Midterm II (Annelids) Flashcards
1
Q
Phylum Annelida
A
- True segmentation
- Phylogeny:
- Class Errantia
– Mobile “polychaetes” - Class Sedentaria
– Tube-dwelling “polychaetes” - Family Siboglinidae
- Family Echiuridae
- Order Clitellata
– “orligochaetes”
–Family Hirudinidae - Class Sipuncula
2
Q
Phylum Annelida 2
A
- Also called “bristle worms”
- Setae
- 15,000 species
– Marine, freshwater, damp terrestrial - Free-living, symbiotic, parasitic
– Deposit feeders, predators, suspension feeders, blood feeders - Closed circulatory system
- Centralized nervous system
3
Q
The Key Transition of annelids
A
Metamerism:
- Body composed of serially repeated units by septa
- Each unit contains components of most organ systems
- Coelom plays a large role!
4
Q
Locomotion: Segments and Coelom
A
- Allows for separation of body tissues (e.g., muscle groups), and eventually body parts (e.g., arthropods)
- Coelom is filled with fluid and serves as a hydrostatic skeleton
– Contraction of longitudinal muscles (causes body to shorten and expand)
– Contraction of circular muscles – (causes body to narrow and lengthen) - Alternate waves of contraction, or peristalsis, allow efficient burrowing
5
Q
Defining Annelid Features
A
- Setae/Chaetae
- Chitinous, epidermal bristles
- Help in burrowing, tubes, and locomotion
- Not seen in the Hirudineans - Parapodia
- Paddle-like “feet”
- Used in swimming, crawling, sensory, respiration, modified gills
- Not seen in many groups (secondary loss)
6
Q
Historical Annelid Divisions
A
- “Polychaetas”: Many setae
- “Oligochaetes”: Few/little chaetae (e.g., earthworms)
- Hirudinean: Leeches, blood suckers (monophyletic)
7
Q
Latest Annelid Phylogeny
A
- Errantia
- Sedentaria
- Clitellata
- Hirudinidae
- Sibolinidae
- Echiuridae - Sipuncula
8
Q
Class Errantia
A
- Motile “polychaete” body plan
– “Many long hairs” - Mostly marine
- Well-developed sense organs and cephalization
- External fertilization with trochophore larvae
9
Q
Class Sedentaria
A
- Include sedentary tube/dwelling
“polychaetes”, beard worms, spoon worms, “oligochaetes”, and leeches - Modified heads for filter feeding or particle feeding..
- .. Or reduced heads for deposit feeding (earthworms, lugworms)
- Tube dwellers
– Calcareous, mucus, sand grains - Cilia, mucus, and food groove tentacles (for food capture)
- Reduced parapodia
– Respiration; or separate\ gills - Reduced setae
– Anchor into burrows and tubes
10
Q
Sedentaria -> Family Siboglinidae (previously phylum pogonophora)
A
- “Beard worms” discovered in 20th century
– around 150 deep sea species often in unique ecosystems - Secrete long chitinous tube-dwellers (up to 1-2 m)
- No mouth or digestive system..
– Absorption
– Via (and depend on) chemoautotrophic bacteria that use H2S
11
Q
Sedentaria -> Family Echiuridae
A
- “spoon worms” ; <150 species
- Spoon = flattened, extensible proboscis
- Secondary unsegmented
- Homologous annelid setae
12
Q
Sedentaria -> Order Clitellata
A
- Synapomorphy: clitellum (reproductive structure)
- “Oligochaete” body plan
- No parapodia, setae reduced/lost
- All hermaphroditic (monoecious)
- All have direct development
–No trochophore larva
13
Q
Sedentaria -> Clitellida -> “Oligochaetes”
A
- 3000 species
- Freshwater, marine terrestrial
- Earthworms!
- Well-developed circulatory, digestive and excretory systems
– Nephridia (filtering, expelling waste) - Ecologically important
– Bioturbation, soil/nutrient cycling, oxygenation
14
Q
Sedentaria -> Clitellata -> Family Hirudinidae
A
- Leeches, 500 species
- Many freshwater, some marine, some terrestrial
- Dorso-ventrally flattened
- Fixed number of segments
- Clitella only during reproduction
- Posterior/anterior suckers
– powerful pharynx
– blood-sucking or carnivorous (other worms) - Features reduced/lost:
- No setae
- No septa (coelem solid connective tissue)
15
Q
Medicinal Leeches
A
- Hirudo medicinalis
- Blood-letting
- Congestion
- Hirudin anticoagulant
