
feeders
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Adhesion in
some
aquatic sp.
Pharyngeal
glands digestion
http://www.miramar.sdccd.net/programs/biol/earthworm/
Subclass Oligochaeta - Feeding and
Digestion
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Crop
Gizzard
Intestine
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Chiton
Only
in lined
Earthworms
Muscular
Used
for
Grinding
storage
Typhosole
http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookDiversity_8.html
- fold in
intestine to
increase
surface area
http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookDiversity_8.html
http://www.miramar.sdccd.net/programs/biol/earthworm/
Subclass Oligochaeta - Circulatory
system
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Similar to other Annelids
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Many have multiple hearts
Contractile Dorsal blood vessel
http://www.backyardnature.net/pix/earthwm1.gif
Blood Flow
Subclass Oligochaeta - Excretion
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Metanephridia
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Usually one pair per segment
emc.maricopa.edu/faculty/farabee/BIOBK/BioBookDiversity_8.html
Subclass Oligochaeta - Respiration
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Mostly by diffusion through the body
wall
A few species have gills
Aquatic tolerate low oxygen
Subclass Oligochaeta - Respiration
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Calciferous
glands
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Secrete
Calcium
Carbonate
Function
not entirely
known.
Thought to
play a role
in CO2
removal
http://www.backyardnature.net/pix/earthwm1.gif
Subclass Oligochaeta Reproduction
 Sexual
Asexual
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- common in aquatic species
Hermaphrodites
Copulation
Breed continuously
 Genital Chaetae hold
the worms together
 In common
earthworms, the
gonopores don’t line
up and the sperm
have to swim
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Male
reproductive
organs
Female
reproductive
organs
Clitellum
http://images.encarta.msn.com/xrefmedia/aencmed/
targets/illus/ilt/T013733A.gif
Subclass Oligochaeta Reproduction
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Clitellum
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Often most pronounced during mating period
Creates mucus for copulation
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Works in conjunction with special muscles to
create slippery furrows for swimming sperm in
earthworms
Creates a cocoon for the eggs
Clitellum
Direct Development
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12 weeks to hatch
Can live several years
http://images.encarta.msn.com/xrefmedia/aencmed/targets/illus/ilt/T013733A.gif
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Earthworms importance to
Agriculture
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Burrowing
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aerates the soil to
provide air and water
for plants
Reduces runoff and
surface evaporation of
water
Encourage growth of
other organisms that
have a detrimental
effect on Nematodes
Earthworms importance to
Agriculture
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Digestion of organic
material
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Per acre per year on
cultivated land, 16,000
pounds (7200 kg) of soil
pass through earthworm
guts and are deposited
atop the soil -- 30,000
pounds
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Fecal material
(castings)
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Rich in nutrients.
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High in Nitrogen,
Magnesium,
Phosphorus, Calcium,
Potash
Neutralizes pH.