chapter 17 annelida: segmented worms annelida: segmented worms
TRANSCRIPT
Chapter 17Chapter 17
Annelida:Segmented Worms
Annelida:Segmented Worms
I. Dividing the BodyI. Dividing the Body
Cons of Coelom – muscle contraction pushed coelom fluid
Benefits of metamerism (segmentation) Better at burrowing Independent movements of segments Fine control possibilities More advanced nervous system required Redundancy = safety factor Evolutionary potential (specialization)
Cons of Coelom – muscle contraction pushed coelom fluid
Benefits of metamerism (segmentation) Better at burrowing Independent movements of segments Fine control possibilities More advanced nervous system required Redundancy = safety factor Evolutionary potential (specialization)
Annelida = seg. wormsAnnelida = seg. worms 15,000 species - Three major classes Polychaeta (10,000+ sp.)
Bristleworms Primarily marine worms
Oligochaeta (approx. 3000 sp.) Earthworms & relatives
Terrestrial & freshwater (few marine)
Hirudinea (<2000 sp.) Leaches
Primarily freshwater with few marine & terrestrial sp.
15,000 species - Three major classes Polychaeta (10,000+ sp.)
Bristleworms Primarily marine worms
Oligochaeta (approx. 3000 sp.) Earthworms & relatives
Terrestrial & freshwater (few marine)
Hirudinea (<2000 sp.) Leaches
Primarily freshwater with few marine & terrestrial sp.
II. Body PlanII. Body Plan Segmented Anterior prostomium
(head side) Posterior pygidium
(tail side) New segments form
@ posterior end before pygidium.
Both circular & longitudinal muscles
Epidermis that secretes…
A non-chitinous cuticle (collagen)
Segmented Anterior prostomium
(head side) Posterior pygidium
(tail side) New segments form
@ posterior end before pygidium.
Both circular & longitudinal muscles
Epidermis that secretes…
A non-chitinous cuticle (collagen)
Coelom (mesodermal) Hydrostatic skeleton
Peritoneum Line coelom; form
mesenteries & septa Mesodermal
epithelium Mesenteries
Secure organs Septa
Divide segments
Coelom (mesodermal) Hydrostatic skeleton
Peritoneum Line coelom; form
mesenteries & septa Mesodermal
epithelium Mesenteries
Secure organs Septa
Divide segments
III. Polychaete Worms (many hairs)
IV. Oligochaeta (few hairs)IV. Oligochaeta (few hairs) Most terrestrial, freshwater, few
brackish & marine Setae – needle-like, chitinous substance
short in earthworms, longer in aquatic oligochaetes
A. Earthworms 2cm to 4m in length
Most terrestrial, freshwater, few brackish & marine
Setae – needle-like, chitinous substance short in earthworms, longer in aquatic oligochaetes
A. Earthworms 2cm to 4m in length
A. EarthwormsA. Earthworms 4 setae per segment Setae are moved by muscles to anchor worm during
locomotion Movement by alternate contraction of circular &
longitudinal muscles (peristaltic) 1) Nutrition:
Scavengers - feed on decaying organic matter; mouthbuccal cavitypharynxesophaguscrop (storage) gizzard (grinding) intestine (typhlosole SA)anus
Chloragogen tissue produces glycogen & fat (like the liver)
2) Circulation and Respiration Double circulatory system: 1) Coelom fluid 2) closed circulatory system
dorsal vessel is like its heart Ventral vessel is like the aorta – delivering blood to organs Hemoglobin (most annelids)
4 setae per segment Setae are moved by muscles to anchor worm during
locomotion Movement by alternate contraction of circular &
longitudinal muscles (peristaltic) 1) Nutrition:
Scavengers - feed on decaying organic matter; mouthbuccal cavitypharynxesophaguscrop (storage) gizzard (grinding) intestine (typhlosole SA)anus
Chloragogen tissue produces glycogen & fat (like the liver)
2) Circulation and Respiration Double circulatory system: 1) Coelom fluid 2) closed circulatory system
dorsal vessel is like its heart Ventral vessel is like the aorta – delivering blood to organs Hemoglobin (most annelids)
3) Excretion: blood fliltration metanephridia: like kidneys Capillaries surrounded by
nephritic tubule
Nitrogenous waste (urea) is pulled out of blood
Excreted through external pore
4) Nervous system: Central NS
cerebral ganglia=“brain” Connectives ventral nerve cords
Sensory NS: Mechanoreception
(touch) Photoreception
(light/dark) cells within the epidermis
Chemoreception (food etc.) receptor organs similar to taste buds interspersed throughout the epidermis
3) Excretion: blood fliltration metanephridia: like kidneys Capillaries surrounded by
nephritic tubule
Nitrogenous waste (urea) is pulled out of blood
Excreted through external pore
4) Nervous system: Central NS
cerebral ganglia=“brain” Connectives ventral nerve cords
Sensory NS: Mechanoreception
(touch) Photoreception
(light/dark) cells within the epidermis
Chemoreception (food etc.) receptor organs similar to taste buds interspersed throughout the epidermis
Niche Aeration & enrichment of soil C. Darwin study: Earthworms are able to
consume their weight in soil every day. Reproduction & Development
Hermaphroditic sexually mature when clitellum appears
Anterior ends emerge for copulation Mating involves simultaneously releasing sperm
from the sperm ducts (cross fertilization). Sperm cells travel via seminal grooves to seminal receptacles.
