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What is metamerism
internal segmentation and external segmentation
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What are the advantages of metamerism?
- 1. Safety and redundancy: if one metamere dies it's not fatal
- 2. Varied and precise body movements: allows for powerful digging
- 3. More refined nervous system: able to move all somites or just one
- 4. Specialized parts
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What does it mean to be schizocoelous?
the coelom develops embryonically as a split in the mesoderm on each side of the gut.
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What is the similarities between Annelida and mollusks?
They have trochopore larvae
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What do Annelida share with Arthropoda?
- 1. Outer, secreted cuticle
- 2. Similar nervous system, ganglia, ventral nerve cord
- 3. Lateral appendages
- 4. Metamerism
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What important ecological role do the common earthworms have?
- Their burrowing increases the drainage and aeration of soils.
- Their migration mixes up the soil, distributing organic matter into deeper layers
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What gives rise to the anus in or the terminal portion of the Annelida?
pygidium
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What is peritoneum?
Layer of mesodermal epithelium, lines body wall, surrounding each compartment within a segment
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Is the prostomium the oldest or youngest part of the annelida body plan?
Oldest
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In general, the setae for Annelida is made up of what substance?
Chitin
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Identify the 4 major parts to the body wall.
- 1. Longitudinal muscles
- 2. Circular muscles
- 3. Epidermis
- 4. Non-chitinous cuticle
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What are Peristaltic contractions?
alternating waves of contraction by longitudinal and circular muscles passing down the body
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What does having a septum allow for?
elongation or widening in restricting areas.
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What are mesentaries?
- double membrane partitions supporting the gut
- run length of organism
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Which class of Annelida does not have a hydrostatic skeleton?
Hirundinea (leeches)
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What is the role of a hydrostatic skeleton?
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Why does a hydrostatic skeleton result?
Coelom is filled with fluid
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True or false. Class Polychaeta has clitellum for reproduction.
FALSE. Oligochaeta and Hirundinea have clitellum but not Polychaeta
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Explain the parapodia in class Polychaeta. What are parapodia? What is/are the function?
- Special sense organs
- used for crawling, swimming, anchoring in tubes
- chief respiratory organ
- much more developed in Polychaeta: eyes and statocysts, notopodium and neuropodium
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True or false. The fertilization in Polychaeta is internal.
- FALSE: Fertilization is external.
- Polychaeta have no permanent sex organs
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Explain the difference between Atokes and Epitokes.
- Atokes have no sex organs
- Epitokes have sex organs, only for a period of time, they go to surface and release gametes
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What species has atokes and epitokes?
Eunia virdis
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What is a typhisole?
chlorogogen cells, outer layer function like the liver
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What is the role of chlorogogen cells?
- synthesis glycogen and fat
- distribute nutrients to coelom
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Explain the circulatory system of the Oligochaeta.
- Closed
- has 4 arotic arches that pump blood into dorsal blood vessel
- blood has ameboid cells and hemoglobin
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How does reproduction occur in Oligochaeta?
- Moneoicious or hermaphroditic
- have glandular structure midway down
- Have clitellum but not until sexually mature
- get in opposite positions (69) for mating
- anchor setae into one another and after copulation, the clitellum breaks, slides over the worm to form a cacoon.
- Eventually the cacoon slips off and a worm emerges from it.
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What makes the class Hirundinea different from other classes of Annelida?
- No parapodia or setae!
- coelom: no distinct compartments, instead filled with connective tissue and muscle
- Have fixed # of segments= 34!
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What is the role of the posterior sucker of hirundinea?
- for attachment and locomotion
- holds organism in place
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What is the role of the anterior sucker of the Hirundinea?
- Attach to prey
- NOTE: smaller than posterior sucker
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Explain how the Arenicola (lugworm) lives and how it retrieves food.
- Lives in L-shaped burrow in mudflats
- Uses proboscis to burrow
- peristaltic movements keeps water coming in
- Water filters through the sand at the head end and worm ingests food-laden sand
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 Identify class.
Polychaeta
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Identify class and species.
- Class: Oligochaeta
- Lumbricus terrestris
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What is a clitellum?
thickened, saddlelike protion of certain midbody segments of many oligochaetes and leeches
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What characteristics do we use to divide Phylum Annelida into its classes?
- segmentation
- distribution of setae
- presence or absence of clitellum
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What are setae?
- thin, chitinous bristles or rods that are secreted by certain cells in the body wall
- used in locomotion and feeding
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What is the function of the cuticle?
- Protective body covering
- reduces water loss
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What are nephridiopores?
small pair of excretory pores
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Function of a gizzard?
Ground up food into smaller pieces
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In Huridinea, the function of the crop is...?
to store blood (storage)
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How do polychaetes, oligochaetes, and hirudineans move?
- Polychaetes and oligochaetes move by setae and their hydrostatic skeleton
- hirudineans have muscular body to move
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