Sperm is then shed along with eggs into a mucous cocoon (produced by the clitellum) which provides a protective environment for the direct development of the juveniles.
Niche Aeration & enrichment of soil C. Darwin study: Earthworms are able to
consume their weight in soil every day. Reproduction & Development
Hermaphroditic sexually mature when clitellum appears
Anterior ends emerge for copulation Mating involves simultaneously releasing sperm
from the sperm ducts (cross fertilization). Sperm cells travel via seminal grooves to seminal receptacles.
Sperm is then shed along with eggs into a mucous cocoon (produced by the clitellum) which provides a protective environment for the direct development of the juveniles.
V. HirudineaV. Hirudinea Primarily freshwater Usually 2 - 6 cm. Some to 30 cm!
Text fig. 17 - 19 Colorful A. Form and Function
fixed number of segments. Suckers for locomotion lack coelomic compartments septa have disappeared
Primarily freshwater Usually 2 - 6 cm. Some to 30 cm!
Text fig. 17 - 19 Colorful A. Form and Function
fixed number of segments. Suckers for locomotion lack coelomic compartments septa have disappeared
1. Nutrition Pharynx & “teeth” (often chitinous) for feeding off the
fluids of other organisms. The gut is often modified to store large amounts of
fluid. Some leeches prey on the other invertebrates while
others prefer vertebrate hosts. Most parasitic leeches detach from their hosts in order to
reproduce. Some species attach their cocoons to their host.
Many leeches feed on blood. They were once used to “bleed” people who were sick. They are still used medicinally to relieve congestion when venous circulation is compromised (inadequate blood return from tissues).
1. Nutrition Pharynx & “teeth” (often chitinous) for feeding off the
fluids of other organisms. The gut is often modified to store large amounts of
fluid. Some leeches prey on the other invertebrates while
others prefer vertebrate hosts. Most parasitic leeches detach from their hosts in order to
reproduce. Some species attach their cocoons to their host.
Many leeches feed on blood. They were once used to “bleed” people who were sick. They are still used medicinally to relieve congestion when venous circulation is compromised (inadequate blood return from tissues).
2. Respiration occurs through the skin except for the gills of
some fish parasites. 3. Excretion
Leeches excrete through pairs of nephridia (10-17)
4. Nervous system Their CNS consists of both anterior & posterior
“brains” as well as 21 pairs of ganglia positioned along the ventral nerve chord.
Sensory modalities include photoreception by ocelli, subcutaneous mechanoreceptors, chemoreception, & thermoreception in at least some.
2. Respiration occurs through the skin except for the gills of
some fish parasites. 3. Excretion
Leeches excrete through pairs of nephridia (10-17)
4. Nervous system Their CNS consists of both anterior & posterior
“brains” as well as 21 pairs of ganglia positioned along the ventral nerve chord.
Sensory modalities include photoreception by ocelli, subcutaneous mechanoreceptors, chemoreception, & thermoreception in at least some.
Modern leech medicine
5. Reproduction Hermaphroditic Cross-fertilize during copulation Sperm are transferred by hypodermic impregnation. The clitellum secretes a mucous cocoon to receive
the sperm and egg. The cocoons are buried in mud or damp soil, and
development direct (oligochaetes). Some parasitic species attach their cocoon to a host.
5. Reproduction Hermaphroditic Cross-fertilize during copulation Sperm are transferred by hypodermic impregnation. The clitellum secretes a mucous cocoon to receive
the sperm and egg. The cocoons are buried in mud or damp soil, and
development direct (oligochaetes). Some parasitic species attach their cocoon to a host.